Technical Paper
Development of Hydromechanical Transmission (HMT) for Bulldozers
1994-09-01
941722
Conventional medium to large-sized bulldozers have a powertrain comprised of a manually operated powershift transmission connected in series with a torque converter. There is a growing need, however, for a power train that is more efficient and easy to operate, thereby increasing bulldozer productivity. One answer to this growing demand is the hydromechanical transmission (HMT) developed by Komatsu for medium to large-sized bulldozers. The HMT consists of a powershift transmission combined in parallel with a hydrostatic transmission (HST) featuring a pair of hydraulic units. The HMT has a continuously variable shifting ratio and achieves high efficiency and automatic shifting. Additionally, it has an electronic controller that controls the transmission ratio to maintain engine speed at the maximum power point. As a result, bulldozers with the HMT demonstrate greatly improved productivity over bulldozers with the conventional powertrain.