JPH02129826A - Relay - Google Patents

Abstract

PURPOSE:To make it possible to easily detect whether a coil is defective or the resistance of a contact is increased by providing photocouplers in parallel to and in series with the coil respectively in the input circuit of a manipulation coil so as to have an error signal output when a difference is produced as the result of mutual comparation of conductivity detection signals from said photocouplers. CONSTITUTION:An electric current of specified voltage is applied to the manipulation coil 1 of a relay from a programmable controller, etc., so as to operate an actuator such as solenoid, etc., by setting a contact 8 to ON. At this juncture, the first and second photocouplers 2a and 2b connected in parallel to and in series with a coil 1 become ON if this coil operates normally so as to allow signal currents to flow from both photocouplers, but these currents become low on account of resistors R1, R2, accordingly the output from an exclusive OR logic element 5 also becomes low and as the result, the error signal from an error output terminal 6 becomes low indicating that an error is not generated. Next, when the malfunction occurs in the coil 1, the output signal from the element 5 becomes high so that the error signal from the terminal 6 becomes high thus the occurrence of an error can be found.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a relay (electromagnetic switch).

[Conventional technology]

Relays are often used in industrial machinery such as press machines and machine tools, as well as in plant systems, but conventional relays have an additional device inside the relay to confirm whether the relay is ON or OFF.
There is a system that has two auxiliary contacts, and confirms whether the relay is ON or OFF by feedback of the signal from the ON/OFF operation. The configuration made it impossible to do so.

[Problem to be solved by the invention]

If the relay does not turn on even after issuing a signal to turn it on, the cause may be a defective operating coil or a defective contact, but there is a problem in that it takes time and effort to determine this.

The present invention has been made in view of the above, and an object of the present invention is to provide a relay in which the details of the failure of the relay can be easily detected when the relay malfunctions and becomes inoperable. It is something to do.

[Means to solve the problem]

In order to achieve the above object, the relay according to the present invention is provided with energization detection means such as photocouplers in the input circuit of the operation coil in a parallel position and a direct position with respect to the operation coil. The configuration includes a comparison means that compares the detection signals and outputs an error signal when a difference occurs between the two signals.

It also includes a resistance detection means for detecting the resistance when the contacts are connected, and a resistance maximum value setting means, and outputs an error signal when the output signals from both of these means are compared and the difference reaches a predetermined value. The configuration includes a comparison means to perform the comparison.

[For production]

When an abnormality occurs in the operating coil of the relay, a detection signal only from the energization detection means connected in parallel to the input circuit of the relay is input to the comparison means, and if a difference occurs in the signals input to the comparison means, the comparison means An error signal is output from the controller to notify that an abnormality has occurred in the operating coil.

Also, if the contact becomes thin due to burnout or the like, and its resistance becomes greater than the resistance set by the maximum resistance value setting means,
An error signal is output from the comparison means that compares this, and
It is possible to detect the occurrence of an abnormality such as resistance in the contacts.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

Figure 1 shows a relay circuit that is capable of detecting a defective relay operating coil.
A second photocoupler 2a and a second photocoupler 2b are interposed in series with the operating coil 1, respectively. R1 and R2 are resistors associated with the respective photocouplers 2a and 2b. Both signal extraction circuits 3a of the above photocouplers 2a and 2b
, 3b are connected to the signal current input terminal 4 via resistors R3 and R4, respectively, and both circuits 3a and 3b
The downstream side of each of the resistors R3 and R4 is connected to the exclusive OR element 5. The output side of this exclusive OR element 5 is connected to an error output terminal 6. Note that C is a capacitor and R5 is a resistor.

The input terminal 7 of the operating coil 1 of the relay is connected to, for example, a programmable controller, and the contacts 8 of the relay are connected to a power source and an actuator such as a solenoid.

In the above configuration, when a current of a predetermined voltage is applied to the operating coil 1 of the relay from a programmable controller or the like, the contact 8 is turned on and an actuator such as a solenoid is operated.

At this time, if the operating coil 1 is normal, both the first and second photocouplers 2a and 2b connected in parallel and series to the operating coil 1 are turned on, and both signal extraction circuits are turned on. A signal current flows through R1 and R2, and as a result, the output from the exclusive OR element 5 also becomes "low", and the error signal from the error output terminal 6 becomes "low". "Low", indicating that there is no error. Conversely, when the power supply to the operating coil 1 is stopped and it is not excited, the two signal currents input to the exclusive OR element 5 are both "high", and the output from the element 5 is "low". This shows that there is no error.

Next, if the operating coil 1 of the relay fails, when voltage is applied to the input circuit 2 of this, the resistor R connected in parallel with it
1 and the first photocoupler 2a, the first photocoupler 2a is turned on, and no current flows through the resistor R2 and the second photocoupler 2b connected in series. Therefore, a "low" signal current is input to the exclusive OR element 5 from both signal extraction circuits of the first photocoupler 2a, and a "high" signal current is input from both signal extraction circuits of the second photocoupler 2b. A "high" signal is output from the exclusive OR element 5, and this is output from the error output terminal 6 as an error signal, whereby a failure of the operating coil 1 is detected.

Note that the time constant of resistor R5 and capacitor C is the same as operation coil 1.
It is set to absorb the delay in contact 8 operation due to

Figure 2 shows a relay circuit that can detect faulty relay contacts, in which both the upstream and downstream sides of the relay contacts 8 are connected via impedance conversion buffer amplifiers 9a and 9b. It is connected to the differential amplifier 10. 11 is a comparator, and this comparator 11 compares the output signal of the differential amplifier 10 and the signal from the resistance maximum value setter 12. 13 is an AND element, to which the output side of the comparator 11 is connected. Furthermore, the signal extraction circuit 3a' of the photocoupler 2a/, which is interposed in parallel with the input circuit 2 of the operating coil 1 of the relay, is connected to the NOT element 14.
It is connected to the AND element 13 via. 15 is an error output terminal.

In the above configuration, when the input circuit of the relay is energized and the contact 8 is turned on, the magnitudes of the voltages on both sides of the contact 8 are compared by the differential amplifier 10.

At this time, if the contact 8 is normal, the voltage difference on both sides of the contact 8 detected by the differential amplifier 10 is smaller than the predetermined set value Vset from the resistance maximum value setter 12, so the output of the comparator 11 is It becomes "low". (Note that since the input circuit of the relay is energized, the photocoupler 2a' is turned on, and the output of the NOT element 14 becomes "high".)
As a result, the signal from the AND element 13 becomes "low",
There is no error signal.

If the cross-sectional area of the contact 8 is reduced due to burnout or the like and it is about to be cut off, the resistance when the contact is turned on increases. The magnitudes of the resistances are compared by the differential amplifier 10, and when the difference becomes larger than the set value Vset, the output of the comparator 11 becomes "high". Further, since the input circuit of the relay is energized, the photocoupler 2a' becomes ONL, and the output of the NOT element 14 becomes "high". Therefore, the output signal from the AND element 13 becomes "high", which serves as an error signal to notify an abnormality.

In the above description, both the embodiments shown in FIG. 1 and FIG. 2 have been explained separately, but the embodiment shown in FIG. 2 may be combined with the embodiment shown in FIG. In this case, there are two error output terminals, one for the operating coil and one for the contact.

〔Effect of the invention〕

According to the present invention, when a relay fails and becomes inoperable, it is possible to determine whether the failure of the relay is due to a defect in the operating coil 1 or an abnormality in which the contacts have resistance. can be easily detected. In particular, in the case of contacts, even if an abnormality occurs that causes resistance in the contact, the relay still satisfies the basic function of the relay, that is, the contact turns ON when the operating coil is energized. However, according to the present invention, this abnormality can be easily discovered.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of the present invention, and FIG. 1 is a circuit diagram for an operating coil, and FIG. 2 is a circuit diagram for a contact. 1 is an operating coil, 2 is an input circuit, 2a, 2b. 2a' is a photocoupler, 5 is an exclusive OR element, 6.1
5 is an error terminal, 8 is a contact, 9a and 9b are buffer amplifiers, 10 is a differential amplifier, 11 is a comparator, 12 is a maximum resistance value setter, 13 is an AND element, and 14 is a NOT element.

Claims (2)

[Claims] (1) In the input circuit 2 of the operating coil 1, energization detection means such as photocouplers 2a and 2b are provided in parallel and direct positions with respect to the operation coil 1, and the detection signals from both energization detection means are compared. A relay characterized in that it is provided with comparison means that outputs an error signal when a difference occurs between the two signals. (2) A resistance detection means for detecting the resistance when the contact 8 is connected, a resistance maximum value setting means, and an error occurs when the output signals from both means are compared and the difference reaches a predetermined value. A relay characterized by being provided with comparison means for outputting a signal.