JPS6345007B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a control circuit for a combustor capable of burning either liquid fuel or gaseous fuel.

(b) Conventional technology Conventionally, in this type of combustor, gaseous fuel is supplied to the burner at the beginning of ignition to perform combustion, and then when the temperature of the burner reaches the vaporization temperature of the liquid fuel, the fuel supplied to the burner is changed to gaseous fuel. Japanese Patent Application Laid-open No. 101135/1983 discloses a device in which combustion is continued by switching from fuel to liquid fuel.

(c) Problems to be solved by the invention In the conventional technology described above, combustion with liquid fuel cannot be performed unless gaseous fuel is used at the beginning of ignition. There was a problem that combustion could not be continued when one was missing. Therefore, the applicant has proceeded with development with the aim of providing a combustor that can ignite and continue combustion with either gaseous fuel or liquid fuel. When gaseous fuels such as gaseous fuels and city gas were supplied to the burner and ignited, it was found that the gaseous fuels mixed with air very well and had better ignitability than vaporized gases due to their characteristics.

Therefore, if either gaseous fuel or liquid fuel is supplied to a burner, but ignition does not occur, and the fuel supply to this burner is stopped after the ignition allowable time has elapsed, the fuel supplied to the burner may be liquid fuel. If there is, the vaporized gas ejected from the burner into the combustion chamber will liquefy due to the low temperature in the combustion chamber, so there is little danger, but if the fuel supplied to the burner is gaseous fuel, the vaporized gas will be ejected from the burner into the combustion chamber. Since the gaseous fuel left in the combustion chamber remains in the combustion chamber, there is a problem in that the gaseous fuel can be ignited by some cause (such as static electricity) and cause an explosion.

Furthermore, if the permissible ignition time is shortened with emphasis on the dangers of gaseous fuels mentioned above, the permissible ignition time for liquid fuel is complicated and time-consuming from supplying it to the burner to converting it into vaporized gas. A problem arose in that it did not ignite within the time limit.

The present invention has been made in view of the above-mentioned facts, and enables a safe and reliable ignition operation to be performed regardless of whether liquid fuel or vaporized fuel is supplied to the burner, and also provides for switching from gaseous fuel to liquid fuel. The purpose is to prevent abnormal combustion during switching.

(d) Means for solving the problems In this invention, (1) a burner A that burns liquid fuel or gaseous fuel;
and (2) an ignition device 17 for igniting this burner A.
(3) liquid fuel supply means 25, 26 for supplying liquid fuel to the burner A; (4) gaseous fuel supply means 24 for supplying gaseous fuel to the burner A; (5) supply to the burner A. The first mode uses only liquid fuel, and the second mode uses only gaseous fuel.
a selection switch 29 for selecting the mode and a third mode for switching from gaseous fuel to liquid fuel;
(6) According to the mode selected by this selection switch 29, only the first selection signal is emitted when the first mode is selected, only the second selection signal is emitted when the second mode is selected, and the second selection signal is emitted when the second mode is selected. A selection circuit 40 that first emits only the first selection signal and then only the second selection signal when selecting the mode No. 3;
and (7) a blower means 11 for supplying combustion air to the burner A when the selection circuit 40 issues any selection signal; fuel switching means 20 which enables the liquid fuel supply means 25, 26 when the selection circuit issues a first selection signal and enables the gaseous fuel supply means 24 when the selection circuit issues a second selection signal; (9) Signal change detection means 47 for detecting a change in the selection signal issued by the selection circuit 40 in the third mode.
(10) a pre-purge timer circuit 55 that outputs an ignition signal after a predetermined period of time from when the air blowing means starts blowing air or when a signal change is detected by the signal change detecting means 47; (11) a pre-purge timer circuit 55 of the selection circuit 40; It has two timers 45 and 46 having different operating times, which are selected according to the selection signal and are operated by the ignition signal of the prepurge timer circuit 55, and are made operable by the fuel switching means. fuel supply means 25,
26 or 24 and an ignition timer circuit 44 that operates the ignition device 17 for an appropriate time by a selected timer; 2
The flame detection circuit 51 continues the operation of 4.

(e) Effect When the first mode (liquid fuel only combustion operation) is selected by the selection switch 29, the selection circuit 40 issues a first selection signal to the blower means 11 and the ignition timer circuit 44. The ignition timer circuit 44 also enables the liquid fuel supply means 25, 26 in response to the first selection signal. When the air blowing means 11 starts blowing air to the burner A, the prepurge timer circuit 55 is activated, and the prepurge timer circuit 55 issues an ignition signal after a predetermined time from the start of air blowing. When this ignition signal is supplied to the ignition timer circuit 44, the ignition timer circuit 44 operates the kerosene timer 45 selected by the first selection signal. The kerosene timer 45 operates the liquid fuel supply means 25, 26 enabled by the fuel switching means 20 and the ignition device 17 for a time suitable for igniting the liquid fuel. If the flame detection circuit 51 confirms ignition during this operating time,
Even after the operating time set by the kerosene timer 45 has elapsed, the flame detection circuit 51 continues to operate the liquid fuel supply means 25, 26.
operation continues.

When the second mode (combustion operation using only gaseous fuel) is selected by the selection switch 29, the selection circuit 44 issues a second selection signal to the blowing means 11 and the ignition timer circuit 44. The ignition timer circuit 44 also enables the gaseous fuel supply means 24 in response to the second selection signal. Air blowing means 1
1 starts blowing air to burner A, the prepurge timer circuit 55 is activated, and the prepurge timer circuit 55 issues an ignition signal a predetermined time after the start of blowing air. When this ignition signal is supplied to the ignition timer circuit 44, the ignition timer circuit 44 operates the gas timer 46 selected by the second selection signal. The gas timer 46 operates the gaseous fuel supply means 24 and the ignition device 17 enabled by the fuel switching means 20 for a time suitable for igniting the gaseous fuel. If the flame detection circuit 51 confirms ignition during this operating time, the gas timer 4
Even after the activation time 6 has elapsed, the flame detection circuit 51 continues to operate the gaseous fuel supply means 24.

When the third mode (combustion operation switching from gaseous fuel to liquid fuel) is selected by the selection switch 29, the selection circuit 40 first issues a second selection signal, and performs the series of gaseous fuel combustion operations described in . will be held.

When the burner A is sufficiently warmed by the combustion of the gaseous fuel, or when a predetermined time has elapsed from the start of combustion of the gaseous fuel, the selection circuit 40 selects the first selection signal instead of the second selection signal. The air is emitted to the blowing means 11 and the ignition timer circuit 44. Furthermore, the fuel switching means 20 performs a switching operation to enable the liquid fuel supply means 25 and 26 instead of the gaseous fuel supply means 24 in response to the second selection signal. Along with this switching, combustion by the gaseous fuel is stopped, and the flame detection circuit 44 also stops the continuation of fuel supply. On the other hand, when the signal change detection means 47 detects a change in the selection signal,
The pre-purge timer circuit 55 operates and burner A
The gaseous fuel left behind is discharged. Thereafter, when the prepurge timer circuit 44 issues an ignition signal, the liquid fuel is ignited in the same manner as in the case described above, and combustion by the liquid fuel is started.

According to this invention, it is possible to perform pre-purging at the start of combustion regardless of whether liquid fuel or gaseous fuel is supplied, and then perform the ignition operation for a time suitable for each fuel. In particular,
In the case of the third mode, pre-purging is performed at the start of combustion of gaseous fuel and at the time of switching from gaseous fuel to liquid fuel, and then ignition operation can be performed for a time appropriate for each fuel. A safe and reliable combustion operation is performed, and abnormal combustion is prevented when switching from gaseous fuel to liquid fuel.

(f) Embodiment An embodiment of the present invention will be described below based on the drawings. A protect thermostat 5, A series circuit consisting of a normally open contact 8 of a heater 6 and a heater relay 7, a series circuit consisting of a contact 10 of a burner motor relay 9 and a burner motor 11, and a transformer 12 are connected.

A normally open delay thermostat 13 connected to the power source 1
An ignition device 17 for igniting burner A, which will be described later, is connected between line c and line a, which are derived from the connection point with fan motor 14 connected to line a, and line a. In addition, a first gas fuel supply means is provided to the gas supply pipe via the contact 19 of the fuel continuation relay 18, the contact 21 of the fuel switching relay 20, and the high limit thermostats 22, 23.
a second gas valve 24 arranged in parallel with the gas valve 76;
Pump 25 and kerosene valve 2 as liquid fuel supply means
The pump 25 and the kerosene valve 26 are connected to the normally closed fixed contact 21' side of the contact 21, and the second gas valve 24 is connected to the normally open fixed contact 21'' side. A series circuit is connected between the normally open fixed contact 4' of the ignition timer 4 and the line a, which is a parallel circuit consisting of an ignition timer motor 27 and a timer lamp 28, and a combustion selector switch 29 as a selection switch. A first gas valve 7 is connected between the line a and the normally open fixed contact 10' of the contact 10.
6 and a series circuit consisting of part of the combustion selector switch 29 are connected. An electronic control circuit 30 is connected to the secondary side of the transformer 12.
0 has the above-mentioned relays 7, 9, 15, as external parts.
In addition to 18 and 20, there is a wind pressure switch 31 as an operation detection means that works when the burner motor 11 is activated, a flame rod 32 for flame detection, a temperature controller 33, a room thermistor 34, a gas lamp 35, a kerosene lamp 36, and a burner temperature detecting device. A burner thermistor 37, a reset switch 38, and a power lamp 39 are connected, respectively.

The combustion selector switch 29 is set to LINE I, which is a mode for combustion operation using only liquid fuel;
It has a line low mode, which is a mode in which combustion is started with gaseous fuel at the time of ignition, and then switches to liquid fuel, and combustion operation is performed, and a line ha mode, which is a mode in which combustion operation is performed only with gaseous fuel. A part of 29 is connected to the control circuit 30.

A selection circuit 40 in the control circuit 30 selects the kerosene lamp 3 when the signal from the changeover switch 29 is LINE I, which indicates that the ignition operation is performed using liquid fuel.
6. Output the first selection signal to the comparison circuit 43 consisting of the inverter 41 and the AND circuit 42 and the kerosene timer 45 in the ignition timer circuit 44. If the signal from the changeover switch 29 is line RO or C which performs the ignition operation using gaseous fuel, the gas lamp 3
5. A second selection signal is output to the gas timer 46, relay 20, and switching timer 47 in the ignition timer circuit 44. Therefore, the ignition timer circuit 44 appropriately determines the allowable ignition time for enabling the ignition device 17 according to the first and second selection signals inputted from the selection circuit 40 using the kerosene timer 45 or the gas timer 46. , and outputs a drive signal during that time. A burner temperature detection circuit 50 having comparators 48 and 49 transmits a signal from the burner thermistor 37 to the relay 7 via the selection circuit 40 and the comparison circuit 43, and a room thermocircuit 52 transmits the signal from the burner thermistor 37 to the temperature regulator 33 and the room thermistor 34. The signal is sent to the AND circuit 54 and the relay 9 via the after-purge timer 53, and to the ignition timer circuit 44 via the pre-purge timer circuit 55.
This is what is output to. The switching timer 47 consists of a timer 58 and a differentiating circuit 57 that receives signals from the selection circuit 40 and a power source 56.

Further, the flame detection circuit 51 transmits the signal from the flame rod 32 to the ignition timer circuit 44 and the relay 1.
8, and the switching timer 47 is output to the selection circuit 40.
The signal from the ignition timer circuit 44 is output to the pre-purge timer circuit 55, and the signal from the ignition timer circuit 44 is output to the relay 15.
Output to.

The selection circuit 40 includes inverters 59, 60,
It consists of AND circuits 61 and 62, a NAND circuit 63, and OR circuits 64 and 65.

Further, the flame detection circuit 51 outputs the flame detection signal from the flame rod 32 to the ignition timer circuit 44 and the relay 18, and the switching timer 47 outputs the signal from the selection circuit 40 to the pre-purge timer circuit 55, so that the ignition A signal from timer circuit 44 is output to relay 15.

A is a burner, and the burner A has a burner head 69 having slits 68, 68 installed at one end opening of a burner body 66 in which a heater 6 and a burner thermistor 37 are embedded, and facing into a combustion chamber 67. Also, a burner motor 1 is installed inside the burner A.
A rotary atomizer is constructed by providing a mixture 70, a cone 71, etc. on one rotating shaft. Further, a liquid fuel supply pipe 72 and a gaseous fuel supply pipe 73 are made to face the other end opening of the burner body 66. 74 is a reciprocal switch that operates in conjunction with the power switch 3; 75;
is a switch that operates in conjunction with the ignition timer 4.

The present invention has the above-mentioned configuration, and its operation will be described below.

A case in which combustion operation is performed using only liquid fuel by setting the combustion selector switch 29 to line 1 will be described below.

When the power switch 3 is closed, the electronic control circuit 30 is energized via the transformer 12, so the power lamp 39 lights up, and the selection circuit 40 sends a first selection signal to the kerosene timer 45 in the ignition timer circuit 44. is output, the kerosene lamp 36 lights up, and the relay 7 is sent via the comparison circuit 43.
is activated, the contact point 8 is closed, and the burner body 66 is heated by the heater 6. The temperature of the burner body 66 is determined by the burner thermistor 37.
When it is detected that the temperature has risen to an appropriate temperature such as 220°C, a signal is output to the comparator 48, the selection circuit 40, the room thermo circuit 52, the after purge timer 53, and the pre-purge timer circuit 55. In response to the signal, contact 10 of relay 9 is switched to normally open fixed contact 10', and burner motor 11 starts operating. In this case, the room thermo circuit 52 compares the signals from the room thermistor 34 and the temperature controller 33, and determines to operate the burner motor 11 when it is determined that the indoor temperature is lower than the set temperature. When the wind pressure switch 31 detects that the operation of the burner motor 11 is normal and outputs an operation signal, the AND circuit 54
This activation signal is input to the ignition timer circuit 44 and the prepurge timer circuit 55 via the ignition timer circuit 44 . Then, the prepurge timer circuit 55 outputs an ignition signal to the ignition timer circuit 44 when approximately 15 seconds, which is a predetermined time period for performing prepurge, has elapsed since the activation signal was input. When the ignition timer circuit 44 receives the ignition signal output from the prepurge timer circuit 55, it starts counting the first allowable ignition time set in the kerosene timer 45 and outputs a drive signal during this time. Accordingly, relay 15
The contact point 16 is closed via the ignition device 17, and the pump 25, the kerosene valve 26, and the ignition device 17 are activated. By operating the pump 25 and the kerosene valve 26, the liquid fuel is guided from the liquid fuel supply pipe 72 onto the cone 71, where it is atomized and vaporized within the burner body 66, mixed with combustion air, and sent to the combustion chamber outside the burner head 69. The burner head 69 is ignited by the igniter 17 in the slits 68, 68 of the burner head 69.
A blue fire is formed and combustion takes place. During the first permissible ignition time during which the ignition timer circuit 44 outputs a drive signal based on the kerosene timer 45, the liquid fuel passes through the liquid fuel supply pipe 72 when the pump 25 and the kerosene valve 26 are activated, and is fed into the burner body 66. It is set to 40 to 50 seconds based on the time it takes for the flame rod to be gasified and ignited by the ignition device 17.
When a flame is detected, the contact 19 is switched by the flame detection circuit 51 and the relay 18, and the operation of the ignition device 17 via the contact 16 is stopped. Further, the flame rod 32 is fired within the first allowable ignition time.
When the flame is not detected, the ignition timer circuit 44
stops outputting the drive signal, the contact 16 of the relay 15 is opened, and the pump 25 and kerosene valve 2
6. The ignition operation is stopped by stopping the operation of the ignition device 17. The opening/closing of the contact 8 by the operation of the heater relay 7 depends on the burner body temperature.
This is done via a burner thermistor 37, a comparator 49, and a comparison circuit 43 so as to operate between 200°C and 300°C.

A case will be described below in which combustion operation is performed using only gaseous fuel by setting the combustion selector switch 29 to the line.

When the power switch 3 is closed, the power lamp 3
9 lights up, the first gas valve 76 is activated, the second selection signal is output from the selection circuit 40, and the gas timer 4 in the ignition timer circuit 44 is activated.
6. A signal is output to the relay 20, gas lamp 35, and switching timer 47, the gas lamp 35 lights up, and the contact 21 is switched to the normally open fixed contact 21'' side, and at the same time, the selection circuit 40, room thermo circuit 52, and after Relay 9 is activated via purge timer 53, and contact 10 becomes normally open fixed contact 1.
Burner motor 1 by switching to 0'
1 operates to supply combustion air to burner A.

Thereafter, the wind pressure switch 31 outputs an activation signal, and the pre-purge timer circuit 55 is activated to 15
Since the ignition signal is output after a pre-purge such as seconds, the ignition timer circuit 44 outputs a drive signal during the second permissible ignition time based on the gas timer 46, operates the relay 15, and closes the contact 16. Then, the ignition device 17 and the second gas valve 24 are operated to perform an ignition operation and ignite the burner A.

When ignition is performed using gaseous fuel as described above, approximately 15 seconds from the start of operation of the burner motor 11 until the prepurge timer circuit 55 outputs an ignition signal is a prepurge time for eliminating unburned gas in the combustion chamber 67. Then, the second ignition allowable time set in the gas timer 46 in the ignition timer circuit 44 is such that the gaseous fuel supplied to the burner A from the gaseous fuel supply pipe 73 is instantaneously supplied into the burner body 66. The time is set at about 9 seconds, taking into consideration the good ignitability and the high risk of ignition. When the flame rod 32 detects a flame during this second ignition allowable time, the contact 19 is switched via the flame detection circuit 51 and the relay 18, and the operation of the ignition device 17 is stopped, but combustion continues.

Next, a case will be described below in which the combustion selector switch 29 is set to line low to start combustion using gaseous fuel during ignition, and then switch to liquid fuel to continue combustion.

When the power switch 3 is closed, the gaseous fuel ignites and starts combustion similarly. When the burner thermistor 37 detects that the temperature of the burner body 66 has risen to the vaporization temperature of the liquid fuel due to combustion with the gaseous fuel, the signal from the comparator 48 is inverted, and the switching timer 47 connected to the output of the inverter 60 , ignition timer circuit 4
Gas timer 46 in 4, signal to gas lamp 35 disappears, kerosene lamp 36, comparison circuit 4
3. A signal is sent to the kerosene timer 45. At this time, the relay 9 continues to operate via the selection circuit 40, the room thermo circuit 52, and the afterpurge timer 53, so the burner motor 11 continues to operate, but the selection circuit 40 outputs the second selection signal instead of the second selection signal. By issuing the selection signal No. 1, the contact 21 of the fuel switching relay 20 is switched, and this switching causes the gas valve 24 to stop operating, thereby stopping combustion. In addition, since the flame is no longer present and the contact 19 of the combustion continuation relay 18 is also switched by the flame detection circuit 51, there is no fear that the combustion will immediately start burning the liquid fuel. Further, the differentiating circuit 57 detects an operation of switching from the combustion control path using gaseous fuel (line α) to the combustion control path using liquid fuel (line β), and the timer circuit 58 and prepurge timer circuit 55 are sequentially activated. Here, the timer 58 and prepurge timer circuit 55 cause approximately
After pre-purging for 20 seconds, the ignition signal is output, and as described above, the ignition relay 15 and combustion continuation relay 1 are activated during the first permissible ignition time by the kerosene timer 45 in the ignition timer circuit 44.
8 is controlled, and burner A continues to burn liquid fuel.

The signal from the power source 56 to the differentiating circuit 57 is for energizing the differentiating circuit 57 at the start of combustion when the power switch 3 is closed to enable it to operate. This differentiation circuit 57 only operates.

(G) Effects of the Invention As described above, the present invention uses an ignition timer circuit to appropriately determine the permissible ignition time when burning liquid fuel and the permissible ignition time when burning gaseous fuel. By taking advantage of the respective characteristics of fuel and gaseous fuel, it is possible to perform ignition operations with high safety and reliability in accordance with each fuel. In addition, when switching from gaseous fuel to liquid fuel, the fuel supply is stopped for a certain period of time, so the liquid fuel can be ignited after all the gaseous fuel remaining in the burner is discharged. Abnormal combustion can be prevented and fuel switching can be performed smoothly.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention;
Figure 2 is a block diagram of the electronic control circuit in Figure 1, Figure 3 is a detailed diagram of the selection circuit in Figure 2,
FIG. 4 is an enlarged sectional view of the main part of the burner, and FIG. 5 is a block diagram of the electric circuit. A... Burner, 11... Burner motor (air blowing means), 17... Ignition device, 20... Combustion switching relay (fuel switching means), 24... Second gas valve (gaseous fuel supply means), 25... Pump (liquid fuel supply means), 26...kerosene valve (liquid fuel supply means),
29...Selection switch (combustion selection switch), 4
0...Selection circuit, 44...Ignition timer circuit, 47
...Switching timer (signal change detection means), 51...
Flame detection circuit, 55...prepurge timer circuit.

Claims (1)

[Claims] 1. (1) A burner A that burns liquid fuel or gaseous fuel; (2) An ignition device 17 for igniting this burner A.
(3) liquid fuel supply means 25, 26 for supplying liquid fuel to the burner A; (4) gaseous fuel supply means 24 for supplying gaseous fuel to the burner A; (5) supply to the burner A. The first mode uses only liquid fuel, and the second mode uses only gaseous fuel.
a selection switch 29 for selecting the mode and a third mode for switching from gaseous fuel to liquid fuel;
(6) According to the mode selected by this selection switch 29, only the first selection signal is emitted when the first mode is selected, only the second selection signal is emitted when the second mode is selected, and the second selection signal is emitted when the second mode is selected. A selection circuit 40 that first emits only the first selection signal and then only the second selection signal when selecting the mode No. 3;
(7) a blower means 11 for supplying fuel air to the burner A when the selection circuit 40 issues one of the selection signals; fuel switching means 20 which enables the liquid fuel supply means 25, 26 when the selection circuit issues a first selection signal and enables the gaseous fuel supply means 24 when the selection circuit issues a second selection signal; (9) Signal change detection means 47 for detecting a change in the selection signal issued by the selection circuit 40 in the third mode.
(10) a pre-purge timer circuit 55 that outputs an ignition signal after a predetermined period of time from when the air blowing means starts blowing air or when a signal change is detected by the signal change detecting means 47; (11) a pre-purge timer circuit 55 of the selection circuit 40; It has two timers 45 and 46 having different operating times, which are selected according to the selection signal and are operated by the ignition signal of the prepurge timer circuit 55, and are made operable by the fuel switching means. fuel supply means 25,
26 or 24 and an ignition timer circuit 44 that operates the ignition device 17 for an appropriate time by a selected timer; 2
A control circuit for a combustor, comprising a flame detection circuit 51 that continues the operation of the combustor.