| 摘要 |
PURPOSE:To improve control accuracy of the smoke, by providing a means for heating a transparent window for emitting or receiving light or a light reflecting plate so as to heat the transparent window or a reflective plate. CONSTITUTION:Laser light from a light emitting element 51 of a detecting part 34 is transmitted to a light projecting part 36 through an optical fiber 38 and emitted into an exhaust passage 23a from a transparent window 43. The emitted light permeates a transparent window 48 of a light receiving part 37, and is incident upon a light receiving element 53 of the detecting part 34 through an optical fiber 39. The light receiving element 53 outputs voltage in accordance with the received amount of light, and the voltage is amplified by an amplifier 55 and output as a smoke detection sigal SA. The smoke detection signal SA changes in accordance with the amount of smoke in exhaust to detect the concentration of smoke. A smoke detector 33 contains heaters 42, 47 to be built inside the light emitting and receiving transparent window 43, 48 facing the exhaust passage 23a, and the transparent windows 43, 48 can be heated. In case of a carbon particle adhering to a side surface of the exhaust passage 23a, if the heaters 42, 47 are electrified, the carbon particle, being immediately sublimated because of high temperature of the transparent windows 43, 48, enables the concentration of smoke to be accurately detected. |
