JP2009145083A - Poor connection detection circuit for electric path connection part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a poor connection detection circuit for an electric path connection part used to early detect a poor connection of an electric path connection part such as a terminal and dispensing with a major change in a structure. <P>SOLUTION: A terminal part 2, connecting two electric paths 1a and 1b to each other, includes a sensor circuit 3 with a photo-coupler 15 turned on by a potential difference arising between the electric paths and a signal output circuit to output a failure detecting signal in response to an on-motion of the photo-coupler 15. A unified detection circuit 4 is provided, into which a plurality of output signals of the sensor circuit 3 are input and which determines that a poor connection has occurred and outputs a poor connection occurrence signal if at least one input failure detection signal satisfies prescribed conditions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a connection failure detection circuit that detects a connection failure in an electric circuit connection portion such as a terminal portion.

In the terminal portion to which the electric wire, the conductor bar or the like is connected, connection failure may occur due to loosening of screws, loosening of plugs, or the like. When such a connection failure occurs in a circuit that supplies a relatively large current, such as a power distribution device or power device, contact resistance between the connected circuits increases and heat is generated, and arc discharge occurs due to the occurrence of a potential difference. . As a result, the terminal part and the surrounding device housing may deteriorate and fire may occur, so it was necessary to detect and deal with it early.
Therefore, as a method for detecting this connection failure, for example, there is a technique disclosed in Patent Document 1. In Patent Document 1, a temperature sensor is attached to a terminal portion, and it is determined that a connection failure has occurred when the temperature becomes a predetermined value or more.

JP 2001-286052 A

  The configuration using the temperature sensor can detect a connection failure by detecting a temperature rise in the connection portion. However, detection of connection failure due to temperature cannot lower the set temperature in order to prevent malfunction, and cannot be determined as connection failure unless the temperature rises. In addition, the configuration in which the temperature sensor is provided in the terminal portion involves a large design change and cannot be easily implemented.

  Therefore, in view of such problems, the present invention provides a connection failure detection circuit for a circuit connection portion that can detect a connection failure of a circuit connection portion such as a terminal at an early stage and does not require a large change in the structure of the terminal portion. For the purpose.

In order to solve the above-mentioned problem, the invention of claim 1 includes a photocoupler that connects two electric circuits and forms a continuous electric circuit, a photocoupler that is turned on by a potential difference generated between the two electric circuits, A sensor circuit including a signal output circuit that outputs an abnormality detection signal in response to an ON operation of the photocoupler, and at least one of the output signals of the sensor circuit provided in the plurality of electric circuit connection portions is input and input When one abnormality detection signal satisfies a predetermined condition, an integrated detection circuit is provided that determines that a connection failure has occurred and outputs a connection failure occurrence signal.
According to this configuration, if the electric circuit connection portion is in a good connection state, a potential difference does not occur and the photocoupler is not turned on. However, when a connection failure occurs such that the contact resistance increases due to loosening of the screw and arc discharge occurs, a potential difference is generated between the two electric paths, the photocoupler is activated by this potential difference, and the sensor circuit performs a detection operation. Thus, since the integrated detection circuit determines the occurrence of connection failure based on the output of the sensor circuit, the occurrence of connection failure can be detected early and accurately. Since the integrated detection circuit does not need to be provided for each sensor circuit, the entire circuit can be configured at low cost.
In addition, this sensor circuit can be configured only by combining a relatively small element using a photocoupler and a resistance element, can be configured in a small space, and can be easily installed in an electric circuit connection portion.

According to a second aspect of the present invention, in the first aspect of the present invention, the photocoupler is an AC input compatible photocoupler that supports bidirectional current.
According to this configuration, the photocoupler is turned on when a potential difference occurs in the connection portion regardless of the direction of the current, so that a connection failure can be reliably detected.

According to a third aspect of the present invention, in the first or second aspect of the invention, the integrated detection circuit has a self-holding circuit that holds a signal for a predetermined time, and continues to output a connection failure occurrence signal for a predetermined time. It is characterized by.
According to this configuration, even if the sensor circuit output is a bowl-shaped pulse signal, the connection failure occurrence signal can be output as a pulse signal of a predetermined width, and it is easy to understand the occurrence of a connection failure, It is possible to reliably operate the notification device or the like.

According to the present invention, when a poor connection state occurs due to loose screws or the like and a potential difference occurs between both electric circuits, the photocoupler is turned on and the sensor circuit outputs an abnormality detection signal, so that the occurrence of a poor connection is detected. can do. This sensor circuit can be configured only by combining a relatively small element using a photocoupler and a resistance element, can be configured in a small space, and can be easily installed in an electric circuit connection portion.
Further, since the integrated detection circuit does not need to be provided for each sensor circuit, the entire circuit can be configured at low cost.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. FIG. 1 is a circuit block diagram showing an example of a connection failure detection circuit of an electric circuit connection part according to the present invention, wherein 1 is an electric circuit comprising a first electric circuit 1a and a second electric circuit 1b, and 2 is a first electric circuit 1a. Terminal portion for connecting the second electric circuit 1b, 3 is a sensor circuit for detecting a connection failure, 4 is an integrated detection circuit for outputting a connection failure occurrence signal based on the output signal of the sensor circuit, 5 is a sensor circuit 3 and It is a power supply circuit that supplies power to the integrated detection circuit 4.

  The sensor circuit 3 is configured as shown in FIG. In FIG. 2, 11 is a pair of input units for inputting voltage information from the terminal unit 2, 12 is a signal output unit, 13 is a power input unit, 14 is a ground unit, 15 is a photocoupler, and 16 is a sensor that outputs a detection signal. This is an output circuit. The terminal portion 2 includes a terminal portion 2a on the first electric circuit 1a side and a terminal portion 2b on the second electric circuit 1b side. These terminal portions 2a and 2b are screw type connection terminals or plug type terminals. It consists of terminals.

  One input part 11a among the input parts 11 is connected to a terminal fitting or screw constituting the terminal part 2a on the first electric circuit 1a side, and the other input part 11b constitutes the terminal part 2b of the second electric circuit 1b. Connected to terminal fittings and screws. The input unit 11 may be connected not to the terminal unit 2 but to the electric circuit 1 in the vicinity thereof.

  Both input portions 11a and 11b are connected via two resistance elements (resistor R1 and resistor R2), and a photocoupler 15 is connected between the resistors R1 and R2 via a resistor R3. . In this way, current flows through the input of the photocoupler 15 via the resistors R1 and R3, and the output of the photocoupler 15 is connected to the sensor output circuit 16 including the transistor T1. 12 outputs a voltage signal.

  The photocoupler 15 is a photocoupler corresponding to an AC input that includes a pair of light emitting diodes and is configured to emit light with respect to a bidirectional applied voltage.

  The integrated detection circuit 4 includes an integrated input circuit 20 to which the output signal of the sensor circuit 3 is input, an average value circuit 21 that averages the input signal, and a signal that exceeds a threshold value compared to a preset threshold value. A determination circuit 22 that outputs a signal, a self-holding circuit 23 that continues to output a signal for a predetermined time after receiving the output signal of the determination circuit 22, and an output circuit that receives the output signal of the self-holding circuit 23 and outputs a connection failure occurrence signal 24.

  FIG. 3 is a circuit diagram showing details of the integrated detection circuit 4. As shown in this figure, the average value circuit 21 and the determination circuit 22 are configured using an OP amplifier, and the self-holding circuit 23 is configured using a plurality of NAND circuits. The output circuit 24 is configured using a photocoupler.

  The operation of the connection failure detection circuit configured as described above is as follows. In the state where the first electric circuit 1a and the second electric circuit 1b are well connected in the terminal portion 2, no potential difference is generated between the first electric circuit 1a and the second electric circuit 1b. However, when the terminal screw is loosened or the like is in a poor connection state, it becomes a high resistance state, specifically between the first electric circuit 1a and the second electric circuit 1b, specifically between the terminal fittings or between the terminal screw and the terminal seat. As a result, a potential difference is generated, and arc discharge occurs. This potential difference occurs at a value close to the power supply voltage applied to the electric circuit at the maximum, and is applied to the photocoupler 15 via the resistors R1 and R3. As a result, the photocoupler 15 is turned on and the transistor T1 is turned on. Thus, the voltage signal is output from the signal output unit 12.

  The integrated detection circuit 4 generates an output signal when a signal exceeding a threshold value is input in the determination circuit 22 after averaging the input signal and the like, and the self-holding circuit 23 generates a pulse signal having a predetermined width. The connection failure occurrence signal is output from the output circuit 24. With this signal, if the interrupting circuit is connected to the subsequent stage, the electric circuit 1 is interrupted, and if a reporting device such as a buzzer is connected to the subsequent stage, the alarm is activated to notify the occurrence of a connection failure. Can do.

  On the other hand, the sensor circuit 3 operates normally even when a reverse current flows in the electric circuit 1 and detects when a potential difference of a predetermined value or more in the reverse direction is generated in the terminal portion 2, and the integrated detection circuit 4 When a signal satisfying the conditions is input, a connection failure occurrence signal is output by the above operation.

Thus, if the electric circuit connection portion is in a good connection state, no potential difference is generated, and the photocoupler is not turned on. However, when a connection failure occurs such that the contact resistance increases due to loosening of the screw and arc discharge occurs, a potential difference is generated between the two electric paths. The sensor circuit detects the occurrence of this potential difference, and the integrated detection circuit determines the occurrence of connection failure based on the output signal of the sensor circuit. Therefore, the occurrence of connection failure can be detected early and accurately, and the occurrence of arc discharge and heat generation It is possible to prevent deterioration of the terminal portion due to the like.
In addition, this sensor circuit can be configured only by combining a relatively small element using a photocoupler, a transistor, and a resistance element. Since the sensor circuit can be configured in a small space, it can be easily installed in an electric circuit connection portion.
Furthermore, by using a photocoupler that supports AC input, the photocoupler is turned on when a potential difference occurs in the connection portion regardless of the direction of the current, so that a connection failure can be reliably detected.
In addition, by having a self-holding circuit, even if the sensor circuit output is a saddle-shaped pulse signal, the connection failure occurrence signal is output as a pulse signal of a predetermined width. Can be operated reliably.

  In the above-described embodiment, the configuration used for the electric circuit composed of two wires has been described. However, even in the case of a three-wire electric circuit such as a three-phase circuit or a four-wire electric circuit, the sensor circuit 3 is provided in accordance with the number of electric circuits. It can be easily handled. Furthermore, since the electric circuit and the connection failure detection circuit are electrically separated by the photocoupler 15, an operation power supply may be introduced from another electric circuit, and a larger number of sensor circuits 3 may be input to the integrated detection circuit 4.

It is a circuit block diagram which shows an example of the connection failure detection circuit of the electric circuit connection part which concerns on this invention. It is a circuit diagram of a sensor circuit. FIG. 2 is a circuit diagram illustrating a specific circuit example of FIG. 1.

Explanation of symbols

  1 .... Electric circuit, 1a..First electric circuit, 1b..Second electric circuit, 2 ... Terminal part (electric circuit connection part), 3..Sensor circuit, 4..Integrated detection circuit, 15..Photocoupler , 20... Integrated input circuit, 22... Judgment circuit, 23.

Claims (3)

A photocoupler that is turned on by a potential difference generated between the two electric circuits, and a signal that outputs an abnormality detection signal in response to the on-operation of the photocoupler in an electric circuit connection part that forms a continuous electric circuit by connecting two electric circuits And providing a sensor circuit with an output circuit,
Integrated detection in which output signals of the sensor circuits provided in a plurality of circuit connection portions are input, and when at least one input abnormality detection signal satisfies a predetermined condition, it is determined that a connection failure has occurred and a connection failure occurrence signal is output. A connection failure detection circuit of an electric circuit connection part, comprising a circuit. The connection failure detection circuit for an electric circuit connection unit according to claim 1, wherein the photocoupler is an AC input-compatible photocoupler that supports bidirectional current. 3. The connection failure detection circuit according to claim 1, wherein the integrated detection circuit has a self-holding circuit that holds a signal for a predetermined time, and continues to output a connection failure occurrence signal for a predetermined time.

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