| 摘要 |
PURPOSE:To provide a positive combustion of a primary flame at a secondary flame hole under an abnormal condition, increase a difference in outputs under a normal condition of the primary flame detecting element and an abnormal condition of the primary flame detecting element and prevent an erroneous operation by a method wherein a primary flame sensing promoting member is arranged downstream of the primary flame sensing element. CONSTITUTION:Gas outputted from the nozzle 3 sucks air from the primary air hole 7, mixed in the inner pipe 2 and then forms a primary flame F1 at the primary flame hole 1. Since the primary flame hole 1 is restricted fro the secondary air with the outer pipe 6, the remaining non-ignited fuel forms a secondary flame F2 with the secondary flame hole 5 and the primary flame sensing promoting member 10 being applied as the flame base part together with the auxiliary air hole located at the outer pipe 6. Then, when an abnormal condition such as a lack of oxygen or the like, the primary flame F1 is moved outward of the outer pipe 6 while the flame is being eliminated. However, since the primary flame is ignited at the secondary flame hole 5 as a source of ignition of the primary flame sensing promoting member 10, the flame may not be contacted with the primary flame sensing element 9 and a difference between the case of normal condition and abnormal condition can be kept large.
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