JPS64609B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a safety device for a combustion machine provided with an oxygen deficiency detection circuit.

Configuration of conventional example and its problems As shown in Fig. 1, the safety device of a combustor having an oxygen deficiency detection circuit is set at a higher level than the misfire detection circuit 11, which is activated when the combustion condition becomes extremely deteriorated. A safety circuit includes an AND circuit 12 that receives as input the output of the oxygen deficiency detection circuit 10 and the output of timer circuits 13 to 17 that operate for a certain period of time after the start of combustion. It was simply connected to the input. This safety device has a timer circuit that locks the output of the oxygen deficiency detection circuit for a certain period of time after the start of combustion, in order to prevent the oxygen deficiency detection circuit from malfunctioning due to instability of combustion immediately after the start of combustion. Consideration has been taken that the oxygen deficiency detection is activated after the timer circuit times out, that is, after combustion becomes stable.

However, according to this configuration, when the indoor temperature, that is, the temperature of the combustion air, is extremely low, the timer circuit enters the same state as if the amount of combustion air had increased even after the time-up, and the combustion The state of instability continues. As a result, there was a problem in which the oxygen deficiency detection circuit was activated and combustion stopped even though there was no oxygen deficiency.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and by changing the detection level of the oxygen deficiency detection circuit according to the indoor temperature, oxygen deficiency caused by unstable combustion when the indoor temperature drops. The purpose is to prevent malfunction of the detection circuit. In other words, when the indoor temperature decreases, the oxygen deficiency detection level also decreases accordingly, and the purpose is to prevent the activation of the oxygen deficiency detection circuit due to a decrease in the combustion signal when the indoor temperature decreases and combustion becomes unstable. This is what I did.
Note that if an oxygen deficiency occurs in this state, combustion will further deteriorate, so the combustion signal will drop and the oxygen deficiency detection circuit will operate to stop combustion.

Structure of the Invention In order to achieve the above object, the present invention provides an amplification circuit whose output voltage changes depending on the indoor temperature, and an amplification circuit in which the output of the amplification circuit is used as a reference input and the other input is connected to a combustion signal. An AND circuit is provided which inputs the output of an oxygen deficiency detection circuit configured with a combustion chamber and the output of a timer circuit that operates for a certain period of time after the start of combustion.
The output of the AND circuit is connected to the safety circuit.

DESCRIPTION OF EMBODIMENTS One embodiment will be described below with reference to FIG.
In Fig. 2, 1 is an AC power supply for the combustion detection circuit;
2 is a burner, 3 is a flame rod inserted into the combustion flame, 4 and 5 are resistors, and 6 is a capacitor.
6 constitute a combustion detection circuit that utilizes the flame rectification effect, and the current value changes depending on the state of the combustion flame, so that the voltage across the capacitor 6 changes. 7 and 8 are resistors that set the misfire detection level. 10 is a detector for detecting oxygen deficiency, 11 is a detector for detecting a misfire, and 12 is an AND circuit, which combines the output of the detector 10 for detecting oxygen deficiency and an amplifier 17 that constitutes a timer circuit that operates for a certain period of time at the beginning of combustion, which will be described later. The output of is the input, and the output constitutes a safety circuit.
It is connected to the input of the OR circuit 37. 13-1
5 is a resistor, 16 is a capacitor, and 17 is an amplifier.
3 to 17, the oxygen deficiency detection circuit 1 for a certain period of time at the initial stage of combustion
A timer circuit is configured to prevent the output of 0 from being sent to the safety circuit. 18 is a thermistor for detecting indoor temperature, and 19 to 22 are resistors, which set a level for normal indoor temperature control. 23 is a detector, 19
~23 constitute a room thermo circuit. 24
is a resistor, 25 is a capacitor, 26 is an AND circuit,
27 is a diode, 28 is a resistor, and this 24
~27 constitute a prepurge circuit. 29 is a resistor, and 30 is an AND circuit, which is an igniter drive circuit which receives the output of the prepurge circuit and the output of the misfire detection detector 11 as inputs. Reference numeral 31 denotes a diode, which controls the operation of a misfire safety timer circuit, which will be described later, according to the output state of the misfire detection detector 11. 32 to 34 are resistors, 35 are capacitors, 36
is an amplifier, and these 32 to 36 constitute a non-ignition safety timer circuit. 37 is an OR circuit which is a reset circuit which receives the output of the non-ignition safety timer circuit and the output of the oxygen deficiency detection circuit as inputs. 38-4
1 is an open collector drive circuit, 42 is a motor drive unit, 43 is a fuel supply electromagnetic pump drive unit, 4
4 is an igniter drive unit, 45 is a two-winding latch relay, which has two coils for setting and resetting,
This relay has the characteristic that once it is set in one of the coils, it continues to maintain that state until a different coil is energized. Reference numeral 46 denotes a contact point of the two-winding latch relay, which becomes open in the event of an abnormality and stops all circuits. 47 is a return switch, 48 is a DC power supply for the control circuit, 49 is a resistor, and 50 is an open collector drive circuit, which is used to prevent malfunction of the oxygen deficiency detection circuit when combustion is stopped. 51 is a resistor, and 52 is a constant voltage diode, which is used to set the upper limit value of the oxygen deficiency detection level. 53 to 56 are resistors, 57 is an amplifier, and these 53 to 57 and the thermistor 18 for indoor temperature detection
to form an amplification circuit, and depending on the room temperature condition, resistor 5
The output voltage of the amplifier 57 is changed by the amplification degree determined by 5 and 56.

To briefly explain the operation in the above configuration, first, when the indoor temperature is within a range that does not worsen the combustion condition, the output level of the amplification circuit 57 is set to be higher than the Zener voltage of the constant voltage diode 52, so the acid The input of the shortage detection detector 10 is regulated by the Zener voltage of the constant voltage diode 52. At this time, the input is OV because there is no combustion, and the output of the oxygen deficiency detector 10 is in the "H" state, but at the same time, the output of the misfire detection detector 11 is also "H".
Therefore, the drive circuit 50 becomes conductive, locking the output of the oxygen deficiency detection detector 10 to the "L" state,
The input of the AND circuit 12 is set to "L". At the same time, since the amplifier 17 also starts charging the capacitor via the resistor 13, its output remains in the "L" state for a certain period of time. In other words, the other input of the AND circuit 12 is also locked to "L" by the timer circuit.

In this state, if the indoor temperature is lower than the setting, the output of the detector 23 becomes "H", power is supplied to the next stage circuit, the motor drive section 42 is turned on, and the pre-purge circuit causes the electromagnetic pump drive section 43 for fuel supply. And the igniter drive unit 44 is turned on and starts the ignition operation,
Transition to combustion.

When combustion starts, a current flows between the flame rod 3 and the burner 2, and the capacitor 6 is charged. Therefore, the input levels of the misfire detector 11 and the oxygen deficiency detector 10 rise, and the relationship of input>input is established, so that the output is reversed from "H" to "L" and normal combustion continues. Furthermore, as the capacitor 16 is charged and the relationship becomes greater than the input of the amplifier 17, the output becomes "H", so the AND circuit 12 is controlled by the output state of the oxygen deficiency detector 10. . The oxygen deficiency level at this time is the normal level set by the constant voltage diode 52, as described above.

Next, when the indoor temperature drops, thermistor 1
Since the resistance value of resistor 8 increases, the input to amplifier 57 decreases, and the output also naturally decreases by the degree of amplification determined by resistors 55 and 56. When the output level of the amplifier 57 becomes lower than the Zener voltage of the constant voltage diode 52, the input to the oxygen deficiency detector 10, that is, the oxygen deficiency level, is determined by the output level of the amplifier 57.
As the indoor temperature decreases, this works to reduce the oxygen deficiency level. As a result, the indoor temperature decreases, the combustion state becomes unstable, and even if the input to the oxygen deficiency detector 10 decreases, the output will not be reversed to "H" because the input has decreased.

If an oxygen deficiency occurs in this state, the combustion condition will further worsen, so the input will further decrease, the output of the oxygen deficiency detector 10 will be inverted to "H", and the input of the OR circuit 37 will be reset by setting it to "H". Activate. Here, when the indoor temperature decreases, the lower limit for oxygen deficiency detection is the misfire detection level. When the indoor temperature rises again, the output level of the amplifier 57 becomes higher, and the oxygen deficiency level also rises. In this way, the oxygen deficiency level is varied between the Zener voltage determined by the constant voltage diode 52 and the misfire detection level according to the indoor temperature, thereby preventing malfunction of the oxygen deficiency detection circuit due to unstable combustion due to the influence of room temperature. .

Effects of the Invention As described above, according to the present invention, when the indoor temperature decreases, by reducing the oxygen deficiency level, combustion instability occurs when the indoor temperature temporarily decreases, and combustion failure occurs when the indoor temperature rises slowly. This has the effect of preventing malfunction of the oxygen deficiency detection circuit due to reasons other than oxygen deficiency, such as stability.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional safety device, and FIG. 2 is a circuit diagram of a safety device according to an embodiment of the present invention. 2...burner, 3...flame rod, 10...
... Oxygen deficiency detection detector, 11 ... Misfire detector, 12
...AND circuit, 13-15...Resistor, 16...
Capacitor, 17... Timer amplifier, 18...
...Indoor temperature detection thermistor, 37...OR circuit, 53-56...resistor, 57...amplifier.

Claims (1)

[Claims] 1. A misfire detection circuit that uses flame rectification to detect misfire conditions such as lack of oil; an oxygen deficiency detection circuit that is set at a higher level than the misfire detection circuit and detects abnormal combustion in the event of oxygen deficiency; The oxygen deficiency detection circuit is equipped with an amplification circuit whose output voltage varies depending on the temperature state, and the oxygen deficiency detection circuit uses the output of the amplification circuit as one input, and uses the input on one side as a combustion signal obtained by rectifying the flame. A safety device for a combustion machine is further characterized in that the output of an AND circuit which inputs the output of the oxygen deficiency detection circuit and the output of a timer circuit that operates for a certain period of time in the initial stage of combustion is input to the safety circuit.