JP2008298655A - Photoelectric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric sensor which allows settings automatically which can reduce maldetection even when an object to be detected, which is conveyed on a production line which produces various kinds of products, is changed or its conveyance speed is changed. <P>SOLUTION: A calculated period which can emit pulsed light only the number of evaluation times within a passing time of a workpiece W (the object to be detected) detected by a detecting sensor 24 as a passing time detecting means, that is, a period allowing detection of the workpiece W is determined as the calculated period by a control section 31 as a control means. The light projection period of a light projection element 11 is set to be the calculated period determined by the control section 31 by a setting section 32 as a setting means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric sensor.

  Conventionally, for example, a reflective photoelectric sensor has been used to detect a workpiece (object to be detected) conveyed on a production line for producing various products. In such a photoelectric sensor, when the work passes through the detection region of the sensor, the pulsed light projected from the light projecting element at a predetermined light projecting period is reflected by the work. Then, the received light signal level based on the signal photoelectrically converted by the light receiving element that has received the reflected pulsed light becomes, for example, a high level, thereby detecting the workpiece. In such a photoelectric sensor, in order to prevent erroneous determination that a high level light reception signal is output due to the influence of noise or the like and the workpiece is not passing through the detection area, the detection state is determined. The detection state is determined only when the number of consecutive highs continuously reaches a predetermined evaluation number.

  However, the same photoelectric sensor is also used when the work flowing through the production line is changed. Accordingly, only pulse light of less than the number of evaluations is projected while the workpiece passes through the detection area. Naturally, even if the workpiece passes through the detection area, the number of consecutive high-level light reception signals becomes the predetermined number of evaluations. As a result, there is a possibility that a problem that the workpiece cannot be detected occurs.

Therefore, for example, in the photoelectric sensor described in Patent Document 1, the number of pulsed lights that can be projected while the workpiece moves in the detection region is automatically detected, and the number is set as the number of evaluations. . Thereby, since it is possible to project pulsed light more than the number of evaluations while passing through the detection region even for a workpiece having a high moving speed, it is possible to detect the workpiece according to various production lines.
JP-A-10-154449

  However, when the photoelectric sensor as in Patent Document 1 is used in a production line that flows a workpiece at a very high speed, only a significantly small number (for example, one time) of pulsed light is projected while the workpiece moves in the detection area. As a result, the number of evaluations may be set low. If such a setting is made, there is a risk of erroneous determination due to the influence of the above-described noise or the like.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to change the detected object conveyed on the production line for producing various products or change the conveying speed. Even if it exists, it is providing the photoelectric sensor which can perform the setting which can suppress a misjudgment automatically.

  In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that light projecting means for projecting pulsed light to a detected object passing through a detection region at a predetermined light projecting period, and light projecting from the light projecting means. The light receiving means for receiving the pulsed light and outputting a light receiving signal of a level corresponding to the amount of light received, the light receiving signal level output from the light receiving means and a threshold value are compared at a timing based on the light projection period, A photoelectric sensor comprising a detection means for outputting a detection result indicating a detection state of the detected object when the same comparison result continues for a predetermined number of evaluations, wherein the detected object passes through the detection region A transit time detecting means for detecting time, a control means for obtaining a calculation period capable of projecting the pulsed light equal to or more than the number of evaluation times within the transit time, and a setting means for setting the calculation period to the projection period And that prepared And effect.

  In this invention, the control period is a calculation period in which pulsed light equal to or more than the number of evaluations can be projected within the passage time of the detection object detected by the passage time detection means, that is, a calculation period in which the detection object can be detected. And the calculation period is set to the light projection period by the setting means. For this reason, in the state where the number of evaluations is maintained at a predetermined value or more according to the use environment or the like, pulsed light of the number of evaluations or more can be projected within the passage time. Accordingly, it is possible to automatically perform a setting that can suppress erroneous determination even when the detected object conveyed on the production line that produces various products is changed or when the conveyance speed is changed.

  According to a second aspect of the present invention, in the photoelectric sensor according to the first aspect, the control means obtains the one having the longest cycle among the calculation cycles in which the pulsed light can be projected for the number of evaluations. This is the gist.

  In the present invention, a relatively long cycle in the calculation cycle capable of detecting the detected object is set as the light projection cycle. Here, when the light projection period is short and long, the deterioration of the light projecting means is obviously more pronounced. To prevent this, in general, the shorter the light projection period, the more light is projected. The light projection current for causing the light to flow through the means is reduced, thereby deteriorating the detection sensitivity (detection distance). In other words, according to the present invention, it is possible to set an optimum cycle that provides the highest noise resistance performance as the light projection cycle in the calculation cycle in which the detection object can be detected.

  The gist of the invention described in claim 3 is that, in the photoelectric sensor according to claim 1 or 2, the passage time detecting means is provided outside so as to be able to detect the detected object. .

In this invention, since the passage time detecting means is provided outside so as to be able to detect the detected object passing through the detection region, it is possible to accurately detect the passing time of the detected object.
According to a fourth aspect of the present invention, in the photoelectric sensor according to the first or second aspect, in the setting mode for setting the light projection period, the passage time detecting unit is based on a light reception signal output from the light receiving unit. The gist of the invention is that the passage time is detected and the calculation cycle corresponding to the passage time is set as the light projection cycle.

  In the present invention, in the setting mode for setting the light projection period, the passage time detecting means detects the passage time based on the light reception signal output from the light receiving means, that is, the passage time of the detected object is detected by its own sensor. Therefore, for example, it is not necessary to provide another detection sensor as the passage time detection means, and the number of parts of the photoelectric sensor can be suppressed.

  According to a fifth aspect of the present invention, in the photoelectric sensor according to the first or second aspect, the passage time detecting means detects the passage time based on data corresponding to the passage time input from the outside. Is the gist.

  In the present invention, the passage time can be easily detected based on data (movement speed or movement direction length of the detected object) corresponding to the passage time input from the outside. Further, for example, it is not necessary to provide another detection sensor as the passage time detection means, and the number of parts of the photoelectric sensor can be suppressed.

  The invention according to claim 6 is the photoelectric sensor according to any one of claims 1 to 5, further comprising storage means in which the calculation period is stored in association with the passage time, and the control means includes: The gist is to obtain the calculation cycle from the storage means.

  In the present invention, since the calculation cycle is obtained from the storage means stored in association with the passage time, the calculation cycle can be easily obtained as compared with the case where the calculation cycle is obtained by arithmetic processing or the like.

  Therefore, according to the above-described invention, even when the detected object conveyed on the production line that produces various products is changed or the conveyance speed is changed, the setting that can suppress the erroneous determination is performed. It can be done automatically.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
The photoelectric sensor 1 according to the present embodiment shown in FIG. 1 is arranged beside a conveyance path (path along the arrow direction in FIG. 1) of workpieces W that are sequentially conveyed at a constant speed. The photoelectric sensor 1 includes a light projecting element 11 that projects pulsed light so as to cross the transport path, and a light receiving element 12 that receives light projected from the light projecting element 11 and reflected by the workpiece W, The presence / absence of the workpiece W conveyed is detected based on the amount of light received by the light receiving element 12. The photoelectric sensor 1 is provided such that at least a part of the workpiece W passes through the detection area of the photoelectric sensor 1.

  The photoelectric sensor 1 includes a light projecting circuit 21 having the light projecting element 11, a light receiving circuit 22 having the light receiving element 12, and an operation of detecting the workpiece W by being electrically connected to the light projecting circuit 21 and the light receiving circuit 22. And a control circuit 23 for performing the above. In the present embodiment, the light projecting circuit 21 constitutes a light projecting means, and the light receiving circuit 22 constitutes a light receiving means. In addition, the photoelectric sensor 1 includes a detection sensor 24 that is configured as a separate body from the sensor 1 and that serves as a passage time detection unit that is disposed beside the workpiece W. The detection sensor 24 is composed of, for example, a photoelectric sensor that can detect the time (hereinafter referred to as the passage time) for the workpiece W to pass through the detection area of the photoelectric sensor 1, and is connected to the photoelectric sensor 1 main body by a connection cable (not shown). It is connected and electrically connected to the control circuit 23 therein.

  The control circuit 23 includes a control unit 31 as a control unit electrically connected to the detection sensor 24, and a setting unit 32 as a setting unit electrically connected to the control unit 31 and the light projecting circuit 21. Have. In addition, the control circuit 23 is electrically connected to the comparison unit 33 electrically connected to the light receiving circuit 22 and detects the workpiece W based on the output from the comparison unit 33. And a counting unit 34 as detection means to be performed.

  The setting unit 32 outputs a light projection pulse signal (see FIGS. 2 and 3) for pulse-lighting the light projecting element 11 to the light projecting circuit 21 based on the output from the control unit 31. In response to the signal, the light projecting element 11 is pulse-lit at a predetermined light projecting cycle. When the light emitted from the light projecting element 11 is reflected by the workpiece W that has entered the detectable region and received by the light receiving element 12, the light receiving element 12 photoelectrically converts the incident light and outputs it to the light receiving circuit 22. The light receiving circuit 22 amplifies the electric signal and outputs it to the comparison unit 33. That is, a light reception signal (analog signal) of a level corresponding to the amount of light received by the light receiving element 12 is input to the comparison unit 33. The light receiving circuit 22 outputs a light receiving signal at the same cycle as the pulse lighting of the light projecting element 11 based on the light projecting pulse signal.

  The comparison unit 33 compares the level of the light reception signal from the light reception circuit 22 with a preset threshold at a timing based on the light projection period, and outputs a high-level or low-level light reception pulse signal to the count unit 34 as a comparison result. To do. In the present embodiment, the comparison unit 33 outputs a high-level light reception pulse signal when the level of the light reception signal is equal to or higher than a threshold value, and outputs a low-level light reception pulse signal when the level is lower than the threshold value (FIGS. 2 and 3). reference).

  The counting unit 34 counts the number of consecutive high-level and low-level light reception pulse signals output from the comparison unit 33. The counting unit 34 outputs a high-level output signal (a detection result indicating a detection state) when the number of consecutive high-level light reception pulse signals reaches a predetermined number of evaluations (four in the present embodiment). To do. Further, a low level output signal (a detection result indicating a non-detection state) is output when the number of consecutive low level light reception pulse signals reaches the number of evaluations. The output signal of the count unit 34 is output to an output circuit (not shown). The high level and low level count values are cleared when the number of evaluations is reached or when the level of the received light pulse signal is inverted. The predetermined number of evaluations is set to a value that considers the usage environment in order to prevent erroneous detection due to the influence of noise or the like.

  In the photoelectric sensor 1 described above, the light projection period of the light projecting element 11 is set to a calculation period that is determined by the control unit 31 according to the passage time of the workpiece W detected by the detection sensor 24. The detection sensor 24 measures the moving speed of the workpiece W moving on the conveyance path and the length in the moving direction of the workpiece W, and each measurement result and data relating to the detection area of the photoelectric sensor 1 input in advance (the workpiece W). The passage time of the workpiece W is detected based on the data such as the detection region width of the photoelectric sensor 1 in the direction along the conveyance path. Then, the detection sensor 24 outputs a signal corresponding to the passage time of the workpiece W to the control unit 31.

  The control unit 31 includes a memory 31a as a storage unit in which the passage time of the workpiece W and the calculation cycle are stored in association with each other, and the comparison unit 33 is included in the memory 31a within the passage time as the calculation cycle. The period in which the high-level light reception pulse signal output from is continuous for the number of evaluations (that is, the calculation period in which pulsed light can be projected for the number of evaluations) is stored. That is, the calculation cycle is a cycle in which the workpiece W can be detected. In the present embodiment, the longest cycle among the calculation cycles in which pulse light can be projected for the number of evaluations is stored. When the control unit 31 receives the output from the detection sensor 24, the control unit 31 obtains a calculation cycle corresponding to the passage time detected by the detection sensor 24 from the memory 31 a and outputs a signal corresponding to the calculation cycle to the setting unit 32. And the setting part 32 sets the calculation period calculated | required by the control part 31 to the light projection period of the light projection element 11. FIG. As a result, the longest calculation cycle in which pulsed light can be projected for the number of evaluations is set as the projection cycle. Note that the light projection pulse signal in FIG. 2 has the light projection period optimized by the setting of the setting unit 32.

  In such a photoelectric sensor 1, the light projection period of the light projecting element 11 can be set to a calculation period in which the work W can be detected in a state where the number of evaluations for detecting the work W is kept constant. For this reason, for example, while suppressing erroneous detection due to the influence of noise or the like, it is possible to set an optimal light projection period according to the case where the workpiece W to be transported is changed and its passing time is changed.

Next, characteristic actions and effects of the present embodiment will be described.
(1) A calculation cycle in which pulsed light can be projected for the number of evaluations within the passage time of the workpiece W (detected object) detected by the detection sensor 24 as the passage time detection means, that is, the workpiece W can be detected. Is calculated by the control unit 31 as a control means as a calculation period. Then, the light projection cycle of the light projecting element 11 is set to the calculation cycle obtained by the control unit 31 by the setting unit 32 as setting means. For this reason, pulse light more than the number of evaluations can be projected within the passage time in a state where the number of evaluations is maintained at a predetermined value or more according to the use environment. Accordingly, it is possible to automatically perform a setting capable of suppressing erroneous determination while enabling detection of the workpiece W according to various production lines.

  (2) The control unit 31 obtains a calculation cycle in which the high-level light reception pulse signal output from the comparison unit 33 continues for the number of evaluations within the passage time of the workpiece W. For this reason, the longest cycle among the calculation cycles in which the workpiece W can be detected is set as the light projection cycle. That is, the light projection period can be set to an optimum period that improves the noise resistance performance.

(3) Since the detection sensor 24 is provided outside so as to be able to detect the workpiece W passing through the detection region, it is possible to accurately detect the passage time of the workpiece W.
(4) Since the calculation cycle is obtained from the memory 31a serving as the storage means stored in association with the passage time, it can be obtained more easily than, for example, a calculation cycle obtained by arithmetic processing or the like.

The embodiment of the present invention may be modified as follows.
In the above embodiment, the control unit 31 has the memory 31a in which the calculation period is stored in association with the passage time, and the period is obtained from the memory 31a. However, the present invention is not particularly limited to this. By calculating from the passage time of the workpiece W without providing the memory 31a, a cycle in which the high-level light reception pulse signal output from the comparison unit 33 continues during the workpiece W passage time may be obtained. .

  In the above embodiment, the detection sensor 24 for detecting the passage time of the workpiece W is provided. However, the present invention is not limited to this, and for example, the setting for setting the light projection period without providing the detection sensor 24 A mode may be provided, and the passing time of the workpiece W may be detected based on the light reception signal output from the light receiving element 12 in that mode. Moreover, you may provide the calculation means which calculates passage time from input data, such as the moving speed and the moving direction length of the workpiece | work W input from a user. According to these configurations, the number of parts of the photoelectric sensor 1 can be suppressed. Further, the passage time can be easily detected based on data corresponding to the passage time input from the outside.

In the above embodiment, the memory 31a is provided in the control unit 31, but is not particularly limited thereto.
In the above-described embodiment, the present invention is embodied in the reflective photoelectric sensor 1, but other than this, for example, a transmissive photoelectric sensor, a fiber sensor, a laser sensor, or the like may be used.

It is a schematic block diagram which shows the photoelectric sensor in this Embodiment. The timing chart which shows the detection operation of the photoelectric sensor before the setting of a light projection period. The timing chart which shows the detection operation of the photoelectric sensor after the setting of a light projection period.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Photoelectric sensor, 11 ... Light projection element, 12 ... Light receiving element, 21 ... Light projection circuit which comprises light projection means, 22 ... Light reception circuit which comprises light reception means, 31 ... Control part as control means, 31a ... Memory | storage Memory as means, 32... Setting section as setting means, 34... Counting section as detection means.

Claims (6)

A light projecting means for projecting a pulsed light with a predetermined light projecting period to the detected object passing through the detection region;
A light receiving means for receiving the pulsed light projected from the light projecting means and outputting a light reception signal of a level corresponding to the amount of light received;
The light reception signal level output from the light receiving means and the threshold value are compared at a timing based on the light projection period, and a detection result indicating the detection state of the detected object is output when the same comparison result continues for a predetermined number of evaluations. A photoelectric sensor comprising:
A transit time detecting means for detecting a transit time through which the detection object passes through the detection region;
Control means for obtaining a calculation cycle in which the pulsed light equal to or more than the number of evaluations can be projected within the passage time;
A photoelectric sensor comprising: setting means for setting the calculation period to the light projection period. The photoelectric sensor according to claim 1,
The photoelectric sensor according to claim 1, wherein the control means obtains one having the longest cycle among the calculation cycles in which the pulsed light can be projected by the number of evaluations. The photoelectric sensor according to claim 1 or 2,
The photoelectric sensor according to claim 1, wherein the passage time detecting means is provided outside so as to be able to detect the detected object. The photoelectric sensor according to claim 1 or 2,
In the setting mode for setting the light projection period, the passage time detection unit detects the passage time based on a light reception signal output from the light reception unit, and a calculation period corresponding to the passage time is a light projection period. A photoelectric sensor characterized by being set. The photoelectric sensor according to claim 1 or 2,
The photoelectric sensor according to claim 1, wherein the passage time detecting means detects the passage time based on data corresponding to the passage time input from the outside. The photoelectric sensor according to any one of claims 1 to 5,
Storage means for storing the calculation period in association with the passage time;
The photoelectric sensor is characterized in that the control means obtains the calculation period from the storage means.

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