|Antonov two-speed alternator. Click to enlarge.|
Simple dual-speed drives can help alternators and other engine ancillaries operate more efficiently by better matching their drive speed to the vehicle requirements and also improve the re-charging of batteries, according to transmission specialist Antonov Automotive Technologies. (Earlier post.)
The characteristics of Antonov’s mechanical module (AMM), essentially a self-controlling automatic two-speed gearset, can be tuned to meet specific vehicle requirements.
The dual-speed technology is based on a simple mechanical shift for an automatic transmission system invented 20 years ago by Roumen Antonov. The principle is to control the shift with the use of centrifugal force and axial thrust generated by helical gears under load. The systems can work as autonomous self-adapting modules without the need for more expensive hydraulic actuation or electronic control.
Mated to an alternator it provides improved alternator matching to give good charge at engine idle without incurring losses at higher engine speeds. In this application, it can also provide a reduction drive to enable a compact front mounted starter-alternator to be used for engine stop-start operation. The company, which is developing the system for OEM applications, says a dual-speed alternator designed for stop-start operation can deliver an 18% saving of electrical energy over a typical light commercial vehicle duty cycle.
It can also be applied as a dual-pulley unit to give a two-speed belt driven alternator, air-conditioning pump and water pump, whereby the accumulated energy saving translates into a 5.6% reduction in fuel consumption. This is achieved with a 2-to-1 gear ratio change at 2,000 rpm.
Ultimately, the company aims to introduce a compact unit that is mounted directly to the engine crankshaft, but this will require much greater development integration with the base engine.
Customers and legislators are placing more demands on vehicle electrical power, with lower emissions meaning smaller petrol and diesel engines, lower engine idle speeds and more stop-start systems. Even daytime headlight legislation is increasing the electrical load.—Chris Baylis, operations director Antonov
The introduction by carmakers of belt-driven stop-start systems and other technical developments, such as downsized engines, is increasing the need for more efficient electrical systems. Vehicle manufacturers also want more engine torque at low engine speeds to improve driveability as well as better fuel efficiency.
Maximizing the overall operating efficiency with fixed drive alternators, water-pumps, superchargers—indeed any crankshaft driven or electric motor ancillary—is becoming more and more difficult. At high engine speeds this can result in unacceptable losses or even excessive speeding outside their most efficient operating range.—Chris Baylis
Applied to an alternator, the Antonov dual-speed module can increase the electrical output for regenerative braking and reduce engine idle speed without battery charging issues. A smaller dual-speed alternator can match the low engine speed output of a larger more expensive alternator, and there is also reduced noise at higher engine speeds.
Another application of Antonov’s AMM device is to facilitate low cost engine downsizing. As demonstrated at the recent Cenex low carbon vehicle event in the UK, it can be used as a 2-speed drive with a centrifugal supercharger. The resultant higher drive ratio at low engine speeds provides a big engine feel from a small engine, allowing for less gear down changing and improved fuel economy.
Antonov is similarly pursuing the development of its mechanical module as a 2-speed electric vehicle transmission, whereby it’s either packaged into the electric motor as part of the reduction gearing, installed as a separate dual-speed unit or as part of the transaxle. The AMM device requires no external control, with its characteristics predetermined at the design stage. The high transmission efficiency of a purely mechanical system ensures minimum losses through the driveline.
Two Antonov epicyclical sets can also be incorporated as a binary system to create a simple fully mechanical fully automatic 4-speed transmission, which is suited for the low-cost cars required in third world and emerging markets. The very low costs are achieving by not having any hydraulic systems or transmission control units. Maximum efficiency is delivered by only slipping two clutches in 1st gear, one clutch in 2nd and 3rd gears, no clutches slipping in 4th gear and no high pressure oil pump.