Wear-condition-sensing device

A wear-condition-sensing device comprising:

• an element configured to generate voltage based on deformation of a tread portion during tire rotation;
• a voltage detection unit configured to detect the voltage generated by the element;
• a speed detection unit configured to detect vehicle speed or tire rotation speed;
• a storage area configured to integrally store waveform data over time of the voltage detected by the voltage detection unit together with the vehicle speed or the tire rotation speed detected by the speed detection unit;
• a calculation unit configured to calculate an index value of voltage change based on the waveform data in a predetermined speed range stored in the storage area;
• and
• a determination unit configured to determine a progress condition of wear of the tread portion by comparing the index value calculated by the calculation unit with reference information corresponding to a predetermined speed range to determine a progress state of wear of the tread portion,
• the predetermined speed range being a range of ±5 km/h from any speed within a range of 30 km/h to 60 km/h, and the reference information being an arbitrary rate of change with respect to the index value of voltage change when the tire was new, wherein
• a sensor module comprising at least the element and the voltage detection unit is fixed to a tire inner surface via a container into which the sensor module is inserted, and
• a width Lc1 of an opening portion of the container and a maximum width Lsm of the sensor module satisfy a relationship of 0.15≤Lc1/Lsm≤0.90.