JPS6314245B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for achieving a steady combustion state after a heat request signal is given, through a pre-purge period, a pilot trial period, a pilot only period, and a main trial period. The present invention relates to a combustion control device having the ability to automatically execute predetermined operating sequences.

[Conventional technology]

In a combustion control system having the above operation sequence, it is necessary to configure the system so that after the pilot trial time has elapsed, it is confirmed that the ignition source operation has ended before entering pilot-only operation. be.

[Problem that the invention seeks to solve]

However, because conventional combustion control devices do not confirm that the ignition source has stopped operating, the pilot-only period may begin measuring while the ignition source is operating, and the pilot flame may not stabilize. There was a problem that there was a risk that the main trial operation would be carried out before the main trial was completed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a combustion control device in which a predetermined pilot stabilization period is always ensured and operational stability is improved.

[Means for solving problems]

As shown in FIG. 1, the combustion control device according to the present invention includes an air amount adjusting means 37 for adjusting the amount of air supplied into the combustion chamber, a pre-purge time measured using a charging time constant, and an ignition trial using a discharging time constant. A first timer circuit A includes a charging/discharging capacitor 84 that measures time and a switching element 85 that becomes conductive when the charging voltage of the charging/discharging capacitor becomes higher than a reference voltage, and a pre-purge end signal from this timer circuit A. The air amount adjusting drive means 40, 101, 102 operate to close the opening of the air amount adjusting means 37 on the condition that the air amount adjusting means 37 is delivered, and the air amount adjusting means 37 has reached a predetermined small opening. an interlock means 69 for detecting the pre-purge end signal, a gate means 124 that operates on the condition of the pre-purge end signal and the operation of the interlock means, and a pilot valve 44 that operates on the condition of the operation of the gate means to start a pilot trial period. A pilot trial means 122 for starting, a flame detection circuit E for detecting that a pilot flame has been established within this pilot trial period, and an output of the flame detection circuit E that conducts under the condition that the gate means 124 is operated. The second timer circuit D is connected to the power supply through the switching means and sets a pilot only period and a main trial period.

[Effect]

In the combustion safety control device according to the present invention, a pre-set pre-purge time is measured by a first timer circuit A after a heat request signal is given,
On the condition that the pre-purge time end signal is output from the first timer circuit, the air amount adjustment drive means 40, 101, and 102 operate to close the opening degree of the air amount adjustment means 37.

When the mentor lock means 69 detects that this opening has reached the minimum opening, the gate means 124 operates under the condition of the pre-purge end signal and the operation of the interlock means 69. Therefore, the pilot trial means 122 is activated, operating the pilot valve 44 to begin a pilot trial period. When the flame detection circuit E detects that a pilot flame has been established within the pilot trial period, the detection output maintains the conductive state of the switching means 95, which has been made conductive under the condition that the gate means 124 is operated, Through this switching means 95, a second pilot-only period and a main trial period are set.
Connect timer circuit D to the power supply.

As a result, the second timer circuit is started only when the first timer circuit has timed up and a pilot flame has been established, so that a predetermined pilot stabilization time is always secured and the operation is stable. Stability can be improved.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 2, a commercial AC power source 21 is directly connected from terminals 1 and 2 to both ends of a primary winding 23 of a step-down transformer 21 via conductors 26 and 27. A load drive control circuit 30 consisting of a large number of output switches or contacts of the present control device is connected between the conductor wire 26 and the conductor wire 27.
External equipment, ie, the combustor load device 40, is connected through a plurality of terminals connected to the combustor load device 40. First, conductor 2
6 to the blower blower motor 41 via the normally open contact 73-4 to the terminal 3, and from the conductor 26 to the terminal 26 via the normally open contacts 73-4, 70-2 and 122-2 and the normally closed contact 122-1. igniter 42 via 4
However, the normally open contacts 73-4, 70-
2 and 160-2 and normally closed contact 160-1
The first fuel supply device 43 is connected to the terminal 7 via the
Furthermore, the connection point 31 between the normally open contacts 122-2 and 160-2 and the normally closed contacts 122-1 and 160-1
From there, the second fuel supply device 44 is connected to the conductive wire 27 via the normally closed contact 134-3 and the terminal 6, respectively. The first and second fuel supply devices 43 and 44 may be configured such that the first fuel supply device 43 is a main fuel supply device and the second fuel supply device 44 is a pilot fuel supply device. It may also be considered as a first and second stage fuel supply device, such as those used in low-high switching combustion systems. The connection point 31 is also directly connected to the terminal 5. This is so that when this combustion control device is used as an intermittent pilot, that is, as a combustion method (IT method) in which both the main valve and the pilot valve are open, switching can be performed by jumping terminals 5 and 6 along the broken line 45. This is for the purpose of Incidentally, in this embodiment, the combustion method (ID method) in which the pilot valve is closed when the jumper wire 45 is not present, that is, the shutoff pilot is opened, is used.
I will explain the case where it is used. Further, an alarm device 46 is connected between the terminal 12 and the terminal 2 to indicate that an abnormality has occurred in the combustion operation. Further, in the control circuit 30, a normally open contact 63-2 or SS2 of a safety shut-off switch and an indicator 33 are connected between conductors 26 and 27.
Furthermore, an indicator 34 indicating whether the present control device is in combustion operation or not, and an indicator 35 indicating whether or not the second fuel supply device 44 is energized are provided.

Furthermore, the load control circuit 30 includes a control circuit that controls the operation of an air supply control device 47 for controlling the amount of combustion air. A damper device is typically used as the air supply control device 47, but any device that can vary the total amount of air supplied into the combustion furnace may be used. Here, the control device includes a well-known recycle motor 48 and a low-high setting device 49, and is disclosed as a well-known two-position control device or ON-OFF control device. The air supply control device 47 can also be operated as a known proportional control device, as will be described later.

On the other hand, the secondary winding 24 of the transformer 22 has a midpoint tap 25, and between this tap 25 and one end of the secondary winding 24, a known diode bridge 26 consisting of four diodes is installed. connected, conductor 27
A positive potential is applied to the conductor 27 and a negative potential is applied to the conductor 28, and a capacitor 29 provided between the conductors 27 and 28 causes the conductor 27 to
A stepped-down DC voltage is supplied between and 28.

A combustion control device 50, which is a main part of this embodiment, is connected between the conductive wires 27 and 28, and a DC voltage is applied thereto. In FIG. 1, in order to more clearly understand the circuit configuration and operation of the combustion control device 50, the circuit structure and operation of the combustion control device 50 are divided into several broken line blocks, and each block will be explained.

As shown in the figure, this combustion control device is composed of five main circuit parts: a first electronic timer circuit A, an air supply source control circuit B, an ignition source control circuit C, a second electronic timer circuit D, and a flame detection circuit E. ing. Among them, the flame detection circuit E is disclosed in, for example, US Pat.
A circuit that utilizes the rectifying effect of flame as shown in No. 3270799 or National Patent No. 3270800;
Alternatively, since a known flame detection circuit such as a circuit that utilizes the optical properties of flame is used, a simplified configuration is disclosed.

One end of the conductor 27 is connected to the conductor 5 via a normally closed contact 63-1 of a safety shutoff switch SS (described later), that is, SS-1, and a start switch or thermostat switch 39 connected to terminals 19 and 20.
1 is supplied with a DC voltage to power the five circuit sections mentioned above. The first electronic timer circuit A includes:
It is mainly formed of a safety cutoff switch drive circuit 53, a start check circuit 54, and a first semiconductor timer circuit 55. The safety cut-off switch drive circuit 53 includes a first series circuit of four resistors 57, 58, 59 and 60 and a diode 61;
Transistor 53 and P-gate thyristor 6
4 and a second series circuit consisting of a safety shut-off switch/heater 63 are provided in parallel between conductors 51 and 28, respectively. As the safety shutoff switch/heater 63, a known bimetal heating manual return type thermal response switch is used, but any type of on-delay manual return switch may be used. The first semiconductor timer circuit 55 is connected via a conductive wire 66 from the connection point of the resistors 59 and 60 of the first series circuit.
In addition, a safety switch 63 and a P-gate thyristor (hereinafter abbreviated as SCR) 64 of the second series circuit
A connection point 65 is connected to the activation check circuit 54.

The startup check circuit 54 includes a wind pressure switch 67 connected to terminal 1 for checking the air supply into the furnace.
6, 17 and 18. A relay 70 for driving the second fuel supply source 44 is connected between the terminal 18 and the conductor 66. Furthermore, in order to check the rotational position state of the combustion air supply control device 47 such as a damper motor by the recycle motor 48, that is, the air supply amount state, two high (large quantity supply state) switch 68 and low (small quantity supply state) switch 69 are activated. It has a monitoring switch.
When the air supply is large, that is, the damper is in the wide open state, the high switch 68 is turned on, and when the air supply is small, that is, the damper is in the small state, the low switch 69 is turned on. When the damper opening is placed in these intermediate areas,
These switches 68 and 69 are off.
The high switch 69 is connected between the terminal 18 and the terminal 14, and the low switch 69 is connected between the terminal 13 and the terminal 15, and the terminals 13 and 14 are connected with a jumper wire. A normally open contact 73-2 and a normally closed contact 73-1 of a relay 73 and a trigger circuit 71 are connected between the terminal 14 and the conducting wire 28,
The signal of this trigger circuit 71 is a semiconductor switch, that is, a P-gate thyristor (hereinafter abbreviated as SCR).
72 gates. Here, the contact point 73-
In series with this thyristor 72, a parallel circuit consisting of a relay 73 and a display device 74 is connected to the power supply conductor 27.
and 28. Further, a twin transistor 76 is connected in parallel to the thyristor 72, and this transistor 76 is provided with a delay circuit consisting of resistors 77 and 78 and a capacitor 79 to ensure a post-purge period, thereby allowing the air supply blower to A ventilation control circuit 75 is configured to control 41.

On the other hand, the terminal 17 is connected to the contact 73 via the resistor 81.
-1 and contact 73-2, and the first semiconductor timer circuit 55 is also supplied with power from this connection point 80. This semiconductor timer circuit 55 mainly utilizes two semiconductor switch elements 85 and 97, and is disclosed in Japanese Patent No. 972,842. This semiconductor timer circuit 55 is provided with a semiconductor switch element, that is, an n-gate thyristor (hereinafter abbreviated as PUT) 85, with a connection point between a resistor 83 and a capacitor 84 on its anode side, and resistors 86 and 87 on its gate side. connection points are connected respectively. On the other hand, the cathode side of this PUT 85 is branched into two current paths via a connection point 90, one of which is connected to the conductor 66 via a diode 93, and the other is connected to the conductor 66 via a resistor 91 and a conductor 94. A pre-purge period end signal or a pilot ignition trial period signal is supplied to an air supply source control circuit B and an ignition source control circuit C, which will be described later. This first electronic timer circuit A
further includes a transistor 95 and a normally open relay contact 70-1 for self-holding or latching the relay 70. This transistor 9
5 also controls the conduction of another transistor 62 via this contact 70-1, thereby controlling the heating of the safety switch heater 63.

Next, the configuration of the air supply source control circuit B will be explained.
A circuit similar to the air supply source control circuit also exists in the combustion method (ID method) which closes the pilot valve when the second electronic timer circuit cutoff pilot, ie, the main valve, opens, which will be described later. Conductor wires 51 and 2
8, a series circuit of a first control relay 101 and a transistor 102 for controlling the combustion air supply source;
four resistors 103, 104, 105 and 106
Three series circuits are provided: a series circuit of transistor 108 and two resistors 109 and 110. Further, another transistor 111 is provided between the connection point of the resistors 104 and 105 and the conductive wire 28, and this transistor 111 and the above-mentioned transistor 108
This forms a well-known latch circuit, and when transistor 111 becomes conductive in response to a signal from conductor 94, transistor 108 also becomes conductive, and both transistors 108 and 111 remain conductive regardless of the presence or absence of an external signal.

The ignition source control circuit C is also supplied with power from the connection point 52 of the first electronic timer circuit A, forming a current path back to the terminal 13 of the start check circuit 54. That is, a diode 121, a parallel circuit of a relay 122 and a display device 123, and a twin transistor 1 are connected between the connection point 52 and the terminal 13.
24 and yet another diode 125 is provided, and the signal at the connection point 128 between the relay 122 and the transistor 124 is connected to the resistor 12.
6 to the base of the transistor 95 mentioned above.

Furthermore, the second electronic timer circuit D is provided between the collector side connection point 127 of the transistor 95 and the above-mentioned connection point 128, and is supplied with DC power from these connection points 127 and 128.
This second electronic timer circuit D mainly includes an air fuel control circuit 140 having a second control relay 134 for controlling both the combustion air supply control source 47 and the second fuel supply device 44, and the first fuel supply device It has a unique configuration having two circuits: a second semiconductor timer circuit 145 with a load relay 160 controlling the timer circuit 43; The air fuel control circuit 140 is
As mentioned above, together with the control circuit B, the air supply amount control circuit is formed. Furthermore, this control circuit 140
is a series circuit of resistor 133, second control relay 134 and transistor 135, and transistor 13
6 and a series circuit of three resistors 137, 138, 139, which are arranged in parallel between conductors 131 and 132, respectively, and a series circuit of a second control relay 134 and a transistor 135, including a transistor 141 and a series circuit of three resistors 137, 138, 139. resistance 14
2,143 series circuits are connected in parallel.
Also, the base of the transistor 135 and the conductor 1
Another transistor 144 is provided between the transistors 32 and 32, which is turned on at the same time as the transistor 141 is turned on. Note that the transistors 136 and 13
The transistors 5 are twinned and function as a latch similar to the transistors 108 and 111 of the air source control circuit B described above.

On the other hand, the second semiconductor timer circuit 145 also has the same circuit configuration as the first semiconductor timer circuit described above. That is, a conductor 158 and a diode 14 are connected to the anode side of an n-gate thyristor (hereinafter abbreviated as PUT) 150 through a resistor 143 and a load relay 160 from one end of the relay 134.
A charging circuit for the capacitor 146 is connected to the capacitor 146 through the conductor 9, and a connection point between the two resistors 147 and 148 provided between the conductive wires 131 and 132 is connected to the gate side. On the other hand, the cathode side of the PUT 150 is branched through a connection point 151 into three conductive wires: a diode 154, a resistor 152, and a resistor 153. Further, the diode 154 is connected to the conductor 161, and the resistor 152 is connected to the transistor 141.
Further, a resistor 153 is connected to the gate of a P-gate thyristor 157.

Finally, the flame detection circuit E includes conductors 27 and 2
The detection circuit 166 has well-known detection terminals 180 and 181 supplied with DC voltage from 8 and AC voltage from conductor 176, and a signal response control circuit 167. As mentioned above, the detection terminal and detection circuit 166 may be of any known type, and various detection terminals such as flame rod detection, ultraviolet detection, or CDS detection and detection circuits suitable for each detection terminal can be used. , is shown here as an abbreviation. Flame signal output 177 is connected to the emitter of transistor 168 through a Zener diode 172, the collector of which is connected to the base of transistor 95 through conductors 174 and 179. on the other hand,
From the base of transistor 168, a zener
It is connected through a parallel circuit of a diode 169 and a resistor 171 to a connection point 52 of the safety switch drive circuit 53 via a conductor 175 and a resistor 173. For this reason, the signal response control circuit 167 is controlled to have the following two functions by utilizing the fact that the potential at the connection point 52 changes with the combustion sequence operation. The first is a function to identify whether the flame response time is fast or slow depending on the sequence period;
is a recovery function in response to a momentary power outage.

The operation of this combustion control device will be explained in relation to the operation sequence diagram of FIG. 2. First, the normal combustion operation of the control device of this embodiment will be described.

First, when the start switch 39 is turned on, the resistors 103, 104, 105, and 106 are simultaneously energized to conduct the transistor 102, turning on the first control relay 101, and the resistors 57, 58,
9 and 60 are also energized, the transistor 62 becomes conductive, and the trigger circuit 71 is energized via the safety switch heater 63 and the air pressure switch 67, which is closed to the terminal 17 due to the absence of combustion air.
2 is turned on and relay 73 is turned on. Therefore, the terminal 10 is connected via each contact of the load drive control circuit 30.
At the same time, the blower 41 is energized from the terminal 3 to introduce air into the furnace. The energization of the relay 73 is
This is done after confirming that there is no disconnection in the safety switch heater 63 and that the contacts of the wind pressure switch 67 are on the zero wind pressure (No Air) side, and then the contacts 73-1 and 73-2 and the wind pressure switch 67 are immediately is reversed, so heating by the heater 63 stops, but the SCR 72 continues to conduct. During this time, the damper controller 47 activates the low state switch 69.
Turn it OFF and wait for the high state switch 68 to turn ON. Various types of damper controllers 47 are used, which usually require a moving time _t1 of several seconds to several minutes from a low position to a high position, but the control device of this embodiment has a configuration that is compatible with any type of damper controller 47. ing. At this point, the damper 37 is in the open position, that is, the high switch 68
is in the ON state, the first semiconductor timer circuit 5
5 starts charging the capacitor 84 with the current supplied through the safety switch heater 63, the wind pressure switch 67 closed to the terminal 18, the high switch 68, the contact 73-2, and the resistor 83, and the pre-purge time T ₁ starts.
time. In this way, when the capacitor 84 is sufficiently charged with the damper 37 fully open and the anode voltage of the PUT 85 reaches the gate voltage, the PUT 8
5 becomes conductive, the capacitor 84 starts discharging, and a signal indicating the end of the pre-purge time is sent from the cathode of PUT 85 to the air supply control circuit B via the resistor 91.
The voltage is applied to the transistor 111 of the ignition source control circuit C and the transistor 124 of the ignition source control circuit C, and these transistors become conductive. Note that at this time, the potential of the conducting wire 66 is
Since the potential is higher than the potential of the PUT cathode 90, the diode 93 is turned off. When transistor 111 becomes conductive, transistor 108 also becomes conductive, and thereafter both transistors 108 and 111 continue to maintain the conductive state during the combustion operation. transistor 111
Due to the conduction, the base bias decreases through the resistor 105, so the transistor 102 becomes non-conductive, the first control relay 101 is turned off, and the air supply control circuit B reverses the contacts of the load drive control circuit 30. The control device 47 begins to move in the direction of closing the damper 37. On the other hand, the transistor 124
is the conductor 6 while the high switch 68 is on.
6, relay 70 cannot conduct due to the relatively high voltage applied through terminals 18, 14 and 13, and high switch 68 is activated by control device 47.
After the transistor 124 is turned off, no current path is formed, so the transistor 124 does not conduct. Therefore, the transistor 124 waits until the damper 37 is closed by the controller 47 and the low switch 69 is turned on again. Also during this period t ₂ ,
The capacitor 84 continues to be discharged during this period t ₂
The resistor 92 is selected to have a relatively large value (for example, 1 MΩ) to prevent rapid discharge at the resistor 92. When it is confirmed that the damper 37 is set to a small opening and the low switch 69 is turned on, the emitter of the transistor 124 becomes the potential of the conductor 28 via the diode 125 and the low switch 69, so the transistor 124 becomes conductive instantly. When the relay 122 turns on, the resistor 12
Since the transistor 95 is conductive through the conductor 96, the two trigger circuits 75 and 97 are connected through the conductor 96.
is energized, transistor 76 and SCR 64
conducts. When transistor 76 turns on, SCR
Since the voltage applied to 72 decreases, SCR72
Turn off, and from now on, relay 73 becomes transistor 76.
controlled by On the other hand, when SCR64 becomes conductive,
As the potential of the conductor 66 rapidly decreases, the diode 93 becomes conductive, and the charge remaining in the capacitor 84 rapidly flows into the SCR 64 through the diode 93, relay 70, wind pressure switch 67, and conductor 65, and this current Relay 70 becomes conductive.
Also, since the contact 70-1 is turned on at this time, the transistor 95, which is already conductive, the contact 70-1,
Diode 61, resistor 59, conductor 66, relay 7
0, the relay 70 is self-maintained by the current flowing through the wind pressure switch 67 and SCR 64. Furthermore, contact point 7
Since the base voltage decreases when 0-1 is closed, the transistor 62 is turned off and the heater 63 stops generating heat.

These operations are performed almost simultaneously with the ON of the low switch 69, and the igniter 42 is connected to the relay 122 via the terminal 4 of the load drive control circuit 30, and the second fuel supply source, ie, the pilot valve, is connected via the terminal 6 of the load drive control circuit 30. 44 are energized by the relays 70, and the pilot ignition trial time _T2 begins. During this pilot ignition trial time _T2 , the charge in capacitor 84 continues to discharge through resistors 91 and 92.

If a flame is not established in the second fuel supply source 44 at this time, the transistor 124 will be non-conductive and the relay 122 will be turned off after the capacitor 84 has finished discharging.
OFF, the ignition source 42 is deenergized, and the transistor 95 also becomes non-conductive. For this reason, relay 70
The self-holding circuit of transistor 95 is also released,
Moreover, since there is no discharge current from PUT85,
Turn off. At the same time, when the contact 70-1 turns OFF, the transistor 62 becomes conductive again, and the safety switch heater 63 begins to heat up due to the current flowing through the SCR 64.
After a few seconds, the normally closed contact 63-1 is shut off, and at the same time, the contact 63-2 is turned on to activate the alarm.

On the other hand, when a flame is established in the second fuel supply source 44, the output 17 of the amplifier 166 of the flame detection circuit E
7 becomes a low potential. However, at this time, the potential of the conductor 175 to the response control circuit 167 is high due to the high potential of the connection point 52, so the Zener diodes 169 and 172 are instantaneously conductive, and the transistor 168 is also connected to the flame signal. Then it becomes conductive instantly. i.e. trial period T ₂
If a flame is detected during this time, a flame signal can be sent to the base 178 of transistor 95 almost instantaneously. Therefore, even if capacitor 84 has finished discharging and pilot firing trial period _T2 is complete, transistor 124 and relay 122 are
Even if the ignition source 42 is turned off, the transistor 95 and the contact 70-1 remain on, the relay 70 continues to hold, and the pilot valve 44 maintains the flame.

Next, transistor 95 is turned on, transistor 124 is turned off, and resistors 163 and 16
When the transistor 162 is turned on via the circuit 4, that is, the establishment of the pilot flame and the end of the pilot trial _T2 are confirmed, only then is power supplied to the second electronic timer circuit D via the conductors 131 and 132. be done. First, charging of the capacitor 146 begins via the resistor 133, second control relay 134, resistor 143, conducting wire 161, relay 160, conducting wire 158, and diode 149. That is, during the pilot-only period or pilot stability period _T3 , the resistance is approximately 1, while checking for disconnections in relays 134 and 160.
43 and a time constant determined by a capacitor 146. After this predetermined stability period _T3 has elapsed, PUT1
When the anode potential of 50 reaches the gate potential,
PUT 150 becomes conductive. First of all, PUT150
The transistor 141 is turned on by the current supplied from the cathode 151 through the resistor 152, and then the transistor 144 is turned on. When the transistor 141 is turned on, the current flowing through the resistor 133 increases, so the transistor 136 is turned on.
At this time, the cathode current of PUT 150 also energizes the trigger circuit 155, and almost instantaneously the SCR 157
conducts. Therefore, the potential of the conductor 161 decreases, so the diode 154 becomes conductive, and the capacitor 1
The charge at 46 flows as a larger current, energizing diode 154, relay 160, and SCR 157, with only relay 160 energized. This relay 160 is held by the current flowing through the transistor 136 that is turned on, the resistor 137, the diode 156, the relay 160, and the SCR 157 that is turned on.
The time from when PUT 150 becomes conductive to when relay 160 turns on is almost instantaneous. With the energization of the relay 160, the next main trial period _T4 begins, and the first fuel supply source or main valve 43 is energized, supplying main fuel into the furnace and a flame already established. Ignition from pilot flame is attempted. At this point, the charge in capacitor 146 has finished discharging, and transistors 141 and 144 are turned off.
do. Therefore, transistor 135, which was previously locked by transistor 144, becomes conductive, and thereafter, during normal combustion, transistors 135 and 136 continue to conduct, thereby energizing second control relay 134. That is, at the same time as the main trial period T ₄ ends, this relay 1
34, the damper controller 47 again drives the damper 37 in the opening direction via the load drive control circuit 30, so that the damper 37 is fully opened and complete normal combustion operation is established in the furnace.

Furthermore, when the start switch 39 is turned off due to the lack of heat demand, this start switch 3
All circuits are deenergized except for relay 73 and detection circuit 166, which are powered without going through 9. Since the relays 70, 101, 122, 140 and 160 are turned off, the damper controller 47 starts driving the damper 37 in the closing direction again. At the same time, the relay 73 switches on the transistor 7 after the period until the discharge of the capacitor 79 of the trigger circuit 75 is completed, that is, the post purge period _T5 .
The relay 73 is energized until 6 becomes non-conductive, and then the relay 73 is turned OFF and the blower 41 is stopped.
Complete one combustion cycle. FIG. 3 graphically represents this one combustion cycle and the relay operation sequence.

As described above, in the present invention, the prepurge period T ₁ ,
The engine enters normal combustion operation according to four starting sequences: pilot ignition trial period T ₂ , pilot stability period T ₃ , and main trial period T ₄ , and further has a post-purge period T ₅ as necessary in the stop sequence. The whole sequence is
Controlled with high reliability or fail-safe by a semiconductor combustion control circuit. Furthermore, the opening/closing operation sequence of the damper, that is, the air supply control devices 37 and 47 for controlling the amount of combustion air supplied to the furnace is inserted into the entire combustion operation sequence of this semiconductor combustion control circuit, and the above-mentioned combustion operation sequence is A major feature of the present invention is that the above-described semiconductor combustion control circuit is combined with a semiconductor air source control circuit that opens and closes the air supply control device based on signals from the semiconductor combustion control circuit to start or end each period. It is something.

That is, the control device 50 starts up only after detecting that the blower 41 is not supplying air into the furnace (No Air). and prepurge period T ₁
Before the start of _the pre-purge period T1, the damper 37 is fully opened and the high switch 68 for the high state interlock is checked, and during the pre-purge period _T1 , the damper 37 is held in the high state, and After the period T ₁ has passed, the damper 37 is activated again.
After setting the valve to a small opening state and confirming the low switch 69 for the low state interlock, the pilot trial period _T2 begins. Therefore, the semiconductor timer circuit 55 for the pre-purge period _T1 performs a timing operation only when the damper 37 is in the open state and the wind pressure switch 67 is monitoring the air supply.

In addition, if a contact welding accident occurs in which both high and low switches 68 and 69 are closed,
Timer circuit 55 and relay 70 are not energized. Furthermore, in the predetermined period T ₁ , once,
After detecting the air supply by the blower 41,
Even in the event of an accident returning to the NoAir state, a circuit for resetting the timer circuit 55 and a lockout circuit are activated. That is, the transistor 62, the safety switch 63, the wind pressure switch 67 returned to the terminal 17 side by NoAir, the resistor 81, the contact 73-2, the high state switch 68, the relay 70, and then the diode and the resistor 8.
The timer circuit 55 is designed so that it cannot operate completely because a current flows through the resistors 82 and 87 and the potential on the gate side of the PUT 85 is kept low mainly by the voltage dividing circuit of the resistors 82 and 91. That is, since PUTQ ₁ is turned on while the anode potential is low, the transistor 111 is turned on and the damper 37 is brought into a small opening state. Therefore, when switch 68 is OFF and switch 69 is ON, transistors 124 and 95 and SCR
64 turns on, but because the discharge current of capacitor 84 is small, relay 70 does not pull in, and relay 1
22 is also not pulled in because no current is supplied from transistor 95 and contact 70-1. Since the transistor 64 is on, the safety switch 63 operates and locks out the circuit through the contact 63-1. In addition, contact 73-1 and contact 7
Since 3-2 is single pole double throw, contact 73-2
When the contact 73-1 is welded, the SCR 72 cannot be triggered, and when the contact 73-1 is welded, the potential of the capacitor 84 does not rise due to the resistance of the resistor 81 and the trigger circuit 71, and the timer circuit 55 cannot be driven. In addition,
The first semiconductor timer circuit 55 is mainly connected to PUT85.
It is composed of SCR64, but the fail-safe nature of this circuit is disclosed in the above-mentioned patent.
Since it is described in the specification of No. 972842, it will be omitted here.

On the other hand, since the second semiconductor timer circuit 145 has substantially the same configuration as the first semiconductor timer circuit 55, a description of its fail-safe property will be omitted. The second control relay circuit 140 and the second semiconductor timer circuit 145 are cleverly coupled. In other words, in a sequence in which the control device is required to have a main trial period _T4 , a failure may occur that shortens this period _T4 , but if this period _T4 is too long or infinite. This prevents malfunctions from occurring. This is because a longer main trial period would result in the air being filled with explosive gas, which would be extremely dangerous. On the other hand, in the event of a failure that shortens the main trial period, the pilot will stop and the flame detector will signal that there is no flame, resulting in a safe stop, and there is no danger.

This control device will be used during this main trial period.
To prevent T ₄ from becoming too long, relay 13
4 cannot be pulled in, the main valve, that is, the relay 160, cannot be pulled in, or even if the relay 160 is turned on, the relay 134 is turned on after the main trial period _T4 has elapsed.
and 160 are both deenergized.
In other words, transistor 136 turns OFF and turns ON.
Otherwise, the transistor 135 will not turn on, so the relay 134 will not turn on. Moreover, at this time,
Since the self-holding current of the relay 160 cannot be generated, the discharge of the capacitor 146 ends instantly, and the relay 16
0 only turns on instantly and cannot be pulled in in reality. Furthermore, if the transistor 136 is turned ON, the transistor 135 will be turned ON, and the relay 134 will be pulled in. Since the potential supplied to the capacitor 146 will drop to the common potential, the PUT 150 will not be able to conduct. , relay 160 does not operate. This also applies when the transistor 135 is in an ON failure. Furthermore, when the transistor 135 has an OFF failure and the relay 134 cannot be pulled in, the transistor 136 cannot be turned on due to the transistor 141 and the resistor 143 at the same time as the PUT 150 is turned off at the end of main trial T ₄ , and the transistor 136 is turned off, so there is no holding current. The tired relay 160 also drops out.

In addition, if a failure occurs in which the transistor 135 cannot be turned off even if the transistor 144 becomes conductive, the relay 135 is turned off at the same time as the relay 160.
also operates, so the main trial period T ₄ becomes zero. That is, according to the present control device, the main trial period _T4 does not become longer even if it becomes zero.

In this embodiment, a case has been described in which both of the two state switches 68 and 69 are used to control the amount of combustion air in the furnace. The damper sequence is also easy to accomplish. For example, when controlling only with the low switch 69, place the switch 69 between terminals 13-15, short-circuit between terminals 18-14, and connect terminals 13-14.
Just remove the jumper in between.

〔Effect of the invention〕

As described above, according to the present invention, the flame detection circuit E
Transistor 95 receives a flame detection signal from
ON and pilot trial period T ₂
As a result, the transistor 162
Only when it is turned ON, an operating current is supplied to the second electronic timer circuit D, and measurement of the pilot only period _T3 is started. Therefore, a predetermined pilot stabilization time is always ensured, and operational stability can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the basic principle of the present invention, Fig. 2 is a circuit connection diagram of a combustion control device according to an embodiment of the present invention, and Fig. 3 is a combustion operation sequence and damper opening/closing operation of the combustion control device. FIG. 3 is a sequence diagram showing a sequence in relation to a relay operation. 30...Load drive control circuit, 40...Load device,
41... Blower, 42... Ignition source, 43... First fuel supply device or main valve, 44... Second fuel supply device or pilot valve, A... First electronic timer circuit, B...
Air source control circuit, C...Ignition source control circuit, D...Second electronic timer circuit, E...Flame detection circuit.

Claims (1)

[Claims] 1. An air amount adjusting means for adjusting the amount of air supplied into the combustion chamber, a charging/discharging capacitor that measures the pre-purge time using a charging time constant and the ignition trial time using a discharging time constant, and a charging voltage of the charging/discharging capacitor. A timer circuit consisting of a switching element that becomes conductive when the voltage becomes higher than a reference voltage, and an air amount that operates on the condition that a pre-purge end signal is sent from this timer circuit to close the opening of the air amount adjusting means. An adjustment drive means, an interlock means for detecting that the air amount adjustment means has reached a predetermined small opening, a gate means that operates on the condition of the pre-purge end signal and the operation of the interlock means, and the gate. a pilot trial means for starting a pilot trial period by operating a pilot valve conditional on the operation of the pilot means; a flame detection circuit for detecting establishment of a pilot flame within the pilot trial period; and the gate means. a second timer circuit connected to the power supply through the switching means and configured to set a pilot only period and a main trial period; Combustion control device with