The University of California-Davis has licensed plug-in hybrid vehicle technology to a Palo Alto start-up called Efficient Drivetrains.Â (read the story here andÂ here)Â The licensed technologyÂ includes a fuel efficient “parallel” hybrid powertrain and a continuously variable transmission (CVT) control system thatÂ automatically selects the optimal power ratio and eliminates the need for gear shifting.Â Efficient Drivetrains plans to partner with auto manufacturers toÂ develop carsÂ that canÂ be recharged using a domestic power supply.Â The license agreement was negotiated by the UC-Davis InnovationAccess Unit, which manages the University’s patent portfolio.Â
The licensed technology was developed by Andrew Frank, a professor of mechanical and aeronautical engineering. Â Dr. FrankÂ is the named inventor on severalÂ U.S. patents relating to drive train system designs and energy management systems for hybrid electric vehicles and plug in hybrid vehicles and has published many articles on the subject. (see Dr. Frank’s publications here)Â
An example ofÂ the CVTÂ control systemÂ is disclosed inÂ U.S. PatentÂ No. 7,261,672.Â TheÂ inventionÂ increases theÂ efficiencyÂ of a vehicle’s acceleration and decelerationÂ by controlling the rate of change of the gear ratio in a continuously variable transmission.Â The system includes a controller that maps and relates various operational characteristics such as torque, speed, oil temperature, differential pressure between pulleys or clamping pressure to the level of each needed to achieve an optimal rate of change of ratio.Â Once the optimum rate is selected, the characteristic is controlled to achieve that rate.Â This systemÂ can beÂ usedÂ in both traditional automobiles and hybrid electric vehicles.
An example of Dr. Frank’s “parallel” hybrid powertrain is described in U.S. Patent No. 6,809,429, which incorporates the idea of inserting an electric motor and its battery and controls between the vehicle’s engine and its transmission.Â The electric motor is coupled to the input shaft of theÂ CVT so it injects power in parallel with the vehicle’s drive train.Â Â Â The systemÂ varies motor torque and rate of change of ratio to reduce the amount of power cycled by the batteries and maximize efficiency and vehicle performance.