The increasing demand for an improved driving level (such as higher efficiency of the driveline, increased driving comfort) and the search for a drastic reduction in emissions and fuel consumption (possible hybridization) strongly point to a future increase in vehicles with automated manual transmissions.
Meeting these requirements is the aim of Development no matter which type of transmission (manual transmission, dual clutch transmission, automatic transmission, continuously variable transmission).
For this reason, better and more efficient hydraulic pumps are needed that will become ever more important in the future.
Among the other pump types, the external gear pump with (axial/radial) clearance compensation mechanisms has proven to be the perfect combination of low manufacturing costs and high product performance, especially for clutch actuation and gear shift operation, where the higher pressure and the reduced flow rate call for high sealing requirements. Thanks to the lower working pressures and high absolute flow, the sealing requirements for transmission lubrication and clutch cooling are less stringent. Clearance compensation mechanisms are not needed and a large variety of pumps can be used.
In this case, the Gerotor type pump is considered to be a good alternative. An integration of the pump within the electrical motor brings several benefits. The most obvious advantages are reduced package and lower tolerances combined with higher performance and improved acoustics.
With fixed displacement pumps, the electrical motor is used to control the speed. This mitigates the flow throttle problems and the viscous friction losses.