| 摘要 |
PROBLEM TO BE SOLVED: To prevent a transmitting level of an electric wave from lowering caused by mismatching of antenna impedance, and to efficiently emitt the electric wave. SOLUTION: In a tire air pressure alarm where a transmitting part 7 storing a pressure detecting part 3, a signal processing circuit 4 and a battery 5 in a case 2 is arranged in a wheel rim 1, and where a valve stem 10 is integrally assembled on the upper part of the case 2, one end part of a metal ring 12 is fixed to the inside of the case 2 by a nut 11, one end part of the metal ring 12 is connected to a power supply line 6 for output of the signal processing circuit 4, the valve stem 10 is fixed to a valve hole of the wheel rim 1 by a grommet and a nut 9, and a tire wheel having the wheel rim 1 is used for an antenna for an electric wave output in the signal processing circuit 4. |
