|The CPT SpeedStart B-ISG in a demonstrator. Inset shows that SpeedStart technology includes fully integrated electronics. Click to enlarge.|
Controlled Power Technologies (CPT) (earlier post) will demonstrate a production-ready version of its next-generation 12V stop-start system at the LCV 2010 conference being held at Millbrook Proving Ground (UK) next week. CPT will demonstrate two vehicles equipped with its SpeedStart technology—a gasoline-powered Audi A4 and a diesel Volvo.
CPT is claiming an overall 7-10% reduction in CO2 emissions for the new system. CPT has said that its current SpeedStart B-ISG system can deliver up to a 5% reduction in CO2 emissions over the New European Drive Cycle when integrated into a modern powertrain, with the potential for even greater savings in real world urban driving situations.
The next-generation belt-driven integrated starter generator (B-ISG) system has a highly responsive control strategy with far fewer stop inhibits, and the additional benefit of efficient energy regeneration during vehicle decelerations. Because of its high power and torque, it addresses known stop-start issues including the problem of driver change of mind, according to CPT.
Driver change of mind (CoM) is a technical challenge for the industry. Anyone who has ever stalled in busy traffic will understand the time it takes to restart with a conventional starter motor. When adapted for stop-start, a conventional starter motor can reach a point of no return when the engine revs drop below a certain speed. The engine can then no longer be prevented from shutting down before it can be restarted. If in the middle of this stop-start event the driver wants to drive on and has a change of mind about stopping, the driver can’t because the conventional stop-start system will have taken over.
In its production-ready form, CPT’s new B-ISG includes intelligent torque and current control with much enhanced “just forget about it and drive” stop-start capabilities. SpeedStart can restart an engine imperceptibly and in less than half the time of a conventional starter motor. With enough power and torque to maximize the number of stop-start events the system can significantly reduce real world fuel consumption and CO2 emissions.
Even under the test conditions of the New European Drive Cycle (NEDC), which includes just 12 stops, SpeedStart’s stop-start capability provides a 3-5% reduction in CO2 emissions. The increased efficiency of its brushless switched reluctance (SR) motor generator, compared with a conventional alternator, provides a further 1% improvement. The use of regenerative charging during vehicle decelerations, combined with an optimized battery storage system, provides a further 3-5% improvement.
For its stop-start application, the SR machine is liquid-cooled, generates peak currents of 205 amps, has a starting torque of 72 N&iddot;m (53 lb-ft) and a maximum continuous output of 2.7 kW. Its system efficiency of approximately 90% over a large area of its generating envelope is much higher than a conventional alternator. With response times of less than 1/100 second (10ms) to establish full current in the windings the SR motor ensures there are no delays, allowing an engine to restart immediately and without hesitation.
Advanced stop-start technology developed as a high volume micro-hybrid solution is a very cost effective way of delivering CO2 reduction across a large vehicle range says CPT. The SpeedStart B-ISG system can integrate with many powertrains and has been demonstrated to crank 2.0-liter diesel engines and gasoline engines up to 4.4-liters. It also accommodates automatic transmissions.