PURPOSE: To provide high detecting precision for a tire air pressure detecting device as well as to decrease its cost with its simple structure.
CONSTITUTION: An iron piston 36 to be reciprocated between an iron tip 33 and a main body part 32 made of brass according to air pressure of a tire and a magnet attached to the tip of the piston 36 are provided in a sensor part 31, and a hall element 5 for detecting magnetism of the magnet 12 is arranged near the main body part 32 of the sensor part 31. When air pressure of the tire is within the preset suitable range, the piston 36 is advanced to the tip 33 side so that the magnet 12 may be surrounded by the tip 33 and the piston 36, while, when air pressure is less than the suitable range, the piston 36 is retreated to the main body part 32 side so that the magnet 12 may be positioned in the main body part 32.
FURUICHI KENJI
YAMAMOTO MASAAKI
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