JP2515124Y2 - Multi-optical axis photoelectric switch - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION The present invention is provided with a plurality of pairs of a light emitting element and a light receiving element, and activates a light receiving signal from a light receiving element which becomes a pair in synchronization with lighting of the light emitting element in a detection area. The present invention relates to a multi-optical axis photoelectric switch adapted to detect a light blocking state in a detection area.

[0002]

2. Description of the Related Art This type of photoelectric switch can detect the presence / absence of an object in a wide detection area and is therefore used, for example, as a safety device for a press machine. The schematic structure is as follows. That is, a plurality of pairs of light emitting elements and light receiving elements forming a pair are provided, and one light emitting element is sequentially emitted toward the detection area in response to a signal from the control circuit. On the other hand, the light receiving element group is connected to a selection circuit having a plurality of input terminals, and only one light receiving element paired with the light emitting element that is emitting light among these light receiving element groups has the light emission timing of the light emitting element. It is activated synchronously by the selection circuit.

In this case, in order to sequentially turn on the light projecting elements, for example, a shift register is connected to each light projecting element, and these shift registers are serially connected. Then, a clock signal is output from the control circuit, and the output state of the shift register is sequentially shifted at the output timing. Further, such a configuration is also used in the selection circuit described above.

A light receiving signal from the light receiving element is amplified by a light receiving amplifier after passing through a selection circuit, compared with a predetermined reference level by a comparison circuit, and when it is determined that the amount of light received by any of the light receiving elements is low, It is determined that an object has entered the optical axis of the light emitting element and the light receiving element in the detection area.

In this case, when one light emitting element is emitting light, only the light receiving signals from the pair of light receiving elements are validated for the following reason. That is, the light emitted from the light projecting element does not always enter only the light receiving element that forms a pair with the light projecting element, and may also enter the light receiving element provided in the vicinity thereof as light of relatively high intensity. Therefore, if the light receiving signals from all the light receiving elements are equally input to one comparison circuit, it is determined that the object is in the light receiving state even though its optical axis is in the light blocking state due to the intrusion of the object, and This is because the intrusion cannot be detected accurately.

[0006]

However, in the conventional structure as described above, when a failure occurs in either the light-projecting or light-receiving shift register, or when malfunction occurs due to noise or the like, Since this cannot be recognized by the control circuit side, there is a situation in which it is impossible to know whether or not the light projecting element and the light receiving element forming a pair are in the operating state at the same time. In such a situation, there are cases where the detection of the light-shielded state cannot be reliably performed, and there is a problem in that the detection is performed on the dangerous side due to erroneous detection or the like.

The present invention has been made in view of the above circumstances, and its purpose is to detect an abnormality in an output state of a shift register quickly and to reliably perform a detection operation in a detection area. It is to provide axial photoelectric switch.

[0008]

A multi-optical axis photoelectric switch of the present invention is provided corresponding to a plurality of light projecting elements for irradiating light toward a detection area and each of the plurality of light projecting elements. A plurality of light-emission shift registers, light-emission control means for applying a control signal to the light-emission shift registers to sequentially turn on the light-emission elements at a predetermined timing, and the light-emission control means are provided so as to form a pair with the light-emission elements. A plurality of light receiving elements that receive light from the detection area, a plurality of light receiving shift registers provided corresponding to the plurality of light receiving elements, and a control signal to these light receiving shift registers to provide the light receiving elements. A light receiving control means for enabling a light receiving signal from the light emitting element in synchronization with a lighting timing of the light emitting element, and a judging means for judging a light blocking state in the detection area based on the light receiving signal from the light receiving element. When the output signal pattern of the last stage of said plurality of shift registers and light-receiving shift register floodlight
It said sheet when detecting the emission is the output signal pattern was different from the output signal pattern that is expected in a normal operating state
It is characterized in that it is provided with a detecting means for informing the outside that the shift register has an abnormal operation .

[0009]

According to the multi-optical axis photoelectric switch of the present invention, the light projecting control means and the light receiving control means sequentially operate each pair of a plurality of light projecting elements and light receiving elements to detect the light blocking state in the detection area. The detecting means detects the output signal pattern of the final stage of the light-projecting and light-receiving shift register and outputs the output signal pattern.
The output signal pattern that appears when the shift register operates normally is detected to detect whether the shift register operates normally. As a result, the operating states of the light-projecting and light-receiving shift registers can always be detected, and when an abnormality occurs, it can be detected promptly, and repair such as a failure can be promptly dealt with.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an eight-optical-axis area sensor used in a safety device of a press machine will be described below with reference to the drawings.

FIG. 3 shows an outline of the electrical structure. This area sensor is composed of a projector 1 and a photoreceiver 2 which are electrically separated.

First, in the projector 1, the eight LEDs (light emitting diodes) 3a to 3h, which are a plurality of projector elements, are connected via a projector circuit 4 to a microcomputer 5 having both projector control means and detector means. ing. The DC power supply circuit 6 is connected to the microcomputer 5 and also connected to the light projecting circuit 4 via the current detection circuit 7 so as to be supplied with a predetermined DC voltage. The current detection circuit 7 is provided with, for example, a current detection resistor that obtains a terminal voltage in proportion to the applied current and the terminal voltage 2
When the terminal voltage is within a predetermined range, one comparator inputs "H" level signals and the other comparator inputs "L" level signals to the microcomputer 5. There is.

As will be described later, the microcomputer 5 is adapted to give a light projecting signal to the LEDs 3a to 3h via the light projecting circuit 4, and the LEDs 3a to 3h respectively have eight optical axes directed toward the detection area 8. Light for detection is sequentially projected.

A display circuit 9 for displaying the operating state of the projector 1 is connected to the microcomputer 5. The display circuit 9 is provided with a display LED 9a (see FIG. 1), and a display signal is given from the microcomputer 5 according to the operating state of the projector 1 as described later.

The light projecting circuit 4 is constructed as shown in FIG. That is, drive circuits 10a to 10h for driving the LEDs 3a to 3h to light up are connected. The drive circuits 10a to 10h are connected to the output terminals of the AND circuits 11a to 11h, respectively. One of the input terminals of the AND circuits 11a to 11h is connected to the output terminals Q0 to Q7 of the light projecting shift registers 12a to 12h, respectively.
The other input terminals of 11 to 11h are connected to the output terminal A of the microcomputer 5.

The data input terminal D0 of the light projecting shift register 12a is connected to the output terminal B of the microcomputer 5, the output terminal Q0 is connected to the data input terminal D1 of the light projecting shift register 12b, and so on. The output terminals and the data input terminals of the optical shift registers 12c to 12h are sequentially connected. The output terminal Q7 of the light emitting shift register 12h is connected to the microcomputer 5
It is connected to the. In addition, the shift register 12a for projecting light
Each clock input terminal CK of 12 to 12h is connected to the output terminal C of the microcomputer 5.

The light projecting circuit 4 is divided into a main circuit section 4a for projecting and driving the LEDs 3a to 3d and a sub circuit section 4b for projecting and driving the LEDs 3e to 3h. Two circuit parts 4 for the optical axis
It is used with a and 4b connected in series. Further, a similar sub circuit unit can be serially connected to the subsequent stage of the sub circuit unit 4b.

Next, in the light receiver 2, eight PDs (photodiodes) 13a to 13h, which are a plurality of light receiving elements, are provided.
Is connected to the microcomputer 15 via the light receiving circuit 14. The microcomputer 15 also has a function as a light reception control means and a detection means. The DC power supply circuit 16 is connected to the microcomputer 15 and supplies power with a predetermined DC voltage. The PDs 13a to 13h are connected to the LEDs 3a to 3
It is arranged toward the detection area 8 so as to form a pair with h.

The output line of the light receiving circuit 14 is connected to the microcomputer 15 via the line check circuit 17 and is also connected to the microcomputer 15 via the detection circuit 18 which is a judging means. The microcomputer 15 is connected with an output circuit 19 for outputting the judgment result and a display circuit 20 for displaying the judgment result.

As will be described later, the light from the detection area 8 received by the photodiodes 13a to 13h is converted into an electrical output signal and input to the microcomputer 15 via the line check circuit 17 and the detection circuit 18. The state in the detection area 8 is determined.

Now, the above-mentioned light receiver 2 is constructed in detail as shown in FIG. That is, each PD 13a to 13h
A conversion circuit 21a for converting the received light signal into an electric signal, respectively.
To 21h are connected. Each conversion circuit 21a to 2
1h is connected to the detection circuit 18 and the line check circuit 17 via the analog switches 22a to 22h, respectively. The output terminals Q0 to Q7 of the light receiving shift registers 23a to 23h are connected to the gates of the analog switches 22a to 22h, respectively.

The line check circuit 17 provides the microcomputer 15 with an "H" level output according to the output voltage of the analog switches 22a to 22h in the ON state and an "L" level output according to the output voltage of the OFF state. It is like this.

The data input terminal D0 of the light receiving shift register 23a is connected to the output terminal a of the microcomputer 15, the output terminal Q0 is connected to the data input terminal D1 of the light receiving shift register 23b, and so on. The registers 23c to 23h are serially connected. The output terminal Q7 of the light receiving shift register 23h is connected to the microcomputer 15. The clock input terminals CK of the light-receiving shift registers 23a to 23h are connected to the output terminal b of the microcomputer 15.

The light receiving circuit 14 includes PDs 13a to 13a.
a main circuit portion 14a for receiving a light receiving signal from d, and P
The sub-circuit section 14b for receiving the light receiving signals from the D13e to 13h is separately provided. In the present embodiment, two circuit sections 14a and 14b for eight optical axes are used in a serially connected state. . Further, a similar sub circuit unit can be serially connected to the subsequent stage of the sub circuit unit 14b.

The detection circuit 18 is a comparison circuit 1 for detecting light shielding.
8a, a comparator circuit 18b for stable incident light detection, and a waveform shaping circuit 18c, each of which receives a detection signal from the light receiving circuit 14 and outputs its output.
Give 5 From the microcomputer 15,
A feedback signal for hysteresis is provided to each of the circuits 18a to 18c.

When a light receiving signal exceeding a predetermined light incident detection level is given, the comparator circuit 18a for detecting light shielding outputs an "H" level signal indicating the light incident state to the microcomputer 1
5 is output. The comparison circuit 18b for stable light incident detection is set to a stable light incident detection level higher than the above-mentioned light incident detection level, and when a light receiving signal exceeding this stable light incident detection level is given, the stable light incident state is obtained. Is supplied to the microcomputer 15. Further, the waveform shaping circuit 18c is adapted to give a synchronization detection signal to the microcomputer 15 when a burst signal is given as a light receiving signal as described later.

The output circuit 19 is composed of an output circuit 19a for detecting output of light shielding and an alarm output circuit 19b for notifying an unstable light entering state, and outputs according to an output signal from the microcomputer 15. The output is given to a load (not shown) connected to the terminal.

The display circuit 20 includes three LEDs 20a, 2
0b and 20c, for example, the LED 20a is red, the LED 20b is yellow, and the LED 20c is green. Then, these LEDs 20a to 20c are responsive to the display output signal from the microcomputer 15,
By operating in a mode such as lighting, extinguishing, or blinking, each is driven in various modes indicating a light receiving state as described later.

Next, the operation of the present embodiment will be described by dividing it into each operation in one cycle (for example, one cycle of 5 msec) shown below with reference to FIGS. 4 and 5. That is,
(1) Standby state, (2) Sync signal detection, (3) Ambient light detection operation, (4) Light shielding state detection operation, (5) Light emitting state detection operation, and (6) Light receiving state detection operation is there.

The time chart of FIG. 4 shows the output signals from the respective parts of the microcomputer 5 in the projector 1 and the output states of the respective parts of the light projecting circuit 4. The parts indicated by A to K in FIG. Corresponds to the output state. The time chart of FIG. 5 shows the output signals from the respective parts of the microcomputer 15 in the light receiver 2 and the output states of the respective parts of the light receiving circuit 14, and in FIG.
This corresponds to the output state of the portion indicated by j. (1) Standby state First, in the projector 1, the microcomputer 5
A pulse signal is input to the data input terminal D0 of the light emitting shift register 12a (see FIG. 4B), and the clock input terminal C of the light emitting shift registers 12a to 12h.
A clock signal is input to K (see FIG. 4C).

As a result, the light emitting shift register 12a
Output terminal Q0 becomes "H" level (see FIG. 4D), and a signal of "H" level is applied to one input terminal of AND circuit 11a. This makes AND
When the "H" level signal is applied to the other input terminal of 11a, the drive circuit 10a is in a state where the LED 3a is turned on.

On the other hand, in the light receiver 2, the microcomputer 15 inputs a pulse signal to the data input terminal D0 of the light receiving shift register 23a (see FIG. 5 (a)).
At the same time, a clock signal is input to the clock input terminals CK of the light-receiving shift registers 23a to 23h (FIG. 5).
(B)).

As a result, the light receiving shift register 23a
The output terminal Q0 of is at "H" level (see FIG. 5 (c)), and the analog switch 22a becomes conductive. As a result, the conversion circuit 21a becomes ready to output the light reception signal detected by the PD 13a to the detection circuit 18.

Then, as described above, the light projected from the LED 3a is set to the standby state which can be detected by the PD 13a. (2) Sync signal detection The microcomputer 5 of the projector 1 includes an AND circuit 11
A burst signal for synchronization is output to each of the other input terminals a to 11h (see FIG. 4A). By this, LED
3a is driven by the drive circuit 10a and projects the light for synchronous detection toward the detection area 8.

On the other hand, in the light receiver 2, the light for synchronization detection projected on the detection area 8 by the LED 3a is transmitted to the PD 1
When received by 3a, the light reception signal is input to the waveform shaping circuit 18c via the conversion circuit 21a and the analog switch 22a. The waveform shaping circuit 18c inputs the synchronization detection signal to the microcomputer 15 when the level of the received light signal reaches a predetermined value.

As a result, the microcomputer 15
Receives a synchronization detection signal, judges that this is a signal of a predetermined length, and outputs a control signal to the light receiving circuit 14 at a predetermined timing in order to perform a predetermined detection operation described below. become. (3) Ambient Light Detection Operation In the projector 1, the microcomputer 5 is kept in a state in which it does not output a signal for a certain period after outputting a burst signal. That is, the "L" level signal is applied to the other input terminal of each of the AND circuits 11a to 11h, and all the LEDs 3a to 3h are turned off.

On the other hand, the light receiver 2 operates as follows in order to detect ambient light during the above-mentioned fixed period in which light is not projected by the light projector 1. That is, the microcomputer 15 uses the light receiving shift registers 23a to 23a.
Seven consecutive clock signals are applied to the clock output terminal CK of h at short intervals.

In the light-receiving shift registers 23a to 23h, the state of the "H" level signal output is shifted from the output terminals Q0 to Q7 each time a clock signal is applied (FIGS. 5C to 5C). See j)). As a result, the analog switch 22a was in the conductive state.
The analog switches 22b to 22h are sequentially shifted to the conductive state, and the light receiving signals of the PDs 13a to 13h are sequentially applied to the detection circuit 18.

Since the light is not emitted from the projector 1, the light receiving signal should not be detected by the above operation. However, if the light receiving signal is detected in this state, the light emitting device 1 is not detected.
Light from other light sources, that is, ambient light, is detected. When the ambient light is detected in this way, the microcomputer 15 causes the red LED 20 of the display circuit 20 to
The "a" level signal is output to the alarm output circuit 19b while giving a blinking signal to "a" to notify the "disturbance light detection state".

The above "disturbance light detection state" is notified when the detection frequency is low, that is, when it is detected even once even in a short time. Furthermore, the "disturbance light detection state" continues for, for example, 6 μsec or more. , Or if it is detected continuously in three cycles, it is determined that the detection frequency is high, and the microcomputer 15 outputs a detection signal to the detection output circuit 19a in addition to the above. In other words, the detection output is made to be in the same state as the light-shielded state due to the intrusion of the object, so that it works on the safe side. The output state is locked and maintained until the power is turned off.

In this case, a time of about 800 μsec is set as the fixed period for detecting the ambient light. (4) Detecting Operation of Light-Shielding State When the ambient light detecting operation is completed, the microcomputer 5 in the projector 1 sequentially outputs pulse signals to the other input terminals of the AND circuits 11a to 11h at predetermined intervals (see FIG. (See A)), the clock signals are sequentially output to the light projecting shift registers 12a to 12h between the pulses of the pulse signal (see FIG. 4C). This allows
First, since the light emission shift register 12a is at the "H" level in the initial state (see FIG. 4D), A
LED during the period when the pulse signal is given to the ND circuit 11a
3a is turned on.

On the other hand, in the light receiver 2, the microcomputer 15 outputs a signal of "H" level to the data input terminal D0 of the light receiving shift register 23a, and
A pulse train is output to the clock input terminals CK of the light-receiving shift registers 23a to 23h at predetermined time intervals.

As a result, the light receiving shift register 23a
A signal of "H" level is output from the output terminal Q0 of the analog switch 22a to bring the analog switch 22a into a conductive state, thereby validating the detection signal of the PD 13a. Therefore, when the above-mentioned LED 3a is turned on, if its optical axis is not shielded by the intrusion of an object,
The light emitted from the LED 3a is detected by the PD 13a, and a signal indicating the "H" level light incident state is output to the microcomputer 15 via the light shielding detection circuit 18a.

When an object enters and blocks the light emitted from the LED 3a, the light receiving signal is not output, and the microcomputer 15 stores that the light blocking is detected once. Then, when the detection of the light shielding is repeated twice or more, the microcomputer 15 determines that the light shielding state, the red LED 20a of the display circuit 20 is turned on, and the output signal is supplied to the output circuit 19a. There is.

Hereinafter, the LEDs 3b to 3h and the PD 13b will be described.
Each of the pairs from 13h to 13h is sequentially operated to transmit and receive the light of each optical axis. Then, the microcomputer 15 detects the presence or absence of the "light-shielding state" due to the intrusion of the object in the same manner as described above. (5) Light emitting state detection operation a. Detecting Operating State of Shift Register In the projector 1, the microcomputer 5 detects whether the operating state of the projecting shift registers 12a to 12h is normal based on the output signal from the output terminal Q7 of the projecting shift register 12h. To do.

That is, the light emitting shift registers 12a to 12a
If 2h is operating normally, you in the detection period of the light-shielding state
There the clock signal output terminal Q7 of the light projecting shift register 12h on the basis of (Fig. 4 (C) reference), the clock signal
"L" level at the first 6 timings of the issue
Then, at the timing of the 7th clock signal, the "H" level
And becomes the "L" level again with the 8th clock signal.
The signal shown in FIG.
It should be output to 5. Smell in the microcomputer 5
The output terminal Q7 at each timing of the clock signal.
The signal level of the normal operation is stored in advance in the microcomputer 5, and after the eighth clock signal is output, the sequence is sequentially stored.
The next stored signal level “H” of the output terminal Q7 and
The output pattern of "L" and the output pattern of normal operation
When comparing and not matching, the light emitting shift register 1
It is determined that a failure has occurred in any of 2a to 12h, a blinking signal is output to the LED 9a of the display circuit 9, and all the light projecting operations are stopped.

As a result, the light emitting shift register 12a
It is possible to notify the occurrence of a malfunction such as the “H” level signal still being output to the output terminal or the shift operation of the output signal is not performed due to the failure of any one of to 12h. Further, all the light projecting operations are stopped, and the same state as the light blocking state due to the entry of the object is made to work on the safe side. And this state is locked,
It is maintained until the power is turned off. b. Detection of Multiple Projection Abnormality As described above, the energization of the LEDs 3a to 3h is performed through the current detection circuit 7, and if the detection voltage appearing according to the energization current is within the predetermined range, two comparators are provided. Output detection signals of "H" level and "L" level, respectively. Then, when the lighting operation is normally performed, the LEDs 3a to 3h are sequentially lit one by one, so that the energizing current value at the time of lighting is within a certain range and the two LEDs are lit. The comparators should be outputting "H" level and "L" level signals, respectively.

In the microcomputer 5, when each of the LEDs 3a to 3h is energized and lit, the detection signal from the current detection circuit 7 is "H" level and "L".
When the level is determined to be normal, otherwise it is determined to be an "abnormal state", a blinking signal is output to the LED 9a of the display circuit 9, and all light projecting operations are stopped.

As a result, the light emitting shift register 12a
To 12h, the AND circuits 11a to 11h, or the drive circuits 10a to 10h have failed and the LEDs 3a to 3h have failed.
A state in which two or more h's are turned on at the same time or no one is turned on can be quickly detected and notified.
In addition, all the light projecting operations are stopped (when two or more are turned on), and the same state as the light blocking state due to the entry of an object is made to work on the safety side. The light emission stopped state is locked and maintained until the power is turned off. (6) Light receiving state detection operation a. Light Incident (Received) Level Detection In the light receiver 2, the received light signals from the PDs 13a to 13h are also input to the stable light incident detection circuit 18b. Then, as described above, the stable detection level in the stable incident light detection circuit 18b is set to a level higher than the detection level of the light shielding detection circuit 18a.

When the light reception signal is given, the stable light detection circuit 18b compares its level with the stable detection level, and outputs P
When the level of the light receiving signal from D13a to 13h exceeds the stable detection level, the microcomputer 15 outputs the detection signal indicating the "stable light entering state". Further, in response to this, the microcomputer 15 determines that all PDs 1
When a detection signal indicating the "stable light input state" from 3a to 13h is obtained, a lighting signal is output to the green LED 20c of the display circuit 20 to notify the "stable light input state", and the stable light input detection circuit. A feedback signal for hysteresis is given to 18b.

On the other hand, an unstable light input state, for example, the optical axis is deviated, or the window of the device (not shown) is dirty, or the level of light projection or light reception is lowered due to adhesion of dust or the like. When it does, it operates as follows. That is, PD
If the light entering state of 13a to 13h is unstable, even if the received light signal exceeds the detection level of the light shielding detection circuit 18a, if it does not exceed the stable detection level of the stable light detection circuit 18b, Microcomputer 15
Is determined to be "unstable light input state".

At this time, the microcomputer 15
First, a lighting signal is output to the yellow LED 20b of the display circuit 20 to display the "unstable light incident state". Then, when this "unstable light incident state" is continuously detected for, for example, 5 seconds, the microcomputer 15 causes the yellow LED 20b.
In addition to outputting the blinking signal, the alarm output circuit 19b is provided with an output signal to notify.

As a result, an unstable light entering state can be promptly detected to call attention, and erroneous detection can be prevented. b. Detecting Operating State of Shift Register In the photodetector 2, the microcomputer 15 detects whether the operating state of the light receiving shift registers 23a to 23h is normal based on the output signal from the output terminal Q7 of the light receiving shift register 23h. .

That is, the light-receiving shift registers 23a to 2
If 3h is operating normally, you in the detection period of the light-shielding state
There clock signal (see FIG. 5 (b)) of the light receiving shift register 23h on the basis of the output terminal Q7 to, said clock signal
"L" level at the first 6 timings of the issue
Then, at the timing of the 7th clock signal, the "H" level
And becomes the "L" level again with the 8th clock signal.
The signal shown in FIG.
It should be output to 15. To the microcomputer 15
In addition, the output is performed at each output timing of the clock signal.
The signal level of the signal Q7 is sequentially stored, and the output pattern in the normal operation is stored in the microcomputer 15 in advance. The eighth clock signal is output.
Of the signal level of the output terminal Q7 stored sequentially after
Output pattern of "H" and "L" and output during normal operation
The pattern is compared with each other, and if they do not match, it is determined that a failure has occurred in any of the light-receiving shift registers 23a to 23h. Then, the microcomputer 15
Outputs a blinking signal to all the LEDs 20a to 20c of the display circuit 20 and gives an output signal to both the detection output circuit 19a and the alarm output circuit 19b to cause an "abnormal state".
Is notified.

As a result, the light receiving shift register 23a
It is possible to notify the occurrence of a malfunction such as the “H” level signal being kept output to the output terminal or the output signal shifting operation not being performed due to the failure of any one of to 23h. In addition, by making the detection output the same as the light-shielded state due to the entry of an object, it works on the safe side. Then, this state is locked and maintained until the power is turned off. c. Detection of Operating State of Analog Switch As described above, the line check circuit 17 is connected to the output terminals of the analog switches 22a to 22h, and the comparison output thereof is input to the microcomputer 15. Then, the microcomputer 15
Is the analog switch 22h, as shown in FIG.
Output voltage is determined according to an output signal from the line check circuit 17 detected at a predetermined timing when the light receiving operation is not performed, that is, at two points of the ON state and the OFF state of the analog switch 22h.

The microcomputer 15 determines that the output signal from the line check circuit 17 is operating normally when the output signal from the line check circuit 17 is inverted from the "H" level to the "L" level upon detection of the above-mentioned two points, and otherwise. In this case, the output line to the detection circuit 18 is broken, or the analog switch 22a
It is determined that there is an “abnormal state” such as any one of to 22h remains on. When the microcomputer 15 determines the "abnormal state", it outputs a blinking signal to all the LEDs 20a to 20c of the display circuit 20, and outputs an output signal to both the detection output circuit 19a and the alarm output circuit 19b. It notifies that it is an "abnormal state".

As a result, the light receiving shift register 23a
To 12h, the analog switches 22a to 22h, or the conversion circuits 21a to 21h, a failure can be detected and notified promptly. Also,
It works on the safe side by setting the detection output to the same state as the light blocking state due to the entry of an object. Then, this state is locked and maintained until the power is turned off.

The detection states of the above various detection operations are summarized as shown in Tables 1 and 2 when they correspond to the respective display states of the light projector 1 and the light receiver 2.

[0059]

[Table 1]

[0060]

[Table 2] According to this embodiment as described above, the output terminal of the light emitting shift register 12h of the light emitting circuit 4 is connected to the microcomputer 5
The output state is detected by connecting to the light emitting shift registers and compared with a normal operation pattern, so that the light emitting shift registers 12a to 12
Since the operation state of h is detected, the occurrence of an abnormal state can be detected quickly, and the light blocking state in the detection area 8 can be detected accurately. Similarly, since the light receiving circuit 14 also detects the operating states of the light receiving shift registers 23a to 23h, it is possible to quickly detect the occurrence of an abnormal state, and thus it is possible to accurately detect the light blocking state in the detection area 8.

In the above embodiment, the ambient light is detected by providing a fixed period for collectively detecting the PDs 13a to 13h. However, the present invention is not limited to this. For example, one optical axis or a plurality of optical axes may be used. The detection may be performed every time the projection of the optical axis is completed.

In the above embodiment, the alarm output circuit 18b is provided. However, the present invention is not limited to this, and the alarm output may be used instead of the alarm output.

Further, in the above embodiment, the case where the present invention is applied to the area sensor having eight optical axes has been described. However, the present invention is not limited to this, and there are a plurality of pairs of a light projecting element and a light receiving element forming the optical axis. It can be applied to all things.

[0064]

As described above, according to the multi-optical axis photoelectric switch of the present invention, the detecting means detects the operating states of the light emitting shift register and the light receiving shift register. It is possible to quickly detect the occurrence of the occurrence of, and therefore, it is possible to always accurately detect the light blocking state in the detection area.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram of a floodlight showing an embodiment of the present invention.

FIG. 2 is an electrical configuration diagram of a light receiver.

FIG. 3 is a block diagram of the overall configuration

FIG. 4 is a time chart showing a signal output state of each part on the projector side.

FIG. 5 is a time chart showing a signal output state of each part on the light receiver side.

[Explanation of symbols]

1 is a light emitter, 2 is a light receiver, 3a to 3h are light emitting diodes (light emitting elements), 4 is a light emitting circuit, 5 is a microcomputer (light emitting control means, detection means), 7 is a current detection circuit,
8 is a detection area, 9 is a display circuit, and 11a to 11h are A
ND circuit, 12a to 12h are light emitting shift registers,
13a to 13h are photodiodes (light receiving elements), 1
4 is a light receiving circuit, 15 is a microcomputer (light receiving control means, detection means), 17 is a line check circuit, 18 is a detection circuit (judgment means), 18a is a light shielding detection circuit, 18b is a stable light detection circuit, and 18c is a waveform. Shaping circuit, 19 is an output circuit, 19a is a detection output circuit, 19b is an alarm output circuit,
20 is a display circuit, 20a is a red LED, 20b is a yellow L
ED and 20c are green LEDs, 22a to 22h are analog switches, and 23a to 23h are light receiving shift registers.

Claims (1)

(57) [Scope of utility model registration request] 1. A plurality of light projecting elements for irradiating light to a detection area, a plurality of light projecting shift registers provided corresponding to each of the plurality of light projecting elements, and these light projecting devices. Projection control means for applying a control signal to a shift register to sequentially turn on the light projecting elements at a predetermined timing; And a plurality of light receiving shift registers provided corresponding to the plurality of light receiving elements,
A light receiving control means for applying a control signal to these light receiving shift registers to enable the light receiving signal from the light receiving element in synchronization with the lighting timing of the light projecting element, and the light receiving control means based on the light receiving signal from the light receiving element. Judging means for judging the light blocking state in the detection area, and output signals of the final stage of the plurality of light emitting shift registers and light receiving shift registers
When detecting a pattern corresponding output signal pattern was different from the output signal pattern that is expected in a normal operating state
Notify outside that the above shift register is malfunctioning
A multi-optical axis photoelectric switch, comprising: