Sumitomo Rubber Industries Limited

Sumitomo Electric Industries, Limited

Akiko Iida

Mikao Nakajima

Hiroto Horie

In accordance with a tire air-pressure reduction detecting apparatus of the present invention, if it is judged that the tires all have a normal air pressure, it is judged whether or not a count value (C) is not less than a steady-state count (L.sub.2), and then if the count value (C) is not less than the steady-state count (L.sub.2), a counter (CNT) is decremented. That is, the count value (C) is kept to the steady-state count (L.sub.2) at the lowest, from which incrementation is started. On the other hand, if it is judged that a tire air pressure is reduced, it is judged whether or not the count value(C) is less than an upper counting limit (L.sub.1), and then if the count value (C) is less than the upper counting limit (L.sub.1), the counter (CNT) is incremented. That is, the count value (C) is kept to the upper counting limit (L.sub.1) at the highest, from which decrementation is started. Then, if the count value (C) is not less than a warning threshold count (N.sub.1), a warning is issued, and if the count value (C) is less than a warning stopping threshold count (N.sub.2), the warning is stopped. Thus, the frequency of the issuance of erroneous warnings can be reduced.

Tire air-pressure reduction detecting apparatus

A tire pressure drop alarm device for judging a pneumatic pressure drop by calculating rotational angular velocities of tires provided for a four-wheel vehicle. When the vehicle is traveling on a road which varies in condition between left and right sides, a front/rear ratio of rotational angular velocities of the tires at the shoulder side of the road changes more markedly than that of rotational angular velocities of the tires at the center side, and a large time differential value appears. Therefore, it is possible to judge the traveling condition of the vehicle when the road condition varies between left and right sides. When it is judged that the traveling condition of the vehicle encounters a road condition which varies between left and right sides, the tire rotation of the four wheels is likely to become unbalanced, giving a false alarm even if the tire pressure does not drop. In this case, the judgment by the pneumatic pressure drop judging means is inhibited to prevent an issuance of a false alarm.

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Osaka, Japan

Akiko Iida