JP2015162386A - Method for adjusting photoelectric sensor and photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for adjusting a photoelectric sensor in which optical axis adjustment is easily made possible by reducing the complexity in installation work, and operation with securing the margin for the light receiving amount in use after adjustment is made possible, and also to provide the photoelectric sensor used for the same.SOLUTION: A method for adjusting a photoelectric sensor includes: a first mode in which a first amount of projected light is projected; and a second mode in which a second amount of projected light is smaller than the first amount of projected light. When a signal indicating existence of an object in a detection region is not sent during both the first mode and the second mode, it is determined that the projected light correctly does not reach a light receiving element 21, that is, an optical axis is not adjusted and matched.

Description

  The present invention relates to a photoelectric sensor adjustment method and a photoelectric sensor, and more particularly to a photoelectric sensor optical axis adjustment method capable of adjusting an optical axis with a simple configuration and a photoelectric sensor used therefor.

  Conventionally, photoelectric sensors for detecting the presence or absence of an object in a predetermined detection area have been widely used. A general photoelectric sensor includes a light projecting unit and a light receiving unit. The light receiving unit determines whether or not to receive light emitted from the light projecting unit based on the amount of received light, and based on this, the object in the detection region is detected. Judgment is made. When a photoelectric sensor including such a light projecting unit and a light receiving unit is used, the amount of light received by the light receiving unit is determined in accordance with the presence or absence of an object that blocks light projected from the light projecting unit in the detection region. It is necessary to change across.

  In a normal photoelectric sensor, the threshold is set appropriately in consideration of the installation environment of the photoelectric sensor, such as controlling the amount of light emitted by adjusting the gain of the light projecting unit or adjusting the power supplied to the light projecting element, and the positional relationship of the surrounding light sources. By setting it to a proper value, it is configured to satisfy the condition.

  By the way, even in the situation where there is no object that blocks the light projected from the light projecting unit in the detection area, the light receiving unit receives light according to the amount of optical axis displacement or the light axis misalignment angle between the light projecting unit and the light receiving unit. The amount will fluctuate. That is, even if there is no object that blocks the light projection, if the amount of received light decreases due to the deviation of the optical axis and falls below the threshold, there is a risk of false detection that an object is present. It was.

  Based on this, it is natural to align the light projecting part and the light receiving part so that the optical axis is not displaced when the photoelectric sensor is installed. In addition, in consideration of the optical axis misalignment caused by transporting the device to which the photoelectric sensor is attached and the optical axis misalignment due to vibration / impact on the photoelectric sensor after the start of use, it is opaque in advance. By installing a sheet, ND filter, and slit between the light projecting unit and the light receiving unit, the optical axis is adjusted with the amount of light received intentionally reduced. After the adjustment is completed, the filter and slit are removed. Even when there is a slight shift in the optical axis and the amount of received light decreases, the amount of received light stably changes across the threshold according to the presence or absence of an object. There is a technique of maintaining (Patent Document 1).

  However, in such a method, each time the optical axis is adjusted, the opaque sheet, the ND filter, and the slit must be attached and removed, especially when installing a large number of photoelectric sensors. Therefore, there is a problem that the installation work of the photoelectric sensor becomes complicated.

JP-A-5-411146

  In view of the above, the present invention reduces the complexity at the time of installation work, can easily adjust the optical axis, and can adjust the received light amount in use after the adjustment and can adjust the photoelectric sensor. An object is to provide a photoelectric sensor used for this.

  The photoelectric sensor adjustment method according to claim 1 of the present invention includes a light projecting unit that emits light toward a detection region, a light receiving unit that receives light that passes through the detection region, a light reception amount in the light receiving unit, and a predetermined amount. A detection unit that determines the presence or absence of an object in a detection region based on the comparison result, a first mode in which a first light projection amount is projected by the light projecting unit, and the light projecting unit. A photoelectric sensor having a second mode for projecting a second amount of light that is less than the first amount of light is projected using at least the second mode when adjusting the optical axis. In operation, at least the first mode is used for light projection.

  According to a second aspect of the present invention, there is provided a photoelectric sensor adjustment method comprising: a light projecting unit that emits light toward a detection region; a light receiving unit that receives light that has passed through the detection region; A detection unit that compares the threshold values of the first detection mode and determines the presence or absence of an object in the detection region based on the comparison result; a first mode that uses the first threshold value as the predetermined threshold value; For a photoelectric sensor having a second mode that uses a second threshold value higher than the first threshold value, at least the second mode is used to determine the presence or absence of an object during optical axis adjustment, and at least during actual operation. The presence or absence of an object is determined using the first mode.

  A photoelectric sensor according to a third aspect of the present invention includes a light projecting unit that emits light toward a detection region, a light receiving unit that receives light that passes through the detection region, a light reception amount in the light receiving unit, and a predetermined threshold value. A detection unit that compares and determines the presence or absence of an object in the detection region based on the comparison result, a first mode in which a first light projection amount is projected by the light projecting unit, and the first mode by the light projecting unit. And a second mode for projecting a second projection light amount smaller than the first projection light amount.

  A photoelectric sensor according to a fourth aspect of the present invention includes a light projecting unit that emits light toward the detection region, a light receiving unit that receives light that passes through the detection region, a light reception amount in the light receiving unit, and a predetermined threshold value. A detection unit that compares and determines the presence or absence of an object in the detection region based on the comparison result, a first mode that uses the first threshold as the predetermined threshold, and the first threshold as the predetermined threshold And a second mode using a second threshold value higher than the threshold value.

  The photoelectric sensor according to a fifth aspect of the present invention is the photoelectric sensor according to the third aspect, wherein the light projecting unit includes a power line for supplying power to the light projecting unit, and the light projecting unit with respect to the light projecting unit. And a single signal line for selectively instructing ON / OFF. When instructed to project light through the signal line, the first mode and the The second mode is configured to perform light projection while switching between the two modes.

  ADVANTAGE OF THE INVENTION According to this invention, the adjustment method of the photoelectric sensor which can reduce the complexity at the time of installation work, can adjust an optical axis easily, and can ensure the operation | movement which ensured the margin of the light reception amount in use after adjustment, and this It is possible to provide a photoelectric sensor to be used.

It is a block diagram which shows the function of the photoelectric sensor which concerns on 1st Example of this invention. It is a schematic block diagram which shows the structure of the photoelectric sensor which concerns on 1st Example of this invention. It is a time chart explaining operation | movement of the photoelectric sensor which concerns on 1st Example of this invention. It is a schematic diagram explaining the relationship between an optical axis and a light projection amount and a light reception amount in the first embodiment of the present invention.

  FIG. 1 is a block diagram illustrating functions of the photoelectric sensor according to the present embodiment. In FIG. 1, 1 is a light projecting unit, 2 is a light receiving unit, and 3 is a detection object whose presence or absence is detected by a photoelectric sensor. The light projecting unit 1 further includes a light projecting element 11 made of, for example, an LED, and a light intensity instruction unit 12. The light receiving unit 2 further comprises a light receiving element 21, made of, for example, a photodiode, a detecting unit 22, and a warning unit 23.

  FIG. 2 is a schematic configuration diagram showing the structure of the photoelectric sensor. In FIG. 2, 13 is a light projection window that projects light from the light projecting element to the detection area, and 24 is a light receiving window that is provided facing the light projection window and guides light coming from the detection area to the light receiving element. . The light projecting unit 1 and the light receiving unit 2 have cables 14 and 25, respectively. The cable 14 emits light to the power supply line 141, the GND line 142, and the light projecting unit 1 for supplying power to the light projecting unit 1. A signal line 143 for transmitting an instruction signal includes a power line 251 for supplying power to the light receiving unit 2 to the cable 25, a GND line 252, and a signal line 253 for transmitting the result of determining the presence or absence of an object in the light receiving unit 2 to an external device. Are included. Each power supply line, GND line, and signal line are shown separately at the end of each cable for the sake of explanation. However, in actuality, for example, they may be appropriately connected to a terminal block in a controller (not shown). It ’s fine.

  Next, the operation of the photoelectric sensor according to this embodiment will be described with reference to FIG. When a light projection instruction signal is given to the light quantity instruction unit 12 through a signal line 143 from an external control device such as a controller such as a PLC, the light quantity instruction unit 12 first projects light with the first light quantity. The light projecting element 11 is controlled (first mode). And the light quantity instruction | indication part 12 measures passage of time with an internal timer counter, and controls the light projecting element 11 to project light with the second light quantity after the predetermined time has passed (second mode). . At this time, in order to change the light amount, means such as fluctuation of the applied voltage to the light projecting element 11 and adjustment of the gain may be used. Thereafter, after the projection instruction signal disappears, control is performed to change the projection light amount from the second light amount to the extinguished state. Thereafter, the same processing is repeated every time a projection instruction signal is input. As an example, when the first light amount is 100%, the second light amount is 50%, and the time until switching to the second light amount is half the length of the projection instruction signal in advance. Although it is conceivable to give the length, it is not limited to this, and it may be set as appropriate according to the installation environment.

  The operation of the light receiving unit 2 at this time will be described. The light receiving element 21 that first obtains the amount of light received based on the first light amount sends a signal based on the amount of received light to the detection unit 22 including a comparator and necessary electronic components such as a microcomputer. The detection unit 22 compares the signal obtained from the light receiving element 21 with a predetermined threshold value set in advance, and when the magnitude of the signal is less than the threshold value, the detection located between the light projecting unit and the light receiving unit. It is determined that there is an object that blocks the light from the light projecting unit 1 in the area, and a signal indicating that is sent from the signal line 253 to the external controller device. On the other hand, if the signal magnitude is equal to or greater than the threshold value as a result of the comparison, it is determined that there is no object in the detection area, and a signal indicating that is sent from the signal line 253 to the external controller device. To do.

  Next, a method of adjusting the optical axes of the light projecting unit 1 and the light receiving unit 2 when installing the above-described photoelectric sensor will be described with reference to FIG. First, the light projecting unit 1 and the light receiving unit 2 are arranged to face each other, and a light projecting instruction signal is given to the light amount instructing unit 12 in a state in which no object serving as a light shielding body is disposed in the detection region. The contents of signals sent from the unit 2 to the controller device are confirmed. At this time, if a signal indicating that an object is present in the detection area is transmitted in both the first mode and the second mode, the light projection does not reach the light receiving element 21 correctly. That is, since it can be determined that the optical axis is not present, the position of either one or both of the light projecting unit 1 and the light receiving unit 2 is adjusted to adjust the optical axis, and then the same operation is performed again. Transmit and receive the light and check if there is an optical axis.

  FIG. 5A schematically shows the state at this time. Reference numeral 15 denotes the optical axis of the light projecting unit 1, 26 denotes the optical axis of the light receiving unit 2, and 41 and 42 denote the distance from the optical axis and the intensity of light projection during the first mode and the second mode, respectively. The distribution of thickness is shown. As shown here, the intensity of light projection can be modeled as having a peak at the optical axis 15 and weakly diffusing as the distance from the optical axis 15 increases. The amount of received light greatly depends on how much light enters the light receiving window 24. That is, the area of a region (shown by hatching in the drawing) surrounded by the dotted line drawn from both ends of the light receiving window 24, the light projection amounts 41 and 42, and the amount of received light are related to each other. In FIG. 5A, either the amount of received light in the first mode (area from the upper right to the lower left hatched area) or the amount of received light in the second mode (area from the upper left to the lower right hatched area). Therefore, it is determined that the signal transmitted from the light receiving element 21 to the detection unit 22 based on the amount of received light is less than a predetermined threshold.

  Also, if it is determined that no object is present in the detection area during the first mode, and if it is determined that an object is present within the detection area during the second mode, then it is strong. In the case of light (the light beam width is wide), a part of the light projection reaches the light receiving element 21, but in the case of weak light (light beam width is narrow), it is considered that the light projection does not reach the light receiving element 21. That is, it can be determined that the optical axes of the light projecting unit 1 and the light receiving unit 2 are shifted by a difference equal to or less than the difference between the light beam width in the first mode and the light beam width in the second mode. In this case, the optical axis adjustment may be completed if the object detection is performed only in the first mode. However, in the gist of the present invention, it is required to adjust the optical axis more precisely.

FIG. 5B shows the state at this time. The area surrounded by the dotted line drawn from both ends of the light receiving window 24 and the light projection amounts 41 and 42 is larger than that in FIG. 5A, indicating that the amount of received light is increasing. However, the area of the region surrounded by the light projecting amount 42 is not sufficiently large, that is, it is determined that the signal from the light receiving element 21 exceeds the predetermined threshold value in the second mode, and that an object is present. It is. In addition, the light beam width in this invention shows the width | variety of the location which has more than fixed intensity | strength among light projections. FIG. 5B illustrates an intensity threshold value with a two-dot chain line in the drawing, the intersection point between the two-dot chain line and the light projection 41 is A, A ′, the intersection point between the two-dot chain line and the light projection 42 is B, Assuming B ′, the light width in the first mode can be represented by the length AA ′, and the light width in the second mode can be represented by the length BB ′.

  Then, as shown in FIG. 5C, when it is determined that no object exists in the detection area in either the first mode or the second mode, the light beam in the second mode is displayed. Even if it is the width, since the light has reached the light receiving unit 2 correctly, it can be determined that the optical axis is adjusted with sufficient accuracy.

A mode of actual operation of the photoelectric sensor having the optical axis adjusted as described above will be described.
In actual operation, whether or not an object exists in the detection area is determined based on the light projection in the first mode and the amount of light received by the light receiving unit 2 in the meantime.
In this operation process, when the optical axis between the light projecting unit 1 and the light receiving unit 2 is slightly shifted due to the influence of an external impact or the like, or the light projecting amount of the light projecting element 11 is decreased due to deterioration over time. It is assumed that a factor such as the presence of an object in the detection region, that is, a factor that reduces the amount of received light occurs.
If the photoelectric sensor according to the present embodiment performs the optical axis adjustment, even under the condition of the second mode in which the amount of emitted light is reduced in advance, in other words, the amount of received light as the amount of emitted light is reduced. Even in a reduced state, if there is no object in the detection area, it is adjusted so that it can be detected correctly (ie, it has a margin for the decrease in the amount of received light). Even if the amount of light received decreases due to a factor, object detection can be performed without problems as long as the amount of decrease does not exceed the amount of decrease in the amount of light received due to switching between the first mode and the second mode at the time of adjustment. Become.

In addition, by using the photoelectric sensor that can use the first mode and the second mode (multiple patterns of light projection amount) as described above, there is a great advantage not only in optical axis adjustment but also in actual operation. It becomes possible to play. An example will be described below.

  When the photoelectric sensor according to the present embodiment determines that there is no object, the light receiving unit 2 starts diagnosis related to the amount of received light as the projected light amount emitted from the light projecting element 11 subsequently changes to the second light amount. To do. As in the case of obtaining the first light quantity described above, the light receiving element 21 that has obtained the received light quantity based on the second light quantity sends a signal based on the received light quantity to the detection unit 22. The detection unit 22 measures the elapsed time with an internal timer counter from the time when the presence / absence of an object is determined based on the first light quantity, and when the same time as the predetermined time set in the light projecting unit 1 has elapsed. The magnitude of the signal is compared with the aforementioned threshold value. If it is determined that the magnitude of the signal is equal to or greater than the threshold value, even if the light projecting element 11 is deteriorated or dirt is attached to the light projecting window 13 or the light receiving window 24 and a certain light shielding effect is obtained, It is determined that object detection is possible. On the other hand, when it is determined that the magnitude of the signal is less than the threshold value, when the light projecting element 11 is deteriorated or dirt is attached to the light projecting window 13 or the light receiving window 24, the first light amount is used. In this case, it is considered that there is a possibility that the object cannot be detected normally. Therefore, a signal is sent to the warning unit 23 so as to issue a warning to the outside. Here, the warning unit 23 may be provided in the light receiving unit 2 such as a buzzer or an LED, which generates a direct warning, or the warning unit 23 is not provided in the light receiving unit 2 or in combination with the warning unit 23. Based on whether or not the signal sent from the detection unit 22 to the external controller device and the light projection instruction signal sent from the controller device to the light amount instruction unit 12 are normally synchronized, the controller device itself For example, it may be determined that there is a possibility that the object cannot be detected normally even with a single light quantity, and for example, a warning display may be generated on an external monitor connected to the controller device.

  In the above description, it has been described that the control for changing the light emission amount from the second light amount to the light-off state is performed after the light emission instruction signal disappears. However, the present invention is not limited to this, and the light is emitted with the second light amount. For the time, a predetermined value may be given in advance, and processing based on an internal timer counter may be performed as in the case of light projection using the first light quantity. That is, the projector may be configured to perform light projection based only on the rise timing regardless of the fall timing of the light projection instruction signal.

  According to the photoelectric sensor described in the present embodiment, a single signal line for the light projecting unit is provided, and more specifically, a signal line 143 that only transmits a 1-bit digital signal is provided, and a plurality of light projection amounts can be obtained. Since the used diagnosis becomes possible, the structure becomes simple. For example, when connecting a light emitting unit of a photoelectric sensor to an external controller device, the light emitting unit of the photoelectric sensor of the present invention only needs to connect one signal line. Compared to the conventional product that has not been achieved, it is possible to obtain great effects such as a reduction in connection time and a reduction in the number of necessary terminals in the controller device.

  In the first embodiment described above, the first mode and the second mode are for adjusting the optical axis using different light projection amounts. However, the first mode and the second mode are not limited to this. The threshold for comparing with the signal obtained from the light receiving element 21 of the detection unit 22 may be changed while the light projection amount remains constant.

  In other words, by setting a higher threshold value in the second mode than in the first mode, (1) for both threshold values in the first mode and the second mode, for a certain amount of projected light. When the signal obtained from the light receiving element 21 is less than the threshold value (2) In the first mode, the signal obtained from the light receiving element 21 is equal to or greater than the threshold value, but in the second mode, the signal obtained from the light receiving element 21 is obtained. When the signal is less than the threshold value (3) In both the threshold values of the first mode and the second mode, the signal obtained from the light receiving element 21 is obtained in three ways when the signal is equal to or greater than the threshold value. Can do.

  Then, the above three results are the same as in Example 1 described above, (1) the optical axis is deviated, and the light projection does not reach the light receiving element 21 correctly. (2) The optical axis is slightly deviated, A state in which the projected light does not reach the light receiving element 21 sufficiently and further optical axis adjustment is required. (3) The optical axis is in alignment, and the amount of light received has decreased due to various factors during use of the photoelectric sensor. Even in this case, there is no problem as long as the reduction amount of the signal from the light receiving element 21 caused by the light amount reduction amount does not exceed the threshold reduction amount associated with the first mode and the second mode switching at the time of adjustment. This means that an object can be detected.

  As described above, the optical axis can be easily adjusted even when only the threshold value is changed while the light emission amount is constant, and the photoelectric operation capable of ensuring a margin of the amount of received light after use after adjustment is possible. A method for adjusting a sensor can be provided.

  As described above, according to the present invention, it is possible to provide a photoelectric sensor that has a simple structure and has a self-diagnosis function related to the amount of received light and that can be efficiently operated.

DESCRIPTION OF SYMBOLS 1 Light projection part 11 Light projection element 12 Light quantity instruction | indication part 13 Light projection window 14, 25 Cable 15 Optical axis 141,251 Power supply line 142,252 GND line 143,253 Signal line 2 Light-receiving part 21 Light-receiving element 22 Detection part 23 Warning part 24 Light receiving window 26 Optical axis 3 Object to be detected

Claims (5)

A light emitting unit that emits light toward the detection region;
A light receiving portion for receiving light coming through the detection region;
A detection unit that compares the amount of light received by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region based on the comparison result;
A first mode for projecting a first light intensity by the light projecting unit;
For a photoelectric sensor comprising a second mode for projecting a second light projection amount less than the first light projection amount by the light projecting unit,
A photoelectric sensor adjustment method, wherein light is projected using at least the second mode during optical axis adjustment, and light projection is performed using at least the first mode during actual operation. A light emitting unit that emits light toward the detection region;
A light receiving portion for receiving light coming through the detection region;
A detection unit that compares the amount of light received by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region based on the comparison result;
A first mode using a first threshold as the predetermined threshold;
For the photoelectric sensor having a second mode using a second threshold value higher than the first threshold value as the predetermined threshold value,
A photoelectric sensor adjustment method characterized in that at least the second mode is used to determine the presence or absence of an object during optical axis adjustment, and at least the first mode is used to determine the presence or absence of an object during actual operation . A light emitting unit that emits light toward the detection region;
A light receiving portion for receiving light coming through the detection region;
A detection unit that compares the amount of light received by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region based on the comparison result;
A first mode for projecting a first light quantity by the light projecting unit, and a second mode for projecting a second light quantity less than the first light quantity by the light projecting unit. Photoelectric sensor. A light emitting unit that emits light toward the detection region;
A light receiving portion for receiving light coming through the detection region;
A detection unit that compares the amount of light received by the light receiving unit with a predetermined threshold and determines the presence or absence of an object in the detection region based on the comparison result;
A photoelectric sensor comprising: a first mode using a first threshold as the predetermined threshold; and a second mode using a second threshold higher than the first threshold as the predetermined threshold. The light projecting unit includes a power supply line for supplying power to the light projecting unit, and a single signal line for selectively instructing the light projecting unit to turn on / off the light projecting. It has,
When instructed to project light through the signal line, the first mode and the second mode are configured to perform projection while switching between each other. The photoelectric sensor according to claim 3.

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