JP3698319B2 - Multi-axis photoelectric sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-optical axis photoelectric sensor including a light projector and a light receiver that sequentially repeat a plurality of optical axis operations for performing light projection and light reception based on a synchronization signal at a predetermined cycle.
[0002]
[Prior art]
As shown in FIG. 1, the multi-optical axis photoelectric sensor is composed of a multi-optical axis projector 1 and a multi-optical axis light receiver 2 that operate synchronously via a synchronous signal line. A plurality of optical axis operations to be performed are sequentially repeated at a predetermined cycle. For example, the optical axes {circle over (1)} to {circle around (4)} are sequentially projected from the projector 1 based on the synchronization signal, and the light receiver 2 is synchronized with the light projection timing of the optical axes {circle over (1)} to {circle around (4)}. Receiving and recognizing the projection output. Such a photoelectric sensor is often used in a factory production line to prevent danger. For example, if a production worker's hand blocks at least one optical axis, the light receiver 2 determines that the light is blocked, and an alarm is notified. And a control signal for stopping the production machine.
[0003]
[Problems to be solved by the invention]
However, for example, as shown in FIG. 2, when a plurality of sets of such photoelectric sensors are installed adjacent to each other, the projection output from the projector 1 of a certain photoelectric sensor has a certain extent from the optical axis. There is a possibility that light enters the light receiver 2 of another photoelectric sensor as shown by a dotted line and becomes interference light, resulting in malfunction. Therefore, a synchronizing signal line is connected between the projector 1 and the receiver 2 that are paired to maintain the synchronization relationship, and only the receiver 2 that is synchronized in timing with the projector output of the projector 1 recognizes the projection signal. By making it possible, the light projection output can be ignored on the side of the light receiver that has no synchronization relationship, so that malfunction due to interference light is prevented for the time being. However, since the timings of the optical axes are hardly matched between photoelectric sensors with originally different synchronization signal cycles, malfunctions are substantially prevented, but the synchronization signal cycles are substantially equal as in the same model ( If the photoelectric sensors are installed adjacent to each other (that is, only slightly different), such a malfunction prevention means is not sufficient. In other words, even if the timings of optical axis movements are shifted at a certain point in time among such a plurality of photoelectric sensors, the subtle time shifts accumulate over time, so that a long period of time can be accumulated. As a result, the time when the timing of the optical axis operation coincides will come. Then, the probability of interfering with each other becomes very high. Therefore, an object of the present invention is to prevent malfunction due to mutual interference when a plurality of sets of photoelectric sensors having substantially the same synchronization signal period are installed adjacent to each other.
[0004]
[Means for Solving the Problems]
To summarize the present invention, there is provided a multi-optical axis photoelectric sensor comprising a projector and a light receiver that sequentially repeats a plurality of optical axis operations for performing light projection and light reception based on a synchronization signal at a predetermined cycle. The interference light confirmation section B is provided before the projection signal recognition section for recognizing the projection output from the projector, and the interference light confirmation section A is provided after the projection signal recognition section. When confirmed, in addition to the normal optical axis processing time on the confirmed optical axis, a predetermined interference light is set so that subsequent interference light does not overlap with the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A. The synchronization signal is generated after the delay time to restart the light projecting / receiving process, and in the next cycle, the light projecting / receiving process is started, and the subsequent interference light is the interference light confirmation section B, the light projection signal recognition section and the interference light confirmation section A. So as not to overlap A multi-optical axis photoelectric sensor to avoid interference light by performing after boss was a predetermined delay time. The predetermined delay time is preferably set so that the subsequent interference light appears immediately after the interference light confirmation section A. Further, when the interference light is confirmed during the interference light confirmation section A, in the next cycle, the light projection / reception process is started, and the subsequent interference light enters the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A. Interference light is avoided by performing after a predetermined delay time set so as not to overlap. In this case, the predetermined delay time is preferably set so that the subsequent interference light appears in the vicinity of the interference light confirmation section B.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described. However, this is merely an exemplary embodiment adopted based on the present invention, and the present invention should not be limitedly interpreted based on matters specific to the embodiment. Rather, the technical scope of the present invention should be determined based on the matters shown in the claims and matters substantially equivalent thereto.
[0006]
An embodiment of the present invention will be described first with reference to FIGS. 1 to 6. A projector 1 and a light receiver that sequentially repeat a plurality of optical axis operations for performing light projection and light reception based on a synchronization signal at a predetermined cycle (1 scan: 6 ms). A multi-optical axis photoelectric sensor composed of 2 is shown, and the projector 1 and the light receiver 2 are placed facing each other so that the optical axes (1) to (4) are aligned. The synchronization signal sent from the light receiver 2 via the synchronization signal line is received by the synchronization signal input circuit 3, and when the microcomputer 4 issues a command based on the synchronization signal, the optical axis selection circuit 5 is based on the command. The light projecting circuits 6 to 9 including light emitting elements such as light emitting diodes are sequentially driven. Sequential projection outputs from the light projecting circuits 6 to 9 are sequentially received by the light receiving circuits 10 to 13 of the light receiver 2 and recognized by the microcomputer 14. This light reception recognition timing is determined based on the synchronization signal. Reference numeral 15 denotes a synchronization signal output circuit.
[0007]
The synchronization signal transmitted from the optical receiver 2 will be described in further detail. The synchronization signal is composed of a start signal, four synchronization signals at regular time intervals, and an end signal, and at a predetermined timing based on each synchronization signal transmitted following the start signal. Each of the light projecting circuits 6 to 9 sequentially performs a light projecting output operation using the optical axes (1) to (4) for a predetermined time. More specifically, referring to FIG. 6, when a synchronization signal is transmitted from the light receiver 2, the projector 1 receives and recognizes the synchronization signal after a delay time of about 2 μs, and after about 12 μs has elapsed from the start time of the synchronization signal, the projector 1. The light projection signal is output with a time width of about 3 μs in the optical axis (1), for example. Thereafter, similar light projection outputs are sequentially performed by the light projecting circuits 7 to 9 on the other optical axes {circle around (2)} to {circle around (4)} on the basis of the synchronization signals that arrive sequentially. The total processing time per optical axis is about 45 μs. Then, after the end signal is transmitted from the light receiver 2 to the projector 1, the light projecting / receiving process in one cycle is completed.
[0008]
On the other hand, in the optical receiver 2, the respective light receiving circuits 10 to 13 are sequentially activated from the time immediately after the end of each synchronization signal to the vicinity of about 45 μs from the start time of each synchronization signal in synchronization with the timing of each synchronization signal. The For example, at the timing when there is a projection output on the optical axis (1), only the light receiving circuit 10 is enabled from immediately after the end of the synchronization signal to immediately before the next synchronization signal. The time for which the microcomputer 14 recognizes the light projection signal received by the light receiving circuit 10 is the light projection signal recognition section indicated by the time width of 15 to 17 μs from the start time of the synchronization signal, that is, the time when the light projection output ends. Immediately after that, it is performed with a time width of about 2 μs. In this way, the light receiver 2 sequentially receives and receives the light projection signal from the light projector 1 for each optical axis in synchronization with the synchronization signal, and the microcomputer 14 recognizes the presence or absence of the light projection signal. The light / light shielding state is determined. For example, if the hand of the production worker blocks the optical axis (1), the light receiver 2 determines that the light is blocked, and sends out a control signal (not shown) for alarm notification, production machine stoppage, and the like.
[0009]
Next, avoidance of malfunction due to mutual interference as in the case where a plurality of sets of the same type of photoelectric sensor including the projector 1 and the light receiver 2 are installed adjacent to each other will be described. First, as shown in FIG. 6, in the light receiver 2, an interference light confirmation section B (Before) is provided before the light projection signal recognition section for recognizing the light projection output signal from the light projector 1. The interference light confirmation section B is about 11.8 μs after the start of the synchronization signal. Further, an interference light confirmation section A (After) is provided after the projection signal recognition section. The interference light confirmation section A is about 25 to 27 μs after the start time of the synchronization signal. Confirmation of whether there is interference light in these interference light confirmation section B and interference light confirmation section A is programmed to be performed by the microcomputer 14, and the incident light is confirmed in interference light confirmation section B or interference light confirmation section A. Then, it is processed as if there was interference light.
[0010]
Next, avoiding malfunction when another adjacent projector is operating with a period slightly longer than the period of the light receiver 2 will be described with reference to FIGS. In this case, every time the periodic operation is repeated, the interference light from other projectors gradually approaches the interference light confirmation section B from the front, but finally the interference light 21 is changed as shown in FIG. When the optical axis {circle over (1)} is confirmed in the interference light confirmation section B of the light receiver 2, in addition to the normal optical axis processing time (about 45 μs) in the confirmed optical axis {circle around (1)}, the subsequent interference After a predetermined delay time (for example, 20 μs) set so that the lights 22,... Do not overlap the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A, a synchronization signal is generated and the light projection / reception processing is resumed. Process. Then, since the next interference light 22 arrives about 45 μs later than the previous interference light 21, this interference light 22 may overlap the next interference light confirmation section B, the projection signal recognition section, and the interference light confirmation section A. Further, the subsequent interference light (not shown) does not overlap the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A. When the light output from the projector 1 on the optical axis {circle around (1)} is recognized in the light projection signal recognition section after the interference light 22, the light receiver 2 receives light on the optical axis {circle around (1)}. Judgment finally. When this projection output is shielded, it is recognized in the projection signal recognition section after the interference light 22, and the light receiver 2 finally determines that there is a shield on the optical axis (1). It is natural to be done. Although the overall length of this period does not change, the operations of the other optical axes {circle around (2)} to {circle around (4)} within this period are delayed as a matter of course due to the delay time (20 μs).
[0011]
However, since there is a limit to simply delaying the synchronization signal every time the interference light gradually approaches from the front and is confirmed in the interference light confirmation section B, the next operation period (the next 1 In the scanning), a predetermined delay time (set so that the subsequent interference light 23, 24,... Does not overlap the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A) is started. For example, interference light is avoided by performing after about 20 μs). That is, as shown in FIG. 8, the start of the light projecting / receiving process is delayed by a predetermined delay time (for example, about 20 μs), in other words, the entire synchronization signal for one scan including the start signal and the end signal is delayed. It avoids light. In this way, interference light that arrives at intervals of about 45 μs, such as interference light 23 and 24, can be accurately avoided. The interference light from other projectors gradually approaches the interference light confirmation section B in the light receiver 2 every time the periodic operation is repeated, so that the interference light becomes the interference light confirmation section B. Then, the interference light avoiding means functions again by the same operation as described above. Note that the delay times in FIGS. 7 and 8 may be different from each other. In addition, the delay time is set so that the subsequent interference light appears in the vicinity immediately after the interference light confirmation section A. The time until the interference light that arrives one after another overlaps the interference light confirmation section B is the longest. It is preferable. The delay time of about 20 μs almost satisfies this condition.
[0012]
Next, malfunction avoidance when another adjacent projector is operating at a slightly shorter period than the period of the light receiver 2 will be described with reference to FIGS. 9 and 10. FIG. In this case, every time the periodic operation is repeated, the interference light from other projectors gradually approaches the interference light confirmation section A later, but finally the interference light 25 is changed as shown in FIG. When it is confirmed in the interference light confirmation section A of the light receiver 2 on the optical axis {circle around (1)}, it is operated as shown in FIG. 10 in the next operation cycle (next one scan). That is, a predetermined delay time (for example, about 34 μs) set so that the subsequent interference light 26, 27 and the like do not overlap the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A is started. Interfering light is avoided by performing later. In other words, interference light is avoided by delaying the entire synchronization signal for one scan including the start signal and the end signal. In this way, interference light that arrives at intervals of about 45 μs, such as interference light 26 and 27, can be accurately avoided. The interference light from other projectors gradually approaches the interference light confirmation section A in the light receiver 2 each time the operation cycle is repeated, so that the interference light becomes the interference light confirmation section A. Then, the interference light avoiding means functions again by the same operation as described above. In addition, after the interference light recognition, the delay operation is postponed until the next operation cycle because the interference light confirmation section A can be provided far away from the projection signal recognition section. This is because there is no possibility that the light overlaps the projection signal recognition section. If the delay time shown in FIG. 10 is set so that the subsequent interference light appears immediately before the interference light confirmation section B, the time until the interference light that arrives one after another overlaps the interference light confirmation section A is the longest. Longer is preferred. The delay time of about 34 μs almost satisfies this condition. In FIGS. 7 to 10, in order to avoid complication, unlike FIG. 6, the light output (black signal) and the timing of the light signal recognition section are purposely matched.
[0013]
As described above, according to the present embodiment, it is possible to accurately prevent malfunction due to mutual interference when a plurality of sets of photoelectric sensors having substantially the same synchronization signal period are installed adjacent to each other. It is possible to accurately prevent dangers. Even if the synchronization signal is generated on the projector 1 side and transmitted to the light receiver 2 side, the projector 1 and the light receiver 2 can be synchronized with each other. It goes without saying that the same applies.
[Brief description of the drawings]
FIG. 1 is an external front view of a photoelectric sensor composed of a projector and a light receiver. FIG. 2 is an external front view of a photoelectric sensor composed of a plurality of photoelectric sensors. Block diagram [Fig. 4] Timing diagram showing signal sequence transmitted from light receiver to projector [Fig. 5] Timing diagram of projector output corresponding to signal sequence from light receiver [Fig. 6] Projector corresponding to synchronization signal -Detailed timing diagram showing the light output and confirmation interval of the receiver [Fig. 7] Timing diagram showing the operation when interference light is confirmed in the interference light confirmation interval B [Fig. 8] Next cycle of Fig. 7 FIG. 9 is a timing diagram when interference light is confirmed in the interference light confirmation section A. FIG. 10 is a timing diagram showing operation in the next cycle of FIG.
1 Projector 2 Receiver (1) to (4) Optical axes B and A Interference light check section

Claims (4)

A multi-optical axis photoelectric sensor composed of a light projector and a light receiver that sequentially repeats a plurality of optical axis operations for performing light projection and light reception based on a synchronization signal at a predetermined cycle. In the light receiver, the light projection output from the light projector is The interference light confirmation section B is provided before the light projection signal recognition section to be recognized, and the interference light confirmation section A is provided after the light projection signal recognition section. When the interference light is confirmed in the interference light confirmation section B, confirmation is made. In addition to the normal optical axis processing time on the optical axis, the synchronization signal is output after a predetermined delay time set so that the subsequent interference light does not overlap the interference light confirmation section B, the projection signal recognition section, and the interference light confirmation section A. Then, the light emitting / receiving process is restarted, and in the next cycle, the light emitting / receiving process start is set so that the subsequent interference light does not overlap the interference light confirmation section B, the light projection signal recognition section, and the interference light confirmation section A At a given delay Multi-optical axis photoelectric sensor to avoid interference light by performing later. 2. The multi-optical axis photoelectric sensor according to claim 1, wherein the predetermined delay time is set so that the subsequent interference light appears immediately after the interference light confirmation section A. A multi-optical axis photoelectric sensor composed of a light projector and a light receiver that sequentially repeats a plurality of optical axis operations for performing light projection and light reception based on a synchronization signal at a predetermined cycle. In the light receiver, the light projection output from the light projector is When the interference light confirmation section B is provided before the light projection signal recognition section to be recognized, the interference light confirmation section A is provided after the light projection signal recognition section, and the interference light is confirmed during the interference light confirmation section A, the following Interference light is avoided by performing the light projecting / receiving process in a period after a predetermined delay time set so that subsequent interference light does not overlap interference light confirmation section B, light projection signal recognition section, and interference light confirmation section A. Multi-optical axis photoelectric sensor. 4. The multi-optical axis photoelectric sensor according to claim 3, wherein the predetermined delay time is set so that the subsequent interference light appears in the vicinity immediately before the interference light confirmation section B.

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