JPS6314247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control device for a burner used in a hot air blower, hot water boiler, or the like. The present invention relates to an improvement in a timer circuit for determining the operation timing of each device constituting a burner in a combustion control device. The purpose of this is to check in advance with a simple circuit as a countermeasure against a failure of a safety timer that stops combustion if ignition does not occur within a predetermined time.

The functions of this type of combustion control device will be explained with reference to FIG. When a combustion start command is given by an operation switch, etc., the combustion blower starts operating,
Air is sent into the combustion chamber to scavenge combustion gas, etc. in the combustion chamber prior to combustion. This is called prepurge. At the same time, the prepurge timer starts counting and measures the prepurge time. When a predetermined period of time has elapsed, a prepurge end signal is issued from the prepurge timer, and the ignition operation begins. That is, in response to the pre-purge end signal, the fuel supply device and the ignition device (ignition transformer) are activated to start the ignition operation. At the same time, the safety timer starts counting.
That is, the prepurge end signal is an ignition operation start signal. The fire then ignites within the time set by the safety timer.
When a flame signal is obtained from the flame detector, the output of the safety timer is cut off, and the fuel supply system continues to operate and enters steady combustion. Note that the ignition device is stopped by a flame signal or the like.

If ignition does not occur within the time set by the safety timer, that is, if no flame signal is obtained, a non-ignition signal is issued by the output of the safety timer, as shown by the broken line. This activates the safety circuit, cutting off power to the fuel supply system, ignition system, and blower, and stopping the burner operation.

In this way, the safety timer is a very important timer because it stops the burner operation in the event of misfire, prevents fuel from being released, prevents danger, and measures safety.

If, in the event of a misfire, the frequency dividing flip-flop constituting the safety timer fails and no longer divides the frequency, the safety time becomes infinite and the aforementioned misfire signal is not output. As a result, the operation is not stopped and fuel continues to be released, creating an extremely dangerous situation.

To deal with this safety timer failure,
It is conceivable to provide two such timers or to provide a check circuit for this timer. but,
According to these, the circuit becomes complicated and is not practical.

The present invention has been made to improve these drawbacks. That is, a safety timer is constructed using a frequency dividing flip-flop which is used to set the prepurge time and whose operation has been confirmed. Furthermore, the present invention relates to obtaining the safety time and the pre-purge time by using the same flip-flop.

The present invention will be explained below with reference to an embodiment shown in FIG. In the middle of the explanation, in order to simplify the naming of the various input terminals, output terminals, and their signal types shown in each figure, the word "terminal" will be omitted and numbers will be added to the signal names. There are things to do. For example, the "clock pulse at terminal 1" is referred to as "clock pulse 1."

In this embodiment, the ignition device stops due to ignition, and resumes operation if the flame goes out midway.

1 is an input terminal for a reference clock pulse, 2 is a timer, and is composed of T flip-flops 3-7. 10 is an RS flip-flop (hereinafter referred to as RSFF) as a memory circuit, and NAND gates 11,
Consists of 12. The prepurge end signal of output ₇ is held at “0”. 15 is a drive terminal for the fuel supply device; 16 is a differential circuit that resets and sets the timer upon completion of the pre-purge;
Two D flip-flops 17, 18, NAND
It consists of a gate 19. 20 and 21 are NAND
The gate 22 is an inverter.

25 is a flame signal terminal from the flame detection circuit, which is "1" when there is a flame. 26 is an inverter, 27 is an AND gate that outputs a misfire signal, and the output _Q7 of timer 2 is input thereto. The output ₇ of the opposite level is input to the RSFF 10. 28 is an AND gate,
29 is a terminal for driving the ignition device. Reference numeral 30 denotes a differential circuit for restarting the operation when the flame is extinguished in the middle, and outputs a pulse of "0" when the flame is extinguished in the middle. Two D flip-flops 31, 32, NAND gate 33
Consists of.

Reference numeral 40 is an input terminal for an abnormality signal such as abnormal heating, which becomes "1" when an abnormality occurs. 41 is an OR gate.

42 is a search circuit for abnormal signals and non-ignition signals, which includes inverters 43, 44, 45, a capacitor 46,
It is composed of a NAND gate 47. 48 is AND
It is a gate.

50 is an RS flip-flop (hereinafter referred to as RSFF) as a safety circuit, and NAND gates 51, 5
Consists of 2. Holds abnormal signals and misfire signals.

Reference numeral 53 is an input terminal for a temperature signal from the temperature detection circuit, which is "1" when the temperature is low. 54 is an AND gate,
55 is a terminal for driving the combustion blower.

The operation of such a configuration will be explained. When the temperature signal 53 becomes "1", the reset of the RSFF 50 is released. AND gate 54 becomes "1" and terminal 5
5, the blower starts operating and pre-purge starts. Further, the reset of RSFF10 is also released. Also, NAND gates 20 and 21 are “0”
Then, timer 2 starts frequency division. This is the start of the prepurge time.

When the predetermined time has elapsed, the output ₇ of the timer 2 is inverted to "0" and the output _Q7 is inverted to "1". RSFF10 is set, NAND gate 11 becomes "1",
Terminal 15 opens the fuel supply. Also
The AND gate 28 becomes "1" and the ignition device starts discharging through the terminal 29. This is the start of the ignition operation.

The output of the RSFF 10 is also input to the differentiating circuit 16, and the NAND gate 19 outputs a pulse of "0" to reset the timer 2. The timer 2 starts frequency division again. This is the start of the safety time.

When ignited by the ignition operation, a flame signal 25 is emitted.
becomes “1”, the inverter 26 becomes “0”,
NAND gate 21 becomes "1" and T flip-flops 4-7 are reset. Further, the AND gate 28 becomes "0" and the ignition device is stopped.
This results in steady combustion.

If there is no ignition, the output _Q7 of timer 2 will become "1" when the safety time ends.
AND gate 27 is “1”, OR gate 41 is “1”
Therefore, at the search timing of the rising edge of the clock pulse of the output of the AND gate 48, the NAND
“0” is output from the gate 47. For this reason
RSFF50 is set, NAND gate 52 becomes "0", AND gate 54 becomes "0",
The blower stops. Also, timer 2, RSFF10
is reset, the AND gate 28 becomes "0", and the ignition device and fuel supply device are stopped. Stop all operations.

The operation of stopping the operation is the same even when the abnormal signal "1" is input from the terminal 40.

If the flame is extinguished during combustion, the differential circuit 30 outputs a pulse of "0", the timer 2 and RSFF 10 are reset, and the operation returns to the flip-purge operation.

Now, if any of flip-flops 3 to 7 fails and no longer divides the frequency, output ₇ becomes "0".
There is no reversal. Therefore, the output of RSFF10
_Q10 remains "0", the sequence does not proceed and the blower continues to operate, the flip-purge time becomes infinite, and the fuel supply system does not open, making it safe. However, timer 2 output ₇
It is not possible to check for a "0" failure.

Since the pre-purge time and safety time are obtained from the same timer 2, the pre-purge time ends and is output.
When Q ₇ becomes "1", "1" appears on AND gate 27. Therefore, there is no search circuit 47.
If the output of the AND gate 27 is directly connected to the RSFF 50 via an inverter, the situation will be the same as a misfire, and the RSFF 50 will operate, which is inconvenient.

In the present invention, the output of the AND gate 27 is searched.
Since it is input to RSFF50, when transitioning from prepurge time to safety time, even if AND gate 27 temporarily outputs "1", OR gate 41, inverter 45, and AND gate 48 will become "1" at the same time. Since there is no output, the output of NAND gate 47 is “0”
This will never happen, and the RSFF50 will never operate. Figure 3 shows the operating waveforms of each part. The number of each waveform indicates the gate in FIG. 2, and the waveform indicates the output of the gate. The wavy line indicates the case of an abnormal signal. At the end of the pre-purge time and transition to the safety time, output ₇ of timer 2
Set RSFF10 and its output _Q10 and timer 2
Since the timer 2 is reset by the differentiating circuit 16 using the clock pulse 1, the output _Q7 of the timer 2 temporarily becomes "1". Therefore, the AND gate 27 which receives the output Q ₇ of the timer 2, the output Q ₁₀ of the RSFF 10, and the output of the inverter 26, which is a flameless signal, temporarily outputs "1".

However, the search circuit 43 uses the pulse of the output of the AND gate 48 synchronized with the clock pulse 1 of the timer 2 for the operation timing, and uses the AND gate 48 and the inverter 4 whose output is delayed.
5 and the temporary output of the AND gate 27 above.
AND gate 4 input via OR gate 41
7 is used to calculate the logical sum. Therefore, as is clear from the waveform in FIG. 3, the logical sum does not hold when the temporary output of the AND gate 27 is generated, so RSFF50 is set when the pre-purge time shifts to the safety time. As a result, the AND gate 54 becomes "0" and the combustion control device does not stop all operations. Therefore, the prepurge time and the safety time can be made the same (the output can be obtained from the same T flip-flop).

The above-mentioned differentiation circuit and search circuit can be obtained with other configurations.

In the above embodiment, the pre-purge time and the safety time are the same, but the same problem occurs in other cases, and this can also be used. For example, Q ₇ and the output Q of the T flip-flop in the previous stage
A NAND gate with input is provided, and its output is
This is the case where the set input is RSFF10 and the safety time is _Q7 or the output Q of the T flip-flop in the previous stage.

As described above, in the present invention, the pre-purge time and the safety time are obtained from the output of the same counter, and if the counter is out of order, the pre-purge time becomes infinite and the ignition operation does not start. Furthermore, since a search circuit is used, the safety circuit will not be activated by the temporary output of the counter when the counter switches from the prepurge timer to the safety timer.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the combustion control device, FIG. 2 is a circuit diagram of the combustion control device according to an embodiment of the present invention, and FIG.
The figure is an operation waveform diagram of each part in FIG. 2. 1... Reference clock pulse input terminal, 2...
Timer, 15... Fuel supply device drive terminal, 16
... Differentiation circuit, 25 ... Flame signal input terminal, 29
... Terminal for driving the ignition device, 30 ... Differential circuit,
40... Input terminal for abnormal signal, 42... Search circuit, 53... Input terminal for temperature signal, 55... Terminal for driving combustion blower.

Claims (1)

[Claims] 1. A combustion blower drive terminal 55 controlled by the operation start signal 53, a clock pulse input terminal 1, and a required number of counters 3 for dividing the frequency of the clock pulse according to the operation start signal 53. - 7, a first memory circuit 10 whose reset input is the operation start signal 53, and whose set input is the output of the timer, and a drive of the fuel supply device controlled by the output of the memory circuit 10. The terminal 15 and the drive terminal 29 of the ignition device, the first circuit 21 that resets and sets the timer 2 when the first memory circuit 10 is set, and the timer 2 receives the operation start signal 53.
The first circuit 21 operates as a pre-purge timer and a safety timer, and the safety timer output is configured to be cut off by the flame signal 25, and the safety timer is the same as the counter that outputs the set input ₇ . A second circuit 27 which receives the timer output Q ₇ , the output Q ₁₀ of the first memory circuit 10, and the no-flame signal 26, and is operated by the output of the second circuit 27, A search circuit 42 operates except for the output temporarily outputted when the first memory circuit 10 is set, and the search circuit 42 uses a pulse synchronized with the clock pulse of the timer 2 for the operation timing. A combustion control device comprising a safety circuit 54 including a second memory circuit 50 which takes the output of the search circuit 42 as a set input and outputs an operation stop signal. 2. The combustion control device according to claim 1, wherein an abnormality signal is input to the search circuit.