JP3231874B2 - Optical area sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical area sensor,
In particular, it relates to a fail-safe one.

[0002]

2. Description of the Related Art Conventionally, as an optical area sensor used in a press machine, a multi-optical axis photoelectric sensor, a so-called optical area sensor, is used because it is necessary to reliably detect a human body or the like (for example, No. 4-19830).

[0003] A conventional optical area sensor has a plurality of optical axes, and a light emitting element and a light receiving element are arranged on each optical axis with a predetermined distance therebetween to constitute a sensor. Then, each sensor is driven periodically to detect an object to be detected such as a human body.

[0004]

However, the above-mentioned conventional optical area sensor can detect an object to be detected by blocking a light beam from the light-emitting element, but a fail-safe optical area sensor that also monitors the drive circuit itself. The appearance of sensors has been awaited.

SUMMARY OF THE INVENTION The present invention has been made to meet the above-mentioned demands, and an object of the present invention is to provide a fail-safe optical area sensor capable of monitoring a drive circuit itself.

[0006]

In order to achieve the above object, a photoelectric sensor according to the present invention comprises a plurality of sensors comprising a light emitting element and a light receiving element provided at a predetermined distance on an optical axis. a sensor unit which is formed by providing said drives the respective sensors periodically, to synchronize with the same optical axis of the light emitting element and a light receiving element is driven, and, alternately one driving the respective sensor Do , do the same operation synchronously
A control unit of the system configuration, detects the coincidence state of the control operation of the control unit of the dual system configuration, while the matching state is detected, outputs an alternating signal corresponding to the drive signals of the sensors An asymmetrical checking unit that performs, when the asymmetrical checking unit detects a mismatched state, or when the sensor unit detects an object to be detected, an asymmetrical switch that outputs an abnormal state detection signal, I have.

[0007]

In the above configuration, the asymmetric switch outputs an abnormal state detection output signal even when the sensor section is normal when the asymmetric control section detects a mismatch, and when the sensor section detects an object to be detected. Outputs abnormal state detection output signal.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a schematic configuration of an optical area sensor according to one embodiment.
And a plurality of sensors P _{1 to} P _n provided in the light receiving section 2 and the light receiving section 2. Each of the sensors P _{1 to} P _n is provided with a light emitting element P ₁ ′ to P _n ′ made of a well-known semiconductor and a light receiving unit on the light transmitting unit 1 side while maintaining a predetermined interval on each optical axis. On the two sides, light receiving elements P ₁ ″ to P
_n ″ to form a detection surface of a predetermined size.

Each of the light emitting elements P ₁ ′ to P _n ′ is configured to be driven by a well-known constant current driving circuit (hereinafter referred to as “driving circuit”) 3 and each light receiving element P _1. “−P _n ” is configured so that an output can be obtained from the amplifier circuit 4 including a well-known comparison circuit and a shaping circuit.

[0010] The control unit 5a (hereinafter, CPU hereinafter), and a control section 5b (hereinafter, referred to as CPU 2) is the same program, and have been configured in dual system to synchronous operation with each other, the sensors P ₁ to P It is configured to drive _n periodically. That is, the control signal from each of the CPUs 1 and 2 is transmitted to the asymmetric type checking unit 6 for detecting the coincidence state of the CPUs 1 and 2, that is, the coincidence state of the operation result.
It is configured to transmit to the drive circuit 3 via the bus line B and the output port 7, and to input port 9,
The output from the amplifying circuit 4 can be input to the asymmetric switch 11 via the bus line B and the output port 10.

When each of the sensors P _{1 to} P _n is driven, the CPU 1 and the CPU 2 set one drive to “high (H)”, “low (L)”, “1”, “0”, or “0”. It is configured such that drive control can be performed alternately as in "1" and "-1".

Further, the asymmetric type checking unit 6 includes a CPU 1
CPU 2 is operating normally, that is, both CPU 1 and CPU 2
When the two operations are in the coincident state, an alternating signal corresponding to an alternating drive signal of each of the sensors P _{1 to} P _n can be applied to the asymmetric switch 11.

Next, the operation of the optical area sensor according to this embodiment will be described with reference to the time chart of FIG.
First, a case where both the CPU 1 and the CPU 2 are normal and the detected object is not detected will be described.

A drive signal based on the coincidence of the operations of the CPUs 1 and 2 is supplied from the asymmetric type checking unit 6 and input to the output port 8 via the bus line B ((a) and (b) of FIG. 2). reference). The drive circuit 3 includes the respective sensors P ₁ to
_Pn is sequentially driven, and at the same time, the output port 10 receives a reception signal (light reception signal) from the amplifier circuit 4 that operates in synchronization with the drive circuit 3 (see FIG. 2C).

The asymmetric type checking unit 6 includes both CPUs 1 and 2
2 is in the normal state, the “1” and “0” alternating signals corresponding to the drive signals (“H” and “L” signals in the example of FIG. 2) of the sensors P _{1 to} P _n are transmitted to the asymmetric switch 11. (See (d) of FIG. 2).

The asymmetric switch 11 has an output port 10
No output is performed because the signal input from the asymmetric type and the signal input from the asymmetric type checking unit 6 are symmetrical. That is, the optical area sensor is determined to be in a normal state (see FIG. 2E).

Now, assume that the CPU 2 goes down for some reason (see FIG. 2). In this case, both CPs
Since the matching state of U1 and CPU2 is lost, the output of the alternating signal from the asymmetric type checking unit 6 disappears (see FIG. 2). Therefore, as shown in FIG. 2, the asymmetric switch 11 outputs an abnormal signal. The same applies, of course, even if the CPU 1 goes down.

Further, if both CPU1 and CPU2 are normal,
Light area sensor according to the non-detection object (in this embodiment the sensor P ₁ to P _n is the human body when provided in the press machine. Therefore, in the present invention, the object to be detected by each sensor P ₁ to P _n Is detected, the abnormal state is detected.) When the abnormal state is detected (see FIG. 2), in this case as well, there is a discrepancy between the output of the asymmetric type checking unit 6 and the output of the output port 10. Upon detection, the asymmetric switch 11 outputs an abnormality detection signal.

As described above, in the optical area sensor according to the present embodiment, the CPU for driving each of the sensors P _{1 to} P _n has a dual system and is capable of monitoring. It can be an area sensor.

[0019]

The optical area sensor according to the present invention has an optical axis line.
Light-emitting element and light-receiving element provided at a predetermined distance above
Sensor section formed by providing a plurality of sensors consisting of
And periodically driving each of the sensors and using the same light
The light emitting element and the light receiving element on the axis are driven synchronously,
One of the sensors is driven alternately, and
A control unit having a dual configuration that performs one operation, and detecting a matching state of the control operation of each control unit of the dual configuration,
While the coincidence state is detected , an asymmetrical checking unit that outputs an alternating signal corresponding to the drive signal of each of the sensors,
When the asymmetric type checking unit detects a mismatched state, or when the sensor unit detects an object to be detected, it has an asymmetric type switch that outputs an abnormal state detection signal,
The drive system of the sensor can also be monitored, and a fail-safe optical area sensor can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical area sensor according to one embodiment of the present invention.

FIG. 2 is a time chart for explaining a detection operation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light transmitting unit 2 light receiving unit 3 drive circuit 4 amplifying circuit 5 a calculation unit (CPU 1) 5 b calculation unit (CPU 2) 6 asymmetric type checking unit 10 output port 11 asymmetric type switch

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-93681 (JP, A) JP-A-4-19830 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01V 8/10 G01V 8/12 H01L 31/12

Claims (1)

(57) [Claims] 1. A sensor section formed by providing a plurality of sensors each including a light emitting element and a light receiving element provided at a predetermined distance on an optical axis, and each of the sensors is periodically driven; synchronize the same optical axis of the light emitting element and a light receiving element is driven, and alternately performs the first drive of the respective sensors, the same dynamic synchronization
A control unit having a dual system configuration for performing operations, and detecting a coincidence state of the control operation of each control unit of the dual system configuration, and corresponding to the drive signal of each sensor while the coincidence state is detected. An asymmetrical checking unit that outputs a changed alternating signal, and an asymmetrical switch that outputs an abnormal state detection signal when the asymmetrical checking unit detects a mismatched state, or when the sensor unit detects an object to be detected, An optical area sensor comprising: