Abstract: To achieve both accuracy in correcting sensing error caused by nonstandard factors of a pulse signal generated by rotation of a rotor to be measured and reduction in cost of an apparatus for doing the same, each passage of rotor sensors which rotate integrally with vehicle tires are sensed to produce pulse signals. The pulse signal periods are sequentially integrated every pulse signal train consisting of multiple pulse signals. When all of the pulse signal periods of the pulse signal train are integrated, the integrated value is stored in memory. The memory always stores the integrated values of the newest one rotation of the rotor to be measured. The pulse signal periods are averaged from the sum of the integrated values. With such a construction, the average of the pulse signal periods can be obtained as a learning reference value in the correction without storing all of the pulse signal periods of one rotation, thereby realizing both correction accuracy and cost reduction.

Abstract: An apparatus for estimating an air pressure of a tire of a tired wheel of a motor vehicle, on the basis of a temperature of the tire as well as a motion of the tired wheel, preferably including a temperature-related variable sensor for detecting a temperature-related variable related to the temperature of the tire, and an estimating device for estimating the air pressure of the tire on the basis of the temperature-related variable as well as the motion of the tired wheel.

Abstract: Pickup coils which generate vehicle wheel speed signals which include vibration frequency components of tires during vehicle cruising are provided. An electronic control unit extracts resonance frequencies of tires from the vehicle wheel speed signals and estimates tire pneumatic pressure based on the extracted resonance frequencies. When an estimated vehicle wheel pneumatic pressure falls below a predetermined critical pneumatic pressure, pneumatic pressure decline warnings are generated and displayed by a display unit. An update switch is provided and when this update switch is turned on when replacing tires, the electronic control unit adjusts and sets the value of the critical pneumatic pressure described above based on the resonance frequency extracted during this time.

Abstract: An absolute vehicle speed determining system is provided. This system includes generally a first sensor for detecting an unsprung vibration frequency component acting on a front wheel and a second sensor for detecting an unsprung vibration frequency component acting on a rear wheel. A phase difference between the unsprung vibration frequency components is found to project an absolute speed of a vehicle based on the phase difference and a wheel base of the vehicle. In addition, a tire condition monitoring system is provided which is designed to monitor properties of the tire, for example, the inflation pressure, the type of tire, or the amount of tire wear using the absolute speed of the vehicle projected.

Abstract: It is an object of the present invention to detect a tire air pressure indirectly with high detection precision.A tire air pressure detecting device includes a speed sensor for outputting a signal corresponding to a rotational speed of a tire, and an electronic control unit which inputs the signal from the speed sensor and performs predetermined arithmetic operations on that signal. The electronic control unit calculates a wheel speed based on the output signal of the speed sensor, performs a frequency analysis for the calculated vehicle speed, and derives a resonance frequency corresponding to the unsprung mass in the vertical and longitudinal directions. The tire air pressure is then detected based on this resonance frequency.

Abstract: It is an object of the present invention to detect a tire air pressure indirectly with high detection precision.A tire air pressure detecting device includes a speed sensor for outputting a signal corresponding to a rotational speed of a tire, and an electronic control unit which inputs the signal from the speed sensor and performs predetermined arithmetic operations on that signal. The electronic control unit calculates a wheel speed based on the output signal of the speed sensor, performs a frequency analysis for the calculated vehicle speed, and derives a resonance frequency corresponding to the unsprung mass in the vertical and longitudinal directions. The tire air pressure is then detected based on this resonance frequency.