| 摘要 |
PROBLEM TO BE SOLVED: To improve both ignition performance and combustion performance by bringing a shutter into contact with an air suction port of a mixing tube when ignited to reduce a primary air amount, and, after ignition, releasing the shutter free to gradually increase a primary air amount entering from the port. SOLUTION: When a solenoid valve 20 is pressed, an internal gas passage is opened, a shutter moving bar 30 simultaneously pushes a shutter 18 to an air suction port 17 to inject a gas. The injected gas flows through a mixing tube 16. Since the shutter 18 is pressed to the port 17, primary air is only slightly sucked. When a flame is adhered to a combustion catalyst 13 so that a temperature of the catalyst 13 becomes a catalytic combustible temperature, a catalytic combustion is started from an upstream side, the flame is extinguished soon, and transferred to a complete catalytic combustion. Then, a flame is formed in a combustion chamber 14, the shutter 18 is moved from the tube 16 side toward a nozzle 15 by a shutter urging spring to increase an area of the port 17.
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