Automatic transmission system for heavy construction vehicles

摘要

Heavy construction machines and vehicles with two speed ranges are provided with an electronically controlled transmission mechanism to select to alternative speed range at pre-determined speeds. One coupling (3) enables the gearbox (2), driven by a hydraulic motor (1), of the machine to operate at a first speed, whilst another (4) is used for a second speed. The couplings are fed with hydraulic fluid through pipes (6, 6`), in turn supplied form a solenoid valve (5), operated by a controller (8). A speed sensor (9) is connected to a drive shaft of the gearbox (2), and a converter (10) provides a signal to the electronic control unit (11) which selects the speed range by means of the valve (5) at pre-determined speed values.