2013-12-13 16:33:06 - Novel synchroniser architecture allows seamless shifts with higher efficiency
Southam, UK, 13 December 2013 – specialist engineering consultancy, Drive System Design (DSD), unveiled technical details of MSYS, its novel transmission for hybrid and electric vehicles (HEVs), at last week’s international CTI Symposium in Berlin. By making fundamental changes to synchroniser layout that allow smoother shifts with higher efficiency, DSD has been able to provide a multi-speed transmission with a 40 percent weight saving and 10-15 percent lower vehicle energy consumption compared to a single-speed EV or HEV transmission.
The powershift elements in the MSYS transmission separate the two basic synchroniser functions of friction and latching and use the enhanced friction capacity of multi-cone clutch assemblies to provide an uninterrupted flow of torque to the wheels while using no energy to
hold the transmission in gear. The increased friction capacity allows the powershift cone clutch to temporarily drive the vehicle during shift events while latching in gear is achieved by dog clutches with self-locking teeth, similar to a conventional synchroniser.
“The main consumer concern holding back sales of electric vehicles is range anxiety,” said DSD technical director, Alex Tylee-Birdsall. “By using an MSYS multi-speed transmission, energy consumption can be improved by up to 15 percent which translates directly into increased range. It permits downsizing of the motor and, by being in the optimum gear ratio more often, extends the time the motor spends operating at high efficiency.”
There is growing recognition of the benefits of multiple ratios for EV transmissions. DSD has taken a unique approach by developing a reliable, highly efficient, seamless gearshift in order to make such transmissions acceptable to the user. “MSYS avoids the disadvantages inherent in other transmission options,” he said. “A DCT consumes energy continually to maintain clutches in the open or closed position (depending on clutch type); an AMT suffers from torque interruption during shift events, and automatics based on epicyclic gear sets add complexity, cost and drag.”
By using proven technologies in a unique arrangement, i.e. synchroniser-derived cone clutches and dog clutches, DSD has been able to seek patent protection for the system while minimising the technical risks during development and enabling system suppliers to make use of their existing expertise. Enhanced friction levels have been achieved in the multi-cone clutches by using forced lubrication with variable flow through the clutch packs. Flow variation permits good thermal management at times of high slip with maximum efficiency at times of lower demand.
Characterisation testing of the cone clutches has shown good linear engagement properties (torque vs applied pressure), enabling the clutch-to-clutch shifting that is an essential part of the MSYS design. The next phase of development will include installation of a prototype transmission in a demonstrator vehicle, allowing calibration to commence. The vehicle will be ready for demonstration to customers during the summer of 2014.
MSYS will be ready for series production during Q4 2016, to support the growing demand from vehicle manufacturers needing to comply with increasingly tight CO2 emissions regulations. A family of MSYS powertrains with different power and torque outputs is planned, to suit the requirements of different target sectors.
DSD is an innovative engineering consultancy specialising in the design , development and control of transmission systems and the integration of driveline systems into vehicles. Founded in 2007, DSD has inherited decades of experience from its key personnel, each of whom are leaders in their individual fields of engineering, and currently employs over 30 staff with particular expertise in driveline refinement, efficiency improvement and hybrid and electric vehicle transmissions. The company won the prestigious “Consultancy of the Year” accolade in the 2010 British Engineering Excellence Awards.
Richard Doherty at Market Engineering
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