JP5076049B2 - Photoelectric sensor - Google Patents

Description

  The present invention relates to a photoelectric sensor that switches a plurality of received light signals to be output by a signal switcher and performs signal processing, and outputs an object detection signal when the received light signal exceeds a set level, and particularly relates to reduction of switching noise.

  Conventionally, it has a plurality of light projecting elements that project light onto an object and a plurality of light receiving elements that receive light reflected or shielded by the object, and a plurality of obtained light reception signals are switched and output by a signal switch A photoelectric sensor is known that detects an object by outputting an object detection signal when the received light signal exceeds a set level after being processed by a processing circuit unit. These light reception signals are very small, and there are some cases where the switching noise generated at the time of signal switching in the signal switch has a great influence on the small light reception signals.

  On the other hand, as a conventional signal switching method for a plurality of received light signals, (1) a plurality of signal switchers are used in parallel and output as separate output signals to the processing circuit unit; (2) a plurality of signal switchers They are used in parallel and output to the processing circuit unit as one output signal. As an example of this, there is a photoelectric sensor that uses a plurality of signal switchers in parallel to deal with disturbance light noise (for example, Patent Document 1).

In the above conventional method, since switching noise such as switching noise generated at the time of signal switching in a signal switching device that receives a plurality of light receiving signals is transmitted to the subsequent circuit, various countermeasures against switching noise are performed for each signal in the subsequent circuit. Has been done. For example, it is known to provide a post-stage circuit with a filter circuit or a circuit that delays until switching noise disappears or becomes extremely small.
JP 2003-133934 A

  However, the level of switching noise is larger than that of a minute light reception signal, so there may be cases where a normal light reception signal cannot be obtained due to the influence, and a switching noise countermeasure circuit such as a filter circuit or delay circuit is simply added to the conventional subsequent circuit. It is difficult to sufficiently remove the switching noise simply by providing the switching noise.

  Also, when increasing the number of received light signals by providing a large number of light receiving elements in order to improve detection accuracy, the conventional technology requires an increase in the switching noise countermeasure circuit in the subsequent circuit by the increase, and this can be dealt with. In addition, there is a problem that the mounting area of the circuit board is increased due to the increase of the switching noise countermeasure circuit, and the photoelectric sensor is increased in size and cost.

  The present invention solves the above-described problems, and can reduce switching noise when a plurality of light receiving signals are input and the light receiving signals are switched by a plurality of signal switching devices, and a large number of light receiving elements are provided. It is an object of the present invention to provide a photoelectric sensor that can easily cope with an increase in the number of received light signals and can be reduced in size and cost.

  In order to achieve the above object, a photoelectric sensor according to one configuration of the present invention includes one or a plurality of signal switching units provided in parallel to which a plurality of light reception signals are input, and the light reception based on a switching signal input. A first signal switching unit that switches to a predetermined light receiving signal among the signals, and a second signal switching that is provided after the first signal switching unit and selects and outputs the predetermined light receiving signal based on an input of the selection signal And when the selection signal is not input to the second signal switching unit, the first signal switching unit switches to the predetermined light reception signal, and the second signal switching unit receives the selection signal. A switching control unit that performs control to output a predetermined light-receiving signal after the switching from the second signal switching unit in the input selection state.

  According to this configuration, the light reception signal is switched by the first signal switching unit when the second signal switching unit is in the non-selected state, and the switched light reception signal is output when the second signal switching unit is in the selected state. Since the switching noise to be transmitted is not transmitted to the subsequent circuit, the switching noise can be easily and reliably reduced, and a stabilized light receiving signal can be obtained.

  A photoelectric sensor according to another configuration of the present invention includes a plurality of signal switching units provided in parallel to which a plurality of light receiving signals are input, respectively, and each of the light receiving signals based on the input of the switching signal in each signal switching unit. A first signal switching unit that switches to a predetermined light reception signal and at least one stage after the first signal switching unit, and selects the signal switch based on an input of a selection signal, and the selected signal switching A second signal switching unit that switches and outputs the predetermined light reception signal from the device, and a selection signal is not input to the second signal switching unit among the plurality of signal switching units of the first signal switching unit. The switching signal is input only to the signal switcher in the selected state and switched to the predetermined light receiving signal, and the second signal switching unit is selected from the plurality of signal switching units of the first signal switching unit. The signal is input A predetermined light reception signal after the switching from the signal switch of the selected state, and a switching control unit which performs control to output from the second signal switching unit.

  According to this configuration, in the photoelectric sensor having a plurality of parallel and serially connected signal switching units, the switching control unit is not selected by the second signal switching unit among the plurality of signal switching units of the first signal switching unit. The switching signal is input only to the signal switcher in the state, the plurality of light receiving signals are switched to the predetermined light receiving signal, and the predetermined light receiving signal after the switching from the signal switching unit selected in the second signal switching unit Is output from the second signal switching unit. As a result, the light reception signal is switched by the first signal switching unit when the second signal switching unit is in the non-selected state, and the light reception signal after the switching is output when the second signal switching unit is in the selected state. Is not transmitted to the subsequent circuit, switching noise can be reduced easily and reliably, and a stabilized light receiving signal can be obtained. In addition, when a large number of light receiving elements are provided and the number of received light signals increases, switching noise can be reduced easily and the mounting area of the circuit board increases, resulting in an increase in the size and cost of the photoelectric sensor. Can be avoided.

  Preferably, the switching control unit is configured to output a predetermined light reception signal in a signal stable state after the switching in the selection state. Therefore, switching noise can be reduced more reliably.

  Preferably, the second signal switching unit sequentially outputs the predetermined light reception signal as a single light reception signal based on an input of the selection signal, and further, disturbing light in the sequentially output light reception signal is detected. A signal noise countermeasure circuit that removes signal noise including the signal noise, and a signal processing unit that processes the light reception signal from which the signal noise has been removed and outputs an object detection signal. Therefore, not only switching noise but also signal noise including disturbance light that normally occurs can be removed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic side view showing a photoelectric sensor according to the first embodiment of the present invention. The photoelectric sensor 1 is, for example, a reflection type, and a plurality of light projecting elements 2 that transmit infrared rays as detection waves, and a plurality of light receiving elements that receive infrared rays transmitted from the plurality of light projecting elements 2 and reflected by an object. 3, the processing circuit unit 5 processes the light reception signal and outputs the object detection signal when the light reception signal exceeds the set level. In this example, the light projecting element 2 and the light receiving element 3 are both four in the object movement direction X (left-right direction) and two in the direction orthogonal to the movement direction X (perpendicular to the paper surface). Is provided.

  FIG. 2 is a block diagram showing a part of the processing circuit unit 5 of the photoelectric sensor 1. This photoelectric sensor 1 has a signal switch 10 for receiving a plurality (two) of light reception signals (Sig-1, Sig-2) and a plurality (two) of light reception signals (Sig-3, Sig-4). An input signal switch 11 is provided in parallel, and a total of four light receiving signals (Sig) are provided based on the input of each switch signal (A / B) and (C / D) in each signal switch 10, 11. -1 to Sig-4) has a first signal switching unit 12 for switching to a predetermined light reception signal (a, b). That is, the switching signals (A / B) and (C / D) can be switched to any one of the four light receiving signals (Sig-1 to Sig-4).

  In this example, a bus switch is used for the first signal switching unit 12. However, the present invention is not limited to this, and another switch may be used.

  In addition, the photoelectric sensor 1 is provided in the subsequent stage of the first signal switching unit 12, selects the signal switching units 10 and 11 based on the input of the selection signal (E / F), and selects the selected signal switching unit 10, 11 includes a second signal switching unit 13 that switches and outputs the predetermined light reception signals (a, b) input from 11. That is, any one of the predetermined light receiving signals (a, b) from the signal switchers 10, 11 can be selected by the selection signal (E / F).

  In this example, a multiplexer that sequentially outputs predetermined light reception signals (a, b) as a single light reception signal based on the input of the selection signal (E / F) is used for the second signal switching unit 13. It is not limited to this, You may use another switch.

  That is, in this embodiment, since the photoelectric sensor 1 processes a plurality (four) of received light signals, a plurality (two) of signal switchers are provided in parallel and are connected in series to a plurality of stages (two stages). ing.

  Further, the photoelectric sensor 1 includes a signal noise countermeasure circuit 14 such as a filter that removes normal noise such as disturbance light and propagation light included in the received light signal, an amplifier circuit 15, and the second signal switching unit 13. And a control unit (CPU) 20. The control unit (CPU) controls the entire photoelectric sensor 1 and includes a switching control unit 16 and a signal processing unit 17 that processes the light reception signal from which the signal noise has been removed and outputs an object detection signal. Yes.

  The switching control unit 16 is a signal switching in a non-selected state in which the selection signal (E / F) is not input to the second signal switching unit 13 among the plurality of signal switching units 10 and 11 in the first signal switching unit 12. The switching signals (A / B) and (C / D) are input only to the detector, and the predetermined light receiving signals (a, b) among the light receiving signals (Sig-1 to Sig-4) are switched. The predetermined light receiving signals (a, b) after the switching from the signal switching unit in the selected state in which the selection signal (E / F) is input to the second signal switching unit 13 among the signal switching units 10, 11 Control to be output from the second signal switching unit 13 is performed.

  That is, the switching control unit 16 is a signal switching unit 10 or 11 that is not selected among the signal switching units 10 and 11 connected to an arbitrary light reception signal (a or b) selected by the second signal switching unit 13. Switch. For example, if the second signal switching unit 13 is selecting a predetermined light reception signal a from the signal switch 10, the non-selected signal switch 11 is switched. If the second signal switching unit 13 is selecting the predetermined light receiving signal b from the signal switch 11, the non-selected signal switch 10 is switched.

  In the time chart of FIG. 3, (a) is a switching signal (A / B) that is input to the first signal switching unit 12, (C / D), (b) is a selection signal that is input to the second signal switching unit 13 ( E / F) and (C) are predetermined light reception signals switched by the first signal switching unit 12, and (D) is an output signal of the second signal switching unit 13.

  In FIG. 3A, when the switching signal (C / D) is input to the signal switch 11 and switched from C to D (switching timing α in the figure), the received light signal as shown in FIG. Sig-3 is switched to the light reception signal Sig-4 and outputs Sig-4 as a predetermined light reception signal b. On the other hand, after the switching timing α in the figure, in (A), when the switching signal (A / B) is input to the signal switch 10 and switched from B to A (switching timing in the figure β), ), The light reception signal Sig-2 is switched to the light reception signal Sig-1, and Sig-1 is output as the predetermined light reception signal a.

  Prior to the switching timing of β shown in the figure, the selection signal (E / F) is input to the second signal switching unit 13 and switched from E to F as shown in FIG. The predetermined light receiving signal b of the signal switch 11 to which C / D) is not input is selected. As shown in (c), this predetermined light receiving signal b is Sig-4 described above, and Sig-4 in a stable state after a lapse of a predetermined time after the switching timing shown in FIG. As described above, the signal is output from the second signal switching unit 13. Therefore, the output signal of the second signal switching unit 13 is not a light reception signal including switching noise immediately after switching of the signal switchers 10 and 11, but a light reception signal in a stable signal state, and switching noise is reduced.

  In this way, the first signal switching unit 12 switches the light reception signal when the second signal switching unit 13 is in the non-selected state, and the switched light reception signal is output when the second signal switching unit 13 is in the selected state. It is possible to gain a stable time until the received light signal is selected and output. Therefore, as compared with the conventional case of simply delaying the signal with the delay circuit, it is possible to stabilize the signal while eliminating the delay circuit and simplifying the structure, and alternately with the signal switchers 10 and 11. Since the light reception signal is switched, the entire operation cycle can be shortened. In addition, the time between the input timing of the switching signal for switching the received light signal by the signal switchers 10 and 11 and the input timing of the selection signal to the second signal switching unit 13 for selecting the non-selected state is switched. The time is set so that the received light signal is sufficiently stabilized.

  As a result, when there are a plurality of parallel and serially connected signal switchers, when the second signal switching unit 13 is in the non-selected state, the first signal switching unit 12 switches the light reception signal, and when it is in the selected state In addition, since the light reception signal after the switching is output, the switching noise generated at the time of signal switching is not transmitted to the subsequent circuit. Therefore, the switching noise can be reduced easily and reliably, and a stabilized light reception signal can be obtained.

  Next, a second embodiment will be described. As shown in FIG. 4, the second embodiment is different from the first embodiment in that the first signal switching unit 12 receives a plurality of (eight) received light signals (Sig-1 to Sig-8). A switcher 10 and a signal switcher 11 to which a plurality of (eight) light reception signals (Sig-9 to Sig-16) are input are provided in parallel, and each of the signal switchers 10 and 11 has four. One of the signals can be switched. The second signal switching unit 13 switches and outputs predetermined light reception signals (a to h) input from the selected signal switchers 10 and 11. Other configurations are the same as those of the first embodiment.

  In the second embodiment, similarly, a signal that is not selected among the signal switchers 10 and 11 connected to an arbitrary light reception signal (ad or e to h) selected by the second signal switching unit 13. The switch 10 or 11 is switched. For example, if the second signal switching unit 13 is selecting predetermined light reception signals a to d from the signal switch 10, the non-selected signal switch 11 is switched. If the second signal switching unit 13 is selecting the predetermined light reception signals e to h from the signal switch 11, the unselected signal switch 10 is switched.

  As shown in the time chart of FIG. 5, in (a), when a switching signal (C / D) is input to the signal switch 11 and switched from C to D (switching timing of γ in the figure), (b) As shown, the light reception signals Sig-9 to Sig-12 are switched to the light reception signals Sig-13 to Sig-16, respectively, and Sig-13 to Sig-16 are output as predetermined light reception signals e to h (for example, e). To do. On the other hand, after the switching timing of γ in the figure, in (A), when the switching signal (A / B) is input to the signal switch 10 and switched from B to A (switching timing of ε in the figure), ), The light reception signals Sig-5 to Sig-8 are switched to the light reception signals Sig-1 to Sig-4, and Sig-1 to Sig-4 are output as predetermined light reception signals a to d (for example, a). To do.

  Prior to the switching timing of the above-described ε, the selection signals (CH1 to CH8) are input to the second signal switching unit 13 and switched from CH1 to CH4 to CH5 to CH8 as shown in FIG. The predetermined light receiving signals e to h (for example, e) of the signal switch 11 to which the switching signal (C / D) is not input are selected. As shown in (b), the predetermined light receiving signals e to h (for example, e) are Sig-13 to Sig-16 described above. Certain Sig-13 to Sig-16 are output from the second signal switching unit 13 as shown in (d). Therefore, similarly to the above, the output signal of the second signal switching unit 13 is not a light receiving signal including switching noise immediately after switching of the signal switchers 10 and 11, but a light receiving signal in a stable signal state, and switching noise is reduced. Is done.

  Thus, similarly to the first embodiment, when there are a plurality of signal switchers connected in parallel and in a plurality of stages, when the second signal switching unit 13 is in a non-selected state, the first signal switching unit 12 receives a light reception signal. Since the received light signal after the switching is output in the selected state by switching, the switching noise generated at the time of signal switching is not transmitted to the subsequent circuit, so that the switching noise can be reduced easily and reliably. In particular, when a large number of light receiving elements are provided and the number of received light signals increases, switching noise can be reduced easily and the mounting area of the circuit board increases, resulting in an increase in the size and cost of the photoelectric sensor. Can be avoided.

  In each of the above embodiments, the first signal switching unit 12 is provided with two signal switching units in parallel, but only one signal switching unit may be provided. In this case, the first signal switching unit 12 has one signal switch for inputting a plurality of light reception signals, and switches to a predetermined light reception signal among the light reception signals based on the input of the switching signal. The second signal switching unit 13 is provided after the first signal switching unit 12 and selects and outputs the predetermined light receiving signal based on the input of the selection signal. When the selection signal is not input to the second signal switching unit 13, the switching control unit 16 switches to the predetermined light reception signal by the first signal switching unit 12, and the second signal switching unit 13. When the selection signal is input to the second signal switching unit 13, the second signal switching unit 13 outputs a predetermined light reception signal after the switching.

  As a result, when the second signal switching unit 13 is in the non-selected state, the first signal switching unit 12 switches the light reception signal, and when the second signal switching unit 13 is in the selected state, the light reception signal after the switching is output. Since the switching noise that is sometimes generated is not transmitted to the subsequent circuit, the switching noise can be reduced easily and reliably, and a stabilized light receiving signal can be obtained.

  In each of the above embodiments, one or two signal switchers are provided in parallel in the first signal switching unit 12, but three or more signal switchers may be provided in parallel. 13 is provided in the subsequent stage of the first signal switching unit 12, but two or more stages may be provided, and the signal switch may be connected in series in three or more stages.

  In each of the above embodiments, a reflective type is used as the photoelectric sensor. However, the present invention is not limited to this, and a transmissive type or a light shielding type may be used.

1 is a schematic side view showing a photoelectric sensor according to a first embodiment of the present invention. It is a block diagram which shows the photoelectric sensor. It is a time chart figure which shows operation | movement of the photoelectric sensor. It is a block diagram which shows the photoelectric sensor which concerns on 2nd Embodiment. It is a time chart figure which shows operation | movement of the photoelectric sensor.

Explanation of symbols

1: photoelectric sensor 2: light projecting element 3: light receiving element 5: processing circuit unit 12: first signal switching unit 13: second signal switching unit 14: signal noise countermeasure circuit 16: switching control unit 17: signal processing unit 20: Control unit (CPU)

Claims (4)

A first signal switching unit that includes one or a plurality of signal switching units provided in parallel to receive a plurality of light reception signals, and switches to a predetermined light reception signal among the light reception signals based on the input of the switching signal;
A second signal switching unit provided at a subsequent stage of the first signal switching unit to select and output the predetermined light reception signal based on an input of the selection signal;
When the selection signal is not input to the second signal switching unit, the first signal switching unit switches to the predetermined light reception signal and the selection signal is input to the second signal switching unit. A photoelectric sensor comprising: a switching control unit that performs control to output a predetermined light reception signal after the switching from the second signal switching unit in a selected state. A first signal switching unit configured to include a plurality of signal switching units provided in parallel to which a plurality of light receiving signals are respectively input, and each signal switching unit switches to a predetermined light receiving signal among the light receiving signals based on the input of the switching signal; ,
At least one or more stages are provided after the first signal switching unit, select the signal switch based on the input of the selection signal, and switch and output the predetermined light reception signal from the selected signal switch A second signal switching unit;
Of the plurality of signal switching units of the first signal switching unit, the switching signal is input only to a signal switching unit in a non-selected state in which a selection signal is not input to the second signal switching unit, and the predetermined signal is input. Switching to a light reception signal, and among the plurality of signal switchers of the first signal switching unit, the predetermined light reception after the switching from the signal switcher in the selected state in which the selection signal is input to the second signal switching unit A photoelectric sensor comprising: a switching control unit that performs control to output a signal from the second signal switching unit. In claim 1 or 2,
The switching control unit is a photoelectric sensor that outputs, from the second signal switching unit, a predetermined light receiving signal that is in a signal stable state after the switching in the selected state. In claim 1 or 2,
The second signal switching unit sequentially outputs the predetermined light reception signal as a single light reception signal based on an input of a selection signal, and
A signal noise countermeasure circuit for removing signal noise including disturbance light in the sequentially output received light signal;
A photoelectric sensor, comprising: a signal processing unit that processes the light reception signal from which the signal noise has been removed and outputs an object detection signal.

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