JP2519310Y2 - Multi-axis photoelectric switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial field of application) The present invention is a multi-light system that includes a plurality of pairs of light projecting elements and light receiving elements and operates based on the fact that one of the optical axes is shielded. The present invention relates to a shaft type photoelectric switch.

(Prior Art) This type of photoelectric switch can detect the presence or absence of an object in a wide range, and thus is used as a safety device of a press machine, for example. Its basic structure is to provide a light projecting element and a light receiving element in a pair so as to form a plurality of optical axes in a region through which an object to be detected passes, and to form a combination of a plurality of transmissive photoelectric switches. Of. With this configuration, even if the detected object enters one optical axis and the optical axis is blocked, the light from the light projecting element of the adjacent optical axis enters the light receiving element of the blocked optical axis. If it is regarded as a light state, it is not possible to reliably detect the entry of the detection object. Therefore, conventionally, a plurality of light emitting elements are sequentially made to emit light at a predetermined timing, and
A synchronous signal corresponding to the light emitting timing is sent to the light receiving circuit side via a signal cable, and only the light receiving element corresponding to the light emitting element emitting light is made effective.

However, this configuration has a big drawback that the wiring work at the time of installation is considerably troublesome because it is necessary to connect the light projecting device and the light receiving device with a signal cable.

Therefore, the present applicant has developed a technology that enables a wireless connection between the light projecting device and the light receiving device, and has already filed an application (Japanese Patent Application No.
-199863). In this system, in addition to a plurality of pairs of light emitting elements and light receiving elements for object detection, a light emitting element and a light receiving element for synchronization are provided, and the light emitting element and the light receiving element for synchronization are used to generate a synchronization signal as an optical signal. This is a configuration for transmitting to the light receiving device. The light receiving device outputs a synchronization signal corresponding to the light emitting timing to the light receiving circuit each time the synchronization light receiving element detects that the synchronization light signal has been received. According to this, there is an advantage that a signal cable for transmitting a synchronization signal to the light receiving device is not required, and the degree of freedom in equipment installation is increased.

(Problems to be solved by the invention) By the way, in this type of photoelectric switch, if extremely strong light such as welding spatter arc enters the light receiving element, it may cause malfunction. When strong light enters the light receiving element, the light receiving element becomes saturated,
Immediately after that, even if the light receiving element is validated by the synchronization signal, the signal from the light receiving element becomes equivalent to the light-shielded state, and it is determined that the object has entered the optical axis. Further, in the configuration in which the synchronizing signal is transmitted to the light receiving device by an optical signal, if the synchronizing light receiving element is saturated by the sputter arc, the synchronizing signal cannot be output to the light receiving circuit, and therefore accurate detection is possible. Will be impossible.

Therefore, an object of the present invention is to enable a wireless connection between a light projecting device and a light receiving device, while preventing malfunction due to intense ambient light such as spatter arc, and moreover, it is possible to achieve reliable synchronization. It is to provide an axial photoelectric switch.

[Structure of the Invention] (Means for Solving the Problems) The multi-optical axis photoelectric switch of the present invention comprises a detection light projecting element and a light receiving element which are provided in pairs so as to form an optical axis for detection. And a synchronization light-projecting element and a light-receiving element provided in pairs so as to form an optical axis for synchronization, and the light emission time of the light-emitting element for synchronization is set longer than the light-emission time of the light-emitting element for detection. And a light projecting circuit that causes each light projecting element to emit light so as to repeatedly scan at a predetermined light projecting timing, and the light projecting timing is set every time it is detected that the synchronization light receiving element is in a light receiving state for a predetermined time. A determination is made by providing a synchronization signal generation unit that outputs a corresponding synchronization signal and a determination unit that detects the light-shielded state of each optical axis by capturing the light reception signal from each detection light receiving element in synchronization with the synchronization signal. Means to scan the state of each optical axis at least in the previous scan Is configured to perform determination on the condition that the light-shielded state is repeated over a plurality of times of scanning, and the synchronization signal generation means is configured to detect the synchronization light-receiving element after the synchronization light-receiving element is in the light-reception state for a predetermined time. If the light receiving element for synchronization does not reach the light receiving state that continues for a predetermined time even after the light emission timing period of the light emitting element for synchronization elapses, from the light receiving element for synchronization that continues to be in the light receiving state for a predetermined time before that. It is characterized in that it is configured to output a synchronization signal at a timing based on the received light signal of.

(Operation) The light signal emitted from the synchronizing light emitting element has a longer light emission period than the light signal emitted from the detecting light emitting element. Therefore, when an optical signal from the synchronizing light emitting element enters the synchronizing light receiving element, the synchronizing signal generating means detects that the synchronizing light receiving element has been in the light receiving state for a predetermined period of time and emits light. A synchronization signal corresponding to the light emission timing in the circuit is output to the determination means. However, when the optical signal from the detecting light emitting element enters the synchronizing light receiving element, it is detected that the synchronizing light receiving element has been in the light receiving state for a predetermined time because the light emitting period of the optical signal is short. Therefore, the synchronization signal is not given to the judging means. In this way, the optical signal for synchronization and the optical signal for detection are clearly distinguished.

On the other hand, the determination means detects the light shielding state of each optical axis by capturing the light reception signal from the detection light receiving element in synchronization with the synchronization signal, and moreover, determines the state of each optical axis at least at the time of the previous scanning. The determination is made on the condition that the stored light-shielded state is repeated over a plurality of times of scanning. Therefore, even if the detection light-receiving element is temporarily saturated by the sputter arc and its optical axis is detected to be in the light-shielded state, the light-receiving state is returned to during the subsequent scanning, so that an erroneous determination is avoided.

Further, even if the synchronizing light receiving element is temporarily saturated by the sputter arc and cannot receive the optical signal from the synchronizing light projecting element, the synchronizing signal generating means receives the light received by the synchronizing light receiving element for a predetermined time. When the state does not occur, the synchronizing signal is output at a timing based on the received light signal from the synchronizing light receiving element that is input before that state. By capturing while synchronizing with the synchronizing signal, the light blocking state of the optical axis can be detected.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

[1] Projecting Device First, the projecting circuit 11 will be described. This is provided with one synchronizing projecting element 12 and a total of three detecting projecting elements 13, 14, 15 and each projecting element 12 is provided. ˜15 are provided so as to project light across the passage area of the object to be detected. In order to control these, a CPU 16, a shift register 17, and four AND gates 18 are provided as shown in the figure. Of these, the CPU 16 outputs a light emission signal S _A as shown in FIG. 2 (A). ,Also
FIG Each output line of the shift register 17 which operates in response to a signal from CPU 16 (B) selection signal S _B shown in ~ (E)
~ S _E is output. Accordingly, the drive circuits 19 for driving the respective light projecting elements 12 to 15 are supplied with the drive signals S _{F to} S _I shown in FIGS. ~
15 is emitted so as to be repeatedly scanned at a timing based on this. Especially, the synchronizing light signal emitted from the synchronizing light projecting element 12 has a longer light emission period than the detecting light signals emitted from the detecting light projecting elements 13 to 15. Specifically, in this embodiment, the pulse group P _S for the synchronizing optical signal of the light projecting signal S _A is a burst signal that repeatedly turns on and off at a frequency of 100 KHZ, for example, and its light emitting period is about 100 μsec. Also, the pulse P _D for the detection light signal of the light projection signal S _A is a single-shot pulse, and the light emission period of the light signal is about 10 μse, which corresponds to 1/10 of the synchronization light signal.
It is c.

[2] Light-Receiving Device Next, the light-receiving circuit 21 will be described. It comprises a light-receiving element for synchronization 22 and a light-receiving element for detection 23 to 25 which are paired with the light-emitting elements 12 to 15 for synchronization and detection. Equipped with. The synchronizing light projecting element 12 and the synchronizing light receiving element 22 form an optical axis for synchronization, and the detecting light projecting elements 13 to 15 and the detecting light receiving elements 23 to 25 form the first to third three lines. An optical axis for detection is formed.

Each of the light receiving elements 22 to 25 is composed of a photodiode, for example, and photoelectrically converts the optical signal from the light projecting elements 12 to 15 into a light receiving signal. These light receiving signals are received by four light receiving amplifiers 26-
The signal is input to the comparator 31 via the analog switch 30 which is amplified by 29 and is selectively activated.
The output signal from 31 is provided to the CPU 32 and the off delay circuit 33. The comparator 31 has a function of shaping the waveform by comparing the received light signal S _R with a reference level. For example, when the received light signal S _R as shown in FIG. The shaped signal S _S as shown is output. Further, the off-delay circuit 33 has a function of delaying the off-timing of the shaping signal S _S from the comparator 31, and therefore, the shaping signal S _S corresponding to the synchronizing optical signal is as shown in FIG. The pulse width is converted into a sufficiently wide pulse (synchronization trigger signal T) having a wide width, and the pulse width of the portion corresponding to the optical signal for detection is slightly increased.

Now, the CPU 32 constitutes the synchronizing signal generating means and the judging means as described below, and has the function shown in FIG. That is, in the initial state immediately after the light receiving circuit 21 is powered on, the CPU 32 gives a signal to the shift register 34 to make the analog switch 30 corresponding to the light receiving element for synchronization 22 conductive and wait for the detection of the synchronization trigger signal T. (Step a).
This synchronization trigger signal T is supplied to the off-delay circuit when the synchronization light-receiving element 22 continues to receive light for a predetermined time.
It is detected based on the input of a wide pulse from 33 to the CPU 32. When the sync trigger signal T is detected in step a, the CPU 32 generates a sync signal S _U as shown in FIG. 3 (U) corresponding to the light projection timing in the light projecting circuit 11 according to the detection timing. . In addition, a signal is given to the shift register 34 at the same time, and gate open signals S _{O to} S _Q as shown in FIGS. The analog switch 30 becomes conductive and the light receiving signals S _K , S _L and S _M from the respective light receiving elements 23 to 25 are input to the CPU 32 via the comparator 31. Then, the shaping signal S _S whose waveform has been shaped by the comparator 31 is taken in the CPU 32 in synchronism with the synchronization signal S _U , whereby it is detected whether or not the corresponding optical axis is in the light-shielded state (step b). ~ D). After that, the synchronization trigger signal T is again detected (step e), and when it is detected, the synchronization timing is updated (step f), and the CPU 32 again generates the synchronization signal S _U based on the synchronization timing. As a result, the gate open signal S _O ~
S _Q is output as shown in FIGS. 3 (O) to (Q), the corresponding analog switches 30 are turned on, and the light receiving signals S _K , S _L , S _M from the light receiving elements 23 to 25 are output. Is input to the CPU 32 via the comparator 31 and is captured in synchronization with the synchronization signal S _U , whereby the detection of the light-shielded state for the corresponding optical axis is repeated (steps b to d).

When the detection of the light shielding state for each optical axis is repeated for each scanning, the states for each optical axis for synchronization and detection are stored in a register (not shown) in the CPU 32,
When both the previous scanning and the current scanning are in the light entering state (“yes” in step g), a signal is given to the output circuit 35 to turn on the output. If the light is blocked at least once in both the previous scanning and the current scanning (“no” in step g), the process moves to the next step h, and the detection optical axis continues twice. It is determined whether or not it is in the light-shielded state. If the detection optical axis is in the light-shielded state twice in succession (“yes” in step h), a signal is given to the output circuit 35 to turn off the output, and the light-shielded state is set only once. In the case (“no” in step h), the output is not turned off even though the light is shielded, and the synchronization trigger signal T
Is detected (step e). Where the predetermined time
When T _O is measured (step i) and the synchronization trigger signal T is detected within the time T _O , the process moves to step f to update the synchronization timing as described above, and the synchronization signal S _U based on the synchronization timing is updated. Is generated. If the synchronization optical axis is in the light-shielded state and the synchronization trigger signal T is not detected within the time T _O (“yes” in step i), as shown in step j, both the previous scanning and the current scanning are performed. At any time, the output is turned off when the synchronizing optical axis is in the light-shielded state. Further, when the light-shielding state is present only during the current scanning (“no” in step i), the synchronization timing is not updated, that is, the light received from the synchronization light-receiving element 22 input last time is received. The synchronization signal S _U is generated at the timing based on the signal S _J to detect the state of the detection optical axis.

[3] Action (a) In the above configuration, when the detected object does not enter any optical axis, the synchronization trigger signal T is periodically detected, and the synchronization timing is updated each time ( In step f), the synchronization signal S _U is sequentially generated. And
Since the light entering state is always detected on the detection optical axis for each scan (“yes” in step g), the output circuit 35 turns on the output.

(B) When the detection object enters the detection optical axis from the above-mentioned state, the optical axis is detected as a light-shielded state. In this case, since the light blocking state continues for a plurality of times of scanning, step h
Then, the output becomes "yes" and the output of the output circuit 35 is turned off.

(C) In addition, if a detected object enters the optical axis for synchronization,
“No” in step g, “no” in step h, “no” in step e, and “yes” in step i. Also in this case, since the light-shielding state continues for a plurality of times of scanning, the result is "yes" in step j, and the output of the output circuit 35 is turned off.

(D) Next, when the object to be detected does not enter any of the synchronizing and detecting optical axes, intense light such as spatter arc is detected by one of the detecting light receiving elements 23 to 25. It is assumed that the light enters at the moment when it is activated. In this case, since the light receiving element is saturated, even if the detection light signals from the detection light projecting elements 13 to 15 enter the detection light receiving elements 23 to 25 immediately after that, a sufficient level is obtained. In some cases, the light receiving signal of is not obtained, and the CPU 32 may detect that the optical axis is in the light blocking state. However, the light receiving element
After that, since the saturated state is immediately recovered, a light receiving signal is generated at the time of the next scanning, and the light entering state is detected. For this reason, the output circuit 35 becomes "no" at step h.
Is not turned off, and malfunction due to sputter arc is avoided.

Further, when the sputter arc is incident on the light receiving element 22 for synchronization, the light receiving element 22 is also saturated, so that the synchronization trigger signal T is detected even when the light signal for synchronization enters the light receiving element for synchronization 22. Instead, it may be regarded as a light-shielded state.
In this case as well, since such a light-shielded state is transient, the synchronization optical signal enters the synchronization light-receiving element 22 and the synchronization trigger signal T is detected during the next scanning.
For this reason, the output of the output circuit 35 is "no" in step j, the output circuit 35 is not turned off, and the malfunction due to the sputter arc is also avoided. Further, even if the synchronization trigger signal T is not detected due to the saturation of the synchronization light receiving element 22 as described above, the CPU 32 synchronizes at the timing based on the light reception signal S _J from the synchronization light receiving element 22 input last time. Since the signal S _U is generated, there is no problem in detecting the state of the detection optical axis at the time of the next traveling, and it is possible to reliably detect the entry of the object into the detection area.

In the above embodiment, the example in which the number of the optical axes for detection is three is shown, but the present invention is not limited to this, and the number of the optical axes may be appropriately set according to the size of the detection region and the required density. It's good. Further, although it is determined that the object has entered when the light blocking state is detected twice consecutively in each optical axis, the number of times is not limited to this, and the number of times is the recovery speed of the light receiving element from the saturated state or the like. It may be appropriately selected in consideration of the above. Further, in the above-described embodiment, the determination as to whether or not the light has entered the optical axis twice consecutively (step g) is made at the time point when one scanning is completed, but the present invention is not limited to this, and each light is not limited. Each time the state of the axis is detected, it may be determined whether or not the light is continuously input twice in each optical axis. Besides, the present invention is not limited to the embodiments described above and shown in the drawings, and various modifications can be carried out without departing from the scope of the invention.

[Effects of the Invention] As described above, the present invention enables wireless connection between the light emitting and receiving devices, and at the same time, prevents malfunction due to intense ambient light such as spatter arc and ensures reliable synchronization. It has an excellent effect that it can be taken.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, FIG. 1 is an overall block diagram, FIG. 2 is a voltage waveform diagram of each part of a light projecting circuit, FIG. 3 is a voltage waveform diagram of each part of a light receiving circuit, and FIG. Is a flowchart. In the drawing, 11 is a light emitting circuit, 12 is a light emitting element for synchronization, 13 to 15 are light emitting elements for detection, 21 is a light receiving circuit, 22 is a light receiving element for synchronization,
23 to 25 are light receiving elements for synchronization, and 32 is a CPU (synchronization signal generation means, determination means).

Claims (1)

(57) [Scope of utility model registration request] 1. A detection light-emitting element and a light-receiving element, which are provided as a pair so as to form an optical axis for detection, and a synchronization which is provided as a pair so as to form an optical axis for synchronization. The light emitting element and the light receiving element for light emission, and the light emitting time of the synchronizing light emitting element are set to be longer than the light emitting time of the light emitting element for detection, and light is emitted so that each light emitting element is repeatedly scanned at a predetermined light emitting timing. A light projecting circuit, a sync signal generating unit that outputs a sync signal corresponding to the light projecting timing each time the sync light receiving element detects that the light receiving element has been in a light receiving state for a predetermined time, And a determination means for detecting a light blocking state of the optical axis by capturing a light reception signal from a light receiving element in synchronization with the synchronization signal, wherein the determination means determines at least the state of each of the optical axes from the previous state. Memorize when scanning and the light blocking state is duplicated. The synchronization signal generating means is configured to make a determination under the condition that the synchronization light receiving element has been repeated over a number of times of scanning, and the synchronization light emitting element is provided with the synchronization light emitting element after the synchronization light receiving element is in a light receiving state for a predetermined time. If the light receiving element for synchronization does not reach the light receiving state that continues for a predetermined time even after the light emission timing cycle of, the light receiving signal from the light receiving element for synchronization that continues to be the light receiving state for the predetermined time before A multi-optical axis type photoelectric switch, which is configured to output a synchronization signal at a timing based on the above.