Correct transmission for E-mobility vehicles

Transcription

1 Correct transmission for E-mobility vehicles SAE 2011 Electronic Systems for Vehicle Propulsion Page 1

2 Agenda Working hypothesis Overview of transmission focus and need Closer look into three needs Torsional vibration insulation Stand by losses Increased number of gears for electric powertrain Summary Page 2

3 Working hypothesis Focus automatically shifted transmissions Abbreviations used: EM Electric Motor ICE Internal Combustion Engine Page 3

4 Mainstream technology Overview Low Medium High Volvo V60 PHEV Toyota prius HEV Time (year) Page 4

5 Mainstream technology Improving ICE efficiency EM to support above ICE transmission EM transmission Torsional vibration insulation High number of gears (8?) Low number of gears (1?) Transmission focus Two main sources of propulsion Synergy optimization Integration optimization Seamless switching between sources of propulsion & gears Low stand by losses Low cold losses Response Small size & low weight Optimizing EM ICE might act as range extender or optimized for few use-cases Increased number of gears (2-3?) Time (year) Page 5

6 Engine torque (Nm) Torsional vibration insulation ICE efficiency Optimum Not available due to: Surplus power for acceleration Response issues for engines with turbo Torsional vibrations Engine speed (rpm) 30kW 20kW 10kW First two might be solved with an EM since it can contribute with both low speed torque and response. Opportunity: Improved torsional vibration insulation Risk: Response, size and weight Page 6

7 Velocity (km/h) Driving distance (km) Losses (kw) Low stand by losses Power losses during NEDC driving Typical for warm transmission for ICE Hybrids introduce operating conditions with transmission in stand-by: Many operating conditions use pure electric or ICE drive. 100 Charge depletion driving distance NEDC Stand by losses (Nm) Velocity profile NEDC Opportunity: Improved stand by losses Risk: Response Time (s) Average parasitic loss (kw) Page 7

8 Low stand by losses an example Hybrid mode: Both sources of propulsion active Pure electric: EM active ICE in stand-by Pure ICE drive: EM in stand-by ICE active Page 8

9 Increased number of gears for EM transmission Source: Gear ratio is a trade off between: Speed range with high efficiency Top speed Take off performance high gear ratio increases wheel torque Velocity span for given gearing η>88% for 1200->4300rpm Gear ratio 7.5 Tyre dim: 225/50 R17 Low efficiency High efficiency 1200rpm 4300rpm 8000rpm Vehicle velocity span (km/h) Page 9

10 Gear ratio Increased number of gears electric motor transmission Velocity span for given gearing Low efficiency High efficiency 7.5 Single speed transmission Increased velocity span with high efficiency Vehicle velocity span (km/h) 17 5 Increased gear ratio 1st gear and thereby take-off Vehicle velocity span (km/h) Opportunity: Increased number of gears for electric motor Risk: Efficiency, size, weight and gear shift quality Page 10 Dual speed transmission Increased top speed

11 Mainstream technology Summary Which transmission attributes will be important for E-mobility vehicles? ICE torsional vibration insulation Stand-by losses Increased number of gears for EM System optimization important and not single attributes Improving ICE efficiency EM to support above Transmission focus Two main sources of propulsion Synergy optimization Integration optimization Optimizing EM ICE might act as range extender or optimised for few use-cases ICE transmission EM transmission Torsional vibration insulation Low number of gears (1?) Increased number of operating conditions with electric propulsion High number of gears (8?) Seamless switching between sources of propulsion & gears Low stand by losses Low cold losses Response Small size & low weight Increased number of gears (2-3?) Time (year) Page 11

12 Thank you for your attention! Page 12