A Development of Tractor's Continuously Variable Transmission Based on Combined Planetary Gear Train (2nd Report, Design and Manufacture of Prototype Transmission and Experiments)

Abstract

A new type of a tractor's continuously variable transmission (CVT), which consists of a 2 K-H type differential gear and a hydrostatic power transmission (HST) is devised. The hydrostatic power transmission (HST) consisted of a hydraulic pump and motor, which is a kind of CVT, has been applied to the smaller horsepower range of the tractor recently. One of concerns of the current HST system is lower efficiency on the power transmission. Then, further improvement for efficiency of the transmission is required more recently. The purpose of this development is to devise an adequate CVT providing with higher efficiency of the transmission in comparison with the current HST systems. Theoretical velocity ratio and efficiency of the CVT are investigated. And a prototype CVT is manufactured and incorporated into the tractor. The experimental results show that the efficiency of prototype CVT is several percent lower than theoretical value, but very nearly value. Then, the high efficient transmission for the tractor is offered. And the design method for the tractor's CVT that has high efficiency is built up.