JP3488338B2 - Flame detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame detecting device used in a combustor such as a fan heater, and more particularly, to a flame detecting device which supplies commercial power to an ignition heater. The present invention relates to a technology that can accurately detect ignition. 2. Description of the Related Art An ignition heater which is red-hot when supplied with a commercial power supply is insulated by ceramics, but has a property that the insulation resistance decreases as the temperature rises. Therefore, if the ground resistance of the housing is small, a flame current starts flowing between the ignition heater and the burner from the moment the burner is ignited and burns, and the flame current that should flow between the frame rod and the burner does not increase. In spite of this, a problem occurs that the ignition detection means cannot detect the flame. As a technique for solving this problem, a technique disclosed in, for example, Japanese Patent Application Laid-Open No. 4-366315 is known. That is, when the first predetermined time has elapsed from the start of ignition, the energization of the ignition heater is stopped, and the flame detection is continued within the second predetermined time thereafter.
Thus, even if the ground resistance of the housing is small, the presence or absence of a flame can be reliably detected within the second predetermined time. [0004] As described above, in the conventional flame detecting device, since the detection of the flame continues for a while even after the energization of the ignition heater is stopped, the ignition operation is switched to the normal combustion operation. Migration is delayed. In addition, in the event of an ignition error, the waiting time until the next ignition operation becomes longer, and the supply of fuel gas to the burner also becomes longer, which causes a large amount of fuel gas to be discharged out of the housing to generate odor. Further, when a flame is formed at the beginning of the ignition operation, the ignition heater also receives heat from both the flame and the power supply at the same time until at least the first predetermined time elapses, so that the temperature rises excessively, and the life is adversely affected. There is. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has as its object to provide a flame detection device that can accurately detect ignition even while commercial power is supplied to an ignition heater. . In order to achieve the above object, a flame detecting device according to the present invention comprises a burner, an ignition heater which is supplied with commercial power and ignites the burner by heating the burner; Flame detection means for detecting a flame from a flame rod to be applied, flame current flowing between the flame rod and the burner, phase inversion means for inverting the phase of an AC voltage to the flame rod during the ignition operation, and flame detection Storage means for storing the phase of the phase inversion means at the time of
The phase inversion means operates from the phase stored in the storage means. According to this structure, since the phase of the AC voltage applied to the frame rod is inverted during the ignition operation, the AC voltage always has the opposite phase to the commercial power supply. I do. In the opposite phase, a normal flame current flows between the flame rod and the burner every half cycle, so that the ignition detection means can reliably detect the flame based on the flame current. An embodiment of the present invention will be described below with reference to the drawings. 1 and 2, reference numeral 1 denotes a grounded burner, above which an ignition heater 2 and a frame rod 3 are provided. The ignition heater 2 is connected in series with the relay 4, and is connected to a commercial power supply 7 via an outlet 5 and a power plug 6. Reference numeral 8 denotes a transformer 8 connected to the commercial power supply 7 like the ignition heater 2. On the secondary side of the transformer 8, diodes 9, 10, a capacitor 11, a regulator 12
Various rectifying and smoothing components are provided, and a microcomputer 13 is provided on the output side. Frame rod 3
Is configured such that an alternating current whose voltage is limited by a zener diode 14 or the like is applied, a relay 15 is provided in the middle of the current path, and a branch of a connection line of the voltage dividing resistors 16 and 17 is connected to a microcomputer. 13 A / D ports. Reference numerals 18 and 19 denote transistors connected in series with the relays 4 and 15, respectively, and their bases are connected to output ports P1 and P2 of the microcomputer 13. The microcomputer 13 has A
An ignition detection means 20 for detecting a flame from a voltage input to the / D port, a phase inversion means 21 for inverting the phase of an AC voltage applied to the frame rod 3 by switching a contact of a relay 15 during the ignition operation, And a storage means 22 for storing the phase of the phase inversion means 21 at the time when is detected. Reference numeral 23 denotes a condenser for smoothing, 24 denotes an oil reservoir for storing kerosene, 25 denotes a pump, 26 denotes a vaporizer for vaporizing kerosene, and 27 denotes a solenoid that opens and closes a nozzle 28 at the tip of the vaporizer 26. The operation of the above configuration will be described with reference to the sequence shown in FIG. When the power plug 6 is inserted into the outlet 5, commercial power 7 is supplied to the transformer 8. When an operation switch (not shown) is operated in this state, preheating of the vaporizer 26 is started. When the preheating is completed for a while, a signal is output from the output port P1, the transistor 18 is turned on, the coil of the relay 4 is excited, and the contact is closed, so that the commercial power supply 7 is supplied to the ignition heater 2. When the ignition heater 2 becomes sufficiently red-hot due to the supply of the commercial power supply 7, the operation shifts to the ignition operation. That is, the pump 2
By the start of 5, the kerosene is pressure-fed to the vaporizer 26, where the vaporized gas is blown out from the nozzle 28 opened by the solenoid 27 to the burner 1 and ignited by the ignition heater 2. At the time of ignition, the outlet 5 and the power plug 6 are applied to the frame rod 3 because the contacts of the relay 15 are on the A side, assuming that A and a and B and b are respectively connected. The AC voltage has the same phase as that of the commercial power supply 7 as shown in FIG. In the figure, the thick solid line shows the waveform of the AC voltage applied to the frame rod 3, and the thin solid line shows the waveform of the commercial power supply 7. Therefore, the flame current flowing at the time of the positive potential based on the rectifying action of the flame is large between the ignition heater 2 and the burner 1 and is reduced between the flame rod 3 and the burner 1 by that much, so if the input voltage of the A / D port is large. Therefore, the ignition detecting means 20 cannot detect the flame. When the time t1 has elapsed since the start of the ignition operation, the phase inverting means 21 functions to output a signal from the output port P2. The transistor 19 is turned on by the signal output, and the contact of the relay 15 is switched to the low side, so that the phase of the AC voltage applied to the frame rod 3 is inverted. That is, as shown in FIG. In the case of the opposite phase, at the time of the plus potential indicated by the diagonal line appearing every half cycle, a normal flame current flows between the frame rod 3 and the burner 1, and the voltage smoothed by the capacitor 22 is supplied to the A / D port. Since the input is made, the ignition detecting means 20 detects the flame after a short time t2. In other words, the apparatus of the present embodiment can detect ignition accurately and reliably even while the commercial power supply 7 is being supplied to the ignition heater 2. When the flame is detected, the storage means 22 stores the phase at the same time. The contents that are actually stored are:
A phenomenon corresponding to the phase, such as detection of a flame when the signal is output from the output port P2, may be used. Further, the output port P1
The power supply to the ignition heater 2 is stopped by the stop of the signal output from, and thereafter, the normal combustion operation is performed. Then, when the fire extinguishing operation is performed, the burner 1 extinguishes the fire due to the solenoid 27 closing the nozzle 28 or the like. When the operation is restarted after the fire is extinguished, the phase inversion means 21 reads the contents stored in the storage means 22,
It works from its contents. That is, the phase inversion means 21 operates simultaneously with the start of the ignition operation, and the contact point of the relay 15 is started from the low side.
Has an opposite phase to the commercial power supply 7. Therefore, after the burner 1 is ignited, the ignition detecting means 20
Can reliably detect the flame in a short time t3, and at the same time, stop the energization to the ignition heater 2. Such re-ignition operation continues until the power plug 6 is unplugged. As a result, the ignition heater 2 is prevented from being simultaneously heated by both the flame and the energization as described in the conventional example, so that the performance is maintained for a long time without excessive temperature rise. it can. As described above, the flame detection device of the present invention can reliably and accurately detect ignition while commercial power is supplied to the ignition heater. In a short time, the temperature of the ignition heater is prevented from becoming excessively high, and the desired performance can be maintained for a long time. Furthermore, when an ignition error occurs, the determination is made during a predetermined ignition operation period, so that the waiting time until the next ignition operation is shortened, and the supply of fuel gas to the burner is longer than necessary. Not
This has a remarkable effect that a problem of causing odor in the surroundings can be effectively prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram illustrating an embodiment of a flame detection device according to the present invention. FIG. 2 is a configuration diagram illustrating a configuration related to a combustion device. FIG. 3 is a sequence diagram illustrating an operation of the embodiment of the flame detection device of the present invention. FIG. 4 is a waveform diagram illustrating a phase relationship between a commercial power supply and an AC voltage applied to a frame rod. [Description of Signs] 1 burner 2 ignition heater 3 flame rod 20 ignition detection means 21 phase inversion means 22 storage means

Claims (1)

(57) [Claims 1] A burner, an ignition heater for igniting the burner which is red-heated by supplying commercial power, a frame rod to which an AC voltage is applied, and a flame rod between the flame rod and the burner. Ignition detection means for detecting the flame from the flowing flame current, phase inversion means for inverting the phase of the AC voltage to the flame rod during the ignition operation, and storage for storing the phase of the phase inversion means at the time when the flame is detected Means, wherein the phase inversion means operates from the phase stored in the storage means.