JP4860323B2 - Photoelectric sensor and photoelectric sensor system - Google Patents

Description

  The present invention relates to a photoelectric sensor that detects a non-detected object by receiving reflected light or transmitted light of light emitted from a light projecting means, and a photoelectric sensor system using the same.

  Conventionally, when the above photoelectric sensors are arranged adjacent to each other, it is known that erroneous detection occurs due to mutual interference with other photoelectric sensors. For this reason, in a photoelectric sensor system including a plurality of such photoelectric sensors, in many cases, each photoelectric sensor constituting the system delays a synchronization signal input from a higher-order photoelectric sensor for a predetermined time to lower-order photoelectric sensors. Configured to deliver sequentially. Then, in synchronization with the synchronization signal, each photoelectric sensor completes its light projecting / receiving / detecting operation in order from the upper level to the lower level, thereby avoiding the problem of mutual interference.

  However, in such a configuration, for example, if an error occurs in the processing time of each photoelectric sensor due to a delicate internal clock difference between the photoelectric sensors, the error is reflected in the delay time of the synchronization signal. And accumulated every time the synchronization signal is transmitted from the upper level to the lower level. For this reason, the lower the photoelectric sensor, the more inconsistent in the delay time, and as a result, there is a possibility that an appropriate light projection interval for avoiding the mutual interference cannot be secured.

Therefore, for example, the photoelectric sensor described in Patent Document 1 is synchronized with the next photoelectric sensor by measuring the period of the input synchronization signal as needed and comparing the measured period with a pre-stored reference period. The delay time when transmitting the signal is corrected to a normal value. As a result, the problem of the disturbance of the light projection interval due to the error in processing time occurring in each photoelectric sensor as described above is avoided.
JP 2002-305433 A

  However, when actually using the photoelectric sensor system, the light projection period may be changed according to the use environment. In such a case, in the conventional configuration, the reference period of each photoelectric sensor is set each time. It must be reset according to the changed light emission period. For this reason, changing the light projection period is an extremely complicated task, and there is still room for improvement in this respect.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a photoelectric sensor and a photoelectric sensor system that can flexibly cope with a change in the light projection period.

  In order to solve the above problem, the invention according to claim 1 is characterized in that a receiving means for receiving a synchronization signal, a light projecting means for intermittently projecting light in response to the synchronization signal, and a light projecting means, A pair of light receiving means; detection means for detecting an object to be detected based on light reception detection by the light receiving means; and transmission means for transmitting the synchronization signal to the outside at a timing delayed from the reception. A photoelectric sensor, comprising a time measuring means for measuring an internal reference period set equal to the period of the synchronization signal, wherein the light projecting means and the transmitting means are delayed by a predetermined time from a reset timing of the time measuring means, and And a correction means for correcting the internal reference period based on a comparison between a reception detection timing of the synchronization signal and a reset timing of the timing means, while executing the light projection and the transmission. The the gist.

  According to the above configuration, each photoelectric sensor caused by the above-described subtle internal clock difference or the like by correcting the internal reference period as needed based on the comparison between the synchronization signal reception detection timing and the timing unit reset timing. The processing time error problem can be solved. The internal reference period itself expands and contracts along with this correction, so that it is possible to flexibly and autonomously respond to changes in the light projection period (transmission period). For this reason, when changing the light projection period, it is only necessary to change the setting of the master unit that outputs the reference synchronization signal. As a result, the setting change operation can be greatly saved.

The gist of the invention described in claim 2 is that it comprises second correcting means for correcting the predetermined time in accordance with the correction of the internal reference period.
According to the above configuration, even when there is a change in the light projecting cycle, the interval between the light projecting and receiving operations between the photoelectric sensors can be more appropriately maintained.

The gist of the invention described in claim 3 is that the correction is provided with an upper limit for the correction amount.
According to the above configuration, for example, in the case where an abnormal situation that requires a significant change in the internal reference period occurs due to, for example, a disturbance in the reception detection of the synchronization signal, it is inappropriate to follow this blindly. It is possible to avoid a situation in which the light projecting / receiving operation is unstable due to the correction.

The gist of the invention described in claim 4 is that it is provided with notifying means for notifying the outside that the correction is required to exceed the upper limit.
According to the above configuration, it is possible to notify the operator of the occurrence of an abnormal situation and prompt confirmation / inspection thereof.

  The invention according to claim 5 is formed by arranging a plurality of photoelectric sensors according to claim 1 or 2 adjacent to each other, and each photoelectric sensor converts a synchronization signal input from a higher-order photoelectric sensor to a lower-order photoelectric sensor. The gist is that it is a photoelectric sensor system that sequentially delivers.

  According to the above configuration, when changing the light projection period, it is only necessary to change the setting of the master unit that outputs the reference synchronization signal, so that the setting change work can be greatly saved. As a result, the light projection period can be changed more flexibly.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric sensor and photoelectric sensor system which can respond flexibly to the change of a light projection period can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, the photoelectric sensor system 1 of this embodiment is formed by combining a plurality (four units) of photoelectric sensors 2 (2a to 2d).

  Each photoelectric sensor 2 controls a light projecting element 3 as a light projecting means, a light receiving element 4 as a light receiving means paired with the light projecting element 3, and a light projecting / receiving operation by the light projecting element 3 and the light receiving element 4. The light projecting element 3 emits light based on the light projection signal Sfl output from the control circuit 5. And the control circuit 5 as a detection means detects a to-be-detected object based on the light reception signal Srl which the light receiving element 4 which received the reflected light or transmitted light of the light irradiated from the light projecting element 3 outputs, The detection result is output to the output terminal Pout as the detection signal Sde.

  Each photoelectric sensor 2 transmits a synchronization light receiving element 7 as a receiving means capable of receiving the synchronization signal Ssyn input as an optical signal from the upper photoelectric sensor 2 and the synchronization signal Ssyn to the lower photoelectric sensor 2. And a synchronizing light projecting element 8 as a transmitting means.

  That is, the photoelectric sensor 2 of the present embodiment employs a so-called optical synchronous photoelectric sensor, and the control circuit 5 of each photoelectric sensor 2 indicates that the synchronization signal Ssyn has been received from the synchronization light receiving element 7. When the reception signal Ssy_in is input, the light projection signal Sfl is output to the light projecting element 3 and the transmission signal Ssy_out is output to the synchronization light projecting element 8 at a timing delayed from the reception detection. Then, as shown in FIG. 2, each photoelectric sensor 2 sequentially delays the input synchronization signal Ssyn from the upper side to the lower side by a predetermined time T0, and sequentially sends it from the upper side at the delayed timing. By completing the light receiving and detecting operation, mutual interference with other adjacent photoelectric sensors 2 and erroneous detection due to this are avoided.

  In the photoelectric sensor system 1 of this embodiment having four photoelectric sensors 2 (2a to 2d), the predetermined time T0 that is a delay time is set to ¼ of the light projection period T of each photoelectric sensor 2. Thus, each photoelectric sensor 2 is configured to intermittently repeat the light projecting / receiving operation at substantially equal intervals.

  In the present embodiment, when the power is turned on, the control circuit 5 of each photoelectric sensor 2 first outputs the transmission signal Ssy_out and determines whether or not the reception signal Ssy_in is input. Then, what has been determined that there is no input of the received signal Ssy_in (in the configuration shown in FIG. 1, the photoelectric sensor 2 a) functions as a so-called “parent device”, and the others (photoelectric sensors 2 b to 2 d) are “ It is designed to function as a “slave unit”.

Next, the mode of synchronous control in each photoelectric sensor will be described.
As shown in FIGS. 1 and 3, in the present embodiment, the control circuit 5 of each photoelectric sensor 2 is provided with an internal counter 10 as a clocking means for clocking (counting) the internal reference period t. The initial value of the internal reference period t is set to the transmission period T ′ of the input synchronization signal Ssyn (corresponding to the light projection period T of the photoelectric sensor 2a as the master unit). After the determination, counting of the internal reference period t is started from the time when the first synchronization signal reception is detected. The control circuit 5 outputs the light projection signal Sfl and the transmission signal Ssy_out at a timing delayed by a predetermined time t0 from the reset timing of the internal counter 10. In the present embodiment, the predetermined time t0 is set to 1/4 of the internal reference period t. Thus, each photoelectric sensor 2 is configured to perform the light projecting / receiving operation and the transmission of the synchronization signal Ssyn to each lower-level photoelectric sensor 2 at a timing delayed by a predetermined time T0 from the input of the synchronization signal Ssyn. (See FIG. 2).

  Further, in the present embodiment, the control circuit 5 compares the reception detection timing of the synchronization signal Ssyn (input timing of the reception signal Ssy_in) with the reset timing of the internal counter 10 so that the internal reference cycle t is transmitted as needed at any time. Correction equal to T ′. Thereby, each photoelectric sensor 2 constituting the photoelectric sensor system 1 is configured to autonomously respond to the change of the light projection period T.

  Specifically, as shown in FIG. 4A, when the light projection period T (transmission period T ′) is shortened, the reception detection timing of the synchronization signal Ssyn is earlier than the reset timing of the internal counter 10. (The place where it was “10 counts” is now “9 counts”). In this case, the control circuit 5 as correction means resets the internal counter 10 at the reception detection timing, and shortens the internal reference period t to be equal to the shortened transmission period T ′. And as shown in FIG.4 (b), when the light projection period T (transmission period T ') becomes long and the reception detection timing of the synchronizing signal Ssyn becomes later than the reset timing of the internal counter 10, ( From “10 count” to “11 count”), the control circuit 5 resets the internal counter 10 at the reception detection timing, and expands the internal reference period t to be equal to the expanded transmission period T ′.

  That is, as shown in the flowchart of FIG. 5, the control circuit 5 determines whether or not there is an input of the reception signal Ssy_in (step 101), and when there is an input of the reception signal Ssy_in (step 101: YES). Subsequently, it is determined whether or not the reception detection timing coincides with the reset timing of the internal counter 10 (step 102). If the timings do not match (step 102: NO), it is subsequently determined whether the reception detection timing is earlier than the reset timing (step 103). If the timing is earlier (step 103: YES). The internal reference period t is shortened (step 104), and when it is late (step 103: NO), it is expanded (step 105). Thus, the internal reference period t is corrected to be equal to the transmission period T ′.

  In this embodiment, when the control circuit 5 corrects the internal reference period t in the above steps 104 and 105, the delay from the detection of the synchronization signal Ssyn to the light projecting / receiving operation and the transmission of the synchronization signal Ssyn based on the correction. The time, that is, the predetermined time t0 is corrected (step 106). Specifically, the control circuit 5 as the second correction unit corrects the predetermined time t0 to ¼ of the corrected internal reference period t. As a result, each photoelectric sensor 2 repeats the light projecting / receiving operation intermittently at a more appropriate interval.

  If the reception detection timing coincides with the reset timing of the internal counter 10 in step 102 (step 102: YES), the control circuit 5 does not execute the processing in steps 103 to 106.

As described above, according to the present embodiment, the following operations and effects can be obtained.
(1) The control circuit 5 is provided with an internal counter 10 that measures (counts) the internal reference period t, and the initial value of the internal reference period t is set to the transmission period T ′ of the input synchronization signal Ssyn. Then, the control circuit 5 outputs the light projection signal Sfl and the transmission signal Ssy_out at a timing delayed by a predetermined time t0 from the reset timing of the internal counter 10. Then, the control circuit 5 compares the reception detection timing of the synchronization signal Ssyn with the reset timing of the internal counter 10 to correct the internal reference period t equal to the transmission period T ′ as needed.

  According to the above configuration, the internal reference period t is corrected at any time based on the comparison between the reception detection timing of the synchronization signal Ssyn and the reset timing of the internal counter 10, resulting in the above-described delicate internal clock difference and the like. The problem of processing time error of each photoelectric sensor can be solved. Then, the internal reference period itself expands and contracts with this correction, so that it is possible to flexibly and autonomously respond to changes in the light projection period T (transmission period T ′). For this reason, when changing the light projection period T, it is only necessary to change the setting of the master unit that outputs the reference synchronization signal Ssyn. As a result, the setting change operation can be greatly saved. Become.

  (2) When the internal reference period t is corrected, the control circuit 5 corrects the delay time from the reception detection of the synchronization signal Ssyn to the light projecting / receiving operation and the transmission of the synchronization signal Ssn based on this, that is, the predetermined time t0. . With such a configuration, even when there is a change in the light projection period T, the interval between the light projecting and receiving operations between the photoelectric sensors 2 can be more appropriately maintained.

In addition, you may change this embodiment as follows.
In the present embodiment, the internal reference period t is corrected to be equal to the transmission period T ′. However, the present invention is not limited to this, and may be configured to increase or decrease by a predetermined level (for example, “± 1” of the internal counter) at the time of one correction.

  Further, an upper limit may be set for the correction amount of the internal reference period t. As a result, when an abnormal situation that requires a significant change in the internal reference period t occurs, the light projecting / receiving operation is destabilized by performing an improper correction that follows this blindly. Can be avoided.

  -Furthermore, you may provide the alerting | reporting means which alert | reports outside that it is a situation which requires the correction | amendment exceeding such an upper limit. As a result, it is possible to notify the operator of the occurrence of an abnormal situation and prompt confirmation / inspection thereof.

In the present embodiment, the photoelectric sensor 2a is configured as the “parent device”. However, the configuration is not limited thereto, and the configuration other than the photoelectric sensors 2a to 2d may be embodied as the “parent device”.
In the present embodiment, each photoelectric sensor 2 is an optical synchronous type, but is not limited to this, and may be embodied in a configuration in which each photoelectric sensor is connected by a synchronization line.

  In the present embodiment, the predetermined time t0, which is a delay time from the detection of reception of the synchronization signal Ssyn to the light transmission / reception operation and transmission of the synchronization signal Ssyn, is set to ¼ of the internal reference period t. However, the present invention is not limited to this, and may be changed as appropriate in accordance with the number of photoelectric sensors 2 to be connected. The correction method for the predetermined time t0 is not limited to “¼ of the corrected internal reference period t”.

The schematic block diagram of a photoelectric sensor and a photoelectric sensor system. Operation | movement explanatory drawing of a photoelectric sensor system. The time chart explaining the aspect of the synchronous control in each photoelectric sensor. (A) (b) The time chart explaining the aspect of the synchronous control in each photoelectric sensor. The flowchart which shows the process sequence of the synchronous control in each photoelectric sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Photoelectric sensor system, 2 (2a-2d) ... Photoelectric sensor, 3 ... Light emitting element, 4 ... Light receiving element, 5 ... Control circuit, 7 ... Light receiving element for synchronization, 8 ... Light emitting element for synchronization, 10 ... Inside Counter, T: Projection period, T ′: Transmission period, T0: Predetermined time, t: Internal reference period, t0: Predetermined time, Sfl: Projection signal, Srl: Light reception signal, Sde: Detection signal, Ssyn: Synchronization signal , Ssy_in ... reception signal, Ssy_out ... transmission signal.

Claims (5)

A receiving means for receiving a synchronization signal, a light projecting means for intermittently projecting light in response to the synchronization signal, a light receiving means paired with the light projecting means, and a detected object based on light reception detection by the light receiving means A photoelectric sensor comprising detection means for detecting an object, and transmission means for transmitting the synchronization signal to the outside at a timing delayed from the reception,
A timing means for timing an internal reference period set equal to the period of the synchronization signal, wherein the light projecting means and the transmitting means delay the light projection and the transmission by a predetermined time from a reset timing of the time measuring means; As well as
Comprising correction means for correcting the internal reference period based on a comparison between the reception detection timing of the synchronization signal and the reset timing of the timing means;
A photoelectric sensor characterized by The photoelectric sensor according to claim 1,
A photoelectric sensor comprising: a second correction unit that corrects the predetermined time according to the correction of the internal reference period. The photoelectric sensor according to claim 1 or 2,
The photoelectric sensor is characterized in that an upper limit is provided for the correction amount. The photoelectric sensor according to claim 3.
A photoelectric sensor, comprising: an informing means for informing the outside that the correction is required to exceed the upper limit.   A plurality of photoelectric sensors according to any one of claims 1 to 4 are arranged adjacent to each other, and each photoelectric sensor sequentially receives a synchronization signal input from an upper photoelectric sensor to a lower photoelectric sensor. Sensor system.

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