The Universal Control and Protection Hydraulic Automaton for Hydromechanical Transmissions

Modern hydromechanical transmissions are equipped with electronic-hydraulic (mechatronic) control systems having much more functional capabilities compared to classic hydraulic systems.

However, automatic hydraulic systems are widely used not only as the basic transmissions' control device and a mechanical part of mechatronic systems but also as an important facility providing reliability and safety of such systems.

At the same time such an application has quite a number of restrictions, especially for transmissions with a great number of gearstages. One of the main reasons is the inability to control more than 3 or 4 stages of gears while using the vehicle's speed as a control parameter. It deals with the parabolic characteristic of the output pressure of centrifugal governor used as the vehicle speed sensor.

This restriction can be eliminated by using a hydraulic detector of torque converter's turbine (i.e. input shaft of gearbox) speed. The paper considers the operating principles, design and testing of such a hydraulic automaton capable of controlling converter's lock-up clutch. It may be used in hydromechanical transmissions as the system's back up and protection or as a self-sufficient hydraulic automaton.