A Novel Strategy for Sizing the Mechanical Pump in a Passenger Car Automatic Transmission

In recent decades, there has been a growing focus on improving overall vehicle efficiency and fuel economy due to growing customer awareness and more stringent environmental regulations. Effort has been placed on improving the engine efficiency and reducing the losses of the transmission and driveline. One essential component of this process is to correctly size the transmission oil pump as it is one of the main energy consumers in the powertrain. Conversely, the oil pump has a critical mission of ensuring reliable and high quality gear shift as well as supplying lubrication and cooling oil to various components in the transmission. This paper outlines a strategy to systematically understand and quantify the main requirements for sizing the oil pump to ensure adequate performance while minimizing the energy consumption of the pump. The proposed framework is a three-legged approach. The first component identifies the main consumers within the automatic transmission and establishes a relationship between the operating parameters, component specific parameters and the specific demand of that particular oil consumer. The second leg looks at various operating conditions and a plethora of load cases are identified. The third leg connects the first two components and proposes the most optimized pump displacement size minimizing the required power to run the pump while meeting the requirements.