DIFFERENTIAL TRANSMISSION MECHANISM FOR A CONSTANT SPEED DRIVE

摘要

A differential transmission mechanism using an output differential for a constant speed drive has desirable characteristics including full utilization of the torque capabilities of the hydraulic trim device associated with the output differential; however, there is a limitation on the utilization of the speed capability of the hydraulic components of the trim device at the low end of the input speed range. The disclosed differential transmission mechanism utilizing an output differential has a hydraulic trim device with a first hydraulic displacement unit having a normally fixed, approximately maximum displacement connected to an element of the output differential and a second hydraulic displacement unit which is of variable displacement connected to a variable speed input shaft. Additional components of the output differential are connected to the input shaft and to an output shaft connectable to a load. A sensing device senses the speed of the output shaft to control the displacement of the variable displacement hydraulic displacement unit to control the displacement thereof to achieve a constant output speed by varying the speed of the normally fixed displacement unit as required. Additionally, a sensor senses the speed of the input shaft and, when the speed of the input shaft is below a predetermined value, controls the displacement of the normally fixed displacement unit to reduce the displacement thereof to effectively make the latter displacement unit a smaller unit which will therefore operate at a faster speed to extend the range of the constant speed drive at the low end of the input speed range.