JPH0711319Y2 - Combustion safety device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] In the present invention, in a thermal device such as a boiler, for example, a fuel control solenoid valve is prevented from malfunctioning due to an unexpected situation such as a ground fault of an energizing circuit. It is related to the safety device.

[Conventional technology and its problems]

In general, a combustion control device used for a boiler or the like is required to have high safety, and a fail-safe property that always operates on the safe side even in case of a failure or the like is required. Unexpected situation of solenoid valve for fuel control (ground fault of control circuit)
The malfunctions caused by should never occur, as they lead to a major accident due to the outflow of fuel.

For this reason, a combustion safety device as shown in Fig. 5 has been proposed. According to this device, ignition is performed on both ends of the fuel control solenoid valve (1) to which an AC power source is applied. Normally open contact (2) of the relay that operates with the start signal,
(3) is inserted, and the ground fault detector (14) is connected in parallel with one of the normally open contacts (3). Therefore, of the latter of the terminals (10) and (11), If one of the fuel control solenoid valves (1) is grounded while the other is connected to the hot line side, the ground fault detector (14) works to shut off the solenoid valve (1). It is turned off, and high safety against ground faults is guaranteed. However, in the same device, when a relay failure or contact welding occurs, the electromagnetic valve in question may open, and it cannot be said to be perfect in terms of fail-safety.

[Means for solving problems]

The present invention has been made in view of the above circumstances and aims to provide a combustion safety device with further improved fail-safety. One set of relay contacts () is provided at both ends of a protected controller (1). 2) and 3) are connected in series, and a power supply state detector (5) and this detector are connected in parallel to a series line including one of these relay contacts and the controller to be protected. And a first rectifier (4) arranged so that their cathode sides face each other, between the relay contact and the protection target controller on the series line, and between the first rectifier and the power supply state detector. A second rectifier (6) arranged so that the cathode side faces the power supply state detector
It is characterized by having inserted.

〔Example〕

A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a circuit diagram when this invention is used in a combustion control device of a boiler. (1) in the figure
Is a fuel control solenoid valve as a controller to be protected, (7) is an AC power source, (8) is an ignition transformer, and a predetermined signal (for example, an operating signal of a combustion device is provided at both ends of the fuel control solenoid valve). ) Is connected to the relay contacts (2) and (3). (9) is a relay contact for operating the ignition transformer.

(4) is a first rectifier, (5) is a power supply state detector, (6)
Is a second rectifier, and in this embodiment, the power supply state detector (5) and the power supply state detector (5) are connected in parallel to the series line (a) including the relay contact (3) and the fuel control solenoid valve (1). A first rectifier (4) arranged so that its cathode side faces the detector is connected through a series line (b), and the first rectifier (4) is connected between the relay contact (3) and the controller to be protected (1). Rectifier (4)
Between the power feeding state detector (5) and the power feeding state detector (5), a second rectifier (6) arranged so that the cathode side faces the power feeding state detector is inserted. Such a circuit configuration can of course be changed for the other relay contact as shown in FIG. With normal wiring, terminals (10)
Is connected to the hot line side, and the terminal (11) is connected to the ground line side.

(12) is a determination circuit for determining whether or not there is an abnormality in the device,
The power supply state detection signal of the power supply state detector (5) and the combustion instruction signal of the combustion control circuit (13) are compared to determine.
When it is determined that there is an abnormality, an interlock signal is issued and the fuel control solenoid valve is shut off.

In the combustion safety device configured as described above, malfunctions of the device in an unexpected situation can be prevented by the following operations. Fig. 3 shows a time chart during normal operation, but each device of the boiler operates according to a preset sequence. When the combustion switch is turned on or when a heat request is generated, a combustion instruction signal is output from the combustion control circuit (13) to instruct the operation of the heating device. First, scavenging the combustion chamber by pre-purge, then move to ignition try, then close relay contacts X1, X2,
The fuel control solenoid valve (1) and the ignition transformer (8) are operated to ignite the burner, and when it is confirmed that a flame has been formed by an appropriate flame detection device, the combustion is continued.

Whether or not there is an abnormality is determined by the determination circuit (12) according to the determination table shown in FIG. When the controller to be protected (1) is in the power supply state, the power supply state detection signal from the power supply state detector (5) which is energized in parallel with the power supply state detection signal becomes an ON signal, and the power supply state detection signal and the combustion instruction signal Are matched,
That is, when both signals are ON signals or OFF signals, the device is operating normally, and the combustion control during normal operation is continued. However, if the power supply state detection signal is an ON signal even if the combustion instruction signal is not output, it is considered that a ground fault or welding of contacts has occurred.In this case, an interlock signal is issued to protect Shut off the controller and issue an alarm at the same time. If the combustion instruction signal is output but the power supply state is not detected, it is possible that the circuit is abnormal or the protected controller itself is abnormal.In this case as well, the interlock signal Is issued to shut off the control target controller and issue an alarm.

In particular, when the relay contacts (2) and (3) are welded, a short circuit is formed in the conventional one (see FIG. 5), so that no current flows in the ground fault detector (14), Although it was difficult to detect, in this invention, the first rectifier (4) connects the power supply state detector (5) and the hot line side of the protection target controller (1), so that even in that case. It can be easily detected.

[Effect of device]

Since the present invention is configured as described above, the controller to be protected does not malfunction not only at the time of a ground fault but also in various unforeseen circumstances such as contact welding and circuit abnormality, so that it is always safe. A combustion safety device that operates and has a high fail-safe property can be provided. Further, depending on the determination condition, an abnormal time can be detected by being divided into two cases, and quick processing and repair corresponding to each case are possible.

Further, even if the power supply state detector fails, according to the present invention, it can be detected by the determination circuit and the interlock can be applied, so that the circuit can be a self-check circuit.

[Brief description of drawings]

1 is a circuit diagram showing an embodiment of a combustion safety device according to the present invention, FIG. 2 is a circuit diagram showing a modification of the embodiment shown in FIG. 1, and FIG. 3 shows the operation of each contact in the circuit. FIG. 4 is a time chart shown in FIG. 4, FIG. 4 is a judgment table of the judgment circuit in the combustion safety device of the present invention, and FIG. 5 is a circuit diagram showing an embodiment of a conventional combustion safety device. (1) …… Protected controller (solenoid valve for fuel control) (2), (3) …… Relay contact, (4) …… First rectifier (5) …… Power supply state detector, (6)… … Second rectifier (7) …… AC power supply, (8) …… Ignition transformer (9) …… Relay contacts, (10), (11) …… Terminal (12) …… Judgment circuit, (13) …… Combustion control circuit (14) …… Ground fault detector

Claims (1)

[Scope of utility model registration request] 1. A combustion control device for use in a thermal device such as a boiler, wherein a pair of relay contacts (2) and (3) are connected in series at both ends of a controller to be protected (1), respectively. A power supply state detector (5) and a first rectifier (4) arranged such that the cathode side faces the detector are provided in parallel with a series line including one of the relay contacts and the controller to be protected. A connection is made between the relay contact on the series line and the protection target controller, and between the first rectifier and the power supply state detector so that the cathode side faces the power supply state detector; Combustion safety device characterized by inserting two rectifiers (6).