Combustion – With indicator or inspection means – Correlated with action of condition responsive burner control
Patent
1980-09-23
1983-06-21
Scott, Samuel
Combustion
With indicator or inspection means
Correlated with action of condition responsive burner control
431 31, 431 69, 431 73, 431 77, F23N 524
Patent
active
043891845
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a combustion control apparatus which controls combustion in a combustor which is a heat source of a hot-water boiler or a hot-air heater.
BACKGROUND ART
A combustion control apparatus includes a memory circuit which generates an alarm signal and generates also a signal for stopping the combustion in the apparatus and which maintains its non-combustion state, when an abnormal condition such as abnormal heating, shortage of a medium (water) to be heated or ignition failure is sensed.
However, malfunction of such apparatus has occurred frequently due to the fact that this memory circuit is generally easily affected by noise, which can easily enter this memory circuit. This malfunction is objectionable as it may lead to an interruption of the combustion in the apparatus.
In the combustion control apparatus, noise is generated due to on-off operation of electromagnetic relays for various external output units driven by combustion control output signals from a combustion control circuit in the apparatus and also due to on-off operation of a fuel supply unit, a combustion blower and an ignition unit driven by the relays above described. Such noise is applied to the memory circuit through an input circuit and gives rise to a source of malfunction of the apparatus.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to prevent the memory circuit from causing a malfunction by being affected by noise generated from the external output units. More precisely, the present invention comprises a circuit which detects an abnormality signal with timing other than the timing of generation of noise from the external output units, and the output of this circuit is applied as an input to the memory circuit. According to the present invention, malfunction due to noise from the external output units can be prevented in spite of a simple structure.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of an embodiment of the combustion control apparatus of the present invention;
FIG. 2 illustrates operation of various units in the combustion control apparatus; and
FIG. 3 shows operating waveforms at various points in FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention will now be described with reference to an embodiment shown in FIG. 1. In order to simplify the designation of and facilitate the understanding of various input signal terminals and output signal terminals shown in the figure, the word "terminal" may be omitted from them, and they may be designated by suffixing the reference numeral to the name of the signal. For example, "reference clock pulse input terminal 1" may be designated as "reference clock pulse 1". Further, a signal at each of the terminals has a digital value of "0" or "1".
The illustrated embodiment is of a type in which the igniting operation is performed after pre-purging, and the operation of the igniter is stopped when ignition is attained.
Reference numeral 1 designates a reference clock pulse input terminal, and 2 designates a reference timer which is composed of counters 3 and 4. Reference numeral 5 designates a timer for timing a pre-purge period (which will be referred to hereinafter as a pre-purge timer), and this timer 5 starts its timing operation after the reference timer 2 has operated. The pre-purge timer 5 is composed of an AND gate 6 and counters 7, 8 and 9. Reference numeral 10 designates a timer for timing a safety period (which will be referred to hereinafter as a safety timer), and this timer 10 starts its timing operation after the pre-purge timer 5 has operated. The safety timer 10 is composed of an AND gate 11 and counters 12 and 13. The counters in these timers 2, 5 and 10 are inverted by a negative edge.
Reference numeral 15 designates an AND gate, 16 an ignition unit drive terminal, 17 an output circuit, 18 an electromagnetic relay, 19 an ignition unit, and 20 a commercial AC power source. The unit 19 is composed of a resistor 21, a diode 22, a condenser 23, a Sydac 24 and an igni
REFERENCES:
patent: 3324927 (1967-06-01), Staring
patent: 3715180 (1973-02-01), Cordell
patent: 3999933 (1976-12-01), Murphy
patent: 4137035 (1979-01-01), Cade
patent: 4145180 (1979-03-01), Bendorf
patent: 4192641 (1980-03-01), Nakagawa et al.
patent: 4239478 (1980-12-01), Tanaka et al.
patent: 4249884 (1981-02-01), Cade
Nakagawa Sumio
Tanaka Toshio
Toudo Kenzi
Green Randall L.
Hitachi , Ltd.
Scott Samuel
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