JP2009033388A - Proximity sensor with output transistor fault diagnosing function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To diagnose that an output transistor gets out of order and to accurately report that to a load side. <P>SOLUTION: There is provided a proximity sensor which includes a detecting circuit 14 varying in output level between high and low states in response to detection of an approach state of a detection body, the detecting circuit 14 generating its detection output in the form of a transistor output. The proximity sensor includes a fault diagnostic circuit 20 which diagnoses a fault state of the output transistor 16a and a fault diagnostic result output transistor 22a having open collector constitution, wherein the fault diagnostic circuit 20 diagnoses normality when a combination of high/low variations in output level of the output transistor 16a correspond to a combination of high/low variations in output level of the detecting circuit 14 and a fault when not, and outputs a fault diagnostic signal of the output transistor 16a from the fault diagnostic result output transistor 22a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a proximity sensor with a function for diagnosing an output transistor having a function capable of diagnosing a failure of an output transistor.

  Proximity sensors can detect the presence or movement of a detection object by replacing it with an electrical signal in a non-contact state with the detection object, and there are many types and various uses. For example, there are a high-frequency oscillation type in which the detection object is a metal, and a capacitance method that can detect even if the detection object is not a metal. Such proximity sensor signal output forms include analog output and on / off output. And a proximity sensor is used as one of the input devices which detect and input the state of a control device to a programmable logic controller (PLC), for example (refer patent document 1).

In the proximity sensor described above, an output current flows from the output unit in accordance with detection of a detection object. When the output transistor is used beyond the maximum rated value, the transistor may be damaged, an abnormality may be caused when the proximity sensor performs detection, or it may be extremely damaged. Also, this excessive output current may be supplied to the load side, which is a problem. In spite of such an abnormality, if the signal input from the proximity sensor is continued as normal to a controller such as a PLC, the control system using the controller is extremely defective. In particular, in the case of using PLC in the field of factory automation (FA) that unattended automation of the process, it is required to avoid as much as possible and to deal with such an excessive output current in advance while the proximity sensor is operating normally. .
JP2002-076871

  The present invention provides a proximity sensor with an output transistor failure diagnosis function that can diagnose a failure when the output transistor has failed and can accurately notify the load side.

  A proximity sensor according to the present invention includes a detection circuit whose output level changes to high and low according to the detection of the proximity state of a detection object. The output form of the detection output from the output terminal of the detection circuit is a transistor output, and A DC 2-wire or DC 3-wire proximity sensor that changes the output level of the transistor output in response to a change in the output level of the detection circuit, and diagnoses a failure state of the output transistor that outputs the detection output A fault diagnosis circuit and a fault diagnosis result output circuit including a transistor having an open collector configuration, wherein the fault diagnosis circuit has a high or low output level of the output transistor with respect to a combination of high and low changes in the output level of the detection circuit. If the combination of changes is a corresponding combination, it is diagnosed as normal. Both are characterized in that which is so outputs a failure diagnosis signal of the output transistor from the open collector of the transistor of the failure diagnosis result outputted in the circuit.

  Here, the output level of the output transistor includes a level that changes in phase with the output level of the detection circuit, and a level that changes in an inverted manner, and includes both cases. For example, when the emitter output of the output transistor is set to the output level of the output transistor, it changes in phase with the output level of the detection circuit, and when the collector output of the output transistor is set to the output level of the output transistor, it is inverted and changed. is there. A combination in which the level of the output level of the output transistor changes is a corresponding combination or a combination that does not correspond includes the in-phase and inversion phase relationships.

  In the present invention, focusing on a DC 2-wire or DC 3-wire proximity sensor in which the output level of the transistor output changes in response to a change in the output level of the detection circuit, the fault diagnosis circuit outputs the output of the detection circuit. The combination of the level change of the output transistor with respect to the combination of the level change of the output transistor diagnoses that the combination of the output level is normal when the corresponding combination is a failure, and the failure when the combination does not correspond. It is possible to accurately and accurately diagnose only the state, and when the fault diagnosis circuit diagnoses that the output transistor is faulty, the fault diagnosis signal corresponding to the fault is sent from the open collector of the fault diagnosis result output transistor. Since it is designed to output, it can be easily output on the load side such as a controller such as a PLC or a relay. The failure state of the transistor can be monitored, so that it is possible to avoid a problem that an excessive output current is supplied to the load side due to the collector-base short of the output transistor, the collector-emitter short-circuit, etc. . Therefore, even though the output transistor is faulty, the signal input from the proximity sensor does not have to be continued to the controller such as the PLC as normal, and the control system using the controller, and in particular, unattended automation of the process When a PLC is used in the field of factory automation (FA), a malfunction due to an excessive output current can be appropriately dealt with due to a failure of an output transistor while the proximity sensor is operating normally.

  In the present invention, one of preferable aspects is that the failure diagnosis circuit is constituted by a microcomputer, and includes a first AD conversion port for capturing the sensor signal transistor output, and a first output for detecting the detection circuit from the detection circuit. 2 AD conversion port and an output port for outputting a fault diagnosis signal input to the base of the fault diagnosis result output transistor, and the transistor output level corresponds to a combination of high and low changes in the output level of the detection circuit A memory for storing a first combination of height changes and a second combination of height changes not corresponding to each other in a table, and a combination of changes in the output level of the detection circuit fetched from both AD conversion ports in the memory. Referring to the table to be stored, the output level of the output transistor is high or low And a CPU for diagnosing that the combination is normal when the combination is the above and failure when the combination is not, and the CPU outputs a failure diagnosis signal of the output transistor to the failure diagnosis result of the output transistor. The output comes from an open collector.

  In this aspect, since the failure diagnosis circuit is configured by the microcomputer having the above-described configuration, it is possible to appropriately deal with a malfunction due to a failure of the output transistor at a higher speed.

  In the present invention, one of preferred embodiments is that the detection circuit is provided with a detection output confirmation terminal separately from the output terminal connected to the base of the output transistor, and the detection output confirmation terminal is connected to the second AD of the fault diagnosis circuit. By connecting to the conversion port, the detection output of the detection circuit is taken into the second AD conversion port.

  In this aspect, the detection output from the detection circuit to the base of the output transistor is not affected, and the detection output input to the second AD conversion port of the microcomputer is suitable for processing by the microcomputer. Therefore, it is possible to appropriately deal with a malfunction due to a failure of the output transistor more accurately and at high speed.

  According to the proximity sensor of the present invention, when the output transistor fails, the failure can be diagnosed and notified to the load side accurately, so that the output current to the load is excessive because the output transistor has failed. In spite of the possibility of causing abnormalities in normal operation, the detection signal from the proximity sensor does not have to be continuously input to the controller such as the PLC as it is normal. As a result, such a controller is used. The control system can be operated more accurately and safely.

  Hereinafter, a proximity sensor according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a block configuration of the entire proximity sensor.

  Referring to FIG. 1, reference numeral 10 denotes an entire DC 2-wire proximity sensor according to the embodiment.

  The configuration inside the proximity sensor 10 will be described.

  A detection circuit 12 detects a detection object. The detection circuit 12 may be an induction type, a capacitance type, or a magnetic type.

  Reference numeral 14 denotes a detection circuit that performs detection processing of the detected object from the detection signal of the detection circuit 12. The detection circuit 14 outputs a detection signal whose output level changes between high and low according to the output of the detection circuit 12. The detection circuit 14 includes an output terminal 14a for display control output of the display circuit 18, an output terminal 14b for detection output to the base of the output transistor 16a, and an output terminal 14c for detection output confirmation.

  16 includes the output transistor 16a having a base connected to the output terminal 14b of the detection circuit 14 and having the output form of the proximity sensor 10 as a transistor output, and an emitter resistor 16b connected to the emitter of the output transistor 16a. This is an output circuit, and the collector output (transistor output) of the output transistor 16a is inverted and changed in response to a change in the output level from the output terminal 14b of the detection circuit 14. The emitter output of the output transistor 16a changes in response to a change in output level from the output terminal 14b of the detection circuit 14.

  A display circuit 18 displays the output of the detection circuit 14. The display circuit 18 is composed of, for example, a light emitting diode, and can display an operation by emitting light or stopping light emission according to a change in level of a display control output output from the output terminal 14a of the detection circuit 14. Yes.

  Reference numeral 20 denotes a failure diagnosis circuit which is characterized by the embodiment and diagnoses a failure of the output transistor 16a, and 22 is a failure diagnosis output circuit which outputs a failure diagnosis signal from the failure diagnosis circuit 20, and this failure diagnosis output circuit 22 includes a failure diagnosis result output transistor 22a having an open collector configuration and a resistor 22b connected between the base and emitter of the transistor 22a. The configurations and operations of the failure diagnosis circuit 20 and the failure diagnosis output circuit 22 will be described in detail later.

  Reference numeral 24 denotes a power supply circuit that is configured by a power supply IC and supplies power to the respective units 12, 14, and 20 in the proximity sensor 10, and is supplied via a load 28 connected to the detection signal output terminal 26 of the proximity sensor 10. Power is generated and supplied from the power source + V to each part in the proximity sensor. An output terminal 30 is connected to the collector of the failure diagnosis result output transistor 22a and outputs a failure diagnosis result signal. A failure diagnosis output load 32 is connected to the output terminal 30, and the power supply + V is supplied to the collector of the failure diagnosis result output transistor 22 a via the failure diagnosis output load 32. Reference numeral 31 denotes a ground terminal of the proximity sensor 10.

  In the proximity sensor 10 having the above configuration, the configuration of the failure diagnosis circuit 20 will be described with reference to FIG. The failure diagnosis circuit 20 is configured by a microcomputer, and is connected to the emitter of the output transistor 16a to take in the emitter output of the output transistor 16a, and to the output terminal 14c of the detection circuit 14 to detect the detection. The second AD conversion port IN2 that takes in the output of the circuit 14 and the output port OUT that is connected to the base of the failure diagnosis result output transistor 22a and outputs a failure diagnosis signal to the base. If the failure diagnosis circuit 20 has insufficient functions as an embedded microcomputer, the AD conversion and DA conversion functions may be externally attached. In this case, the port need not be provided with AD conversion and DA conversion functions.

  The failure diagnosis circuit 20 includes a memory 20a and a CPU 20b. The memory 20a stores a failure diagnosis execution program described below for the CPU 20b, a program memory for storing a failure diagnosis determination program, a memory for providing a work area for the CPU 20b, and a table described below. Memory.

  The memory 20a is a table shown in FIG. 3 showing the first combination of high and low changes in which the emitter output level of the transistor 16a corresponds to the combination of high and low changes in the output level of the detection circuit 14, and the second combination of high and low changes that do not correspond. And remember. In this table, the combination of changes in the output level of the detection circuit 14 fetched from the AD conversion port IN2 of the failure diagnosis circuit 20 is H (high level) and L (low level), and the emitter output of the output transistor 16a is output. As the level, the combination of the high and low changes of the output level is H (high level) and L (low level). If the output transistor 16a is not faulty, the emitter output level of the output transistor 16a becomes H, L corresponding to the combination H, L of the level change of the output level of the detection circuit 14 as normal. When the collector and base of the output transistor 16a are short-circuited and failed, the emitter output level of the output transistor 16a becomes H and H. When the collector and emitter of the output transistor 16a are short-circuited and failed, The emitter output level of the output transistor 16a is H, H. When the collector / emitter of the output transistor 16a is broken and malfunctions, the emitter output level of the output transistor 16a is L, L.

  The CPU 20b refers to the above table stored in the memory 20a and corresponds to the combinations H and L of the output level change of the output level of the detection circuit 14, and the combination of the level change of the emitter output level of the output transistor 16a is H. , L is diagnosed as normal, and other combinations are diagnosed as failure. When the CPU 20b diagnoses that the output transistor 16a is faulty, it outputs a fault diagnostic signal corresponding to the fault from the output terminal 30 to the load 32 via the fault diagnosis result output transistor 22a via the output port OUT. It is like that. The failure diagnosis circuit 20 includes a memory for storing an operation control program for the CPU 20b and others, but is not shown.

  In the above-described embodiment, the proximity sensor is a direct current 2-wire type, but can be similarly applied to a direct current 3-wire type as shown in FIG. 4, parts corresponding to those in FIG. 1 are denoted by the same reference numerals. The fault diagnosis circuit 20 in the DC 3-wire proximity sensor is the same as that of the DC 2-wire system, and the description thereof is omitted.

  In the above embodiment, the output transistor 16a is an npn type. However, the output transistor 16a can be similarly applied to a pnp type.

  In the above embodiment, the failure diagnosis circuit 20 receives the emitter output of the output transistor 16a, but includes the case where the collector output of the output transistor 16a is input.

FIG. 1 is a block diagram of a direct current 2-wire proximity sensor according to an embodiment of the present invention. FIG. 2 is an internal block diagram of the failure diagnosis circuit of FIG. FIG. 3 is a diagram showing a table stored in the memory of the failure diagnosis circuit. FIG. 4 is a block diagram of a DC 3-wire proximity sensor according to another embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Proximity sensor 12 Detection circuit 14 Detection circuit 16 Output circuit 20 Fault diagnosis circuit 22 Fault diagnosis output circuit

Claims (3)

It has a detection circuit whose output level changes depending on the detection of the proximity state of the detection object, the output form of the detection output from the output terminal of this detection circuit is a transistor output, and the change in the output level of the detection circuit A DC 2-wire type or DC 3-wire type proximity sensor in which the output level of the transistor output changes corresponding to
A failure diagnosis circuit for diagnosing a failure state of the output transistor that outputs the detection output; a failure diagnosis result output circuit including a transistor having an open collector configuration;
Provided,
The failure diagnosis circuit is normal when the combination of the output level of the output transistor and the combination of the change of the output level of the output transistor corresponding to the combination of the change of the output level of the detection circuit is normal, and it is a failure when the combination is not compatible. A proximity sensor with an output transistor fault diagnosis function, wherein a fault diagnosis signal for an output transistor is output from an open collector of a transistor in the fault diagnosis result output circuit. The failure diagnosis circuit is composed of a microcomputer,
A first AD conversion port for capturing the sensor signal transistor output;
A second AD conversion port for capturing the output of the detection circuit from the detection circuit;
An output port for outputting a fault diagnosis signal to be input to the base of the fault diagnosis result output transistor;
And having
A memory for storing, in a table, a first combination of high and low changes corresponding to the transistor output level with respect to a combination of high and low changes in output level of the detection circuit, and a second combination of high and low changes that do not correspond;
When the combination of the change in the output level of the detection circuit fetched from both the AD conversion ports is referred to the table stored in the memory and the combination of the change in the output level of the output transistor is the above combination, it is normal. A CPU that diagnoses a failure when the combination does not correspond to the above;
With
2. The proximity sensor with an output transistor fault diagnosis function according to claim 1, wherein the CPU outputs a fault diagnosis signal of the output transistor from an open collector of the fault diagnosis result output transistor.   The detection circuit is provided with a detection output confirmation terminal separately from the output terminal connected to the base of the output transistor, and the detection output confirmation terminal is connected to the second AD conversion port of the failure diagnosis circuit, thereby detecting the detection circuit. The proximity sensor with an output transistor fault diagnosis function according to claim 2, wherein the detection output is taken into the second AD conversion port.

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