JP4386186B2 - Signal input device - Google Patents

Description

  The present invention relates to a signal input device for taking a signal from a sensor (for example, a photoelectric sensor, a proximity sensor, etc.) into a control device or the like, for example, a signal input device embodied as a communication slave unit or the like of a programmable controller. .

  A building block type programmable controller (PLC) used in the field of factory automation (FA) is composed of a plurality of units. These units include, for example, a power supply unit that supplies power, a CPU unit that controls the entire PLC, and an input device that inputs signals from input devices such as switches and sensors installed at appropriate positions in FA production equipment and equipment equipment. Communicates input and output signals with an input communication slave unit (hereinafter simply referred to as “input slave unit”) via an output unit that sends control output to an output device such as a unit or actuator, or a fieldbus. Examples include a communication master unit, a communication unit for connecting to a communication network such as Ethernet (registered trademark), and communicating with an external personal computer.

  Control in the CPU unit of the PLC is pre-registered by fetching the input signal input from the input unit or the input signal input from the input slave unit via the communication master unit into the I / O memory of the CPU unit (IN refresh). Perform logical operation based on user program written in user program description language (for example, ladder language) (user program execution), write the operation execution result to I / O memory and send it to output unit, or via communication master unit In this process, the data is sent to an output communication slave unit (hereinafter simply referred to as “output slave unit”) (OUT refresh), and then a so-called peripheral service process (peripheral process) is cyclically repeated.

Thus, the programmable controller (PLC) system which provided the communication master unit and the communication slave unit, and enabled it to drive the output apparatus installed remotely via them is described in various literature (for example, (See Patent Document 1).
JP 2003-150244 A

  Various input devices (for example, a photoelectric sensor, a proximity sensor, a limit switch, a push button switch, and the like) are connected to a signal input device such as an input unit or an input slave unit included in the above-described programmable controller system. As a connection structure for connecting a signal input device and an input device, there are a cord connection method through an electric cord and a plug-in connection method in which cases are directly connected through a plug and a socket. In the case of the cord connection method, generally, the electric cord is drawn out from the case of the input device in a fixed manner or a connector detachable manner. The connection between the core wire drawn from the tip of the electric cord and the input device is a screw-fixing structure or press-fit structure using a terminal block on the input device side and a crimp terminal piece on the core wire side, or a plug on the core wire side and a signal input device. This is done via a connector structure using a side receptacle. In the case of the plug-in connection method, a plug or socket is arranged on the case side of the signal input device, and a socket or plug is arranged on the input device side corresponding to this. Thereby, both are mechanically and electrically connected for each case.

  When the input device is an active input device that operates by receiving power supply from the signal input device side, such as a photoelectric sensor or a proximity sensor, the wiring method employed in the connection structure is a three-wire type or a two-wire type. There is a line type.

  More specifically, when a three-wire wiring method is adopted, three terminals of a power receiving terminal, a ground terminal, and a signal terminal are provided on the input device (for example, photoelectric sensor, proximity sensor, etc.) side. Exists. An internal circuit (for example, a sensor circuit unit) of the input device operates by being supplied with power through a power receiving terminal and a ground terminal. The sensing signal generated as a result of the operation is output from the signal terminal to the outside. On the signal input device side (for example, input unit, input communication slave unit, etc.) for this, the device side power supply terminal to be connected to the power supply terminal of the input device and the device side to be connected to the ground terminal of the input device The current values flowing through the three terminals of the ground terminal, the device-side signal terminal to be connected to the signal terminal of the input device, and the internal signal line connected to the device-side signal terminal are divided into an on-current state and an off-current state. There is a discrimination binarization circuit that performs discrimination binarization. And the output state of this discrimination binarization circuit is taken into the apparatus as the on / off state of the three-wire sensor to be connected. That is, if the output state of the discrimination binarization circuit is the on-current state, the connection target 3-wire sensor (for example, a photoelectric sensor, a proximity sensor, etc.) is input as the on-state, and conversely the discrimination binarization circuit. If the output state is an off-current state, the three-wire sensor is input as an off state.

  In the case of an input device adopting a two-wire wiring system, there are two terminals on the input device side: a power supply terminal that is used for both power reception and control output, and a ground terminal. The internal circuit of the input device operates by being supplied with power through these two terminals. A sensing signal generated as a result of the operation is output from the above-described power supply terminal to the outside. In response to this, on the signal input device side, it is connected to the power supply terminal of the input device, the device-side power supply terminal that is used for both feeding and sensing signal input, and the device-side ground to be connected to the ground terminal of the input device There is a discriminating binarization circuit that discriminates the current value flowing through the internal power line connected to the terminal and the internal power line connected to the device side power supply terminal or the internal ground line connected to the device side ground line into an on current state and an off current state. To do. And the output state of this discrimination binarization circuit is taken into the apparatus as the on / off state of the two-wire sensor to be connected. That is, if the output state of the discrimination binarization circuit is an on-current state, the connection target two-wire sensor (for example, a photoelectric sensor, a proximity sensor, etc.) is input as an on state, and conversely the discrimination binarization circuit. If the output state is an off current state, the two-wire sensor is input as an off state.

  Incidentally, a function of detecting an abnormality of an input device connected to a PLC input slave unit, which is one of signal input devices, has been conventionally incorporated. When the input slave unit detects an abnormality of the input device connected to it, it means that it is sent via the fieldbus to the configurator on the fieldbus (the configurator operation software is installed in the personal computer) or the communication master unit on the PLC. Is notified. The configurator that has been notified of the abnormality of the input device performs a specific display (indication of abnormality) on the configurator screen in order to notify the system administrator of the fact. The information sent to the communication master is further sent to the upper personal computer through the peripheral service processing by causing the CPU unit to turn on the patrol light or sound the buzzer. As a result, the system administrator and the field worker can take quick measures such as replacing the input device related to the failure.

  Conventionally, in order to detect an abnormality in an input device, the method adopted by the input slave unit is to use an overcurrent detection unit and a low current detection unit for the current flowing through the power supply path to the input device existing in the input slave unit. To monitor. For example, in the case of an input slave unit corresponding to a three-wire input device having three terminals of a power supply terminal, a ground terminal, and a signal terminal, the power supply path (for example, the ground line) in the input slave unit is excessively connected. A current detection unit and a low current detection unit are interposed. The overcurrent detection unit is a positive temperature coefficient thermistor (commonly known as a polyswitch) that is interposed in the power supply path and substantially increases the resistance value when the current flowing through the power supply path exceeds a predetermined upper limit value. When the potential difference between both ends of the positive characteristic thermistor exceeds a specified value, it can be configured with a comparator that determines and outputs an overcurrent. The low current detector switches and switches (on to off) a low current when a minute resistance interposed in the power supply path and a potential difference between both ends of the minute resistance fall below VBE (forward potential difference between the base and the emitter). A bipolar transistor can be used.

  The electric cord connecting the input slave unit and the input device includes a power line, a ground line, and a signal line as core wires. If the sheath of the electric cord is damaged and the power line and ground line are short-circuited in the middle of the electric cord, or if the power line and ground line are short-circuited on the terminal block of the input communication slave unit, It can be determined by the detection signal. In the electrical cord connecting the input communication slave unit and the input device, the power line or ground line is disconnected or the power line or ground line is disconnected from the terminal block of the input communication slave unit. It can be determined by the detection signal.

  However, since the above-described abnormality determination method merely monitors the current value via the overcurrent detection unit and the low current detection unit, the monitored current value increases the normal on-current value. Unless it shows a value exceeding or showing a value significantly lower than the normal off-current value, no abnormality determination is performed. Therefore, even if the generated failure can be detected, the failure before the occurrence cannot be predicted. In particular, in recent years, in automobile production lines, etc., a large number of photoelectric sensors and proximity sensors are used in a poor environment where coolant is poured. It has been pointed out that there is a problem that a large loss is caused by the occurrence of products, and for the solution, it is desired to predict a leakage failure occurring in these sensors.

  The present invention has been made in view of the above-described technical background, and the object of the present invention is to enter, for example, coolant into a two-wire or three-wire sensor such as a proximity sensor or a photoelectric sensor to be connected. The present invention provides a signal input device having a function of accurately predicting a leakage failure before the leakage failure occurs.

  Another object of the present invention is to provide a signal input device capable of visually or audibly informing when a leakage failure is predicted as described above.

  Another object of the present invention is to provide a signal input device that can flexibly apply the above-mentioned leakage prediction to various types or types of sensors.

  Another object of the present invention is that when a leakage failure occurs in a two-wire or three-wire sensor such as a proximity sensor or photoelectric sensor to be connected due to, for example, intrusion of coolant, the leakage failure occurs. An object of the present invention is to provide a communication slave unit of a programmable controller having a function of accurately predicting the occurrence of occurrence before it occurs.

  Another object of the present invention is to provide a communication slave unit of a programmable controller that can be recognized by the programmable controller when a leakage fault is predicted in the sensor of any channel. There is to do.

  Another object of the present invention is to provide a communication slave unit of a programmable controller capable of appropriately setting the leakage fault detection specification of each channel by remote control via communication.

  Still other objects and operational effects of the present invention will be easily understood by those skilled in the art by referring to the following description of the specification.

The signal input device according to the present invention includes a device-side power supply terminal to be connected to a sensor-side power supply terminal of a 2-wire sensor, a device-side ground terminal to be connected to a sensor-side ground terminal of the 2-wire sensor, and a device side A discrimination binarization circuit for discriminating and binarizing the value of the current flowing through the internal power supply line connected to the power supply terminal or the internal ground line connected to the apparatus-side ground terminal into an on-current state and an off-current state; Then, the output state of the discrimination binarization circuit is taken into the apparatus as the on / off state of the two-wire sensor to be connected. The signal input device further includes a current measuring means for measuring a current value flowing through an internal power line connected to the device-side power supply terminal or an internal ground line connected to the device-side ground line, and an output state of the discrimination binarization circuit. Is set in advance between the measured current value measured by the current measuring means when the is in the off-current state, and the normal off-current value and the normal on-current value of the two-wire sensor. Based on the current value, the leakage information generating means for generating information corresponding to the leakage degree of the two-wire sensor to be connected, and the information corresponding to the leakage degree generated by the leakage information generating means are output to the outside And an earth leakage information output means.

  According to such a configuration, in a two-wire sensor (for example, a proximity sensor), when leakage is started between the power supply terminal and the ground terminal due to intrusion of coolant or the like, as the degree of leakage progresses, Since the current flowing through the internal power supply line or the internal ground line in the off-current state increases significantly compared to the normal value, information corresponding to the degree of leakage is based on the measured current value and the preset current value. This makes it possible to predict a leakage fault.

  Here, “leakage failure” widely means a state in which the sensor becomes unusable due to the progress of leakage. This leakage fault includes, for example, a state where the leakage current increases, so that it cannot be distinguished from normal on-current, and the sensor cannot be determined whether it is on or off. .

  Moreover, various aspects are included for “based on the measured current value and the set current value”. Among these modes, for example, (1) one step somewhere intermediate between the off current value at normal time (consumed in the sensor internal circuit) and the off current value at abnormal time (at the time of electric leakage failure) Or, there are two or more set current values, and when the measured current value exceeds this value, the information corresponding to the degree of electric leakage (“leakage fault is imminent”, “leakage level is about to reach”, etc.) (2) Set current value (current increase rate in this case) somewhere between the off-current increase rate at normal time and the off-current increase rate on the way to an abnormal time (at the time of electric leakage failure) It is possible to include information that generates information corresponding to the degree of electric leakage (such as “leakage of electric leakage failure”) when the increase rate of the measured current value exceeds this.

  At this time, as the “measurement current value”, for example, the measurement current value after the end of the current fluctuation period in the on-off transition period is obtained by delaying the measurement timing by a timer or constantly monitoring the current value to be measured. It is preferable to obtain. This is because even if it is determined as the off-current state, the actual current value to be measured does not instantaneously become the off-current value.

  Another aspect of the signal input device of the present invention is a device-side power supply terminal to be connected to the sensor-side power supply terminal of the 3-wire sensor and a device-side to be connected to the sensor-side ground terminal of the 3-wire sensor. The current value flowing through the ground terminal, the device-side signal terminal to be connected to the sensor-side signal terminal of the 3-wire sensor, and the internal signal line connected to the device-side signal terminal is discriminated into an on-current state and an off-current state. A discriminating binarization circuit for converting into a value. Then, the output state of the discrimination binarization circuit is taken into the apparatus as the on / off state of the three-wire sensor to be connected. This signal input device has a current value flowing through a line on the side where the sensor signal current and the sensor control current are merged, of the internal power line connected to the device side power terminal and the internal ground line connected to the device side ground terminal. The first current measuring means for measuring and the measured current value measured by the first current measuring means when the output state of the discrimination binarization circuit is the off-current state (or the on-current state) On the basis of the set current value for the off-current state (or on-current state) set, the leakage information generating means for generating information corresponding to the degree of leakage of the three-wire sensor to be connected, and leakage information generation And a leakage information output means for outputting information corresponding to the degree of leakage generated by the means to the outside.

  According to such a configuration, in a three-wire sensor (for example, a proximity sensor), due to coolant intrusion or the like, leakage occurs between the power supply terminal and the ground terminal or between the signal terminal and the ground terminal. When the current starts, the current flowing through the internal power supply line or the internal ground line in the off-current state increases as compared with the normal value as the degree of electric leakage progresses, so the measured current value and the preset set current value Based on the above, information corresponding to the degree of electric leakage is generated, and it is possible to predict an electric leakage failure.

  Here, “leakage fault” and “based on the measured current value and the set current value” are as described above. Also at this time, as the “measurement current value”, for example, the measurement current value after the end of the current fluctuation period in the on-off transition period, for example, by delaying the measurement timing by a timer or constantly monitoring the current value to be measured, etc. It is preferable to obtain This is because even if it is determined as the off-current state, the actual current value to be measured does not instantaneously become the off-current value.

  At this time, in a preferred embodiment, there is provided a second current measuring means for measuring a current value flowing through an internal signal line connected to the apparatus-side signal terminal, and in order to generate information corresponding to the degree of electric leakage, When the output state of the value circuit is an off-current state, the measured current value measured by the second current measuring means may be further used. According to such a configuration, the reliability of the information corresponding to the degree of electric leakage can be further enhanced by taking into account the current of the internal signal line in the off-current state as a determination factor. At this time, it is preferable to acquire the measured current value after the end of the current fluctuation period in the on-off transition period as the measured current value for the above reason.

  In a preferred embodiment, in the above-described invention, it is preferable to have a set value changing means for changing the set current value to be compared with the measured current value. According to such a configuration, versatility is improved by appropriately adjusting the set current value in accordance with the type and model of the sensor.

  The communication slave unit of the programmable controller according to the present invention corresponds to each of the channels, the external interface unit for a predetermined number of channels connected to the external device, the communication unit for communicating with the programmable controller, and each channel. And a memory having a storage area.

  The external interface unit of the channel to be connected to the sensor in the external interface unit includes a device-side power supply terminal to be connected to the sensor-side power supply terminal of the 2-wire sensor and a sensor-side ground terminal of the 2-wire sensor. The device side ground terminal to be connected to the internal power line connected to the device side power supply terminal or the current flowing through the internal ground line connected to the device side ground terminal is differentiated into an on-current state and an off-current state. And a discriminating binarization circuit.

  Further, the control unit periodically updates the state of the input signal of the channel assigned to the sensor in the memory according to the output state of the discrimination binarization circuit of the external interface unit of the corresponding channel, In response to an input signal transmission request from the programmable controller via communication, an input signal transmitting means for reading the input signal of the corresponding channel from the channel memory and transmitting it to the programmable controller is provided. .

  In this communication slave unit, among the external interface units for a predetermined number of channels, the external interface unit to be connected to the sensor has current measuring means for measuring the value of the current flowing through the internal power supply line or the internal ground line. Provided, and when the output state of the discrimination binarization circuit is an off-current state, the control unit is based on the measured current value measured by the current measuring means and the preset set current value, Leakage information generation means for generating information corresponding to the degree of leakage of the two-wire sensor connected to the corresponding channel, and leakage information output for outputting information corresponding to the degree of leakage generated by the leakage information generation means to the outside Means.

  According to such a configuration, while maintaining the function of the programmable controller as a communication slave unit, the degree of electric leakage related to each of the two-wire sensors (for example, proximity sensors and photoelectric sensors) connected to each channel is shown. Information can be generated and output to the outside, and a leakage failure can be predicted. In other words, if a leakage fault occurs in a two-wire sensor such as a proximity sensor or photoelectric sensor to be connected due to, for example, intrusion of coolant, accurately predict that before the leakage fault occurs. Is possible.

  The communication slave unit of the programmable controller according to the present invention corresponds to each of the channels, the external interface unit for a predetermined number of channels connected to the external device, the communication unit for communicating with the programmable controller, and each channel. And a memory having a storage area.

  Among the external interface units, the external interface unit of the channel to be connected to the sensor includes a device-side power supply terminal to be connected to the sensor-side power supply terminal of the 3-wire sensor and a sensor-side ground terminal of the 3-wire sensor. The device side ground terminal to be connected to the device side signal terminal to be connected to the sensor side signal terminal of the three-wire sensor, and the current value flowing through the internal signal line connected to the device side signal terminal as the on-current state There is provided a discrimination binarization circuit that binarizes and discriminates into an off-current state.

  Further, the control unit periodically updates the state of the input signal of the channel assigned to the sensor in the memory according to the output state of the discrimination binarization circuit of the external interface unit of the corresponding channel, In response to an input signal transmission request from the programmable controller via communication, an input signal transmitting means for reading the input signal of the corresponding channel from the channel memory and transmitting it to the programmable controller is provided. .

  Among the external interface units for a predetermined number of channels, the external interface unit to be connected to the sensor includes a sensor signal among an internal power line connected to the device side power terminal and an internal ground line connected to the device side ground terminal. First current measurement means for measuring a current value flowing through a line on the side where the current and the sensor control current merge is provided, and the control unit has an output state of the discrimination binarization circuit in an off-current state (Or on-current state) based on the measured current value measured by the first current measuring means and the preset current value for the off-current state (or on-current state) Leakage information generation means for generating information corresponding to the degree of leakage of the target 3-wire sensor, and information corresponding to the degree of leakage generated by the leakage information generation means is output to the outside. And electrostatic information output means, are provided.

  According to such a configuration, while maintaining the function of the programmable controller as a communication slave unit, the degree of electric leakage related to each of the three-wire sensors (for example, proximity sensors and photoelectric sensors) connected to each channel is shown. Information can be generated and output to the outside, and a leakage failure can be predicted. In other words, if a leakage failure occurs in a three-wire sensor such as a proximity sensor or photoelectric sensor to be connected due to, for example, intrusion of coolant, accurately predict that before the leakage failure occurs. Is possible.

  In a preferred embodiment of the communication slave unit corresponding to the above-described three-wire sensor, the communication slave unit has second current measuring means for measuring a current value flowing through an internal signal line connected to the device-side signal terminal, which corresponds to a degree of electric leakage. In order to generate information, when the output state of the discrimination binarization circuit is an off-current state, the measured current value measured by the second current measuring unit may be further used. According to such a configuration, the reliability of the information corresponding to the degree of electric leakage can be further enhanced by taking into account the current of the internal signal line in the off-current state as a determination factor.

  In a preferred embodiment of the communication slave unit corresponding to the two-wire sensor or the three-wire sensor described above, the leakage information output means is applicable in response to the arrival of a predetermined transmission request via communication. It may be configured to be leakage information transmission means for transmitting the leakage information of the channel to the transmission request source. According to such a configuration, when a leakage failure is predicted in the sensor of any channel, the fact can be recognized on the side of a programmable controller, a host computer, or the like connected through communication.

  In a preferred embodiment of the communication slave unit corresponding to the above-described 2-wire sensor or 3-wire sensor, the leakage information output means visually displays information corresponding to the degree of leakage generated by the leakage information generation means to the outside. Or may be output audibly. According to such a configuration, when the leakage failure prediction is performed in the sensor connected to one of the channels, the fact is also notified visually or audibly on the communication slave unit side.

  In a preferred embodiment of the communication slave unit corresponding to the two-wire sensor or the three-wire sensor described above, the set current value of the corresponding channel is determined in response to the arrival of a predetermined request via communication. You may make it further contain the setting electric current value update means updated to the value taught by the request | requirement or the learned value. According to such a configuration, it is possible to appropriately set the leakage fault detection specification for each channel via communication.

  As is apparent from the above description, according to the present invention, when a leakage failure occurs in a 2-wire or 3-wire sensor such as a proximity sensor or a photoelectric sensor to be connected due to, for example, intrusion of coolant or the like. It is possible to accurately predict the occurrence of an electrical leakage failure before it occurs.

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  A configuration diagram of the entire PLC system including an input slave unit to which the present invention is applied is shown in FIG. As shown in the figure, the entire PLC system is composed of one PLC main body 1, two input slave units 2 and 2, one output slave unit 3, and one input / output slave unit. 4 are connected via a fieldbus 5 by communication. Incidentally, what is indicated by reference numeral 6 in the figure is a configurator constituted by a personal computer. As is well known to those skilled in the art, the configurator 6 is an information processing apparatus having a function of managing the network constituting the field bus 5 in an integrated manner.

  The PLC main body 1 includes a power supply unit 101, a CPU unit 102, an I / O unit 103, and a communication master unit 104. These units 101 to 104 are detachably attached to the PLC bus 105 laid on the backplane. The power supply unit 101 supplies power to the CPU unit 102, the I / O unit 103, and the communication master unit 104 via a power line on the backplane. The CPU unit 102 performs overall control of the entire PLC body 1. The I / O unit 103 has a function of taking input data from various input devices (for example, sensors and switches) and sending output signals to various output devices (for example, relays and actuators). The communication master unit 104 is used to perform data communication with the input slave units 2 and 2, the output slave unit 3, and the input / output slave unit 4 via the field bus 5.

  Of the two input slave units 2, 2, for example, 16 sensors 7, 7,... Are connected to the input slave unit 2 depicted on the left side in the drawing. As these sensors 7, sensor internal circuits operate upon receiving power supply, such as a photoelectric sensor, a proximity sensor, a displacement sensor, etc., and as a result, a sensor output signal is generated, Output function. In this example, the input slave unit 2 operates with power supplied from a DC power source 11 that is a local power source, and the input slave unit 2 is also connected to, for example, 16 sensors 7, 7,. Power is supplied from the DC power supply 11 through the power supply.

  Of the two input slave units 2, 2, for example, 16 switches 8, 8,... Are connected to the input slave unit 2 depicted on the right side in the drawing. As these switches 8, 8, passive switches such as limit switches and push button switches are employed. In this case as well, the input slave unit 2 operates with power supplied from the DC power supply 11.

  Various output devices such as a relay 9 and an actuator 10 are connected to the output slave unit 3. The output slave unit 3 operates with power supplied from the DC power supply 11, and output devices such as the relay 9 and the actuator 10 connected to the output slave unit 3 are also supplied with power from the DC power supply 11 via the output slave unit 3. The

  Input devices such as the sensor 7 and output devices such as the relay 9 are connected to the input / output slave unit 4 in a mixed manner. The input / output slave unit 4 also operates by being supplied with power from the DC power supply 11, and the sensor 7 and the relay 9 connected to the input / output slave unit 4 are also supplied with power from the DC power supply 11 through the input / output slave unit 4. Is done.

  As is well known to those skilled in the art, the control in the CPU unit 102 of the PLC main body 1 is an input slave unit via the input signal input from the input unit constituting the I / O unit 103 or the communication master unit 104. The input signals input from 2 and 2 are taken into the I / O memory of the CPU unit 102 (IN refresh), and logical operation is performed based on a user program written in a pre-registered user program description language (for example, ladder language) ( (User program execution), the operation execution result is written in the I / O memory and sent to the output unit constituting the I / O unit 103, or sent to the output slave unit 3 via the communication master unit 104 (OUT refresh). After that, so-called peripheral service processing (peripheral processing) It is a process, such as repeatedly performed cyclically.

  Next, an external view of the input slave unit 2 to which the present invention is applied is shown in FIG. As shown in the figure, the input slave unit 2 has a rectangular parallelepiped box-shaped case 201. The case 201 can be mounted on a DIN rail (not shown) via a DIN rail mounting hook 202. On the front surface side of the case 201, 16 connector sockets 203, 203,... Each connector 203, 203... Is provided with four terminals. As shown on the right side in the figure, an electrical cord 701 is drawn out from the amplifier case of the fiber photoelectric sensor 7a, and a connector plug 702 is attached to the tip thereof. Similarly, the electrical cord 701 is also drawn from the proximity sensor 7b, and the connector plug 702 is attached to the tip thereof. These connector plugs 702 and 702 are detachably attached to the connector socket 203 on the case 201 side described above. As shown in the figure, it goes without saying that four terminals (terminal pins) are also built in the connector plug 702 on the sensor side.

  On the upper part of the case 201 of the input slave unit 2, there are 16 operation indicator lamps 205, one network status (MS) indicator lamp 206, one module status (NS) indicator lamp 207, and two Rotary switches 208 and 209 are provided.

  Each of the 16 operation indicator lamps 205 displays the operation state of various sensors connected to each of the 16 connector sockets 203. In this example, a yellow light is assigned to an on-state sensor, a light is turned off to an off-state sensor, and a red light is assigned to an abnormal sensor. In this embodiment, the notification of the leakage failure prediction of the sensor (for example, proximity sensor, photoelectric sensor, etc.) of the corresponding channel is made by the red lighting state of the operation indicator lamp. The network status indicator lamp 206 displays the state of network communication (communication with the master). The module status indicator 207 displays the operating state of this slave unit. In this example, green lighting is assigned to the normal state, and red lighting is assigned to the abnormal state. Therefore, by observing the network status indicator lamp 206 and the module status indicator lamp 207, the operator can understand the operation state of the input slave unit 2 and the state of the network (field bus 5) to which the input slave unit 2 is connected. it can. The two rotary switches 208 and 209 are used to set the node address of the input slave unit 2. In the figure, the rotary switch 209 located on the left side is assigned to one digit, and the rotary switch 208 located on the right side is assigned to the tens digit. For example, when setting the address “12”, “1” is set, and “2” is set to the right rotary switch 208. A field bus connector 204 for connecting to the field bus 5 is provided on the left side of the front surface of the case 201.

  In the example of FIG. 2, the electrical cord 701 extending from the sensor side and the input slave unit 2 are connected to each other via the connector plug 702 and the connector socket 203, but this may be replaced with terminal block connection. it can. In that case, 16 sets of terminal blocks each having four terminals are provided on the input slave unit 2 side, and each of the four electric wires (core wires) drawn from the electric cord 701 on the sensor side has, for example, A crimp terminal piece is attached, and both are electrically connected by screwing or a press-fit structure.

  A block diagram showing the electrical hardware configuration of the input slave unit is shown in FIG. As shown in the figure, the input slave unit 2 includes a microprocessor (MPU) 21, a ROM 22, a RAM 23, a fieldbus communication unit 24, a sensor interface unit 25, a display unit 26, and an operation unit 27. Including. These circuit elements 21 to 27 are connected to each other via an internal bus 28, and operation power to these circuit elements 21 to 27 is supplied from the DC power supply 11 described above.

  The microprocessor (MPU) 21 implements various functions necessary as an input slave unit by executing various system programs stored in the ROM 22 as necessary. The ROM 22 stores a system program for causing various functions necessary for the input slave unit. Various system programs which will be described later with reference to flowcharts are also stored in the ROM 22. The RAM 23 is used as a work area when the microprocessor (MPU) 21 executes various system programs. In addition, the RAM 23 includes various information (for example, an ON state) regarding each of the 0th to 15th channels , OFF state, short circuit (leakage) state, non-short circuit (non-leakage) state, etc.) are stored. The fieldbus communication unit 24 is connected to the fieldbus 5 via the fieldbus connector 204 and executes data communication control with the communication master unit (see FIG. 1) 104. As described above with reference to FIG. 2, the display unit 26 includes 16 operation indicator lamps 205, one network status indicator lamp 206, and one module status indicator lamp 207. The operation unit 27 includes two rotary switches 208 and 209 as described above with reference to FIG.

  Next, the sensor interface unit 25 will be described in detail. The sensor interface unit 25 includes 16 external interface units (not shown) corresponding to 0 channel to 15 channels. Sensors (eg, photoelectric sensors, proximity sensors, etc.) 7 can be connected to these 16 external interface units. As described above, the connection between the sensor 7 and the external interface unit is performed via the connector socket 203 and the connector plug 702. As will be described below, in the present invention, when a leak is started in any of these sensors 7 due to the intrusion of the coolant, before the final short circuit fault (leakage fault) is reached. In addition, it is possible to predict this and notify the fact by the red lighting of the operation indicator lamp 205, or to notify the programmable controller side via communication.

  Here, the earth leakage failure of the sensor, which is a problem of the present invention, particularly, the earth leakage failure of the most frequent proximity sensor will be described in detail with reference to FIGS.

  A sectional view of the proximity sensor showing the coolant intrusion path is shown in FIG. In the figure, a is a proximity sensor, b is a sensor case, c is a detection coil assembly, e is a sealing resin, f is a sensor cord, g is an outer skin, and h is a core wire. As is apparent from the figure, the proximity sensor a has a cylindrical case b. The tip of the case b is closed by the detection coil assembly e. In the sensor case b, a circuit assembly d is accommodated, and the gap is filled with a sealing resin e. A sensor cord f is drawn out from the rear end portion of the sensor case b, and the sensor cord f has a core wire h in the outer skin g.

  By the way, this type of proximity sensor a is often installed in an inferior environment where coolant flows down in an automobile production line or the like. In such a case, the detection coil assembly c and the circuit assembly d in the sensor case b are temporarily sealed with the sealing resin e, but the circuit assembly d repeatedly expands and contracts due to the generated heat. The coolant penetration from the outer skin g of the sensor cord f cannot be completely prevented. Therefore, as indicated by the arrows in the figure, the coolant that has entered from the sensor cord f enters the case b through the sensor cord f, resulting in a leakage current in the circuit assembly d. For this reason, when this type of proximity sensor a is left under a condition where coolant is poured for a long time, the core wires h and h are finally short-circuited due to the leakage current, resulting in malfunction.

  An equivalent circuit showing normal leakage current and short-circuit current is shown in FIG. In the figure, i is a proximity main circuit, j is a short-circuit current path, k is a load, l is a power supply, IL1 is a normal leakage current, and IL2 is a short-circuit current. As is apparent from the figure, there is a normal leakage current IL1 in order to operate the proximity main circuit i even when the proximity sensor a is in a normal state. On the other hand, when the short circuit current path j is generated due to the entry of the coolant into the proximity sensor a, the short circuit current IL2 flows. When the short-circuit current IL2 becomes a value that cannot be ignored, the load k malfunctions.

  Although the value of the normal leakage current IL1 varies depending on the type of the proximity sensor, the value of the normal leakage current IL1 maintains a substantially constant value when looking at a specific type of proximity sensor product. For example, as shown in FIG. 29, regarding the product of the applicant company (form E2EC), there are four types of product variations, but the value of the leakage current in the normal state is approximately 0.5 to 0.7 mA. It is in the range. As shown in FIG. 30, when looking at other products of the same company (form E2E-X □), although there are three types of product variations, the value of the leakage current in the normal state is 0.4-0. It is within the range of 6 mA. As shown in FIG. 31, when looking at other products of the same company (E2-X □ D □), there are four types of product variations, but the value of leakage current in the normal state is about 0.4 to It is within the range of 0.5 mA.

  FIG. 32 shows a graph of the change in leakage current with time due to the penetration of the proximity sensor coolant. As described above, the value of the leakage current at the normal time is substantially constant, and is maintained at, for example, a normal leakage current level (I0) or lower. On the other hand, when leakage current begins to flow due to coolant intrusion or the like, the entire leakage current (normal leakage current IL1 + short-circuit current IL2) gradually increases and eventually exceeds the load operation level (I1). Become. However, since there is a region that does not belong to any of the normal leakage current level (I0) and the load operation level (I1), if the failure prediction detection level (I2) is set in this region, the leakage current Prior to reaching the load operation level (I1), it is possible to predict a failure and notify the outside to that effect. In the present invention, a short-circuit failure (leakage failure) can be predicted for the 2-wire and 3-wire proximity sensors based on the above operating principle.

  Next, FIG. 4 shows a circuit diagram (part 1) in a connection state between the external interface unit (for one channel) of the input slave unit and the two-wire proximity sensor.

  First, the two-wire proximity sensor 7A will be described in detail. The two-wire proximity sensor 7A has a power terminal P1 and a ground terminal G1 as external terminals. A proximity main circuit 71 and an output transistor 72 are built in the sensor 7A. The proximity main circuit 71 is for realizing an operation as a proximity sensor, and includes, for example, a detection coil, an oscillator, a comparator for switching, and the like. The proximity main circuit 71 is connected between the power supply terminal P1 and the ground terminal G1, and operates with power supplied from these terminals. “H” indicating an object detection state or “L” indicating an object non-detection state is output to the output terminal OUT of the proximity main circuit 71. In this example, the output transistor 72 is an NPN type, the collector terminal is connected to the power supply terminal P1, the emitter terminal is connected to the ground terminal G1, and the base terminal receives a signal from the output terminal OUT of the adjacent main circuit. Entered. As is apparent from the figure, a leakage current (normal leakage current) that flows through the proximity main circuit 71 flows between the power supply terminal P1 and the ground terminal G1 even when no leakage occurs. . On the other hand, as described above, this type of two-wire proximity sensor 7A is often installed in a poor environment in which coolant is poured, particularly in an automobile production line. In that case, the coolant enters the case of the sensor 7A and electric leakage is started. The reference sign L in the figure is the path of the leakage current at the time of this leakage.

  Next, the external interface unit 25A will be described in detail. The external interface unit 25A has a power supply terminal P2 and a ground terminal G2 as external terminals. The external interface unit 25A is connected to the internal bus 28 via the internal bus interface 2510. Further, the external interface unit 25A is supplied with power from the DC power supply 11. More specifically, the positive side terminal of the DC power supply 11 is connected to the power supply terminal P2 via the internal power supply line PL, and the negative side terminal is connected to the ground terminal G2 via the internal ground terminal GL. A resistor 2501 and a resistor 2502 are inserted in series in the internal power supply line PL. The photocoupler 2503 functions as a discrimination binarization circuit that discriminates the value of the current flowing through the internal power supply line PL into an on-current state and an off-current state. The light emitting diode 2504 of the photocoupler 2503 is connected in parallel with the resistor 2502. The phototransistor 2505 of the photocoupler 2503 is pulled up to the internal power supply line PL via the resistor 2506, and an output signal is generated at the collector terminal. Therefore, the photocoupler 2503 is “L” when the current flowing through the internal power supply line PL is equal to or greater than a specified value (on-current state), and conversely, “H” when the current is less than the specified value (off-current state). " The above-mentioned prescribed value is determined in advance according to the ON state and OFF state of the two-wire proximity sensor 7A. However, even if the current flowing through the internal power supply line PL is in the on-current state, this does not necessarily mean that the sensor 7A is in the on-state. That is, as described above, if a large amount of leakage current exists through the leakage current path L, a large current flows through the internal power supply line PL even if the output transistor 72 is in the OFF state, and the photocoupler 2503 May mistake this as an on-current state. In order to solve this problem, in the present invention, a current measuring means for measuring a current value flowing through the internal ground line GL is provided. This current measuring means includes a current detection resistor 2507 and an AD converter 2508. That is, the current detection resistor 2507 is inserted in the internal ground line GL2, and the potential difference between both ends of the resistor 2507 is converted into a multi-bit digital signal through the AD converter 2508. The AD converter 2508 is set to a resolution of, for example, about 10 bits so that a weak current flowing through the internal ground line GL can be detected. Note that the insulation separation circuit 2509 provided on the output side of the AD converter 2508 is configured by, for example, providing a large number of photocouplers in parallel. The on / off current state of the photocoupler 2503 and the detected current value of the AD converter 2508 obtained in this manner are taken into the internal bus 28 via the internal bus interface 2510 and finally used for calculation in the MPU 21.

  The two-wire proximity sensor 7A and the external interface unit 25A are connected by a sensor cord 701. That is, the power terminal P1 of the sensor 7A and the power terminal P2 of the external interface unit 25A are connected via the power core 701P in the sensor cord 701. Similarly, the ground terminal G1 and the ground terminal G2 are connected to each other in the sensor cord 701. It is connected via a ground core wire 701G. Incidentally, what is indicated by the symbol Ig is a current flowing through the internal ground line GL.

  FIG. 5 shows a circuit diagram (part 2) of the connection state between the signal input unit (for one channel) of the input slave unit and the two-wire proximity sensor. The circuit shown in FIG. 5 differs from the circuit shown in FIG. 4 only in the position of the current detection resistor. That is, in the case of the circuit of FIG. 4 described above, the current detection resistor 2507 is inserted in the internal ground line GL, whereas in the circuit shown in FIG. It is inserted in the internal power line PL. The AD converter 2512 converts the potential difference between both ends of the current detection resistor 2511 into a multi-bit digital signal. In addition, in FIG. 5, the same components as those in FIG.

  Next, the short-circuit prediction principle employed by the present invention will be described. FIG. 6 shows a graph showing a change with time in the proximity of the sensor OFF current of the proximity sensor, and FIG. 7 shows an example of the state change and the flowing current. As is clear from these figures, in the normal state where no leakage occurs, the value of the sensor OFF current is maintained at the normal OFF current (Ioff), but the leakage starts due to intrusion of the coolant. Then, the value of the sensor OFF current gradually increases and finally shifts to a leakage fault state, that is, a short circuit state. Therefore, in the present invention, as shown in FIG. 6, a short-circuit prediction threshold (Ith) is provided to perform a short-circuit prediction associated with a leakage. As shown in FIG. 7, taking one of the proximity sensor products of the applicant company as an example, the current at normal OFF is about 0.4 mA, and the current at normal ON is about 3 to 7 mA. Therefore, the short-circuit prediction threshold (Ith) for failure prediction may be set to 1.2 mA or more, for example.

  Next, FIG. 8 shows the relationship between the ON / OFF state of the photocoupler and the current (when normal). If the output transistor 72 of the sensor 7A changes from the OFF state to the ON state at a certain point in time, the current flowing through the internal ground line GL changes from a normal OFF current (about 0.4 mA) to a normal ON current (about 3 to 7 mA). ). In the meantime, when the current flowing through the internal ground line exceeds a threshold value Ith (on / off) for distinguishing between the on-current state and the off-current state, at time t0, the on / off state of the photocoupler 2503 is , Instantaneous transition from the OFF state to the ON state. Thereafter, when the output transistor 72 in the sensor 7A again changes from the on state to the off state, the current in the internal ground line falls below the threshold value Ith (on / off) at time t1, and the photocoupler 2503 is in the on state. It changes instantaneously from OFF to OFF state. Thereafter, as long as the sensor 7A is normal, the OFF current flowing through the internal ground line GL is maintained at about 0.4 mA. Thereafter, when the output transistor 72 in the sensor 7A changes from the OFF state to the ON state again, the current of the internal ground line GL also starts increasing, and exceeds the threshold value Ith (on / off) at time t4. Then, the photocoupler 2503 instantaneously changes from the OFF state to the ON state. Thereafter, the same operation is repeated. On the other hand, when the leakage starts with the intrusion of the coolant and the current value Ier exceeds the short-circuit prediction threshold value Ith (er) as indicated by the phantom line in the figure, based on that, It is possible to predict that the degree of electric leakage has progressed considerably and the short-circuit state is imminent.

  However, it should be noted that even if the photocoupler 2503 changes from the ON state to the OFF state due to the change of the output transistor 72 in the sensor 7A from the ON state to the OFF state, the change point There is some delay time from the time t1 when the current actually drops to the normal OFF current (about 0.4 mA) from the internal ground line. That is, even in a normal state where no short circuit has occurred, the current of the internal ground line has a short circuit failure threshold value Ith (er) within a certain period of time immediately after the photocoupler changes from the ON state to the OFF state. If this is not taken into consideration, there is a possibility that even if the sensor 7A is normal, it is predicted that a short-circuit failure will be near. Similarly, another point to be noted is that, as shown at time t3, in the process in which the output transistor 72 in the sensor 7A changes from the off state to the on state, the sensor 7A is normal. In other words, there may be a state in which the photocoupler is in the OFF state and the current of the internal ground line exceeds the short-circuit threshold value Ith (er). Therefore, if a short-circuit failure is predicted immediately based on the fact that the photocoupler is OFF and the current of the internal ground line exceeds the threshold value Ith (er) during such a period, the state of the sensor 7A is mistakenly recognized. Will be.

  Therefore, in the present invention, even if it is determined at time t1 that the photocoupler is in the OFF state and the current of the internal ground line exceeds the threshold value Ith (er), this is immediately recognized as nearing short circuit. Without referring to this, the current of the internal ground line at time t2 further delayed by the time Td is referred to, and if this is equal to or less than the threshold value Ith (er), the sensor 7A is determined to be normal. Further, at time t3, even if the photocoupler is in an OFF state and the current of the internal ground line exceeds the threshold value Ith (er), the photo at time t5 that is further delayed by time Td is not immediately recognized as being short-circuited. With reference to the ON / OFF state of the coupler, if this is the ON state, the sensor 7A is determined to be normal. In the short-circuit check process (step 905) described in detail later, the determination algorithm described above with reference to FIGS. 6 to 8 is incorporated.

  Next, a general flowchart showing the processing contents of the input slave unit is shown in FIG. The system program shown in this flowchart is stored in the ROM 22 shown with reference to FIG.

  In the figure, when the process is started by turning on the power, an initialization process is first executed, and various flags and registers are initialized (step 901). This initial setting can include updating the channel information shown in FIG.

  When the initialization process (step 901) is completed, a reception check process (step 902) is subsequently executed. In this reception check process (step 902), it is checked whether any message has come from the communication master unit 104 or the configurator 6 shown in FIG. 1 via the fieldbus communication unit 24 shown in FIG. . As a result of the reception check, if it is determined that there is no reception (step 903 YES), the input update process (step 904), the short circuit check process (step 905), and various service processes (step 906) are executed in order.

  In the input update process (step 904), a process of updating the photocoupler state information for each channel stored in the RAM 23 is executed. That is, as shown in FIG. 12, channel information of the input slave unit is stored in the RAM 23. This channel information stores the photocoupler state, failure prediction flag, and OFF threshold current (for short circuit prediction) for each of channels 0 to 15. In this input update process (step 904), the state of the photocoupler 2503 included in the external interface unit of each channel is read, and the process of writing this in the state region of the photocoupler of the corresponding channel is executed. .

  When the input update process (step 904) is completed, a short circuit check process step 905), which is a main part of the present invention, is executed. A detailed flowchart of the short-circuit check process (for one channel) regarding the two-wire sensor is shown in FIG. Hereinafter, the details of the short-circuit check process will be described with reference to the flowchart of FIG. 11 and the waveform diagram of FIG.

  When the process is started in FIG. 11, it waits for the photocoupler 2503 to change from the ON state to the OFF state (step 1101). In this state, when the photocoupler 2503 changes from the ON state to the OFF state (step 1101 OFF), a waiting process for a predetermined time (step 1102) is executed. Here, the fixed time means the time Td described above with reference to FIG.

  When the waiting process for a predetermined time (step 1102) is completed, the state of the photocoupler 2503 is referred again (step 1103). If the photocoupler 2503 is still in the OFF state (step 1103), the current monitoring process (step 1104) is executed assuming that the current fluctuation period in the on / off transition period has ended and the current has already shifted to the current stabilization period. Is done. In this current monitoring process (step 1104), a process of reading the current Ig flowing through the internal ground line GL into the CPU via the current detection resistor 2507 and the AD converter 2508 shown in FIG.

  When the current monitoring process (step 1104) ends, it is determined whether or not the monitored current value Ig is equal to or greater than the short-circuit prediction threshold Ith (er) (step 1105). Here, if the current Ig is less than the threshold value Ith (er), steps 1103 to 1105 are repeatedly executed as long as the state continues.

  If the state of the photocoupler returns from the OFF state to the ON state in this state (YES in step 1103), the process returns to the beginning of the program again to wait for the photocoupler to change from the ON state to the OFF state. The above is the operation in a normal state where no leakage occurs in the sensor 7A.

  On the other hand, when a leak occurs in the sensor 7A, in the determination process (step 1105), it is determined that the threshold value is exceeded (YES in step 1105). A process (step 1106) for confirming the state of the photocoupler is executed later. Thereafter, it is determined whether or not the state of the photocoupler has changed (step 1107). Here, if a true leakage occurs in the sensor 7A, it is determined that there is no change in the state of the photocoupler (NO in step 1107), and in this case, a short circuit shown in FIG. The prediction flag is set to “1”, and at the same time, the short-circuit prediction LED lighting process (the operation indicator lamp 205 shown in FIG. 2 is lit red) is executed (step 1108).

  As described above with reference to FIG. 8, when the current monitoring process (step 1104) is performed at time t3 and an incorrect current value is measured, in the determination process of step 1107, Since it is determined that the state has changed (YES in step 1107), the process is returned to the beginning of the program, and the short-circuit prediction operation (step 1108) is not erroneously executed.

  As shown in FIG. 12, as a result of the short-circuit check process being executed in each channel, the content of the short-circuit prediction flag constituting the channel information is set to “1” or “0” for each channel. In this example, only the four channels are set to “1”, whereby the state nearing a short circuit is stored in the four-channel sensor 7A.

  Returning to FIG. 9, when the short circuit check process (step 905) is completed, various service processes (step 906) are executed. In these various service processes (step 906), the learning process shown in FIG. 13 is executed as one of the service processes.

  That is, FIG. 13 shows a detailed flowchart of the learning process (for one channel) included in various service processes. When the process is started in the same figure, it waits for the state of the photocoupler to change from the ON state to the OFF state (Step 1301 OFF), executes a waiting process for a certain time (Step 1302), and at the end, Reference is again made to the state of the photocoupler (step 1303), and current monitoring processing is executed only when this is still in the OFF state (step 1303 OFF) (step 1304). The reason why such complicated processing is performed is to monitor the current value in the current stabilization period while avoiding the current fluctuation period in the on-off transition period, as described above.

  After monitoring the current (step 1304), the state of the photocoupler is confirmed after a certain period of time (step 1305) as in the previous case, and only when there is no change in the state (step 1306 NO), the monitored current value Is recorded (step 1307), and after waiting for a learning process end command to be received by an operation from the operator or the end of the timer (step 1308 YES), the process proceeds to a threshold value generation process (step 1309). In this threshold value generation process, the threshold value is calculated from the recorded current value. This calculation is executed by, for example, obtaining a peak value or an average value and setting 1.5 times as a threshold value.

  As a result of executing the processing shown in FIG. 13, the normal OFF current value is automatically monitored, and it is confirmed that the monitored value is not for the current fluctuation period. In addition to recording, a threshold value for short circuit prediction is automatically obtained from the recorded current value by a predetermined arithmetic expression, and so-called learning processing is executed. The threshold value thus learned is stored in the channel memory as an OFF threshold current (for short-circuit prediction) for each channel, as shown in FIG.

  Returning to the flowchart of FIG. 9, following the reception check process (step 902), when it is determined that there is reception (NO in step 903), the received message is decoded (step 907). If the received message is an input transmission request (YES in step 908), an input data reading process (step 909) and a short-circuit prediction flag reading process (step 910) are executed. Here, in the input data reading process (step 909), the state of the photocoupler is read as input data from the channel information shown in FIG. In the short-circuit prediction flag reading process (step 910), the content of the short-circuit prediction flag included in the channel information is read.

  Subsequently, a response message creation process is executed (step 911), a response message is created in a predetermined format using the previously read input data and the short-circuit prediction flag, and the response message thus obtained is transmitted ( In step 912), the signal is transmitted to the transmission source node (communication master unit 104, configurator 6, host PC, etc.) by the action of the fieldbus communication unit 24.

  In the example described with reference to FIG. 9, the value of the short-circuit prediction threshold is constantly updated by the learning process, but this is limited to the case where a predetermined message arrives by communication. Alternatively, it may be executed selectively. FIG. 10 shows a short-circuit prediction threshold update process (teaching process, learning process) based on the result of decoding the communication message. The process shown in FIG. 10 is replaced with the determination process (step 908) in the flowchart of FIG.

  That is, in FIG. 10, when it is determined that the decrypted message is a short-circuit check threshold teaching request (step 1003 YES), threshold teaching processing (step 1004) is executed. In this threshold value teaching process (step 1004), the channel name and the short-circuit check threshold value are read from the received and decoded message, and are read when the corresponding channel in the channel information shown in FIG. Stored as threshold current (for short circuit prediction). On the other hand, as shown in FIG. 14, the optimum short circuit prediction threshold value for each sensor type is stored in advance in the short circuit prediction threshold value table held on the tool side of the PLC. In this example, the short-circuit threshold for sensor type A is 1.2 mA, the short-circuit prediction threshold for sensor type B is 1.0 mA, and the short-circuit prediction threshold for sensor type C. The value is 2.0 mA. These short-circuit prediction threshold values are obtained in advance corresponding to each sensor type. Then, by editing the sensor type and the short-circuit prediction threshold according to a predetermined format, a transmission message is generated, and this is transmitted from the PLC communication master unit 104 via the field bus to the corresponding communication slave unit. On the slave unit side, this is received and decoded, and the short-circuit prediction threshold value and the corresponding channel information corresponding to the sensor type are extracted, and this is stored in the memory as channel information as shown in FIG.

  In the example shown in FIG. 10, not only the threshold value teaching process (step 1004) but also the threshold value learning process (step 1006) is activated via message communication. . That is, if the received and decoded message is a short-circuit check threshold learning request (step 1005 YES), threshold learning processing (step 1006) is executed. The contents of the threshold learning process (step 1006) are the same as the threshold learning process (see FIG. 13) described above.

  Next, a communication slave unit capable of predicting a short circuit with respect to the three-wire sensor will be described. FIG. 15 shows a circuit diagram (No. 1) in a connection state between the external interface unit (for one channel) of the input slave unit and the three-wire proximity sensor.

  The 3-wire proximity sensor 7B has a power supply terminal P1, a ground terminal G1, and a signal terminal S1. A proximity main circuit 73 and an output transistor 74 are built in the case of the sensor 7B. The proximity main circuit 73 is supplied with power through the power supply terminal P1 and the ground terminal G1. The output transistor 74 is an NPN type in this example, and has a collector terminal connected to the signal terminal S1 and an emitter terminal connected to the ground terminal G1. The output terminal OUT of the proximity main circuit 73 outputs “H” in the object detection state and “L” in the object non-detection state. Therefore, the output transistor 74 is turned on in response to the signal “H” from the output terminal OUT of the proximity main circuit 73 in the object detection state, and conversely, in the object non-detection state, the signal “H” is output from the output terminal OUT. In response to L ″, it is turned off. As in the case of the two-wire proximity sensor, a constant operating current (normal leakage current) flows through the proximity main circuit 73 as well. When the coolant enters the three-wire proximity sensor 7B, as indicated by three white arrows in the figure, the first leakage current path L1, the second leakage current path L2, and the third leakage current path L3 Three leakage current paths are generated.

  The external interface unit 25B has a power supply terminal P2, a ground terminal G2, and a signal terminal S2. The external interface unit 25B is also supplied with power from the DC power supply 11. That is, the positive terminal of the DC power supply 11 is connected to the power supply terminal P2 via the internal power supply line PL. The negative terminal of the DC power supply 11 is connected to the ground terminal G2 via the internal ground line GL. The internal ground line GL2 is inserted with a current detection resistor 2521. A resistor 2514 and a resistor 2515 are inserted in series in the internal signal line SL connected to the signal terminal S2. The external interface unit 25B is connected to the internal bus 28 via the internal bus interface 2520. The photocoupler 2516 functions as a discrimination binarization circuit that binarizes the current value flowing through the internal signal line SL into an on-current state and an off-current state. The light emitting diode 2517 of the photocoupler 2516 is connected in parallel with a resistor 2515 that constitutes an internal signal line. A phototransistor 2518 of the photocoupler 2516 is pulled up to the internal power supply line PL via a resistor 2519. Therefore, the photocoupler 2516 is turned on when the current flowing through the internal signal line SL exceeds a specified value, and is turned off when the current is less than the specified value. When the photocoupler 2516 is on, the collector output of the phototransistor 2518 is “L”, and conversely, when the photocoupler 2516 is off, it is “H”.

  A potential difference between both ends of the current detection resistor 2521 inserted in the internal ground line GL is converted into a multi-bit digital signal by the AD converter 2522. The AD converter 2522 is connected to the internal bus interface 2520 via the isolation circuit 2523. Therefore, the ON / OFF state of the photocoupler 2516 and the measured current value output from the AD converter 2522 are sent to the internal bus 28 by the action of the internal bus interface 2520 and finally read into the microprocessor.

  The three-wire proximity sensor 7B and the external interface unit 25B are connected via a sensor cord 702. More specifically, the power terminal P1 on the sensor side and the power terminal P2 on the interface side are connected via a power core wire 702P in the sensor cord 702. Similarly, the signal terminal S1 on the sensor side and the signal terminal S2 on the interface side are connected via a signal core wire 702S. Similarly, the sensor-side ground terminal G1 and the interface unit-side ground terminal G2 are connected via a ground core wire 702G. When the proximity sensor 7B is normal, only the normal leakage current due to the operation of the proximity main circuit 73 flows through the internal ground line GL when the output transistor 74 is in the OFF state. Further, when the output transistor 74 is in the on state, the on-current of the output transistor 74 is added and flows as compared with the above-described normal leakage current. On the other hand, after the three systems of leakage current paths L1 to L3 are formed due to the intrusion of the coolant, even if the output transistor 74 is in the OFF state, it passes through the three systems of leakage current paths L1 to L3. The leakage current that flows is added and flows. Further, when the output transistor 74 is in the on state, the power supply terminal P1 and the signal terminal S1 are connected by the leakage current path L3, so that the on-current value is larger than that in the normal state. This flows to the internal ground line GL.

  An example of the state change of the photocoupler and the flowing current is shown in FIG. From the above considerations, when looking at an example of the proximity sensor of the applicant company, the current at normal OFF is about 10 mA and the current at normal ON is about 13 to 17 mA, while the current at OFF in the case of leakage is 11 mA or more. In the case of leakage, the ON current is 19 mA or more. Therefore, it can be seen that the threshold current for OFF short-circuit prediction may be 11 mA or more, and similarly, the ON threshold current for short-circuit prediction may be 19 mA or more.

  FIG. 17 shows the relationship between the ON / OFF state of the photocoupler and the current of the internal signal line (normal time). As shown in the figure, when the connected 3-wire sensor 7B is normal, the value of the current flowing through the internal signal line is about 13 to 17 mA when the output transistor 74 is on, and is off. In that case, the value is about 10 mA. If the current value exceeds the threshold value Ith (on / off) in the transition period in which the current of the internal signal line changes from the off-state current value to the on-state current value with a predetermined delay time, the photocoupler is turned off. Change to ON state. Similarly, when the current value falls below the threshold value Ith (on / off) in the transition period in which the current of the internal signal line changes from the ON-state current value to the OFF-state current value, the photocoupler changes from the ON state to the OFF state. To change. On the other hand, as described above, when leakage occurs in the three-wire sensor 7B, the current value at OFF becomes 11 mA or more, and the current value at ON becomes 19 mA or more. Therefore, the threshold value Ith (er.off) for short circuit prediction is set to an appropriate value of 11 mA or more, and the threshold value Ith (er.on) value for similar short circuit prediction is set to 19 mA or more. If set to an appropriate value, the current value of the internal signal line in the OFF state or ON state of the photocoupler is compared with these two threshold values Ith (er.off) and Ith (er.on). Short circuit prediction can be performed.

  FIG. 18 shows a detailed flowchart (part 1) of the short-circuit check process (for one channel) regarding the three-wire sensor. The processing shown in this flowchart implements the determination algorithm described above with reference to FIGS.

  When processing is started in FIG. 18, first, the state of the photocoupler 2516 is referred to. If the photocoupler is in an OFF state (step 1801 OFF), a predetermined time is waited (step 1802). Only when the photocoupler is in an OFF state (step 1803 OFF), the current value monitoring process is performed. (Step 1804), the value of the current flowing through the internal signal line SL is measured, and even if the value is equal to or greater than the threshold value Ith (on / off) (step 1805 YES), the photocoupler after a certain time has passed. (Step 1806), and only when the state is OFF (step 1807 OFF), the short-circuit prediction flag ON and short-circuit prediction LED lighting processing (step 1810) are executed. Note that the details of the individual processes described above are substantially the same as those described above with reference to FIG.

  On the other hand, when the photocoupler is in the ON state (step 1801 ON), the current value is immediately monitored (step 1807), and the measured current value is equal to or greater than the threshold value Ith (er.on). If there is a condition (YES in Step 1808), a short-circuit prediction flag ON and a short-circuit prediction LED lighting process (Step 1810) are executed.

  Even if the sensor state is determined to be in the OFF state (step 1801 OFF), if the photocoupler state has changed from the OFF state to the ON state after waiting for a certain time (step 1802) (step 1802) When step 1803 is ON), the process proceeds to the same processing as when the photocoupler is in the ON state (step 1801). Further, after waiting processing for a certain time (step 1802), even if the state of the photocoupler is still OFF (step 1803 OFF), as a result of the current value monitoring processing (step 1804), the measured current value is When the threshold value Ith (er.off) is not reached (NO in Step 1805), Steps 1803-1805 are repeated to wait for the state change of the photocoupler or the monitored current value to exceed the threshold value thereafter. To do.

  On the other hand, if it is determined that the photocoupler is in the ON state (step 1801 ON) and the current is monitored (step 1807), the monitored current value is less than the threshold value Ith (er.on) ( As long as the state of the photocoupler is ON, the monitored current value exceeds the threshold value Ith (er.on) by repeating steps 1807 to 1809 (step 1808 YES), or the photocoupler The process waits for the state to change from the ON state to the OFF state. If the state changes (step 1809 OFF), the process proceeds to the process when the state of the photocoupler is the OFF state.

  By executing these processes, as shown in FIG. 17, in the transition period in which the current of the internal signal line changes, malfunction caused by monitoring the current value is prevented in advance. That is, even when the photocoupler is determined to be in the OFF state at time t1, as long as the current value of the internal signal line is not greater than or equal to the threshold value Ith (er.off) at time t2 delayed by time Td. Short circuit prediction operation is not performed. Further, even if the current value of the internal signal line exceeds the threshold value Ith (er.off) at time t3, unless the photocoupler state is determined to be OFF at time t4, which is further delayed by time Td, The short circuit prediction operation is not performed.

  FIG. 19 shows a table showing channel information storage contents of the input slave unit. As shown in the figure, the channel information of the input slave unit includes a photocoupler state, a short-circuit prediction flag, an abnormality detection value (1), and an abnormality detection value (2). Here, the abnormality detection value (1) corresponds to the ON threshold current Ith (er.on), and the abnormality detection value (2) corresponds to the OFF threshold current Ith (er.off). The contents of these items are stored for each channel. The item of the state of the photocoupler is periodically updated in the input update process (step 904) as described above with reference to FIG. Further, the item of the short circuit prediction flag is updated in the short circuit prediction process (step 1810) in the flowchart of FIG. Each item of the abnormality detection value (1) and the abnormality detection value (2) can be updated by learning processing or teaching processing, as in the previous example.

  FIG. 20 shows a detailed flowchart (part 1) of the learning process for the three-wire sensor included in the various service processes (step 906) shown in FIG. In this process, the values of the off-time threshold value Ith (er.off) and the on-time threshold value Ith (er.on) are updated voluntarily and periodically without using message communication. When the process is started in FIG. 20, the state of the photocoupler 2516 is referred to (step 2001). Here, when it is determined that the photocoupler is in the OFF state (step 2001 OFF), after waiting for a certain time (step 2002), the photocoupler is still in the OFF state (step 2003 OFF). The current value monitor (step 2004) is performed, and then the state of the photocoupler is reconfirmed after a certain period of time (step 2005). Only when the OFF state is maintained (NO in step 2006), the current at the OFF time The value is recorded (step 2007), and after waiting for a predetermined learning mode end condition to be satisfied (YES in step 2008), the process proceeds to threshold value generation processing (step 2012).

  On the other hand, as a result of referring to the state of the photocoupler, when it is determined that the photocoupler is in the ON state (step 2001), the current value is immediately monitored (step 2009), and the monitored measurement value is recorded as the ON-time current value. (Step 2010), the process waits for a predetermined learning mode end condition to be established (YES in Step 2011), and proceeds to threshold value generation processing (Step 2012).

  In this threshold value generation process (step 2012), the OFF threshold value Ith (er.off) is calculated from the stored OFF current value, and the ON threshold value Ith (er.on) is determined from the ON current value. ). This calculation is performed, for example, by obtaining a peak value and setting 1.5 times as a threshold value.

  The ON threshold current Ith (er.on) and the OFF threshold current Ith (er.off) thus obtained are the abnormality detection values (1) constituting the channel information, as shown in FIG. And stored as an abnormality detection value (2) and used for determination processing for short circuit prediction.

  In the flowchart of FIG. 20, when it is determined that the state of the photocoupler has changed from the OFF state to the ON state (step 2003 ON), or when it is determined that there is a state change (step 2006 YES), ON / OFF It is regarded as a current fluctuation period in the transition period, and the OFF-time current value recording process (step 2007) is not executed.

  As described above with reference to FIG. 10, also in this embodiment, the ON threshold value and the OFF threshold value are set by the teaching process or the learning process, respectively, via message communication from the programmable controller. be able to. FIG. 21 is a diagram (part 1) showing the contents of the short-circuit threshold value table of the three-wire sensor held on the tool side of the PLC in that case. As is apparent from the figure, on the tool side of the PLC, the ON threshold value Ith (er.on) and the OFF threshold value Ith (er.off) are provided for each sensor type (A, B, C). Is stored. These threshold values are set to appropriate values by calculation in advance based on the actual measured signal current values in each sensor type. These on-time threshold value and off-time threshold value are sent to the input slave 2 side via message communication performed between the communication master unit 104 and the input slave unit 2. Then, as described above with reference to FIG. 10, the threshold value teaching process (step 1004) or the threshold value learning process (step 1006) is executed, and the threshold values are set appropriately. The Rukoto.

  Next, FIG. 22 shows a circuit diagram (part 2) in a connection state between the external interface unit (for one channel) of the input slave unit and the three-wire proximity sensor. In this embodiment, not only the value of the current flowing through the internal ground line GL but also the current flowing through the internal signal line SL is used for the short-circuit prediction determination process. This is because when the short-circuit prediction between the signal line and the ground line is performed, if the judgment is made only with the current flowing through the internal ground line GL, the difference between the normal current and the abnormal current is small. In order to avoid this, the current flowing through the signal line is monitored at the time of OFF.

  That is, in FIG. 22, in addition to the two resistors 2514 and 2515, a current detection resistor 2514 is further inserted in series in the internal signal line SL. Is converted into a multi-bit digital signal. Similarly to the previous example, a current detection resistor 2521 is also inserted in the internal ground line GL, and a potential difference between both ends of the resistor 2521 is converted into a multi-bit digital signal via the second AD converter 2522b. The digital signal output from the first AD converter 2522a and the digital signal output from the second AD converter 2522b are taken into the internal bus interface 2520 via the isolation circuits 2523a and 2523b, respectively. In addition, in FIG. 22, about the same component as the example of FIG. 15, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  An example of the state change of the photocoupler and the flowing current is shown in FIG. As shown in FIG. 5A, when attention is paid to the power supply line current value when the photocoupler is in the ON state, the normal ON current is about 13 to 17 mA, and the ON current when the electric leakage occurs is 19 mA or more. For this reason, in order to identify both, it is understood that an appropriate value of 19 mA or more should be selected as the short-circuit prediction threshold value Ith (er.on). Further, as shown in FIG. 5B, when attention is paid to the signal line current value when the photocoupler is in the OFF state, the current value at the normal OFF time is about 0.1 mA, and the current value at the normal ON time is about 3 to 7 mA. It can be seen that the current at OFF when the electric leakage occurs is 1 mA or more. Therefore, it is understood that when short-circuit prediction is performed based on the signal line current value in the OFF state, a value of 1 mA or more may be set as the short-circuit prediction threshold Ith (er.off).

  FIG. 24 shows the relationship between the ON / OFF state of the photocoupler and the current (when normal). As is apparent from the figure, when the sensor 7B is normal, the value of the current flowing through the internal signal line SL is about 3 to 7 mA when ON, and about 0.1 mA when OFF. Similarly, the current value flowing through the internal ground line is about 13 to 17 mA when ON. Therefore, in this determination algorithm, for the internal signal line SL, an appropriate value of 1 mA or more is set as the short-circuit prediction threshold Ith (er.off) to be compared with the OFF-time current value. Similarly, for the internal ground line GL, an appropriate value of 19 mA or more is set as the short-circuit prediction threshold value Ith (er.on) to be compared with the current value at ON. When the photocoupler is in the OFF state and the current value flowing through the internal signal line SL is equal to or greater than the threshold value Ith (er.off) (see time t2), or the photocoupler is in the ON state and the internal When the value of the current flowing through the ground line GL exceeds the OFF-time threshold value Ith (er.on), short-circuit prediction is performed assuming that the short-circuit is approaching.

  FIG. 25 shows a detailed flowchart (part 2) of the short-circuit check process (for one channel) regarding the three-wire sensor. This short-circuit check process is also executed in the short-circuit check process (step 905) in the flowchart described above with reference to FIG.

  In the figure, when processing is started, the state of the photocoupler is referred to (step 2501). Here, if it is determined that the photocoupler is in the OFF state (step 2501 OFF), after executing a waiting process (step 2502) for a predetermined time (Td), the state of the photocoupler is referred again (step 2503). Only when it is determined that the state of the photocoupler is OFF (step 2503 OFF), current value monitoring processing is executed via the first AD converter 2522a (step 2504). If it is determined that the monitored signal line current value is equal to or greater than the OFF-time threshold value Ith (er.off) (YES in step 2505), the state of the photocoupler is confirmed again after a predetermined time (step 2506). Only when the state of the photocoupler is still OFF (step 2507 OFF), the short-circuit prediction process (step 2511) is executed. On the other hand, when the photocoupler is determined to be in the ON state (step 2501 ON), current monitoring is immediately performed via the second AD converter 2522b (step 2508), and the monitored ground line current value is the ON threshold value. Only when it is equal to or greater than Ith (er.on) (YES in step 2509), the short-circuit prediction process (step 2511) is executed. In this short-circuit prediction process (step 2511), a short-circuit prediction flag ON process and a short-circuit prediction LED lighting process are executed.

  In the flowchart of FIG. 25, if the state of the photocoupler has changed from the OFF state to the ON state, a transition to a process corresponding to the ON state is performed. If it is determined that the monitored signal line current value is less than the OFF-time threshold value Ith (er.off) (NO in step 2505), the processing in steps 2503 to 2505 is repeated. If the photocoupler state changes from the OFF state to the ON state after a predetermined time has elapsed (step 2507 ON), the process proceeds to the ON state handling process. Further, if the monitored ground line current value is less than the ON threshold value Ith (er.on) and the photocoupler is still in the ON state, steps 2508 to 2510 are performed. Is repeated. In the meantime, if the state of the photocoupler changes from the ON state to the OFF state (step 2510 OFF), the transition to the OFF state handling process is performed. The ON threshold value Ith (er.on) and the OFF threshold value Ith (er.off) used in the above determination process may be set in either the learning process or the teaching process. When setting in the teaching process, the procedure is as described above with reference to FIGS. At this time, FIG. 26 is a diagram (part 2) showing the contents of the short-circuit threshold value table of the 3-wire sensor held on the tool side of the PLC. As is apparent from the figure, the optimum ON threshold value Ith (er.on) and OFF threshold value Ith (er.off) are stored for each of the sensor types (A, B, C). By transmitting these threshold values in a predetermined format to the input slave unit 2 via the communication master unit 104, the threshold value teaching process is executed as described above with reference to FIG. It will be.

  FIG. 27 shows a flowchart (part 2) showing details of the learning process for the 3-wire sensor included in various services. When the process is started in the figure, the state of the photocoupler is referred to (step 2701). If it is determined that the photocoupler is in an OFF state (step 2701 OFF), the photocoupler state is referred to again through a waiting process for a predetermined time (step 2702) (step 2703). Only in the OFF state (step 2703 OFF), the current value of the internal signal line SL is monitored via the first AD converter 2522a (step 2704), and the state of the photocoupler is confirmed after a predetermined time (step 2705). However, only when the state of the photocoupler has not changed (step 2706 NO), the monitored OFF current value is recorded (step 2707), and a predetermined learning mode end condition is awaited (step 2706). 2708 YES), shift to threshold value generation processing (step 2712) It takes place. On the other hand, when it is determined that the photocoupler is in the ON state (Step 2701 ON), the current value of the internal ground line GL is monitored via the second AD converter 2522b (Step 2709), and the current value at ON thus obtained is It is recorded (step 2710), and after waiting for establishment of a predetermined learning mode end condition (step 2711 YES), the process proceeds to threshold value generation processing (step 2712).

  In this threshold value generation process (step 2712), the OFF threshold value is calculated from the recorded OFF current value, and the ON threshold value is calculated from the ON current value. As this calculation method, for example, a peak value is obtained and 1.5 times thereof is set as a threshold value.

  As is clear from the description of the above embodiments, according to the present invention, a leakage failure occurs in a 2-wire or 3-wire sensor such as a proximity sensor or a photoelectric sensor to be connected due to, for example, intrusion of coolant. When this occurs, it is possible to accurately predict the occurrence of the leakage failure before it occurs.

It is a block diagram of the whole PLC system containing the input slave unit to which this invention was applied. It is an external view of an input slave unit to which the present invention is applied. It is a block diagram which shows the electric hardware constitutions of an input slave unit. FIG. 7 is a circuit diagram (part 1) in a connection state between an external interface unit (for one channel) of an input slave unit and a two-wire proximity sensor. FIG. 6 is a circuit diagram (part 2) in a connection state between a signal input unit (for one channel) of an input slave unit and a two-wire proximity sensor. It is a graph which shows a time-dependent change accompanying the coolant penetration | invasion of the sensor OFF electric current of a proximity sensor. It is a figure which shows the example of the state change of a photocoupler, and the electric current value which flows. It is a figure which shows the relationship (at the time of normal) between the ON / OFF state of a photocoupler, and an electric current. It is a general flowchart which shows the processing content of an input slave unit. It is a detailed flowchart of message decoding execution. It is a detailed flowchart of the short circuit check process (for 1 channel) regarding a 2-wire type sensor. It is a figure which shows the channel information storage content of an input slave unit as a table | surface. It is a detailed flowchart of the learning process (for 1 channel) included in various services. It is a figure which shows the content of the short circuit prediction threshold value table hold | maintained at the tool side of PLC. FIG. 6 is a circuit diagram (part 1) in a connection state between an external interface unit (for one channel) of an input slave unit and a three-wire proximity sensor. It is a figure which shows the example of the state change of a photocoupler, and the flowing electric current. It is a figure which shows the relationship (at the time of normal) between the ON / OFF state of a photocoupler, and the electric current of an internal ground line. It is a detailed flowchart (the 1) of the short circuit check process (for 1 channel) regarding a 3-wire type sensor. It is a figure which shows the channel information storage content of an input slave unit as a table | surface. It is a detailed flowchart (the 1) of the learning process for 3-wire type sensors included in various services. It is the figure (the 1) which shows the content of the short circuit threshold value table of the 3-wire type sensor hold | maintained at the tool side of PLC. FIG. 6 is a circuit diagram (part 2) in a connection state between an external interface unit (for one channel) of the input slave unit and a three-wire proximity sensor. It is a figure which shows the example of the state change of a photocoupler, and the flowing electric current. It is a figure which shows the relationship (at the time of normal) between the ON / OFF state of a photocoupler, and an electric current. It is a detailed flowchart (the 2) of the short circuit check process (for 1 channel) regarding a 3-wire type sensor. It is the figure (the 2) which shows the content of the short circuit threshold value table of the 3-wire type sensor hold | maintained at the tool side of PLC. It is a detailed flowchart (the 2) of the learning process for 3-wire type sensors included in various services. It is explanatory drawing of the trouble resulting from the coolant penetration | invasion of a proximity sensor. It is a leakage current characteristic (form E2EC). This is a leakage current characteristic (E2EQ-X □). It is a leakage current characteristic (E2E-X □ D □). It is a graph of a time-dependent change of the leakage current accompanying the coolant penetration | invasion of a proximity sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 PLC main body 2 Input slave unit 3 Output slave unit 4 Input / output slave unit 5 Fieldbus 6 Configurator 7 Sensor 7A Two-wire proximity sensor 7B Three-wire proximity sensor 7a Fiber type photoelectric sensor 7b Proximity sensor 8 Switch 9 Relay 10 Actuator 11 DC power supply 21 MPU
22 ROM
23 RAM
24 Fieldbus communication unit 25 Sensor interface unit 25A External interface unit 25B External interface unit 26 Display unit 27 Operation unit 28 Internal bus 71 Proximity main circuit 72 Output transistor 73 Proximity main circuit 74 Output transistor 101 Power supply unit 102 CPU unit 103 I / O Unit 104 Communication master unit 201 Case 202 DIN rail mounting hook 203 Connector socket 204 Fieldbus connector 205 Operation indicator lamp 206 Network status indicator lamp 207 Module status indicator lamp 208, 209 Rotary switch 701 Sensor code 701P Power supply core wire 701G Ground core wire 2501 , 2502 Resistance 2503 Photocoupler 2504 Light-emitting diode 2505 Phototra Gist 2506 Pull-down resistor 2507 Current detection resistor 2508 AD converter 2509 Isolation circuit 2510 Internal bus interface 2511 Current detection resistor 2514, 2515 Resistor 2516 Photocoupler 2517 Light emitting diode 2518 Phototransistor 2519 Pull-down resistor 2520 Internal bus interface 2521 Current detection resistor 2522 AD converter 2522a First AD converter 2522b Second AD converter 2523 Insulation circuit 2523a, 2523b Insulation isolation circuit 2524 Current detection resistor G1 Sensor side ground terminal G2 External interface side ground terminal GL Internal ground line Ig Ground current IL1 Normal leakage current IL2 Short circuit current L1 L3 Leakage path P1 Sensor side power supply terminal P2 External Interface side power terminal PL Internal power line S1 Sensor side signal terminal S2 External interface side signal terminal SL Internal signal line Td Delay time a Proximity sensor b Sensor case c Detection coil assembly d Circuit assembly e Sealing resin f Sensor code g Skin h Core wire i Proximity main circuit j Short-circuit current path k Load l Power supply

Claims (13)

A device-side power supply terminal to be connected to the sensor-side power supply terminal of the two-wire sensor;
A device-side ground terminal to be connected to the sensor-side ground terminal of the two-wire sensor;
A discrimination binarization circuit that discriminates the value of the current flowing through the internal power supply line connected to the device-side power supply terminal or the internal ground line connected to the device-side ground terminal into an on-current state and an off-current state, and ,
A signal input device configured to capture the output state of the discrimination binarization circuit into the device as an on / off state of a two-wire sensor to be connected,
A current measuring means for measuring a current value flowing through an internal power line connected to the apparatus-side power supply terminal or an internal ground line connected to the apparatus-side ground line;
When the output state of the discrimination binarization circuit is an off-current state, the measured current value measured by the current measuring means , the normal off-current value of the two-wire sensor, and the normal on-current value A leakage information generating means for generating information corresponding to the degree of leakage of the two-wire sensor to be connected based on a preset current value set between
And a leakage information output means for outputting information corresponding to the degree of leakage generated by the leakage information generation means to the outside.   The signal input device according to claim 1, wherein the measured current value is a measured current value after the end of the current fluctuation period in the on-off transition period. A device-side power supply terminal to be connected to the sensor-side power supply terminal of the three-wire sensor;
A device-side ground terminal to be connected to the sensor-side ground terminal of the three-wire sensor;
A device-side signal terminal to be connected to the sensor-side signal terminal of the three-wire sensor;
A discrimination binarization circuit for discriminating and binarizing the current value flowing through the internal signal line connected to the device side signal terminal into an on-current state and an off-current state,
A signal input device configured to capture the output state of the discrimination binarization circuit in the device as an on / off state of a three-wire sensor to be connected,
A first value for measuring a current value flowing in a line on the side where the sensor signal current and the sensor control current merge among the internal power supply line connected to the device-side power supply terminal and the internal ground line connected to the device-side ground terminal. Current measuring means,
When the output state of the discrimination binarization circuit is an off-current state (or on-current state), the measured current value measured by the first current measuring means and a preset off-current state (or on-current state) Leakage current information generating means for generating information corresponding to the leakage level of the three-wire sensor to be connected based on the set current value of
A signal input device, further comprising: a leakage information output means for outputting information corresponding to the degree of leakage generated by the leakage information generation means to the outside.   The signal input device according to claim 3, wherein the measured current value is a measured current value after the end of the current fluctuation period in the on-off transition period. A second current measuring means for measuring a current value flowing through an internal signal line connected to the device-side signal terminal;
In order to generate information corresponding to the degree of electric leakage, the measured current value measured by the second current measuring means is further used when the output state of the discrimination binarization circuit is an off-current state. The signal input device according to claim 3, wherein the signal input device is a signal input device.   The signal input device according to claim 5, wherein the measured current value is a measured current value after the end of the current fluctuation period in the on-off transition period.   The signal input device according to claim 1, further comprising a set value changing means for changing a set current value to be compared with the measured current value. External interface units for a predetermined number of channels connected to external devices,
A communication unit for communicating with a programmable controller;
A memory having a storage area corresponding to each of the channels,
In the external interface part, the external interface part of the channel to be connected to the sensor
A device-side power supply terminal to be connected to the sensor-side power supply terminal of the two-wire sensor;
A device-side ground terminal to be connected to the sensor-side ground terminal of the two-wire sensor;
There is provided a discrimination binarization circuit for discriminating and binarizing the value of the current flowing through the internal power supply line connected to the device-side power supply terminal or the internal ground line connected to the device-side ground terminal into an on-current state and an off-current state. In addition, the control unit
Input update means for periodically updating the state of the input signal of the channel assigned to the sensor in the memory according to the output state of the discrimination binarization circuit of the external interface unit of the corresponding channel;
In response to an input signal transmission request from the programmable controller via communication, an input signal transmitting means for reading the input signal of the corresponding channel from the channel memory and transmitting it to the programmable controller is provided. A communication slave unit of the controller,
Among the external interface units for a predetermined number of channels, the external interface unit to be connected to the sensor is provided with current measuring means for measuring the value of the current flowing through the internal power supply line or the internal ground line, and the control unit includes Is
When the output state of the discrimination binarization circuit is an off-current state, the two wires connected to the corresponding channel based on the measured current value measured by the current measuring means and the preset current value set in advance Leakage information generating means for generating information corresponding to the leakage level of the sensor,
A communication slave unit of a programmable controller, comprising: a leakage information output means for outputting information corresponding to the degree of leakage generated by the leakage information generation means to the outside. External interface units for a predetermined number of channels connected to external devices,
A communication unit for communicating with a programmable controller;
A memory having a storage area corresponding to each of the channels,
In the external interface part, the external interface part of the channel to be connected to the sensor
A device-side power supply terminal to be connected to the sensor-side power supply terminal of the three-wire sensor;
A device-side ground terminal to be connected to the sensor-side ground terminal of the three-wire sensor;
A device-side signal terminal to be connected to the sensor-side signal terminal of the three-wire sensor;
A discriminating binarization circuit for discriminating and binarizing the current value flowing through the internal signal line connected to the device side signal terminal into an on-current state and an off-current state. In the department
Input update means for periodically updating the state of the input signal of the channel assigned to the sensor in the memory according to the output state of the discrimination binarization circuit of the external interface unit of the corresponding channel;
In response to an input signal transmission request from the programmable controller via communication, an input signal transmitting means for reading the input signal of the corresponding channel from the channel memory and transmitting it to the programmable controller is provided. A communication slave unit of the controller,
Among the external interface units for a predetermined number of channels, the external interface unit to be connected to the sensor includes a sensor signal among an internal power line connected to the device side power terminal and an internal ground line connected to the device side ground terminal. First current measuring means for measuring a current value flowing in a line on the side where the current and the sensor control current merge is provided, and the control unit includes:
When the output state of the discrimination binarization circuit is an off-current state (or on-current state), the measured current value measured by the first current measuring means and a preset off-current state (or on-current state) Leakage current information generating means for generating information corresponding to the leakage level of the three-wire sensor to be connected based on the set current value of
A communication slave unit of a programmable controller, comprising: a leakage information output means for outputting information corresponding to the degree of leakage generated by the leakage information generation means to the outside. A second current measuring means for measuring a current value flowing through an internal signal line connected to the device-side signal terminal;
In order to generate information corresponding to the degree of electric leakage, the measured current value measured by the second current measuring means is further used when the output state of the discrimination binarization circuit is an off-current state. The communication slave unit of the programmable controller according to claim 9.   The leakage information output means is a leakage information transmission means for transmitting leakage information of a corresponding channel to a transmission request source in response to arrival of a predetermined transmission request via communication. Item 11. A communication slave unit of a programmable controller according to any one of Items 8 to 10.   The leakage information output means outputs the information corresponding to the degree of leakage generated by the leakage information generation means to the outside visually or audibly. Programmable controller communication slave unit.   A set current value updating means for updating the set current value of the corresponding channel to the value taught by the request or the learned value in response to the arrival of a predetermined request via communication; The communication slave unit of the programmable controller according to any one of claims 8 to 12.

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