EP0884534A1 - Flammendetektion und Regelung des Brennstoffstromes zu dem Brenner - Google Patents

Flammendetektion und Regelung des Brennstoffstromes zu dem Brenner Download PDF

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Publication number
EP0884534A1
EP0884534A1 EP98304553A EP98304553A EP0884534A1 EP 0884534 A1 EP0884534 A1 EP 0884534A1 EP 98304553 A EP98304553 A EP 98304553A EP 98304553 A EP98304553 A EP 98304553A EP 0884534 A1 EP0884534 A1 EP 0884534A1
Authority
EP
European Patent Office
Prior art keywords
flame
valve
control
responsive
electrodes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98304553A
Other languages
English (en)
French (fr)
Inventor
Barry Ian Chuter
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kigass Electronics Ltd
Original Assignee
Kigass Electronics Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kigass Electronics Ltd filed Critical Kigass Electronics Ltd
Publication of EP0884534A1 publication Critical patent/EP0884534A1/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
    • F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means

Definitions

  • the present invention relates to flame detection and also controlling the flow of fuel, such as gas, to a burner.
  • a flame detector comprising
  • the means for producing the flame indicator signal is energised solely by the capacitive means, it is highly unlikely that a flame will be falsely indicated.
  • the flame detector is wholly electronic it is inherently more reliable than an electro-mechanical device. Also it can be manufactured in quantity more cheaply than an electro-mechanical device.
  • the capacitive means comprises a capacitor in parallel with the spaced electrodes, having one terminal connected to one of the said electrodes and another terminal connected to the other of the said electrodes and a resistor connected in series with the parallel arrangement of the capacitor and spaced electrodes.
  • a flame detector in accordance with said one aspect of the invention, a fuel flow control valve which is electrically energisable to maintain a flow of fuel to the burner, and means responsive to the signal indicative of the flame to control the energisation of the valve.
  • the fuel is preferably gas.
  • the flow control apparatus is more reliable and cheaper than an electro-mechanical device.
  • a preferred embodiment comprises means for responsive to electrical power greater than a predetermined threshold flowing to the valve for de-energising the valve.
  • the responsive means may be a fuse or P.T.C resistor. If a fault condition develops whereby excessive current flows to the solenoid, the current is limited or cut-off to de-energise the valve.
  • the means for producing the flame indicative signal maybe an oscillator, the oscillator producing a mark-space waveform having a predetermined mark-space ratio for maintaining the valve open. If, due to a fault, the waveform tends more towards DC, the net current flowing to the valve will increase: the responsive means will then limit the current or cut it off.
  • the valve comprises a solenoid and the energisation control means comprises a control electrode connected to receive the flame indicative signal and a controlled path the controlled path, the solenoid, and responsive means being in series between terminals for receiving electrical energy for energising the valve.
  • the energisation control means There is no separate power supply for the energisation control means which therefor cannot falsely maintain the valve open in the absence of the flame indicative signal.
  • a flame is produced by a gas burner (not shown) between a pair of electrodes 1 one of which is connected to an AC mains terminal 8 via a resistor 9 (R2).
  • the equivalent circuit 2 of the flame is the series arrangement of a resistor R1 and diode D1 across the electrodes 1.
  • a capacitor 10 (C1) is connected in parallel with the electrodes 1 (and thus the flame) and in series with the resistor 9.
  • the charge on the capacitor 10 is used to energise a low-power oscillator 3 an example of which is shown in Figure 2.
  • the capacitor 3 is the sole power-supply for the oscillator. Thus in absence of a flame the oscillator does not function once the capacitor 3 discharges to a level too low to operate the oscillator.
  • the oscillator in this example, produces a square wave having a mark: space ratio of 1:3.
  • the square wave is a control signal, indicative of the presence of a flame, applied to the control electrode or base of a high gain transistor 4 (TR1).
  • TR1 high gain transistor 4
  • the transistor 4 may be replaced by, inter alia an FET, Darlington pair, an SCR, or a high gain current amplifier.
  • the collector-emitter path of transistor 4 is connected in series with a solenoid 5 and free-wheel diode 5a of a gas control valve and a positive temperature coefficient (PTC) resistor 6 or alternatively a fuse 6a between a +12V dc rail 7 and ground. (The rail 7 could be provided with e.g. 12V ac.)
  • PTC positive temperature coefficient
  • the transistor 4 has no power supply separate from the valve. It therefore has no source of power to falsely maintain the valve open.
  • the solenoid 5 When the solenoid 5 is energised the valve is maintained open and allows gas to flow to the burner.
  • the energising current supplied to the solenoid is pulsed being controlled by the transistor 4 in response to the pulsed control signal produced by the oscillator 3.
  • the pulsed energisation is sufficient to maintain the valve open.
  • the pulsed control signal is produced only if a flame is present between the electrodes 1. Thus if the flame fails, the control signal is not produced and the valve closes cutting off the gas supply to the burner.
  • the circuit of Figure 1 is arranged to minimise the risk of failing with the valve open. Because the oscillator 3 is energised solely by the capacitor 10, it is unable to produce a control signal indicative of a flame by false operation except in the unlikely presence of another fault which energises the oscillator. Resistors fail open-circuit so if resistor 9 fails, C1 will not charge and oscillator 3 will not operate so valve 10 will close.
  • capacitor 10 fails as a short circuit, oscillator 3 will not operate. If capacitor 10 fails open-circuit then, an asymmetrical sine wave is produced in the presence of a flame. In the absence of a flame a sine wave is produced across the open-circuit. The oscillator may operate in short bursts but in either case insufficient to open the valve.
  • the PTC 6 or fuse 6a will act to reduce or cut-off the current to the solenoid closing the valve and cutting off the gas supply to the burner.
  • the oscillator 3 which is energised only by the charge on the capacitor 10, may be a CMOS integrated circuit comprising two CMOS inverting amplifiers 20, 21 in series, and having capacitive (22) and resistive (23) feed back paths to cause the circuit to oscillate at the desired frequency and mark-space ratio.
  • the circuit of Figure 1 or Figures 1 and 2 may be provided in domestic and industrial gas appliances such as heaters, boilers, ovens and hobs.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Combustion (AREA)
  • Regulation And Control Of Combustion (AREA)
EP98304553A 1997-06-13 1998-06-09 Flammendetektion und Regelung des Brennstoffstromes zu dem Brenner Withdrawn EP0884534A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9712447.3A GB9712447D0 (en) 1997-06-13 1997-06-13 Flame detection and controlling the flow of gas to a burner
GB9712447 1997-06-13

Publications (1)

Publication Number Publication Date
EP0884534A1 true EP0884534A1 (de) 1998-12-16

Family

ID=10814190

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98304553A Withdrawn EP0884534A1 (de) 1997-06-13 1998-06-09 Flammendetektion und Regelung des Brennstoffstromes zu dem Brenner

Country Status (2)

Country Link
EP (1) EP0884534A1 (de)
GB (1) GB9712447D0 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2367172A (en) * 2000-04-26 2002-03-27 Pektron Group Ltd Flame detection apparatus

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3853455A (en) * 1973-09-24 1974-12-10 Kidde & Co Walter Burner control apparatus
US4019854A (en) * 1976-02-27 1977-04-26 International Telephone And Telegraph Corporation Direct spark ignition system utilizing gated oscillator
GB1509705A (en) * 1975-05-22 1978-05-04 Pactrol Controls Ltd Monitoring gas fuel burners
JPS5642018A (en) * 1979-09-14 1981-04-20 Hitachi Heating Appliance Co Ltd Safety controller for combustion
JPS6195601A (ja) * 1984-10-17 1986-05-14 Hitachi Ltd Ｃｍｏｓ発振回路
DE4027090A1 (de) * 1990-08-28 1992-03-05 Kromschroeder Ag G Verfahren und anordnung zum ueberwachen einer brennerflamme

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3853455A (en) * 1973-09-24 1974-12-10 Kidde & Co Walter Burner control apparatus
GB1509705A (en) * 1975-05-22 1978-05-04 Pactrol Controls Ltd Monitoring gas fuel burners
US4019854A (en) * 1976-02-27 1977-04-26 International Telephone And Telegraph Corporation Direct spark ignition system utilizing gated oscillator
JPS5642018A (en) * 1979-09-14 1981-04-20 Hitachi Heating Appliance Co Ltd Safety controller for combustion
JPS6195601A (ja) * 1984-10-17 1986-05-14 Hitachi Ltd Ｃｍｏｓ発振回路
DE4027090A1 (de) * 1990-08-28 1992-03-05 Kromschroeder Ag G Verfahren und anordnung zum ueberwachen einer brennerflamme

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 005, no. 097 (M - 075) 24 June 1981 (1981-06-24) *
PATENT ABSTRACTS OF JAPAN vol. 010, no. 275 (E - 438) 18 September 1986 (1986-09-18) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2367172A (en) * 2000-04-26 2002-03-27 Pektron Group Ltd Flame detection apparatus
GB2367172B (en) * 2000-04-26 2004-02-18 Pektron Group Ltd Detection apparatus and a method of detection

Also Published As

Publication number Publication date
GB9712447D0 (en) 1997-08-13

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