Hydraulic Power Assist − A Demonstration of Hydraulic Hybrid Vehicle Regenerative Braking in a Road Vehicle Application

With the desire for improved fuel economy for road vehicles, there has been increased interest in Hydraulic Hybrid Vehicle (HHV) technology. The inherent power density of HHV makes significant benefits from regenerative braking possible in higher- mass vehicles. Other advances in hydraulic components make HHV practical in a passenger vehicle.

A vehicle to demonstrate Hydraulic Power Assist (HPA), a type of HHV using primarily regenerative braking, was built by Ford Motor Company Advanced Powertrain working jointly with the United States Environmental Protection Agency (USEPA) Advanced Technology Division, in the context of a Cooperative Research and Development Agreement (CRADA). A full size Sport Utility Vehicle was fitted with a hydraulic pump/motor and valve block provided by Ifield Technologies, and carbon fiber accumulators developed by the US EPA. The pump/motor was connected to the vehicle driveshaft in parallel with the conventional powertrain, and a development control system integrated the hydraulic system with the powertrain and braking systems. The vehicle demonstrated the ability to improve fuel economy on a start/stop city- typical driving cycle. It also demonstrated the ability to smoothly integrate hydraulic power with friction braking and with the conventional engine- based powertrain, and to achieve reasonable noise levels. This report includes a description of the system, and initial fuel economy, performance and noise results.