FIELD

The present disclosure relates to a road surface state determination device which detects by a tire side device vibration received by each tire, generates road surface data representing a road surface condition based on vibration data, transmits the road surface data to a vehicle body side system, and determines the road surface condition based on the road surface data.

BACKGROUND

Conventionally, there is proposed a road surface condition determination device that includes an acceleration sensor on a back surface of a tire tread, detects vibration applied to the tire by the acceleration sensor, and determines the road surface condition based on a detection result of the vibration. This road surface state determination device determines the road surface condition by generating data representing a road surface condition based on a vibration waveform of the tire detected by the acceleration sensor and transmitting the data of each road wheel to a vehicle body side receiver and the like.

In the road surface condition determination device, data communication is performed from the tire side device including the acceleration sensor or the like provided on the tire side to a vehicle body side system such as a receiver provided on the vehicle body. Therefore, it is preferable that data transmission from the tire side device is performed when the angle at which the tire side device is positioned with respect to the center of the tire is a desirable angle for data communication.

For example, in one conventional tire pressure monitoring device having a pressure sensor or the like provided on a tire side and a receiver provided on a vehicle body side, data transmission is performed when the pressure sensor is rotated to a predetermined angle with respect to the center of the tire in one rotation of the tire. This device measures the angle of the pressure sensor at a timing when the tire pressure reaches a peak value in one rotation of the tire, and measures a time period from the timing of the peak value to a pre-measured timing at which the pressure sensor is rotated to an angle at which data communication becomes good. Then, air pressure data is transmitted after a fixed time period from the timing of the peak value of the tire air pressure so that the data communication is performed satisfactorily.

SUMMARY

According to the present disclosure, a road surface condition determination device comprises a tire side device attached to each tire of a vehicle, and a vehicle body side system provided in a vehicle body.

The tire side device includes a vibration detection unit configured to output a detection signal varying with a magnitude of vibration of the tire, a first control unit configured to generate road surface data indicating a road surface condition appearing in a waveform of the detection signal and measurement data for use in measuring a reception strength by the vehicle body side system, estimate an existence angle indicating a position of the tire sided device relative to a predetermined position of the tire based on the waveform of the detection signal, and cause a transmission of the road surface data at a transmission timing determined based on the existence angle, and a first data communication unit configured to transmitting the road surface data or the measurement data.

The vehicle body side system includes a second data communication unit configured to receive, by bilateral communication with the tire side device, the road surface data and the measurement data transmitted from the first data communication unit, and a second control unit configured to determine a road surface condition of a traveling road surface of the vehicle based on the road surface data, measure a reception strength of the measurement data, store a reception strength of the measurement data in one rotation of the tire, and set a transmission angle to the existence angle at which a reception strength of the measurement data is higher than a predetermined value in one rotation of the tire.

