JP5227072B2 - Signal output device - Google Patents

Description

  The present invention relates to a signal output device that is connected to a two-contact safety device such as an emergency stop switch or an open / close detection switch, and outputs an operation state of the safety device and a contact abnormality occurrence state.

  An emergency stop switch used in a factory is provided with two contact points that are opened and closed by operating a single operation member in order to improve the reliability of detection of an operation state. Even when the first contact or wiring of the two contacts cannot output the operation signal of the operation member due to an abnormality such as a short circuit or welding, the operation signal of the operation member can be output from the normal second contact. As a two-contact type safety device used in a factory, there is an open / close detection switch for detecting an open / close state of a gate for restricting entry into a hazardous area in addition to an emergency stop switch.

Operation signals of safety devices such as an emergency stop switch and an open / close detection switch are input to the signal output device. The signal output device outputs a detection signal based on an operation signal output from the two contacts of the safety device. The output of the signal output device is input to a drive device of a drive motor, for example. When the safety device has two b contacts (hereinafter referred to as “2b contacts”), the signal output device outputs an on signal if both of the two output signals of the safety device are on. If any of the two output signals is off, an off signal is output. When the two output signals of the safety device are different, the signal output device determines that a contact abnormality has occurred in the safety device and outputs an off signal (see, for example, Patent Document 1).
Japanese National Patent Publication No. 11-502305

  However, the conventional intrinsically safe explosion-proof signal output device cannot detect a short circuit or a failure of an internal circuit between two contacts or wiring. In addition, the relay used in the non-explosion-proof signal output device consumes a large amount of current, and is difficult to use in the intrinsically safe explosion-proof signal output device.

  The object of the present invention is to detect an abnormality such as a short circuit or welding occurring at two contacts or wiring of a safety device, and also to detect a failure of an electronic circuit inside the apparatus. An object of the present invention is to provide a signal output device that can be applied to safety equipment.

  The signal output device according to the present invention is a signal output device connected to a two-contact safety device, and includes a two-phase signal generation circuit and a signal monitoring circuit. The two-phase signal generation circuit generates two inverted signals having opposite phases and supplies the two inverted signals to the two contacts of the safety device. The signal monitoring circuit outputs two monitoring signals based on the output signals of the two contacts of the safety device.

  According to this configuration, the two inversion signals having opposite phases are supplied from the two-phase signal generation circuit to each of the two contacts of the safety device. If the two contact points of the safety device are both normal, the output signals of the two contact points are inverted at a predetermined cycle so as to be in opposite phases. When an abnormality occurs in at least one of the two contacts and these wirings and an abnormality occurs in one or both of the respective output signals, it is determined that a failure has occurred in the safety device or the signal output device.

The signal monitoring circuit includes first and second photocouplers each having a light emitting element driven by respective output signals of two contacts of the safety device, and each of an input terminal and an output terminal of the first photocoupler is a second. Connected to the output and input terminals of the photocoupler .

  When both of the two contacts of the safety device are normal, the light emitting elements of the first and second photocouplers are driven and monitoring signals are output from both. When an abnormality such as a short circuit between the two contacts occurs and the output signals of the two contacts of the safety device have the same phase, the light emitting elements of the first and second photocouplers are not driven, and the first and second No monitoring signal is output from the photocoupler. The occurrence of an abnormality such as a short circuit between two contacts can be detected depending on whether or not a monitoring signal is output.

  It is preferable to further include a mismatch detection circuit that detects whether or not a failure has occurred depending on whether or not two monitoring signals output from the signal monitoring circuit match. The mismatch detection circuit can detect the occurrence of an abnormality such as a short circuit between two contacts based on the monitoring signal.

  It is possible to separate between the safety device and the signal monitoring circuit by further providing an insulating means arranged in each of the two-terminal input lines for the signal monitoring circuit, and to be used for a safety device having an intrinsically safe explosion-proof structure. become able to.

  The insulating means can be constituted by a photocoupler and can also serve as a signal monitoring circuit. Thereby, the circuit configuration can be simplified.

  According to the present invention, it is possible to detect an abnormality such as a short circuit or welding occurring in two contacts of the safety device or their wiring, and it is also possible to detect a failure of an electronic circuit inside the apparatus. It can be applied to structural safety equipment.

  In the following, the signal output device of the present invention will be described as an example applied to a safety device with an intrinsically safe explosion-proof structure, but the signal output device of the present invention is also applicable to a safety device with a non-explosion-proof structure and other devices. can do.

  FIG. 1 is a block diagram of a signal output apparatus according to an embodiment of the present invention. The signal output device 10 outputs a detection signal 100 indicating the operation state of the operation member of the emergency stop switch 20 which is the safety device of the present invention and the occurrence state of the terminal abnormality. The emergency stop switch 20 includes two contacts 21A and 21B configured with 2b contacts in order to improve reliability. As an example, the emergency stop switch 20 is an intrinsically safe safety device used in an explosive gas atmosphere. The safety device may be a two-contact type door switch that detects an open / closed state of an entrance / exit door to a hazardous area in a factory.

  The signal output device 10 includes a power supply circuit 11, a voltage limiting circuit 12, a two-phase signal generation circuit 13, separation circuits 14A and 14B, a signal monitoring circuit 15, signal output circuits 16A and 16B, and a mismatch detection circuit 17.

  The power supply circuit 11 supplies power to each circuit in the signal output device 10. The voltage limiting circuit 12 limits the voltage of the power source supplied to the two-phase signal generation circuit 13 to a voltage required for the intrinsically safe explosion-proof structure. The two-phase signal generation circuit 13 is composed of an oscillation circuit, generates two inverted pulse signals having opposite phases from the power source supplied from the voltage limiting circuit 12, and supplies the two contact points 21A and 21B of the emergency stop switch 20 respectively. Apply.

  The separation circuits 14A and 14B correspond to the insulating means of the present invention, and the emergency stop while insulating between the two contacts 21A and 21B of the emergency stop switch 20 having an intrinsically safe explosion-proof structure and the signal monitoring circuit 15 having a non-explosion-proof structure. The output signal of the switch 20 is transmitted to the signal monitoring circuit 15.

  The signal monitoring circuit 15 outputs two monitoring signals based on the output signal of the emergency stop switch 20 transmitted via the separation circuits 14A and 14B. The signal output circuits 16 </ b> A and 16 </ b> B amplify the monitoring signal output from the signal monitoring circuit 15 and supply the amplified signal to the mismatch detection circuit 17.

  The mismatch detection circuit 17 determines whether or not there is an abnormality such as a short circuit or welding of a contact or wiring in the emergency stop switch 20 based on whether or not the two monitoring signals match. The detection signal 100 of the mismatch detection circuit 17 is supplied to, for example, a drive device that controls driving of a motor that is a power source of equipment in a factory. The drive device controls driving of the motor based on the detection signal 100 supplied from the mismatch detection circuit 17.

  FIG. 2 is a circuit diagram illustrating an example of a circuit configuration of the signal output device 10. The two-phase signal generation circuit 13 includes an oscillation circuit 131, current limiting resistors 132A to 132C, a resistor 133, a transistor 134, and amplifier circuits 135 and 136.

  The oscillation circuit 131 forms an inversion pulse with a predetermined frequency based on the power supply power of the power supply circuit 11 supplied via the voltage limiting circuit 12 having an intrinsically safe explosion-proof structure. The current limiting resistors 132A to 132C limit the current value of the inversion pulse output from the oscillation circuit 131 to be equal to or lower than the intrinsic safety explosion-proof reference value. The resistor 133 and the transistor 134 constitute an inverting amplifier circuit.

  The inversion pulse whose current value is reduced below the intrinsic safety explosion-proof reference value by the current limiting resistors 132 </ b> A to 132 </ b> C is amplified by the amplifier circuit 135 and then supplied to the contact 21 </ b> A via the signal lines 41 and 42. The inversion pulse is inverted and amplified by the resistor 133, the transistor 134, and the amplifier circuit 136, and then supplied to the contact 21B via the signal lines 43 and 44. Therefore, the inversion pulse supplied to the contact 21A and the inversion pulse supplied to the contact 21B are always in opposite phases.

  Output signals from the contact 21A and the contact 21B are input to the signal monitoring circuit 15 via the separation circuits 14A and 14B. Each of the separation circuits 14A and 14B is configured by a photocoupler as an example, but may be configured by a transformer.

  As an example, the signal monitoring circuit 15 includes a first photocoupler 151A and a second photocoupler 151B. The photocouplers 151A and 151B include light emitting elements (light emitting diodes) that are driven by output signals from the two contacts 21A and 21B of the emergency stop switch 20, respectively. The input terminal (the anode of the light emitting diode) and the output terminal (the cathode of the light emitting diode) of the photocoupler 151A are connected to the output terminal and the input terminal of the photocoupler 151B, respectively.

  When the two contacts 21A and 21B of the emergency stop switch 20 are both normal and closed, the output signals of the two contacts 21A and 21B are in opposite phases, and current flows through the light emitting elements of the photocouplers 151A and 151B. The monitoring signal is output from both.

  When an abnormality such as a short circuit between the two contacts 21A and 21B or a wiring abnormality occurs and the output signals of the two contacts 21A and 21B are in phase, no current flows through the light emitting elements of the photocouplers 151A and 151B, and the photocoupler 151A , 151B no longer outputs a monitoring signal.

  When the separating means 14A and 14B are constituted by photocouplers, they can be shared with the photocouplers 151A and 151B of the signal monitoring circuit 15.

  The two monitoring signals output from the signal monitoring circuit 15 are input to the signal output circuits 16A and 16B. The signal output circuits 16A and 16B include amplifier circuits 161A and 161B, respectively. The monitoring signals amplified by the amplifier circuits 161A and 161B are input to the mismatch detection circuit 17.

  As described above, the signal detection device 10 detects the output signals of the two contacts 21A and 21B of the emergency stop switch 20 using the reverse pulses of the opposite phases. When the two contacts 21A and 21B are normal and the operation member of the emergency stop switch 20 is not operated, the photocouplers 151A and 151B are alternately turned on. When the two contacts 21A and 21B are normal and the operation member of the emergency stop switch 20 is operated, no current flows through the light emitting elements of both the photocouplers 151A and 151B, and both the photocouplers 151A and 151B are turned off.

  When a short circuit or welding occurs between the two contacts 21A and 21B, the input terminal sides of both light emitting elements of the photocouplers 151A and 151B are at the same potential, so that no current flows through the light emitting elements, and the photocouplers 151A and 151B. Both turn off.

  When the operation member of the emergency stop switch 20 is operated, or when a short circuit or welding occurs between the two contacts 21A and 21B or between the signal lines (wirings) 41 to 44, the signal monitoring circuit 15 None of the monitoring signals are output. At this time, the mismatch detection circuit 17 does not output a detection signal, power is not supplied to the drive source, and the drive source of the machine can be stopped.

  Since the signal detection apparatus 10 includes the separation circuits 14A and 14B, the signal detection apparatus 10 can be used by being connected to a safety device having an intrinsically safe explosion-proof structure installed in a hazardous area. However, the signal detection device 10 can be used by connecting to a safety device that is not an intrinsically safe explosion-proof structure. In this case, the voltage limiting circuit 12 and the separation circuits 14A and 14B can be omitted.

  Further, when the wiring distance between the emergency stop switch 20 and the signal output device 10 is long, the stray capacitance of the wiring becomes large, and when the frequency of the two-phase signal is high, the signal is attenuated and the signal is normally transmitted. Can not be. Therefore, it is necessary to reduce the frequency of the two-phase signal. However, when the frequency of the two-phase signal is lowered, the capacitor capacity of the circuit is increased, the transformer is increased, and the signal output device 10 is increased in size. Therefore, a frequency conversion circuit may be interposed between the photocoupler 151A and the amplifier circuit 161A and between the photocoupler 151B and the amplifier circuit 161B. As a result, the capacitor capacity between the amplifier circuits 161A and 161B and the transformer and the size of the transformer itself can be prevented, and the signal output device 10 can be miniaturized.

  In addition, as shown in FIG. 3, the mismatch detection circuit 17 in the signal detection device 110 can be omitted by using the mismatch detection circuit 3 that may be provided in an external device such as a safety relay module or a safety controller. . A highly versatile signal detection device 110 can be provided.

  Further, by performing processing corresponding to one a contact and one b contact (hereinafter referred to as 1a-1b contact) in the mismatch detection circuit 3 of the signal detection circuit 110, as shown in FIG. The present invention can also be applied to 1a-1b contact safety devices such as the non-contact safety switch 120.

  FIG. 4 is a block diagram of a signal detection device 210 according to another embodiment of the present invention. The signal detection device 210 is connected to the plurality of emergency stop switches 20. The signal detection device 210 includes a plurality of monitor circuits 18. Each monitor circuit 18 includes a current limiting resistor 18A, a separation circuit 18B, and an output circuit 18C.

  Based on the output signals of the plurality of monitor circuits 18, the operated emergency stop switch 20 among the plurality of emergency stop switches 20 can be identified.

  FIG. 5 is a block diagram of a signal detection device 310 according to still another embodiment of the present invention. The signal detection device 310 includes a drive circuit 19 and is used as a safety device for the door switch 220 for restricting entry / exit into a hazardous area. The drive circuit 19 includes a current limiting resistor 19A, a separation circuit 19B, and an input circuit 19C. The drive circuit 19 supplies a voltage output to the locking solenoid 221 of the door switch 220. The drive circuit 19 may supply a contact output.

  Each of the signal lines 41 to 44 is constituted by a shield wire of each core, and each shield is connected to a circuit ground terminal, whereby not only a short circuit between the contact 20A and the contact 20B but also the contact 20A or the contact 20B. An internal short circuit can also be detected. For example, in the signal detection circuit 10 shown in FIG. 1, when the signal line 41 is short-circuited to the shield, no current flows through the emergency stop switch 20, and when the signal line 42 is short-circuited to the shield, no current flows through the separation circuit 14A.

  The above description of the embodiment is to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments but by the claims. Furthermore, the scope of the present invention is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1 is a block diagram of a signal output device according to an embodiment of the present invention. It is a circuit diagram which shows an example of the circuit structure of the signal output device. It is a block diagram of the signal detection apparatus which concerns on another embodiment of this invention. It is a block diagram of the signal detection apparatus which concerns on another embodiment of this invention. It is a block diagram of the signal detection apparatus which concerns on another embodiment of this invention.

Explanation of symbols

10-signal detection device 12-voltage control circuit 13-2 phase signal generation circuit 14A, 14B-separation circuit 15-signal monitoring circuit 17-mismatch detection circuit 20-emergency stop switch (safety device)

Claims (4)

A signal output device connected to a two-contact safety device,
A two-phase signal generation circuit that generates two inverted signals having opposite phases and supplies the two inverted signals to each of the two contacts;
A signal monitoring circuit that outputs two monitoring signals based on output signals from the two contacts;
Equipped with a,
The signal monitoring circuit includes first and second photocouplers including light emitting elements that are driven based on respective output signals of the two contacts, and an input terminal and an output terminal of the first photocoupler, respectively. A signal output device connected to an output terminal and an input terminal of the second photocoupler . Signal output device according to claim 1, further comprising a mismatch detecting circuit in which two monitoring signal outputted from the signal monitoring circuit detects the presence or absence of a failure depending on whether or not match. Signal output device according to claim 1 or 2 further comprising an insulating means disposed in each of the input lines of the second contact relative to the signal monitoring circuit. The signal output device according to claim 3 , wherein the insulating unit also serves as the signal monitoring circuit.

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