JP4129768B2 - Detection device - Google Patents

Description

  The present invention relates to a detection device that detects an object, and more particularly to a detection device suitable for detecting the proximity of an object, such as a photoelectric sensor, a high-frequency proximity sensor, or a capacitive proximity sensor.

  Conventionally, for example, there is a photoelectric sensor as a detection device that detects the proximity of an object. This photoelectric sensor is a detection device including a projector and a light receiver, and can be roughly classified into a transmission type and a reflection type. The transmission type photoelectric sensor basically has a configuration in which a light projector (light projecting unit) and a light receiver (light receiving unit) are opposed to each other with a predetermined distance. Then, when an object enters the optical path formed between the projector and the light receiver, the proximity of the object is detected by detecting a change in the amount of light received (detected amount) blocked by the object.

  On the other hand, a reflective photoelectric sensor has a configuration in which a light projector (light projecting unit) and a light receiver (light receiving unit) are arranged with their optical axes aligned, and the light emitted from the light projector is reflected by an object. An object is detected by detecting light with a light receiver. In other words, the reflection type photoelectric sensor has no reflected light from the object when there is no object on the optical axis, and when there is an object on the optical axis, the reflected light with the intensity corresponding to the distance to the object is not emitted. Object detection is performed by using the received light.

  The photoelectric sensor is a detection device that detects the optical state in the optical path formed between the light projector and the light receiver in this manner as a change in the amount of light received (detected amount) by the light receiver. It is used for various purposes such as detection and object determination. For example, it is used as a photoelectric switch that compares a predetermined set value with the amount of received light, determines the presence or absence of an object between the projector and the light receiver, and outputs a binary value.

  By the way, in this type of photoelectric sensor, for example, the deterioration of the characteristics of the projector and the receiver over time, the change of the optical characteristics due to the contamination of the detection target (object), the change of the brightness of the background, the projector and the receiver It cannot be denied that the amount of light received by the light receiver gradually decreases with a change in the mounting state of the light receiver (hereinafter referred to as a change with time). Therefore, a detection switch that detects and displays such a decrease in the amount of received light is known (see, for example, Patent Document 1). While this detection switch detects an abnormality in the internal state of the detection switch by the internal abnormality determination means, an abnormality due to an external influence (such as short-circuiting or disconnection of the output line, light amount deterioration) of the detection switch is detected by the external abnormality determination means. To detect. And when abnormality is identified by an internal abnormality diagnostic means and an external abnormality judgment means, it is comprised as a thing provided with the display part which identifies and displays them.

By the way, as a coping method that takes the least amount of time with respect to the change with time of the photoelectric sensor described above, the setting value is often changed first. If the sensitivity of the photoelectric sensor becomes so severe that it cannot be dealt with by changing this setting value, the root cause of changes over time, such as re-adjusting the sensitivity or adjusting the mounting position of the projector and / or receiver, etc. Has been done to remove.
JP-A-5-327449

  However, in the above-described photoelectric sensor, although it is displayed that a decrease in the amount of received light has occurred due to a change over time or the like, it is not possible to display how much the amount of received light has decreased. There is a problem that the method must be trial and error. That is, the set value is changed a little at the beginning, and if the problem occurs, the set value is further changed. If the problem is not resolved at this time, the sensitivity is further adjusted. If the problem persists, you will have to deal with it by trial and error, such as reattaching the projector and receiver. Therefore, there has been a problem that it is impossible to appropriately and efficiently cope with a decrease in the amount of received light due to a change with time. Alternatively, when the shape of the detection object and its reflectance and transmittance are different, the detection object may not be detected, and it is necessary to adjust the sensitivity each time.

  In addition, although the photoelectric sensor has been described as an example here, it can be seen that the current flowing in the oscillation circuit provided in the detection device has changed due to the electromagnetic induction effect accompanying the proximity of the detection object, for example, another type of detection device. For high-frequency proximity sensors that detect and detect objects, and capacitive proximity sensors that detect objects by detecting that the capacitance has changed due to electrostatic induction due to the proximity of the object to be detected However, there is a problem that the setting of the threshold value for separating the presence / absence of an object and the response to the above-described change with time are trial and error and cannot be performed efficiently.

  The present invention has been made in consideration of such circumstances, and the object of the present invention is to output information on the degree of change in the detection value caused by a change over time, and to detect the proximity of an object with certainty. It is to provide a possible detection device.

In order to achieve the above-described object, a detection device according to the present invention is a detection device that detects the proximity of an object from the detection level of a detection signal output by a detector,
First threshold value setting means for setting a first threshold value of the detection level indicating the presence of the object with a detection level under a predetermined measurement condition as a reference value;
Second threshold value setting means for setting a second threshold value of the detection level at which the presence of the object cannot be detected from a reference value of the detection level;
A comparator that compares the detection level of the detector with the first threshold and outputs a signal indicating the presence or absence of an object;
A detection error occurs when the detection level of the detection signal output from the detector is within the range indicated by the first threshold value and the second threshold value, and the change direction of the detection level of the detection signal is reversed. And an extreme value judging means for outputting a signal.

For this reason, a threshold value for identifying a decrease in output of a detection signal due to a change in detection characteristics due to deterioration of characteristics over time or contamination of a detection target (object), a change in the attachment state of a detection device, or the presence or absence of an object ( Detection error information indicating that there is a setting error in (first threshold value) and the object cannot be detected can be output.
Preferably, a counter that further counts the number of outputs of the detection error signal output by the extreme value determination means,
When the extreme value determination means outputs a detection error signal, it is preferable to include a storage unit that holds the detection level of the detection signal output by the detector and the count number of the counter.

  That is, in the invention according to claim 2, when the detection amount for performing object detection is decreased due to a change over time or the like, or when the setting of a threshold value (first threshold value) for identifying the presence or absence of an object is not appropriate, The number of detections of a detection signal that falls below a predetermined threshold (first threshold) for identifying the presence or absence of an object and the detection level at that time are stored in the storage unit. For this reason, it is possible to more reliably grasp the degree of change in the detection signal due to a change with time and the like, and a setting error in the threshold value (first threshold value) for identifying the presence or absence of an object.

  More preferably, the detector includes a light projector and a light receiver that form a predetermined optical path, and the light emitted from the light projector or the reflected light thereof is received by the light receiver and the optical in the optical path is detected from the detection level. It is comprised as a detection apparatus which detects a general condition.

  According to the detection device of the present invention, it is possible to grasp the degree of change in the detection signal due to a change over time and the like, and a threshold setting error that identifies the presence or absence of an object, and the adjustment operation of the detection device can be easily performed. It becomes. In addition, the number of times the object could not be detected due to changes over time and the like are counted, and since the detection level of the detection signal at this time is held, the frequency of erroneous detection of the presence of an object and the reception level at that time (error Detection value). For this reason, the detection apparatus according to the present invention can set the threshold of the reception level for determining the presence (proximity) of the detection target with reference to the detection level of the detection signal. It is possible to obtain a practically significant effect such as being able to capture changes in the sensor detection value due to the above.

  Hereinafter, an embodiment of a detection apparatus according to the present invention will be described with reference to the drawings, illustrating a photoelectric sensor that detects the presence or absence (proximity) of an object. FIG. 1 is a detection apparatus according to an embodiment of the present invention, and shows a schematic configuration of a photoelectric sensor. In this figure, 1 is a projector made up of a light emitting diode (LED) that emits laser light with a wavelength of 660 nm, for example, and 2 is a light receiver made up of a photodiode (PD) that receives the laser light directly or its reflected light. . These projector 1 and light receiver 2 may constitute a transmissive photoelectric sensor, or may constitute a reflective photoelectric sensor. Here, a description will be given of a transmissive photoelectric sensor that directly projects light from the projector 1 to a predetermined object detection target region and the light receiver 2 directly receives light from the object detection target region.

  The light receiver 2 used in this photoelectric sensor outputs a signal having a level corresponding to the intensity of received light (amount of received light). The photoelectric sensor provided with the light receiver 2 captures a change in the detection level R of the light receiver 2 to detect the presence or absence of the detection target object by, for example, crossing the detection target object using a transport mechanism (not shown) in the detection target region. It comes to judge. That is, as shown in FIG. 2, when the detection target reaches the detection target region, the light reaching the light receiver 2 is blocked by the detection target, and the detection level R gradually decreases. When the detection target reaches the substantially central portion of the detection target region, the light shielding amount becomes maximum and the detection level R of the light receiver 2 becomes minimum. Thereafter, as the detection target moves away from the detection target area as the detection target moves, the light shielding amount by the detection target decreases and the detection level R gradually increases. In this way, when the detection target is in the detection target region, the change in the detection level R has a minimum value, that is, a minimum value.

  An output signal (detection level) output from the light receiver 2 is amplified through a preamplifier (head amplifier) including a frequency selection filter (not shown), and then digitally converted through an A / D converter 3. For example, the signal processing circuit 4 composed of a microcomputer or the like is loaded every 200 μs, for example. The signal processing circuit 4 basically compares the threshold value SP set and held in the threshold value / limit value setting unit 5 with the detection level R by the light receiver 2 provided from the A / D converter 3. The level determination unit (comparator) 6 outputs a determination signal indicating the presence or absence of an object in the detection target region. The determination signal from the level determination unit (comparator) 6 is output externally as a detection signal from the photoelectric sensor device.

  Incidentally, the threshold value SP set in the threshold value / limit value setting unit 5 is, in the case of a transmissive photoelectric sensor, the light amount (light shielding amount) that is blocked when the detection target passes through the detection target region is less than a predetermined amount (threshold value). It becomes a reference value of a detection determination level for detecting an object depending on whether or not it falls below. The threshold / limit value setting unit 5 sets and holds a direct incident light level limit value L1 that is a light incident level slightly higher than the threshold value SP, as will be described in detail later. This direct incident light level limit value L1 indicates that the detection signal of the detection level R received by the light receiver 2 is a change in detection characteristics due to deterioration of characteristics over time or the shape of a detection object (object), or attachment of a detection device. The detection level of the light receiver 2 is set in consideration of output fluctuations of the detection signal (such as changes with time) associated with a change in state.

  In the signal processing circuit 4, the detection level R output from the A / D converter 3 enters the level range between the threshold value SP set in the threshold value / limit value setting unit 5 and the direct incident light level limit value L 1. An extreme value determination unit 7 is provided for determining whether or not an extreme value is included in the detection signal output from the A / D converter 3 when there is a light amount. Further, in the signal processing circuit 4, when the extreme value determination unit 7 determines that the detection signal output from the A / D converter 3 includes an extreme value, the detection error output by the extreme value determination unit 7 A counter that receives the signal (ERR signal) and counts the number of detections of the extreme value and a storage unit 9 that holds the number of detections counted by the counter 8 are provided.

  Basically, in the detection apparatus configured as described above, the present invention is characterized in that the detection level R is the threshold value SP set in the threshold value / limit value setting unit 5 and the direct incident light level limit value L1. Is in the level range between and, it is determined whether or not there is an extreme value (minimum value) in the detection signal, and the number of detections and the detection level R are held in the storage unit 9. The detection signal of the detection level R received by the optical receiver 2 using the number of detections of the extreme value and the detection level held in the storage unit 9 is caused by the deterioration in characteristics over time and the shape of the detection object (object). This is to detect a change in the output of the detection signal (such as a change with time) due to a variation factor such as a change in detection characteristics or a change in the attachment state of the detection device.

  Specifically, the threshold value / limit value setting unit 5 of the detection device according to the present invention, for example, when an object to be detected (detection target object) is positioned at a predetermined position in the detection target region (with an object), It sets so that it may become the detection level R which can detect the light reception amount obstruct | occluded by this detection target object. That is, the detection level R of the light received by the light receiver 2 when the detection target does not exist in the detection target area is [100], and the detection level R when the detection target exists in the detection target area is [100]. 30], the threshold value / limit value setting unit 5 sets the value (threshold value) of the detection level R for judging the presence / absence of the detection target with reference to the margin as [50], for example. Then, the signal processing circuit 4 detects a detection level (threshold value) in which the detection level R detected by the light receiver 2 and converted into a digital signal by the A / D converter 3 is lower than the threshold value SP set in the threshold value / limit value setting unit 5. > Detection level), the signal processing circuit 4 determines that the detection target exists in the detection target region.

  Further, the threshold / limit value setting unit 5 sets a value assuming the detection limit level in consideration of the above-described variation factor as the value of the above-described direct incident light level limit value L1. Specifically, when there are a plurality of types of detection objects and the sizes thereof are different, for example, as described above, it is assumed that [50] is set as the threshold when the object exists in the detection target area. Then, when an object having a smaller outer shape than this object arrives in the detection target region, if the detection level R is [50], the same value as the above-described threshold value is obtained. In this case, it is conceivable that the detection object may be missed due to the above-described variation factors. In order to be able to detect such an object, the direct incident light level limit value L1 is set, for example, as [70].

  Thus, when the detection level R of the light receiver 2 is in the range of [50] to [70], the extreme value determination unit 7 determines whether or not the minimum value exists in the detection level R. Specifically, the determination is made from three consecutive detection levels detected at predetermined time intervals. That is, as shown in FIG. 3A, if three consecutive detection levels are Nb1, Nb2, and Nb3, Nb1> Nb2> Nb3 and there is no extreme value. On the other hand, as shown in FIG. 3B, Nb1, Nb2, and Nb3 at three consecutive detection levels have Nb1> Nb2 <Nb3 and have extreme values (in this case, Nb2 is a minimum value).

  The extreme value determination unit 7 that has detected the presence of the extreme value (minimum value) in the detection level R in this manner gives the number of detections and the detection level to the storage unit 9 for holding. Then, it is only necessary to determine whether or not the set threshold value SP is an appropriate value by using the number of extreme value detections and the detection level held in the storage unit 9. That is, when the threshold value SP is set to [50] and the detection target exists in the detection target region, the detection level R of the light receiver 2 is in the range of [50] to [70] and the detection level When an extreme value (minimum value) exists in R, the value of the threshold value SP may be reset based on the detection level held in the storage unit 9.

By doing so, the detection signal of the detection level R received by the light receiver 2 changes in the detection characteristics due to the deterioration of the characteristics over time and the shape of the detection target (object), or the change in the attachment state of the detection device. As a result, it is possible to detect an output fluctuation (such as a change with time) of the detection signal due to a fluctuation factor such as, and to set the threshold value SP optimally based on this detection level.
The operation of the signal processing circuit 4 that performs the extreme value determination as described above will be described in more detail with reference to the flowchart shown in FIG. In this flowchart, Nb1, Nb2, and Nb3 represent registers that sequentially hold three consecutive detection levels detected at predetermined time intervals as described above. In the following description, it is assumed that the detection device (photoelectric sensor) has already been operated and some detection level values are held in Nb1, Nb2, and Nb3.

  First, the signal processing circuit 4 holds the detection level R detected by the light receiver 2 in the register Nb3 (step S1). Next, the signal processing circuit 4 compares the detection level R detected by the light receiver 2 in step S1 with the direct incident light level limit value L1 (step S2). At this time, if the detection level R detected by the light receiver 2 is equal to or less than the direct incident light level limit value L1, the signal processing circuit 4 determines whether Nb2 is a minimum value, so that Nb2 <Nb3 and Nb2 <Nb1 Is determined (step 3). The signal processing circuit 4 that has determined that Nb2 is the minimum value in step S3 counts up the minimum value detection counter CN that has detected the minimum value, and holds the minimum value in the storage unit 9 as Rmin (step S4). ).

The signal processing circuit 4 that detects and holds the minimum value in this way prepares for the input of the next detection level R that is captured at a predetermined time interval. Is moved to Nb1 holding the detected value, and the value of Nb3 holding the current detected value is moved to Nb2 holding the previous detected value (step S5).
In step S2, the signal processing circuit 4 compares the detection level R detected by the light receiver 2 in step S1 with the direct incident light level limit value L1, and as a result, the detection level R detected by the light receiver 2 is the direct incident light. If it is determined that the level limit value L1 is exceeded, it is determined that the detection target does not exist in the detection target region, and is prepared for detection of the next detection level R that is captured at a predetermined time interval (step S5). In addition, the signal processing circuit 4 that has determined that there is no minimum value in step S3 prepares for the detection of the next detection level R that moves to step S5 and is captured at a predetermined time interval.

  Thus, the detection apparatus according to the present invention sets the threshold value SP of the detection level R for determining the presence of the detection object in the threshold value / limit value setting unit 5 as described above, and sets the detection limit level in consideration of the detection variation factor. The direct incident light level limit value L1 is set according to the assumed value. When a detection level R of a level between the threshold value SP and the direct incident light level limit value L1 is detected, the detection device determines whether or not an extreme value (minimum value) exists in the detected value. Yes. When an extreme value is detected, the detection device holds the number of detections and the extreme value (minimum value) in the storage unit 9. Therefore, by setting the threshold value SP of the detection level R in the threshold value / limit value setting unit 5 based on the number of detections and the value of the detection level R at this time, it is possible to reliably detect the detection target. Become.

  In addition, the detection device according to the present invention calculates the number of detections and the detection level R between the threshold SP set in the threshold / limit value setting unit 5 and the direct incident light level limit L1 as described above. Since it is held in the storage unit 9, after the detection device is installed and adjusted, for example, when the detection accuracy of the detection object decreases due to a change over time or the like, specifically, whether the detection device has a cause, It is also possible to easily identify the cause such as whether there is a problem in the setting of the threshold value SP, whether the quality of the detection target is bad, or conversely, the defective product is determined as a good product.

  In the above-described embodiment, the number of detections of the detection level R and the detection level R between the threshold value SP and the direct incident light level limit value L1 are held in the storage unit 9. In addition, history information such as an average value, a maximum value, and a minimum value of the detection level R may be held. In this case, by statistically analyzing the history information, it can be used for preventive maintenance against a change with time of the inspection apparatus.

  Next, a second embodiment of the detection apparatus according to the present invention will be described with reference to the drawings, illustrating a photoelectric sensor that detects the presence or absence (proximity) of an object. This photoelectric sensor is different from the above-described first embodiment in that the laser light projected from the projector 1 is irradiated onto the inspection object, and the laser light reflected from the inspection object is received by the light receiver 2. The presence or absence of the inspection object is detected from the change in the detection level R. That is, Example 2 constitutes a reflective photoelectric sensor. Incidentally, the schematic configuration of the detection apparatus according to the present invention is the same as the photoelectric sensor shown in FIG.

  The light receiver 2 used in this photoelectric sensor outputs a signal having a level corresponding to the intensity of received light (amount of received light). The photoelectric sensor including the light receiver 2 receives the reflected light reflected from the detection object by the light receiver 2 by traversing the detection object using a transport mechanism (not shown) in the detection object region. The presence / absence of a detection object is determined based on a change in the detection level R output from the light receiver 2. That is, in this photoelectric sensor, when the detection target reaches the detection target region, the amount of reflection of light reaching the light receiver 2 by the detection target increases and the detection level R gradually increases. When the detection target reaches the substantially central portion of the detection target region, the amount of reflected light is maximized and the detection level R is maximized. Thereafter, as the object to be detected moves away from the area to be detected, the amount of light reflected by the object decreases and the detection level R gradually decreases. As described above, when the detection target is in the detection target region, the detection level R has the maximum value, that is, the maximum value.

  Incidentally, the threshold value SP set in the threshold value / limit value setting unit 5 is, in the case of a reflective photoelectric sensor, the amount of light (light shielding amount) reflected from the detection target when the detection target passes through the detection target region. It becomes a reference value of a detection determination level for detecting the presence depending on whether or not it falls below a predetermined amount (threshold). The threshold value / limit value setting unit 5 sets and holds a reflected light level limit value L2 that is a reflected light level that is slightly smaller than the threshold value SP, as will be described in detail later. This reflected light level limit value L2 indicates that the detection signal of the detection level R received by the light receiver 2 is a change in detection characteristics due to deterioration of characteristics over time or the shape of the detection object (object), or the state of attachment of the detection device The detection level of the light receiver 2 is set in consideration of fluctuations in the output of the detection signal (such as changes over time) associated with changes in the light level.

  Basically, in the detection apparatus configured as described above, the present invention is characterized by a level between the threshold value SP set in the threshold value / limit value setting unit 5 and the reflected light level limit value L2. When there is an incident light amount within the range, it is determined that an extreme value (maximum value) exists in the detection signal, and the number of detections and the detection level are held in the storage unit 9. The detection signal of the detection level R received by the optical receiver 2 using the number of detections of the extreme value and the detection level held in the storage unit 9 is caused by the deterioration in characteristics over time and the shape of the detection object (object). A change in detection signal output (such as a change with time) caused by a change factor such as a change in detection characteristics or a change in the attachment state of the detection device is determined.

  Specifically, the threshold value / limit value setting unit 5 of the detection device according to the present invention, for example, when an object to be detected (detection target object) is positioned at a predetermined position in the detection target region (with an object), The laser beam projected from the projector 1 is set to a detection level R that can detect the amount of received light reflected by the detection object. That is, when the detection level R when the detection target does not exist in the detection target area is [0] and the detection level R when the detection target exists in the detection target area is [70], the threshold / limit In the value setting unit 5, the threshold value is set as, for example, [50] by looking at the margin. Then, the signal processing circuit 4 detects a detection level (threshold>) in which the detection level detected by the light receiver 2 and converted into a digital signal by the A / D converter 3 exceeds the threshold SP set in the threshold / limit value setting unit 5. The signal processing circuit 4 determines that the detection target exists in the detection target region.

  Further, the threshold / limit value setting unit 5 sets a value assuming the detection limit level in consideration of the above-mentioned various fluctuation factors as the value of the reflected light level limit value L2. Specifically, when the size of the detection target object is different, for example, as described above, [50] is set as a threshold when the detection target object exists in the detection target region, and the outer shape is smaller than the detection target object. If the detection level R is [50] when the target object reaches the detection target region, the same value as the above-described threshold value is obtained. In this case, there may be a case where a detection object having a small outer shape is missed due to the above-described variation factors. In order to enable detection of a detection object having such a small shape, the reflected light level limit value L2 is set as [30], for example.

  Then, when the detection level R of the light receiver 2 is in the range of [30] to [50], the extreme value determination unit 7 determines whether or not there is a maximum value in the detection level R. The extreme value determination unit 7 that has detected the presence of the extreme value (maximum value) in the detection level R gives the number of detections and the detection level to the storage unit 9 to be held. Thus, it is only necessary to determine whether or not the set threshold value SP is an appropriate value by using the number of detections of the extreme value and the detection level held in the storage unit 9. That is, when the threshold value SP is set to [50] and the detection target exists in the detection target region, the detection level R of the light receiver 2 is in the range of [30] to [50] and the detection level If there is an extreme value (maximum value) in R, the value of the threshold value SP may be reset based on the detection level held in the storage unit 9.

By doing so, the detection signal of the detection level R received by the light receiver 2 changes in the detection characteristics due to the deterioration of the characteristics over time and the shape of the detection target (object), or the change in the attachment state of the detection device. As a result, it is possible to detect an output fluctuation (such as a change with time) of the detection signal due to a fluctuation factor such as, and to set the threshold value SP optimally based on this detection level.
The operation of the signal processing circuit 4 that performs such maximum value determination will be described in more detail with reference to the flowchart shown in FIG. In this flowchart, St1, St2, and St3 represent registers that sequentially hold three consecutive detection levels detected at predetermined time intervals as described above. In the following description, it is assumed that the detection device (photoelectric sensor) has already been operated and that some value of detection level R is held in St1, St2, and St3.

  First, the signal processing circuit 4 holds the detection level R detected by the light receiver 2 in the register St3 (step S6). Next, the signal processing circuit 4 compares the detection level R detected by the light receiver 2 in step S6 with the reflected light level limit value L2 (step S7). At this time, when the detection level R detected by the light receiver 2 is equal to or greater than the reflected light level limit value L2, the signal processing circuit 4 determines whether St2 is a local maximum value, so that St2> St3 and St2> St1 are satisfied. It is determined whether it is established (step 8). The signal processing circuit 4 that has determined that St2 is the maximum value in this step S8 counts up the maximum value detection counter CS that has detected the maximum value, and holds this maximum value in the storage unit 9 as Rmax (step S9). ).

The signal processing circuit 4 that has detected and held the local maximum value in this way prepares for the detection of the next detection level R that is captured at a predetermined time interval. The process shifts to St1 holding the detected value of St3, and moves the value of St3 holding the current detected value to St2 holding the previous detected value (Step S10).
In step S7, the signal processing circuit 4 compares the detection level R detected by the light receiver 2 with the reflected light level limit value L2 in step S6. As a result, the detection level R detected by the light receiver 2 becomes the reflected light level limit. When it is determined that the value is lower than the value L2, it is determined that the detection target does not exist in the detection target region, and prepares for detection of the next detection level R that is captured at a predetermined time interval (step S10). In addition, the signal processing circuit 4 that has determined that there is no maximum value in step S8 moves to step S10 and prepares for detection of the next detection level R that is captured at a predetermined time interval.

  Thus, the detection apparatus according to the present invention sets the threshold value SP of the detection level R for determining the presence of the detection object in the threshold value / limit value setting unit 5 as described above, and sets the detection limit level in consideration of the detection variation factor. The reflected light level limit value L2 is set from the assumed value. When a detection level R of a level between the threshold value SP and the reflected light level limit value L2 is detected, the presence or absence of an extreme value (maximum value) is detected in the detected value. When an extreme value is detected, the number of detections and the extreme value (maximum value) are stored in the storage unit 9. For this reason, the detection target (object) is reliably detected by setting the threshold SP of the detection level R in the threshold / limit value setting unit 5 based on the number of detections and the value of the detection level R at this time. Is possible.

  Further, as described above, the number of detections between the detection level R and the threshold value SP to the reflected light level limit value L2 set in the threshold value / limit value setting unit 5 and the detection level R are held in the storage unit 9. Therefore, after the installation and adjustment of the photoelectric sensor device, for example, when the detection accuracy of the detection object is lowered due to a change over time or the like, specifically, there is a problem with the photoelectric sensor or the threshold SP setting. It is also possible to easily determine the cause such as whether there is a problem, whether the quality of the detection object is poor, or whether the defective product is determined as a good product.

  In the embodiment described above, the number of detections of the detection level and the detection level R between the threshold value SP and the reflected light level limit value L2 are held in the storage unit 9; You may comprise so that history information, such as an average value of level R, a maximum value, and a minimum value, may be hold | maintained. In this case, by statistically analyzing the history information, it can be used for preventive maintenance against a change with time of the inspection apparatus.

  Next, a third embodiment of the detection apparatus according to the present invention will be described with reference to the drawings, illustrating a photoelectric sensor that detects the presence (proximity) of an object. This embodiment is a detection device that combines the first and second embodiments described above, and has the same configuration as the first and second embodiments described above. That is, this detection device can be used as either the transmission type or the reflection type photoelectric sensor described above. Here, it demonstrates based on the flowchart shown in FIG. 6, and the description is abbreviate | omitted about the place which operate | moves similarly to 1st and 2nd embodiment mentioned above.

  In this flowchart, Nb1, Nb2, Nb3 and St1, St2, St3 are registers for sequentially holding three consecutive detection levels detected at predetermined time intervals as shown in the first and second embodiments. It represents. Incidentally, Nb1, Nb2, and Nb3 are registers used in the case of the transmission type photoelectric sensor, and St1, St2, and St3 are registers used in the case of the reflection type photoelectric sensor. In the following description, it is assumed that the detection device (photoelectric sensor) has already been operated and some detection level R value is held in Nb1, Nb2, Nb3 and St1, St2, St3.

  First, the signal processing circuit 4 compares the detection level R detected by the light receiver 2 with a detection level threshold value SP indicating the presence of the detection target (step S11). In step 11, the signal processing circuit 4 determines that the photoelectric sensor is a transmission type when the detection level R is a detection level R greater than the threshold value SP. On the other hand, in step S11, when the value of the threshold value SP is larger than the detection level R, the signal processing circuit 4 determines that the photoelectric sensor is a reflection type. In this way, the signal processing circuit 4 determines whether the photoelectric sensor is a transmission type or a reflection type in step S11.

  In step S11, when the signal processing circuit 4 determines that the photoelectric sensor is a transmissive type, the signal processing circuit 4 initializes Nb1, Nb2, and Nb3 used to determine the minimum value of the reflective photoelectric sensor (step S12). . This initialization is performed to initialize the maximum value (MAX: for example, a light reception level of 100%) that can be taken by the photoelectric sensor. Hereinafter, step S13 to step S17 correspond to step S1 to step S5 of the flowchart showing the operation of the above-described reflective photoelectric sensor, respectively, and thus description thereof will be omitted.

  On the other hand, when the signal processing circuit 4 determines in step S11 that the photoelectric sensor is reflective, it initializes St1, St2, and St3 used to determine the maximum value of the transmissive photoelectric sensor (step S18). ). This initialization is performed to initialize the minimum value (MIN: for example, 0% light reception level) that can be taken by the photoelectric sensor. Hereinafter, step S18 to step S23 correspond to step S6 to step S10 of the flowchart showing the operation of the above-described transmission type photoelectric sensor, respectively, and thus description thereof is omitted.

  As described above, the detection device according to the present invention determines whether or not it is a reflection type or transmission type photoelectric sensor by comparing the detection level R of the light receiver 2 with the threshold value SP. Therefore, it is possible to correspond to either a reflection type photoelectric sensor or a transmission type photoelectric sensor. For this reason, what was used as a reflective photoelectric sensor, for example, can also be used as a transmissive photoelectric sensor.

  Of course, as shown in the above-described embodiment, the detection apparatus according to the present invention sets the threshold SP of the detection level R for determining the presence of the detection target in the threshold / limit value setting unit 5, and sets the detection variation factor. Direct incident light level limit value L1 or reflected light level limit value L2 is set as a value assuming an expected detection limit level. When a detection level R of a level between the threshold value SP and the direct incident light level limit value L1 is detected, the presence or absence of an extreme value (minimum value) is detected in the detected value. Alternatively, when a detection level R of a level between the threshold value SP and the reflected light level limit value L2 is detected, the detection device according to the present invention detects whether the detection value has an extreme value (maximum value). ing. When these extreme values are detected, the signal processing circuit 4 holds the number of detections and the extreme value (minimum value) in the storage unit 9. By setting the threshold value SP of the detection level R in the threshold value / limit value setting unit 5 based on the number of times of detection held in the storage unit 9 and the value of the detection level R at this time, the detection target (object) is surely detected. Can be detected.

  Moreover, when the detection accuracy of the detection target decreases due to, for example, a change over time after the photoelectric sensor device is installed and adjusted by using the extreme value held in the storage unit 9, specifically, the photoelectric sensor Easily identify the cause, such as whether there was a cause, or there was a problem in setting the threshold value SP, whether the quality of the detection object was bad, or conversely, the defective product was judged as a good product It is also possible to do this.

  The present invention is not limited to the embodiment described above. For example, as shown in FIG. 7, the present invention can also be applied to a high-frequency (inductive) proximity sensor that utilizes the fact that the current flowing in the oscillation circuit changes due to the electromagnetic induction effect accompanying the proximity of the object to be detected. This high frequency (inductive) proximity sensor is configured to include a detection coil L that constitutes a part of a high frequency oscillation circuit, and a conductive detection object S (for example, in the vicinity of the detection coil L). This is a detection device that utilizes the fact that the internal resistance component and the self-inductance component of the detection coil L change due to the electromagnetic induction action when (metal) is present or approaches. The oscillation circuit of the high-frequency proximity sensor forms an LC parallel resonance circuit between the detection coil L and a capacitor C connected in parallel, and is oscillated and driven by an oscillator 12.

The output of the oscillator 12 is amplified and output to a level suitable as an input signal for the detection circuit 13 at the next stage. The analog signal output from the detection circuit 13 is converted into a digital signal (reception level) corresponding to the level of the high frequency signal by the A / D converter 3 and given to the signal processing circuit 4.
In principle, the high-frequency (inductive) proximity sensor configured as described above detects the presence or absence of the detection object S close to the detection coil L, changes the internal resistance component of the detection coil L, that is, for detection. This is considered as a change in Q of the coil L. This change in Q is detected as a change in the amplitude of the oscillator 12.

Also in the high-frequency proximity sensor configured as described above, the amplitude value of the high-frequency oscillation circuit changes when the detection object S comes close to the detection coil L, as in the above-described photoelectric sensor. When the amplitude value (threshold value) is reached, the detection object S can be detected as being present.
For this reason, the number of detections of the detection signal that does not satisfy the threshold for detecting the detection target S, even if there is an error in the threshold setting of the reception level in addition to the fluctuation of the amplitude of the oscillator 12 due to changes over time, Since the threshold value (reception level corresponding to the amplitude level of the oscillator 12) is held in the storage unit, an appropriate threshold value that does not cause a detection error can be set.

  Alternatively, the inspection apparatus according to the present invention can be applied to a capacitance-type proximity sensor that utilizes the fact that the capacitance changes due to the electrostatic induction accompanying the proximity of an object to be detected as shown in FIG. is there. This capacitive proximity sensor is provided with a detection capacitor C that detects the proximity of an object, and a coil L that constitutes a resonance circuit with the detection capacitor. An oscillator 12 is provided that oscillates and drives a resonance circuit including the detection capacitor C and the coil L. As the oscillation output of the oscillator 12, a voltage signal proportional to the frequency is output by the f / V converter 14 for converting the frequency into a voltage. The voltage signal converted by the f / V converter 14 is applied to the A / D converter 3 and converted to a digital signal, and then applied to the signal processing circuit 4 described above.

  In principle, the electrostatic induction type proximity sensor configured as described above changes the capacitance of the detection capacitor C when the detection object (dielectric) S is brought close to the detection capacitor C. Is detected as a change in the oscillation frequency of the LC resonance circuit composed of the coil L and the capacitor C, and the presence of an object is detected. This change in oscillation frequency is converted into a digital signal (reception level) by the f / V converter 14 and the A / D converter 3. Then, when the value of this digital signal, that is, the oscillation frequency of the LC oscillation circuit reaches a predetermined frequency (threshold), it can be detected that the detection object S is present. For this reason, even if there is a change in the capacitance of the detection capacitor C accompanying a change with time or the like, or an error in the threshold setting, the number of detection signals that do not satisfy the threshold for detecting an object, Since the threshold value (reception level corresponding to the oscillation frequency) is stored in the storage unit, an appropriate threshold value that does not cause a detection error can be set.

The block diagram which shows schematic structure of the photoelectric sensor concerning one Embodiment of this invention. The figure which shows the change of the reception level of the photoelectric sensor shown in FIG. The figure which shows the extreme value detection state of the reception level shown in FIG. The flowchart which shows the action | operation of the signal processing circuit of a transmissive photoelectric sensor. The flowchart which shows the action | operation of the signal processing circuit of a reflection type photoelectric sensor. The flowchart which shows the action | operation of the signal processing circuit of the photoelectric sensor shown in FIG. The block diagram which shows schematic structure of the high frequency type proximity sensor concerning another embodiment of this invention. The block diagram which shows schematic structure of the capacitive proximity sensor concerning another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light projector 2 Light receiver 3 A / D converter 4 Signal processing circuit 5 Threshold value / limit value setting part 6 Comparator 7 Extreme value determination part 8 Counter 9 Memory | storage part

Claims (3)

A detection device that detects the proximity of an object from a detection level of a detection signal output by a detector,
First threshold value setting means for setting a first threshold value of the detection level indicating the presence of the object with a detection level under a predetermined measurement condition as a reference value;
Second threshold value setting means for setting a second threshold value of the detection level at which the presence of the object cannot be detected from a reference value of the detection level;
A comparator that compares the detection level of the detector with the first threshold and outputs a signal indicating the presence or absence of an object;
A detection error occurs when the detection level of the detection signal output from the detector is within the range indicated by the first threshold value and the second threshold value, and the change direction of the detection level of the detection signal is reversed. An extreme value determination means for outputting a signal. The detection apparatus according to claim 1, further comprising a counter for counting the number of times of output of the detection error signal output by the extreme value determination means;
A detection apparatus comprising: a storage unit that holds a detection level of a detection signal output from the detector and a count number of the counter when the extreme value determination unit outputs a detection error signal.   The detector includes a light projector and a light receiver that form a predetermined optical path. The light emitted from the light projector or reflected light thereof is received by the light receiver and the optical condition in the optical path is detected from the detection level. The detection device according to claim 1, wherein the detection device is a photoelectric sensor.

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