PURPOSE: To perform accurate detection of a slip by a method wherein ultrasonic waves are transmitted at the same emission angle to a road surface and the outer peripheral surface of a tyre, irregular reflection waves from the two surfaces are received at the same receiving angle in a synthesized state in which the irregular reflection waves are interfered with each other, and from the beat frequency of the synthesized waves, a tyre slip is detected.
CONSTITUTION: During running of a vehicle, irregular reflection waves from the outer peripheral surface of a tyre 4a and a road surface 2, both receiving ultrasonic waves from sensors S1 and S2 for transmission, are interfered with each other at the same receiving angle θ2, and are received by a sensor R1 for receipt in a state in which the irregular reflection waves produce synthesized waves. The receiving signal (synthesized wave signal) is amplified to input it to an AM detecting circuit 16, a beat signal equivalent to the envelope of the synthesized signal is detected, and the frequency thereof is detected by a frequency counter 18. After the synthesized signal is amplified and the waveform thereof is shaped, the signal is inputted to a frequency counter 26 to detect the frequency of the synthesized signal itself. Based on outputs from the counters 18 and 26 and the frequency of a transmission signal from an oscillator 8, the slip ratio of a tyre is computed by a computing part 20.
OKAZAKI TOSHIMI
OKADA SEIJI
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