Proposal of a measurement method for the tension of crawlers’ rubber tracks by using their inner structure

Half-tracked tractors equipped with front wheels and a rear oscillating crawler unit are popular. However, the track tension fluctuates caused by the variation in the unit's perimeter because the hitch point of the oscillating frame is set separately from the drive axis of the drive sprocket. It is considered that this fluctuation in the track tension could influence driving performance. Moreover, driving performance factors might be optimized by actively controlling the track tension. Therefore, this paper aims to propose a measurement method for track tension fluctuation, which focuses on the inner structure of the rubber track. The rubber track contains a structure of capacitors constructed with a steel cord as a capacitor plate and the rubber between the steel cords as the electric material. When the tension force acts upon the rubber track, changing the distance between the steel cords, the capacitance would be changed. This capacitance variation was measured in the oscillating frequency by a CR oscillating circuit that utilized the characteristic of a capacitor. A fundamental experiment with a test piece cut out of a rubber track was carried out to evaluate the effectiveness of the proposed tension measurement, which uses steel cords arranged inner the rubber track. As a results, it was theoretically confirmed that the oscillating frequency was reduced by increasing the tension load, and a stable value with a high correlation between the tension load and the oscillating frequency. In conclusion, this study has demonstrated the possibility for stable measurement of crawler tension.