United States Patent [19] [ii] Patent Number: 5,006,844
Ohta et al. [45] Date of Patent: Apr. 9, 1991
[54] TIRE ABNORMALITY DETECTING DEVICE
[75] Inventors: Katsuhiro Ohta; Hisami Masuda;
Mamoru Makishima, all of Tokyo,
Japan
[73] Assignee: TDK Corporation, Tokyo, Japan
[21] Appl. No.: 373,846
[22] Filed: Jun.29,1989
[30] Foreign Application Priority Data
Jul. 4, 1988 [JP] Japan 63-89200[U]
[51] Int. CI.' B60C 23/02
[52] U.S. CI 340/448; 340/449
[58] Field of Search 340/448, 449, 445;
73/146.5; 336/192; 333/185, 219, 175
[56] References Cited
U.S. PATENT DOCUMENTS
3,665,387 5/1972 Enabnit 340/448
4,052,696 10/1977 Enabnit 340/448
4,118,678 10/1978 Goshima et al 333/185
4,300,118 11/1981 Matsudaetal 340/448
4,312,001 1/1982 Marzolf 340/448 X
4,314,221 2/1982 Satou et al 336/212 X
4,393,364 7/1983 Suda et al 336/192 X
4,605,845 8/1986 Takeda .
4,737,761 4/1988 Dosjoub et al 340/448
4,758,922 7/1988 Ishigaki et al 333/219 X
4,761,996 8/1988 Schmid et al 340/448 X
4,790,179 12/1988 Hettich et al 340/448 X
FOREIGN PATENT DOCUMENTS
2296170 9/1975 France .
2342860 2/1977 France .
5510159 6/1978 Japan .
53-151366 12/1978 Japan .
A tire abnormality detecting device has a first unit to be provided on a vehicle body side and a second unit to be provided on a tire side. The first unit includes an electrical signal generating source for generating a specific electrical signal, a first coil device, for generating an induction voltage in receipt of the electrical signal, and a device for detecting a change in the induction voltage of the first coil device. The second unit includes a second coil device adapted to be magnetically connected to the first coil device, a third coil device having a magnetic core formed of a temperature sensing magnetic material to form a resonance circuit in cooperation with the second coil device, and a switch mechanism for changing a time constant of the resonance circuit in response to a change in air pressure in a tire. With this construction, the abnormal reduction in air pressure in the tire and/or the abnormal increase in temperature of the tire can be detected.
4 Claims, 4 Drawing Sheets
