JPH02285713A - Photoelectric switch - Google Patents

Abstract

PURPOSE:To keep the automatic recovery function by increasing luminous quantity of a light radiating from a projection means when a light receiving level of a light receiving means is lower than a predetermined level. CONSTITUTION:An optical pulse from a light projection circuit 2 radiates to a detection object synchronously with a pulse signal from an oscillation circuit 1, a light receiving circuit 3 receives a light projected from the light projection circuit 2 and converts it into an electric signal is response to the light reception quantity. A comparator 4 detects whether or not an input level of the circuit 3 is a level A or over and the photoelectric switch is operationable when the level is higher than the level A, and not operationable when the level is lower than the level A. A comparator circuit detects whether or not a light incident level is a level B or over and it is the stable light incident state when the level is higher than the level B and it is the unstable light incident state when the level is higher than the level A. A light projection current control circuit 12 is operated when the input light level is lower than the level B and an output of a self-diagnosis signal delay circuit 9 is supplied to increase the light projection current supplied to the light projection circuit 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a photoelectric switch, and particularly to a photoelectric switch having an automatic repair function that automatically increases the amount of light emitted when the amount of light received decreases. .

[Prior Art] FIG. 4 is a schematic block diagram showing the electrical configuration of a conventional photoelectric switch. FIG. 5 is a diagram showing a received light waveform of the photoelectric switch shown in FIG. 4. Next, a conventional photoelectric switch will be described with reference to FIGS. 4 and 5.

The photoelectric switch has an oscillation circuit 1, a light emitter circuit 2, a light receiver circuit 3, comparators 4 and 5, a light input display circuit 6, signal delay circuits 7 and 9, a control output circuit 8, a self-diagnosis ML output circuit 10, and a self-diagnosis output. A display circuit 11 is included.

The oscillation circuit 1 outputs a pulse signal.

The light projection circuit 2 emits pulsed light synchronized with the pulse signal from the oscillation circuit 1 to the object 20 to be detected. The light receiving circuit 3 receives the light emitted from the light projecting circuit 2 and converts it into an electrical signal according to the amount of received light. The comparator 4 detects whether the input level of the light receiving circuit is equal to or higher than level A shown in FIG. If level A or higher,
The photoelectric switch is operable and becomes inoperable below level A. The comparator 5 detects whether the incident light level is equal to or higher than level 8 shown in FIG. If the incident light level is level 8 or higher, it is a stable light incident state, and if it is below level B and level A or higher, it is an unstable light incident state.

The light-indicating circuit 6 lights up when the light is in the incoming state, that is, when the incoming light level is level 8 or higher, to indicate that the light is in the incoming state. The control output circuit 8 is the object to be detected 2
It outputs a control output to the outside depending on the presence or absence of 0, and is connected to the signal delay circuit 7.

Similarly to the input display circuit 6, the control output circuit 8 also operates when the incident light level is level A or higher. The self-diagnosis output circuit 10 is for outputting a warning signal by the self-diagnosis output display circuit 11 when the incident light level is between level A and level B, that is, in an unstable state, and the signal delay circuit 9 connected to.

The level of light received by the light receiving circuit 3 is initially level 8.
However, if the optical axis of the photoelectric switch shifts or the lens for projecting and receiving light becomes dirty, the light intensity decreases and becomes unstable. The function of self-diagnosing an unstable state and outputting a warning signal in this way is called a self-diagnosis function.

[Problems to be Solved by the Invention] However, such a conventional self-diagnosis function merely issues a warning and does not have a self-repair function.

Therefore, an object of the present invention is to provide a photoelectric switch that self-repairs when the received light level becomes unstable.

[Means for Solving the Problems] A photoelectric switch according to the present invention includes a light projecting means for emitting detection light, a light receiving means for receiving the light emitted from the light projecting means, and a light receiving means. a determining means for determining whether or not the level of the received light signal is lower than a predetermined level; and a light amount control means for increasing the amount of emitted light.

[Function] The photoelectric switch according to the present invention increases the amount of light emitted from the light projecting means when the light reception level of the light receiving means becomes lower than a predetermined level.

Embodiment of the Invention FIG. 1 is a schematic diagram showing the electrical configuration of a photoelectric switch according to an embodiment of the invention. FIG. 2 is a diagram showing a self-repair mechanism of the photoelectric switch shown in FIG. 1. Next, the first
The configuration of an embodiment of the present invention and the principle of the self-repair function will be explained with reference to the drawings and FIG.

The photoelectric switch shown in FIG. 1 is the same as the one shown in FIG. 4, except that a light emitting current control circuit 12 is provided between the signal delay circuit 9 and the light emitting circuit 2. The same reference numerals are given to the parts, and the description thereof will be omitted.

The light emitting current control circuit 12 is activated to increase the light emitting current supplied to the light emitting circuit 2 when the incident light level falls below level B and the output of the self-diagnosis signal delay circuit 9 is thereby given. It is something.

In FIG. 2, the collector of a transistor 16 is connected to the light emitting element 21 included in the light emitting circuit 2, and one end of a resistor 17 is connected to the emitter of the transistor 16.
The other end of the resistor 17 is grounded. Transistor 15 is connected in parallel to transistor 16 . That is, the light projecting element 21 is connected to the collector of the transistor 15. The emitter of the transistor 15 is the V-1 conversion circuit 14
, and the other end of the V-I conversion circuit 14 is grounded. Transistor 15 and transistor 16
Each base of is connected to an output terminal of a comparator 22 which outputs a pulse signal from the oscillation circuit 1. V-1 conversion circuit 14
The output voltage from the integrating circuit 13 is applied to the input terminal of the integrating circuit 13 when an H level (v2) signal is output from the signal delay circuit 9.

When the output of the signal delay circuit 9 becomes H level, the integration path 1
3 starts charging, and the output voltage of the integrating circuit 13 gradually increases. This voltage is converted into a current by the V-1 conversion circuit 14. As a result, the resistance between the emitter of the transistor 15 and the ground decreases, and the light emitting current flowing through the light emitting element 21 to which a constant voltage is applied increases. The oscillation circuit 1 is connected to the bases of the transistors 15 and 16 via a comparator 22.
Since the pulse signal is given to the light emitting element 21, as the light emitting current increases, the light emitting element 21 lights up in pulses more brightly. When the light incident level of the light receiving circuit 3 recovers to level B, that is, the stable light incident level, the comparator 5 is turned off and the output of the self-diagnosis delay circuit 9 becomes L level. As a result, the resistance of the V-1 conversion circuit 14 increases, so the current flowing through the light projecting element 21 decreases, and the amount of light emitted from the light projecting element 21 decreases. As a result, when the incident light level decreases and becomes below level B again, the comparator 5 is turned on. After being delayed by the signal delay circuit 9 for a certain period of time, the output of the signal delay circuit 9 becomes H level. In this way, the light emitting current is repeatedly restored (increased) and decreased.

FIG. 3 is a waveform diagram for explaining the operation of the photoelectric switch mentioned above. In particular, FIG. 3(a) shows the change over time in the incident light level, and FIG. 3(b) shows the self-diagnosis output circuit. shows the output of As shown in Figure 3 (a), the incident light level gradually decreases due to misalignment of the optical axis and dirt on the lens, but when the self-repair function is activated, it reaches level B, which is a stable incident light level.
recover to.

As shown in FIG. 3(a), when the decrease in the incident light level is small, the recovery time Ta is short, and as the decrease in the incident light level increases, Ta becomes longer.

The time Tc from when the output of the self-diagnosis signal delay circuit shown in FIG. The degree of light level reduction is T a /
It can be expressed by T c.

If the incident light level decreases further and it becomes impossible to recover to level B, which is a stable input level after time point X, the self-diagnosis output will continue to be output. At this time, the amount of light emitted will decrease from the maximum repairable level to a state where there is no self-repair function, that is, at the same rate of change as in the past.

Therefore, the lifespan can be extended until the amount of incident light decreases to level A or lower. Therefore, it can be used for a longer period of time T than conventional photoelectric switches.

Note that when the output of the signal delay circuit 9 is at H level, the self-diagnosis output indicator included in the self-diagnosis display circuit 11 is turned off. When the output of the signal delay circuit 9 is at L level, the opposite is true. Therefore, the self-diagnosis output indicator light continues to light up when stable light is received, and starts blinking at a certain cycle when the condition becomes unstable.As the condition worsens, the frequency of blinking increases, and if the condition worsens, the light goes out. Therefore, it is possible to know the degree of deterioration of the photoelectric switch and to repair it at an early stage before it becomes unusable.

This characteristic is extremely effective as an indicator for optical axis alignment and sensitivity adjustment.

[Effects of the Invention] As described above, according to the present invention, when the light receiving level of the light receiving means becomes lower than a predetermined level, the amount of light emitted from the light projecting means is increased. , the photoelectric switch will automatically repair.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram showing the electrical configuration of a photoelectric switch according to an embodiment of the present invention. FIG. 2 is a diagram showing a self-repair mechanism of the photoelectric switch shown in FIG. 1. FIG. 3 is a waveform diagram for explaining the operation of the photoelectric switch shown in FIG. 1. FIG. 4 is a schematic block diagram showing the electrical configuration of a conventional photoelectric switch. FIG. 5 is a diagram showing a received light waveform of the photoelectric switch shown in FIG. 4. In the figure, 2 is a light emitter circuit, 3 is a light receiver circuit, 4 and 5
is a comparator, 9 is a signal delay circuit, 10 is a self-diagnosis output circuit, 12 is a light emitting current control circuit, 13 is an integration circuit, 14 is V
-1 conversion circuit, 15 and 16 are transistors, and 21 is a light projecting element.

Claims (1)

[Scope of Claims] Light projecting means for emitting detection light; light receiving means for receiving the light emitted from the light projecting means; and a level of a light reception signal received by the light receiving means is set in advance. a determining means for determining whether or not the received light level is lower than a predetermined level; A photoelectric switch comprising a light amount control means for increasing the amount of light.