Tire side device and road surface condition determination device containing same

A tire side device that is attached to a tire provided in a vehicle and is used in a tire device configured to determine a road surface condition of a traveling road surface of the vehicle, the tire side device, comprising:

• a vibration detection unit configured to output a detection signal corresponding to a magnitude of vibration of the tire;
• a control unit having a feature amount extraction part configured to extract a feature amount of the detection signal during one rotation of the tire;
• and
• a transmission unit configured to transmit a road surface data including the feature amount extracted by the feature amount extraction part, wherein
• the control unit includes
• a feature amount storage part configured to store the feature amount in a past extracted by the feature amount extraction part as a previous feature amount,
• a change determination part configured to determine whether or not there is a change in the road surface condition based on a present feature amount and the previous feature amount stored in the feature amount storage part, when the feature amount extracted at a time of a present rotation of the tire by the feature amount extraction part is referred to a present feature amount, and transmit the road surface data including the present feature amount by the transmission unit when there is a change in the road surface condition,
• a vehicle speed estimation part configured to estimate a vehicle speed of the vehicle, and
• an algorithm switching part configured to switch based on the vehicle speed estimated by the vehicle speed estimation part whether to transmit the road surface data from the transmission unit when the change determination part determines that the road surface condition is changed, or to transmit the road surface data without determining whether or not the road surface condition is changed by the change determination part.