| 摘要 |
PURPOSE:To make available the detection of burning abnormalities such an oxygen-starvation and a back-fire, by providing a part of oxygen concentration cell type sensor in a burnt exhaust gas passage and its remaining part in an unburnt gas passage. CONSTITUTION:An oxygen concentration cell type sensor 10 is formed in a hollow cylindrical configuration, having its part of outer surface electrode 11a placed in a burnt exhaust gas passage 6 and the remaining part 11a'' thereof in an unburnt gas passage 12. While the top end 13 of inner surface electrode 11b is closed, the opening 14 of opposite end thereof is opened to atmosphere. When the shortage of combustion air causes an oxygen-starvation burning state, the oxygen differential pressure of burnt exhaust gas passage 6 decreases excessively and thereby creating a great difference of oxygen differential pressure between the inner surface electrode 11b and the outer surface electrode 11a'. In consequence, the oxygen concentration cell type sensor 10 generates an electromotive force and interrupts a combustion circuit upon the sensor output exceeding a specific level Z. When a flame is shifted from a burner head 4 into the unburnt gas passage 12 with a result of back-fire, the outer surface electrode 11a'' is completely wrapped by a flame for thereby reducing the oxygen differential pressure of outer electrode 11a'' excessively to make greater the difference of oxygen differential pressure between it and the outer surface electrode 11b. Thus, the sensor output is indicated as a level higher than Z. |
