| 摘要 |
PROBLEM TO BE SOLVED: To provide a gas sensor capable of miniaturizing the whole device, by miniaturizing a measuring chamber for measuring the gas concentration of evaporating fuel or the like, using ultrasonic waves. SOLUTION: The measurement chamber 30 on this gas sensor 1 is separated into a measuring chamber upper part 31 and a measuring chamber lower part 32 by reflecting plates 18, 19 tilted downwardly by 45 degrees. A purge gas has a passage from a gas inflow hole 28 to a gas outflow hole 29 via the measuring chamber lower part 32, and replacement of the gas in the measuring chamber upper part 31 is performed via an interval between each tip part 22, 23 of the reflecting plates 18, 19 or via a clearance with the sidewall of a casing 2. The ultrasonic waves, transmitted from an ultrasonic element 10, enter a reflecting surface 17 via reflecting surfaces 15, 16, and are reflected in the same axial direction. The reflected waves follow the same path as the propagation path of the transmitted waves, and are received as received waves by the ultrasonic element 10. By not providing a partition wall in the measurement chamber 30, the propagation path of the ultrasonic waves is not formed linearly, and the measuring chamber 30 is miniaturized. COPYRIGHT: (C)2005,JPO&NCIPI
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