JPH07111447A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To prevent optical interference between photoelectric switches with a simple system by adjusting a light projection timing of plural photoelectric switches provided in parallel. CONSTITUTION:Two - three photoelectric switches are provided in parallel and when a signal is inputted simultaneously, the projection timing has an order depending on a difference from the switches. After the light projection of the projector 3a lighted at first is started, a light reception timing detection circuit 19 of a controller 3c' discriminates the overlapped sequence of a concerned light projection timing with a light projection timing of other photoelectric switch based on a light reception signal from a light receiving device 3b. An automatic adjustment circuit 20 deviates light projection timings depending on the result of discrimination to continue light projection and reception while avoiding the overlapping and when the light projection timings are overlapped, the same operation is repeated to avoid overlapping. Thus, optical interference among the photoelectric switches is prevented with simple circuit configuration and low cost and miniaturization are attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric switch control system for preventing optical interference between photoelectric switches when two or three photoelectric switches are arranged in parallel.

[0002]

2. Description of the Related Art A control switch for an automatic door is shown in FIGS.
As shown in, the opening / closing switch 2 for detecting the front and rear area D of the door 1 and the safety switch 3 for detecting the space along the door traveling path are used together. As the opening / closing switch 2, for example, a reflection type photoelectric switch provided above the doorway is used,
Main control for opening and closing the door 1 is performed by detecting the approach of a person or the like to the door. The safety switch 3 includes the projector 3a and the light receiver 3
b is arranged so as to face the door storage portions 4 on both sides of the door to prevent the door from being closed when a person or an object is left near the traveling path.

In order to ensure detection, the safety switch 3 generally has three different mounting heights (see FIG. 5 (b)).
A, B, C) are provided. The safety switch 3 generally adopts a two-wire type sensor configuration at present due to a demand for downsizing corresponding to the thickness of the door storage portion 4 and simplification of wiring work.

Here, the two-wire sensor refers to a sensor in which a light projector 3a and a light receiver 3b are connected to a controller 3c only by two electric wires 5, as shown in FIG. With this configuration, the controller 3c includes a light emitting element 6 such as an LED on the projector 3a.
Is directly supplied to supply the operating voltage to the light receiver 3b.

In the light receiver 3b, the photoelectric conversion output of the light receiving element 7 such as a photodiode is received by the light receiving detector 8, and when it exceeds a predetermined level, the output unit 9 supplies the power supply circuit 10 with it.
Short-circuit a part of. The drop in the input terminal voltage due to this short circuit becomes an output signal to the controller 3c. Power supply circuit 10
Secures the operating voltage of the light receiver 3b even during this voltage drop. The controller 3c determines the presence / absence of an object from the output of the light receiver and outputs it as a door control signal.

[0006]

As shown in FIG. 5 (b), when a plurality of photoelectric switches A, B, C are provided side by side,
Optical interference may occur between adjacent photoelectric switches, resulting in malfunction. This is because, for example, when the object 11 remains in the space sandwiched between the lower photoelectric switches A, and the lower photoelectric switch A is normally in the light-shielding state, the intermediate position or the upper photoelectric switches B and C are This is a problem that the projection light of the light projector 3a enters and is determined to be a light receiving state, and the closing operation of the door 1 cannot be prohibited.

As a method of preventing this optical interference, a method of changing the modulation frequency of each photoelectric switch, and a method of connecting each photoelectric switch with a signal line for synchronization so that the light emitting cycles of the photoelectric switches do not overlap Can be considered.

However, the method (1) complicates the structure of the modulation / demodulation circuit, especially the demodulation circuit, increases the size and cost of the device, and requires frequency setting at the time of installation, resulting in complicated installation work. In addition, the method (2) increases the number of wires and impairs the simplification of construction, which is a merit of the two-wire sensor.

Therefore, an object of the present invention is to provide a structure for automatically canceling the state where the light emitting cycles of the respective photoelectric switches overlap when two or three photoelectric switches are provided side by side to prevent the interference operation. And

[0010]

SUMMARY OF THE INVENTION A photoelectric switch provided by the present invention comprises a light emitter and a light receiver which are arranged opposite to each other, and a light emitter intermittently emits modulated light at a predetermined cycle, and an object is received from a light reception signal of the light receiver. In a configuration in which two to three photoelectric switches each including a controller for determining presence / absence and outputting the same are provided, the controller of each photoelectric switch compares the light emission timing with the light reception signal with its own light emission timing. It is characterized in that a light receiving timing detection circuit for detecting the light emission timing and a light emitting timing automatic adjusting circuit for automatically shifting the light emitting timing when the light emitting timings overlap each other are provided.

Specifically, the light receiving timing detection circuit and the light emitting timing automatic adjusting circuit continue the current light emitting timing to detect the light receiving detection when the light receiving detection start timing is as scheduled. When the start timing is earlier than planned and the non-light receiving detection start timing is later than planned, the next light emission is started immediately after detecting non-light receiving, the light receiving detection start timing is earlier than planned, and non-light receiving detection starts. When the timing is as scheduled, one projection / reception time (one projection duration T _B plus time T _D required to detect non-reception after completion of projection) has elapsed. Configured to start later.

[0012]

In the above structure, the self-projection timing is delayed and overlaps with the projection timings of other photoelectric switches.
It is detected when the light reception is detected earlier than the scheduled timing. Further, in this case, when the non-light receiving timing is delayed from the scheduled timing, it is determined that the own light projecting timing is the second one because there is a photoelectric switch that overlaps at a later timing than itself. When the non-light receiving timing coincides with the scheduled timing, the light emitting timing of the self is the final, so it is determined as the third timing.

When the second judgment is made, the next light projection is started immediately after the non-light reception is detected, and when the third judgment is made, one projection / reception time (one projection continuation time The light emission is started after the time T _D, which is the time required to detect non-light reception after the light emission is added to T _B , has elapsed.

After that, the light projection timings of the first, second, and third photoelectric switches are shifted in this order and do not match, thereby preventing optical interference.

When two of the three photoelectric switches overlap, the photoelectric switch that overlaps with a delay becomes the third determination, and optical interference is similarly prevented. This is also the case when two photoelectric switches are used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is a photoelectric switch 3 as shown in FIG.
At the controller 3c, the overlapping of the light emission timing is detected from the light reception signal r detected from the output of the light receiver 3b, and the light emission timing is automatically adjusted. In order to perform such an operation, the controller 3C 'is used in the present invention.
Is configured as shown in FIG.

In the controller 3c 'of FIG. 1, 12
Is a light emitting pulse generation circuit which intermittently outputs a modulation pulse p in accordance with a predetermined light emitting cycle based on a predetermined reference clock,
A light emitting element 6 of the projector 3a receives the modulated pulse p.
A high-speed driver circuit for supplying a light emission current to the light source, a voltage supply circuit 14 for supplying a predetermined voltage to the light receiver 3b, and a light receiver 15 for a change in the load state of the light receiver 3b (voltage change due to a short-circuiting operation of the output unit 10). 3b is a signal detection circuit for taking out the detection signal q, 16 is a light receiving determination circuit for discriminating the light receiving state and the non-light receiving state from the detection signal q and outputting the light receiving signal r, and 17 is generating the light receiving signal r for its own modulation pulse p An object presence / absence determination circuit that outputs the determination signal s indicating the presence / absence of an object to the outside as a door control signal via an output circuit 18 such as a relay through a time test to determine the presence / absence of an object, and 19 modulates the received light signal r A light-receiving timing detection circuit that compares the generation times of the pulses p and determines the overlapping state when the own light-projecting timing overlaps that of another photoelectric switch, 20 is a light-receiving timing detection Automatic adjustment circuit of the light emitting timing of shifting the light emitting timing of the light projection pulse generating circuit 12 according to the judgment of the road 19, 21 is a power source circuit of the controller. It should be noted that in the above configuration, generation of the light projection pulse (1
2), detection of received light signal (16), object presence / absence determination (1
7), the overlap judgment of the projection timing (19), and the automatic adjustment of the projection timing (20) are performed by the microcomputer 2
2 is practical.

The operation when the controller 3c 'of FIG. 1 is used will be described below.

The basic operation of detecting the presence / absence of an object is as follows. As shown in FIG. 2, for example, the light projecting pulse generation circuit 12 generates a modulated pulse p at T _A time intervals for T _B time (T _B << T _A ), and projects light at the timing of this modulated pulse p. The light receiver 3b which receives the light of 3a outputs the detection signal q to the controller 3c 'at this timing when there is no light shield. The light receiving determination circuit 16 of the controller 3c 'outputs the light receiving signal r to the detection signal q when the arrangement of the pulses q continues for T _C time (T _C <T _B ).
0 "(light receiving state), and when this pulse q is not continuously input for T _D time, the light receiving signal r is changed to" 1 "(non-light receiving state). The signal r is tested with its own modulated pulse p to determine the presence or absence of an object, and the determination signal s is output as a door control signal through the output circuit 18.

Next, the avoidance operation of the respective photoelectric switches when the light projecting periods overlap will be described. It is assumed that the three photoelectric switches 3'are turned on at the same time when the operation of the automatic door is started. Although each photoelectric switch is manufactured according to the same standard, the light emitting cycle is shifted due to individual differences (a slight difference in the frequency of the oscillator, a difference in the operation start time), and the light emitting timing is ranked.

When the light projecting timings of the three photoelectric switches 3'overlap, the received light signal r of each photoelectric switch 3'is
X ₁ , X ₂ , X ₃ of FIG.
It becomes a pattern of seeds.

Since the projection timings overlap,
The “0” (light reception detection state) of each of the light reception signals r of X ₁ , X ₂ , and X ₃ is detected by the slowest projector 3a after the time T _C has elapsed from the start of projection of the projector 3a which emitted the light first. It continues until T _D time elapses after non-light emission. In contrast,
The fall and rise of the received light signal r when only its own light projection is detected can be calculated as scheduled timing based on its own modulated pulse p, as shown by the dotted line in FIG. Therefore, by comparing the detected light reception signal r with the scheduled timing, it is possible to determine the overlapping order of the own light projection timing and the light projection timing of another photoelectric switch. This judgment is made by the light receiving timing detection circuit 1
9, the procedure is as shown in FIG.

When the light reception signal r falls (light reception starts),
Compare this to the scheduled timing. When they match, it can be determined that the self is the earliest projection timing.
This is the case for X ₁ in FIG. If the rising edge does not coincide with the scheduled timing, it means that there is a photoelectric switch with a light projecting timing earlier than itself, so the timing at which light is not received is further compared with the scheduled timing.
If they match, it can be determined that it is the _third (X _{3 in} FIG. ₃ ) having the latest light emission timing, and if they do not match, the own light emission timing is the second (X _{2 in} FIG. 3). ) Can be determined.

If there is an overlap in the projection timing in the above judgment, the projection timing automatic adjusting circuit 20 shifts the projection timing of the photoelectric switch 3'to avoid the overlap of the projection timing. Although this shifting method is arbitrary, the following method is adopted in consideration of minimizing the recovery time to the normal light emitting / receiving operation.

As shown in FIG. 3, in the case of the earliest light emitting timing, the current light emitting timing is continued (at this time, the current light emitting / receiving operation can also be processed assuming that there is no error). In the second case, when the current light receiving state ends (when the light receiving signal r becomes “1”), light emission is started at the same time and the light emitting and receiving operation is performed again. In the case of the third case, the second light emitting / receiving operation time (the time T _D required until non-light reception is detected after the completion of the light emission for one light emitting duration time T _B) is further added.
(Time added) is waited for and the light emission is started.

As described above, even after the light projecting timing is shifted, the light projecting period T _A is not changed, the light projecting and receiving operations are continued, and when the light projecting timings are overlapped again, the above operation is performed. To avoid.

The operation of avoiding the overlapping of the light emitting timings is similarly performed when two of the three photoelectric switches overlap. In this case, the third process is performed with respect to the light emitting timing of the later photoelectric switch. By this processing, when the light emitting timings of the remaining photoelectric switches overlap, the above processing is further performed, but the light emitting duration time T _B is 1/100 of the light emitting period T _A.
Since it is as small as about 10, the frequency of the above processing is small.

Even when two photoelectric switches are provided side by side, the avoidance operation is performed in the same manner as described above, and the present invention can be effectively implemented. Although the above description has been made on the two-wire type sensor, the present invention is not limited to the two-wire type sensor, and is an effective means for preventing optical interference when the photoelectric switches cannot be synchronized with each other.

[0029]

According to the present invention, when two to three photoelectric switches are installed in parallel, the frequency modulation system, which is costly and difficult to miniaturize, and the synchronizing signal line system, which causes a trouble in installation work, are not adopted. It is possible to prevent optical interference between the photoelectric switches.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a two-wire photoelectric switch showing an embodiment of the present invention.

FIG. 2 is a signal waveform diagram showing a basic operation of projecting and receiving light in the photoelectric switch of FIG.

FIG. 3 is a signal waveform diagram for explaining overlapping patterns X ₁ , X ₂ , X _{3 of} light emission timings and the avoidance operation thereof when three photoelectric switches of FIG. 1 are provided side by side.

FIG. 4 is a flowchart showing a procedure for determining an overlapping state of light emission timings.

FIG. 5 is a plan view (a) and a front view (b) showing an installation example of a photoelectric switch (safety switch) which is a target of the present invention.

FIG. 6 is a block diagram showing the configuration of a photoelectric switch used as a safety switch in FIG.

[Explanation of symbols]

 3'photoelectric switch 3a light emitter 3b light receiver 3c 'controller 12 light emission pulse generation circuit 16 light reception determination circuit 17 object presence / absence determination circuit 19 light reception timing detection circuit 20 light emission timing automatic adjustment circuit p modulation pulse q detection signal r light reception signal

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical indication H04B 10/22

Claims (2)

[Claims] 1. A photoelectric converter comprising a light emitter and a light receiver arranged opposite to each other, and a controller for causing the light emitter to intermittently emit modulated light at a predetermined cycle, and determining and outputting an object presence or absence from a light reception signal of the light receiver. In the configuration with two or three switches installed side-by-side, the start timings of the received light detection and the non-received light detection are compared to their own projection timings in the controller of each photoelectric switch, In some cases, if the light reception detection start timing is earlier than planned and the non-light reception detection start timing is later than planned, the light reception detection start timing is earlier than planned, and the non-light detection detection start timing is as planned. According to the result of the above-mentioned judgment, the light-emission timing is shifted by a predetermined time, and each photoelectric switch A photoelectric switch, which is provided with an automatic light-emission timing adjustment circuit that prevents the light-emission cycles of the switches from overlapping. 2. A circuit for automatically adjusting the light emission timing comprises:
In the above case, the current light projection timing is continued, the next light projection is started immediately after non-light reception is detected in the above case, and 1
The present invention is characterized in that it is started after a lapse of a single projection / reception time (a single projection duration T _B plus a time T _D required to detect non-reception after completion of projection). The photoelectric switch according to claim 1.