JPS6235566B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a combustion safety control device that has a function of automatically performing operations necessary for igniting a burner according to a predetermined sequence, and in particular, The present invention relates to a combustion safety control device equipped with means for adjusting the amount of air supplied to the combustion chamber.

[Conventional technology]

In a combustion safety control device that has the function of supplying combustion air into the combustion chamber, during the pre-purge operation that is performed prior to ignition, the amount of air is maximized to ensure a reliable pre-purge, and the ignition that is performed after the pre-purge is During operation, it is necessary to minimize the amount of air so as not to interfere with ignition and flame stabilization. Also, after the prepurge operation is completed,
It is desirable to measure the ignition trial time after confirming that the air amount has reached its minimum.

[Problem that the invention seeks to solve]

However, in the past, the air blast was not throttled during the ignition trial, so there was a problem in that ignition could not be guaranteed.

This invention was made to solve the above problems, and aims to provide a combustion safety control device that ensures reliable ignition and has excellent operational stability and safety.

[Means for solving problems]

As shown in FIG. 1, the combustion safety control device according to the present invention includes a damper driving means 4 connected to an AC power source 1 via a damper opening direction selection means 4K1.
0, maximum opening detection means 43 for detecting the maximum opening state of the damper 41 driven by the damper driving means 40, minimum opening detection means 44 for detecting the minimum opening state, and the damper opening direction selection. Means 4K
Relay 4K and transistor Q that switch and control
3 connected in series, a latch circuit B in which the second transistor Q7 is made conductive on the condition that the first transistor Q6 is made conductive to maintain the conductive state of the first transistor, and the maximum opening degree. Maximum opening confirmation means 43 that is closed by the operation of the detection means 43
A timer circuit C connected in series with A, an ignition control circuit D directly connected to transistor Q8, and relay circuit A, latch circuit B, timer circuit C, and ignition control circuit D connected in parallel via thermoswitch TH. A DC power supply 7, a gate circuit E connected in parallel to the DC power supply 7 via a minimum opening confirmation means 44A that is closed by the operation of the minimum opening detection means 44, and a first gate circuit E of the latch circuit B. a pulse detection circuit F whose output side is connected to the base of the transistor Q6; the base of the transistor Q3 of the relay circuit A is connected to the positive electrode side of the DC power supply 7 and the output side of the latch circuit B; The output side of C is connected to the input side of the gate circuit E and the pulse detection circuit F, and the gate circuit E
A charging/discharging capacitor whose output side is connected to the base of a transistor Q8 in series with the ignition control circuit D, and a charging/discharging capacitor whose output side is connected to the base of a transistor Q8 in series with the ignition control circuit D, and the timer circuit C is configured to measure the pre-purge time with a charging time constant and the ignition trial time with a discharging time constant. It is constructed as a switching element that becomes conductive when the charging voltage of the discharge capacitor becomes higher than the reference voltage.

[Effect]

In the combustion safety control device according to the present invention, when the thermo switch TH is closed due to a heat request, the transistor Q3 is turned on, so the relay circuit A is also closed, and the relay 4K changes the damper opening direction selection means 4K1 in the direction of opening the damper 41. select. Thereby, the damper driving means 40 drives the damper 41 to the maximum opening position.

When the maximum opening degree detection means 43 detects the maximum opening degree of the damper 41 and closes the maximum opening degree confirmation means 43A, the power supply 7 is connected to the timer circuit C and measurement of the pre-purge time begins. Therefore, prepurge is effectively performed under the maximum air volume due to the damper being at its maximum opening.

When the timer circuit C times up after a predetermined time and sends out a prepurge end signal, the pulse detection circuit F detects the rise of the prepurge end signal and excites the latch circuit B. As a result, the output of the latch circuit B clamps the transistor Q3 and opens the relay circuit A even if there is a signal from the thermoswitch TH. select. Thereby, the damper driving means 40 drives the damper 41 to the minimum opening position.

When the minimum opening degree detection means 44 detects the minimum opening degree of the damper 41 and closes the minimum opening degree confirmation means 44A, the gate circuit E is activated and the charge stored in the capacitor of the timer circuit C is used to detect the minimum opening degree of the damper 41. The transistor Q8 also becomes conductive, and the power supply 7 is connected to the ignition control circuit D, and an ignition trial is executed.
Therefore, this ignition trial is stably performed under the minimum air volume.

Incidentally, since the gate circuit E is energized until the pre-purge end signal due to discharge of the capacitor of the timer circuit C disappears, the ignition trial time is determined by this energization time.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, a primary winding of a transformer 2 is connected between both ends of the AC power supply 1, and an air supply control device 40, a fan motor 3,
A pilot burner valve 4, a main burner valve 5, and an igniter 6 are connected to each other. The air supply control device 40 is for controlling the total flow rate of air supplied into the combustion chamber, and includes, as a typical example, a damper 41 and a recycle motor 42 for adjusting its opening degree, and a damper 41.
A two-position control device is shown having a high switch 43 that is turned on at a high position, which is a large opening, and a low switch 44, which is turned on at a low position, which is a small opening.

Further, a rectifying and smoothing circuit consisting of a diode bridge 7 and a capacitor C1 is connected to the secondary winding of the transformer 2, and its output is supplied to a subsequent electronic circuit. That is, when a switch that is turned on when there is a heat demand, such as a thermostat TH, is turned on, a voltage is applied to the voltage divider circuit consisting of resistors R1 to R4, and the transistor Q
1 is conductive.

When transistor Q1 conducts, its collector current flows through the set coil L1 of the safety relay, the closed contact of the normally closed wind pressure switch AF, the resistor R5, and the normally closed contact 1K1 of the relay 1K to the gate of the thyristor Q2. Thyristor Q
2 conducts, and its load, relay 1K, operates, turning off its two normally closed contacts 1K1, 1K2, and its three normally open contacts 1K3, 1K4, 1K.
Turn on 5.

When the contact 1K4 is turned on, operating current is supplied to the fan motor 3 via the normally closed contact 2K2 of the relay 2K. In other words, the energization of relay 1K requires that there is no disconnection in the set coil L1 of the safety relay, and that the wind pressure switch AF is on the normally closed contact side (that is, it is not welded on the open contact side).
This will be done after confirming. Note that the safety relay is not pulled in because the current flowing through the wind pressure switch AF is minute.

On the other hand, transistor Q3 receives a base bias applied from a voltage dividing circuit made up of resistors R6 to R9, becomes conductive immediately after thermostat TH is turned on, and operates relay 4K. This relay 4
The contact 4K1 is switched by the operation of K, and the recycle motor 42 of the air supply control circuit 40 operates to bring the damper 41 to the wide open position. This operation gradually increases the amount of air supplied to the combustion chamber, which is detected and the wind pressure switch AF is activated.
is switched from the normally closed contact side to the open contact side, and when the opening degree of the damper 41 reaches the high position, the low switch 44 is turned off and the high switch 43 is turned on.

In this state, from the open contact side of the wind pressure switch AF, the contact 43 of the high switch 43, which has become closed,
A. A charging current flows into the capacitor C2 via the contact 1K3 and the resistor R10, which are already turned on, and the measurement of the prepurge time T1 starts from this point. The measurement of this pre-purge time T1 is performed using a resistor R.
This is performed by the operation of PUT Q4, which compares the terminal voltage of capacitor C2 with the first set voltage set by R1 to R4 and R11, R12.

As capacitor C2 continues to charge and its terminal voltage reaches the set voltage, PUT Q4 becomes conductive and a signal indicating the end of pre-purge time T1 is supplied to the base of transistor Q5, which is a twin transistor, via resistor R13. , its emitter side is contact 4 of low switch 44 which is already turned off.
4A, this transistor Q5 does not conduct and waits for low switch 44 to turn on. However, the prepurge time end signal is
It passes through diode D1, is pulsed by capacitor C3, and is then supplied to the base of transistor Q6, making it conductive.

Note that the discharge current of capacitor C2 flows through diode D1 and resistor R14, but resistor R1
The discharge of the capacitor C2 is suppressed by selecting the resistance value of the capacitor C2 to be a large value of about 1 MΩ.

When transistor Q6 becomes conductive, resistors R6 to R
Transistor Q7, which had been kept off by receiving a base bias from the voltage divider circuit consisting of 9, becomes conductive, and resistors R15 and R connected to its collector side become conductive.
Since base bias is provided to transistor Q6 by transistor Q6, transistors Q6 and Q
7 is stable in a conductive state. Also transistor Q6
When becomes conductive, the base bias of transistor Q3 is pulled down, turning off transistor Q3 and rendering relay 4K inoperative. As a result, the contact 4K1 is switched, and the damper 41 starts to be closed to a small opening degree by the recycling motor 42. The damper 41 is set to a large opening, and the time from when the high switch 43 is turned on until the transistor Q3 is turned off corresponds to the pre-purge time T1, and then the damper 41 is moved to a small opening and the high The ignition trial time T2 starts from the time when the switch 43 is turned off and the low switch 44 is turned on.

When low switch 44 is turned on and its contact 44A is closed, transistor Q5, which receives a base bias through resistor R13, becomes conductive because its emitter side is closed. This causes the pace of transistor Q8 to be biased by the divided voltage of resistors R17 and R18.
becomes conductive, and its collector current is supplied to the gate of thyristor Q9 via resistor R19.
9 turns on.

On the other hand, at the same time as transistor Q5 becomes conductive,
The base of transistor Q10 is biased by the voltage divided by resistors R20 and R21, making the transistor conductive, and relay 3K, which is its load, operates. That is, when the low switch 44 is turned on by moving the damper 41 to a small opening, the relays 2K and 3K are activated instantly, and the respective contacts 2K2 and 3K1 are turned off, and the normally open contact 2K is turned on.
3, 2K4, 3K2, and 3K3 are turned on. For this purpose, the pilot burner valve 4 and the igniter 6
operate at the same time to attempt to ignite the pilot burner.

As a result, the output current on the cathode side of PUT Q4 flows through diode D2, closed contact 3K3, relay 2K, air pressure switch AF, and thyristor Q9.
flows through the relay 2K and operates the relay 2K.
Discharge of capacitor C2 is promoted. relay 2k
When the normally open contact 2K1 is turned on by the operation of the transistor Q8, the collector current of the transistor Q8 also flows through the contact 2K1 and the resistor R3 to the relay 2K, and maintains it by itself.
Turning on transistor Q8 short-circuits the emitter and base of transistor Q1, turning off transistor Q1. The period from when the low switch 44 is turned on until the discharge of the capacitor C2 is completed and the transistor Q5 is turned off corresponds to the ignition trial time T2. That is, when the capacitor C2 is discharged and the transistor Q5 is turned off, the transistor Q10 is turned off and the relay 3K is de-energized, thereby ending the ignition trial. Note that since the capacitor C2 is rapidly discharged via the relay 2K, the ignition trial time T2 is set to an appropriately short time.

Normally open contact 3K of relay 3K in series with relay 2K
3 is connected in order to prevent a situation in which relay 2K operates even though relay 3K does not operate. Now, when the pre-purge time T2 has ended and PUT Q4 is conductive, the flame detection circuit
Assuming that the FC detects a false flame, if contact 3
If K3 is not present, there is a possibility that the relay 2K will operate and the ignition operation will begin before the damper 41 closes to a small opening. In such a situation, the ignition trial will begin with a strong air flow, and ignition will not be possible.
Therefore, an extremely dangerous situation arises in which raw gas is released. Contact 3K3 prevents such malfunction.

Furthermore, when transistor Q10 becomes conductive, a portion of its collector current also flows through diode D3 to capacitor C4, instantaneously charging it, and is then supplied to the base of transistor Q11 through resistor R22, making it conductive. Therefore, thyristor Q2 is shunted, but the operation of relay 1K is maintained by transistor Q11.

As is clear from the above description, the electronic timer circuit mainly composed of PUT Q4 has the function of measuring both the prepurge time T1 and the ignition trial time T2. That is, starting from the point in time when the high switch 43, which indicates that the damper 41 has reached a large opening, is turned on, charging of the capacitor C2 starts as shown in FIG. 3, and the anode voltage of PUT Q4 increases. The level gradually rises, and when it reaches a certain gate voltage level determined by a voltage divider circuit consisting of resistors R11 and R12, PUT Q4 becomes conductive. This is the prepurge time T1, and a prepurge end signal is generated at this point.

Furthermore, when PUT Q4 becomes conductive, a current necessary to conduct the transistor Q6 flows from its cathode side, but since the conduction of the transistor Q6 is performed by a pulse from the pulse generation circuit consisting of the resistor R14 and the capacitor C3, the capacitor C
The amount of discharge in No. 2 is small.

Then, after the low switch 44 is turned on,
The charge on capacitor C2 is rapidly discharged through relay 2K, and its terminal voltage drops to the conduction voltage ED of PUT Q4, at which point the ignition trial time T2 ends.

In addition, in FIG. 3, t2 indicates the time from when the damper 41 starts closing from a high position with a large opening when PUT Q4 is turned on until it reaches a small opening when the low switch 44 is turned on. .

The operations up to this point proceed automatically, but the subsequent operations differ depending on whether the ignition is successful or unsuccessful within the ignition trial time T2.

(When ignition is successful) When ignition is attempted from the time when relays 2K and 3K operate, and a flame is established within ignition trial time T2, flame detector F detects this flame and the flame detection circuit FC is transistor Q
Since the base of transistor Q8 is grounded to the common potential through a resistor, transistor Q8 is maintained in a conductive state even after the ignition trial time T2 has passed and transistor Q5 has been turned off. Therefore, thyristor Q9 remains conductive and relay 2K continues to be held in operation.

Further, at the same time as the transistor Q5 turns off, the transistor Q10 turns off, so the relay 3K becomes inactive and the contact 3K2 turns off, thereby stopping the operation of the igniter 6, and from this point on, the pilot Stabilization time T3 begins.

Further, at the same time that transistor Q10 is turned off, the anode potential of diode D3 decreases and discharge of capacitor C4 begins. When the capacitor C4 has finished discharging, the transistor Q11 is turned off, and therefore the relay 1K is deactivated. The time from when transistor Q10 is turned off until relay 1K becomes inactive is pilot stabilization time T3. This turns off the normally open contacts 1K4 and 1K5, but the normally closed contact 1K2
When turned on, the main burner valve 5 operates, fuel is supplied to the main burner, and from this point on, a steady combustion state begins.

Furthermore, when transistor Q11 turns off, thyristor Q2 is also already turned off, so
The base potential of the transistor Q3, which was held at a low level via the resistor R23, changes to the resistors R23 and R23.
8 and rises to a high level determined by the voltage division ratio of R9, transistor Q3 becomes conductive again, and relay 4K operates again. Here, the resistance value of R23 is selected so that the current does not pull in the relay 1K. As a result, the contact 4K1 is switched, and the recycling motor 42 moves the damper 41 in the opening direction again. This condition continues until there is no longer a demand for heat and the thermostat TH is turned off.

FIG. 4 shows the operation sequence of each part when ignition is successful.

(When ignition fails) If ignition does not succeed within the ignition trial time T2, the flame detection circuit FC does not ground the base of the transistor Q8 to the common potential via the resistor, so that the capacitor C2 is not discharged. Once finished and transistor Q5 is turned off, transistor Q8 is turned off and therefore transistor Q
1 is turned on. That is, at this point, both the transistor Q1 and the thyristor Q9 connected in series with the set coil L1 of the safety relay are in a conductive state, and the safety relay is pulled in by the current flowing through this circuit, and its contact LS
is turned off.

As a result, the power to the circuit after contact LS is cut off, all relays 1K to 4K become inoperable, and each contact of the load drive control circuit 30 is turned off by the thermostat.
Returns to the state before TH was turned on.

The safety relay will not return as it is, and contact LS
and reset coil L2 connected via resistor R24 and reset switch RS so as to bypass thermostat TH. It's getting old. The same operation can be obtained by using a thermal safety cutoff switch instead of the safety relay, and connecting the heater to the set coil L1 position and the cutoff switch to the contact LS position.

Furthermore, if the low switch 44 has a closed welding failure, when the high switch 43 is turned on at the start of the pre-purge operation, the transistors Q1,
Set coil L1, open contact of wind pressure switch AF,
Contact 43A of high switch 43 and low switch 4
The safety relay operates with the current flowing through the contact 44A of No. 4. If the high switch 43 is welded, the safety relay will operate with the current flowing through the same path when the low switch 44 is turned on during the ignition trial.

Note that if the high switch 43 is omitted, the fifth
As shown in the figure, a jumper wire 45 may be used to connect the terminals 11 and 12 to which the high switch 43 is connected. Furthermore, since the low switch 44 can be canceled by connecting the terminals 13 and 14 with a jumper wire, the present invention can also be applied to systems that do not have the air supply control device 40.

As described above, according to the present invention, when the timer circuit measures the prepurge time, the damper is opened to the maximum opening degree, so the prepurge is effectively performed under the maximum air volume. Furthermore, the timer circuit starts measuring the ignition trial time only when the interlock means confirms that the amount of air supplied into the combustion chamber is at a minimum. Therefore, ignition is always performed reliably, and operational stability and safety are greatly improved.

Further, the configuration of this embodiment has an excellent property of operating on the safe side even when the contact 43A of the high switch 43 and the contact 44A of the low switch 44 are welded. In other words, the contact 44 of the low switch 44
If A is welded, the safety relay operates when the high switch 43 is turned on, that is, at the start of prepurge. Also, the contact 43 of the high switch 43
If A is welded, the safety relay will operate when the low switch 44 is turned on, ie, at the beginning of the ignition trial.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the basic principle of the present invention, Fig. 2 is a circuit diagram of a combustion safety control device according to an embodiment of the invention, Fig. 3 is a graph showing the operation of the timer circuit of the device, and Fig. 4 The figure is a sequence diagram when normal ignition occurs, and FIG. 5 is a partial circuit diagram showing the connections when the high switch is omitted. 1... AC power supply, 2... Transformer, 3... Fan motor, 4... Pilot burner valve,
5... Main burner valve, 6... Igniter, 7
... Diode bridge, 30 ... Load drive control circuit, 40 ... Air supply control device, 41 ... Damper, 42 ... Recycle motor, 43 ... High switch, 44 ... Low switch, 45 ... Jumper wire , TH...Thermostat, 1K~4K...Relay, F...Flame detector, FC...Flame detection circuit, AF
...Wind pressure switch, L1...Set coil, L2
...Reset coil, LS...Contact, RS...Reset switch.

Claims (1)

[Claims] 1. A damper driving means connected to an AC power supply via a damper opening direction selection means, a maximum opening detection means and a minimum opening detection means of a damper driven by the damper driving means, and a damper opening direction selection means. a relay circuit in which a relay and a transistor are connected in series to switch and control the means; a latch circuit in which a second transistor is made conductive on the condition that the first transistor is made conductive to maintain the conductive state of the first transistor; a timer circuit connected in series with the maximum opening degree confirmation means that is closed by the operation of the maximum opening degree detection means;
The ignition control circuit is directly connected to the transistor, the DC power source is connected in parallel with the relay circuit, the latch circuit, the timer circuit, and the ignition control circuit via a thermoswitch, and the minimum opening detection means is activated. a gate circuit connected in parallel to the DC power source via a minimum opening confirmation means; and a pulse detection circuit having an output side connected to the base of the first transistor of the latch circuit; is connected to the positive side of the DC power supply and the output side of the latch circuit, the output side of the timer circuit is connected to the output side of the gate circuit and the pulse detection circuit, and the output side of the gate circuit is connected to the output side of the ignition control circuit. A charging/discharging capacitor is connected to the base of the transistor, and the timer circuit measures the pre-purge time with a charging time constant and measures the ignition trial time with a discharging time constant, and when the charging voltage of the charging/discharging capacitor becomes higher than the reference voltage. A combustion safety control device comprising a switching element that conducts.