A U.K. automotive consortium is developing a modular hybrid system that could span micro-hybrid to full plug-in hybrid electric vehicles (PHEV). An added aim of the project is to achieve minimum investment costs for production systems both in terms of new hardware and/or new vehicle architecture.
The consortium, which includes Jaguar Land Rover, electronics specialist Smart Power Solutions, and transmission specialist Drive System Design, is led by engineering consultancy Integral Powertrain. Funding has been provided as part of the U.K. Technology Strategy Board’s Integrated Delivery Program and by the U.K. government’s Dept. of Transport.
The project is called Ultra Cost-Efficient Hybrid Powertrain (UCEHP) and is based on a conventional transverse engine and gearbox layout. A statement issued by the consortium explained that for micro-hybrid applications, Integral Powertrain’s variable ratio (VR) crankshaft pulley and high-efficiency brushless permanent magnet B-ISG (Belt Integrated Starter Generator) would be used to provide stop-start capability.
The VR pulley facilitates the use of a lower torque motor for a given engine size. It has been designed to permit cost-effective, refined, and fast stop-start operation on various engines including large diesels.
Integral Powertrain claims that compared to other B-ISG micro-hybrids, the system offers a lower overall cost because the cost of the VR pulley is “more than compensated for by significant savings in the motor, motor drive, electrical storage, and FEAD (front end accessory drive) systems resulting from the lower torque requirement.”
Applying the system to full-hybrids requires only the upgrading of the onboard electrical storage capacity to enable air-conditioning use while the engine is stopped. This can be achieved by the B-ISG driving the compressor while the VR pulley freewheels on the crankshaft.
Use of the B-ISG in this way is aimed at providing a markedly lower cost alternative to an electric air-conditioning compressor.
The relatively high-power ISG machine, combined with the increase in electrical storage capacity, also enhances the potential for regenerative braking, explains Integral Powertrain Technical Director, Luke Barker.
“Typical CO2 savings for this configuration are 8-10% on the NEDC test," he said.
Full hybrid functionality is achieved by the addition of a second brushless permanent magnet traction motor integrated with a conventional low-cost AMT (automated manual transmission) and a further upgrade in battery capacity.
Active control of the two electrical machines provides the simple AMT with enhanced gearshift quality. It also allows rapid and refined transition between different operating modes because, as Barker explained, "the high power ISG allows the necessary control of engine speed—a key feature that is not apparent in other systems.”
The hybrid capabilities are designed to include electric-only drive at light load/low speed conditions and improved regenerative energy recovery. Compared to conventional powertrains, this arrangement has been shown to offer typical CO2 savings of 25-30%, said Barker.
He added that the UCEHP strategy "allows conversion of existing low-cost powertrains to full-hybrid capability with minimal impact on proven hardware or vehicle architecture, dramatically reducing development risk and both engineering and capital investment.”
The consortium program will address the engineering of all key subsystems together with the control strategy covering battery management, IC engine, and electrical machines. In particular, detailed simulation will be employed to optimize cost benefit ratios and to ensure refined gear shifting and mode switching.
First hardware will be on test in the second quarter of 2010.