If you look at the specs sheets of most electric cars these days you’ll see that it might have large torque figures, but they’re also complemented by 0 to 100 km/h acceleration times that aren’t that fantastic as well as rather low top speeds. This is actually because most EVs run on a single speed transmission, so there’s only one gear that has to be balanced to do both the work of ‘pick up’ and ‘cruising’.
Tesla had originally planned for the Elise-based Tesla Roadster to have a two-speed transmission but apparently it was too challenging and it settled for a BorgWarner single-speed transmission. Having more than one transmission ratio will enable manufacturers to downsize electric motors and keep them running longer at the medium loads and speeds where peak efficiency of over 95 percent is possible, translating into potentially more performance, greater range and longer lasting batteries. The single speed transmission in current EVs force the motor to run outside its optimum efficiency range most of the time.
Zeroshift has been working on a multi-speed gearbox for electric vehicles (EVs) that needs no clutch – a damper inside the gear hubs and electronic control of the motor make ratio changes seamless without interruption. The synchromesh in a regular manual gearbox is replaced with paired interlocking rings that change ratios without interrupting the torque. To provide the required levels of shift refinement, Zeroshift’s concept uses electronic control of the electric motor or motors to match the shaft speeds and an integrated a passive damper system within the drive hub to isolate any vibrations.
“Our studies suggest that by using a compact, multi-speed transmission and a smaller electric motor, manufacturers can gain an operating efficiency of up to 10 percent. You can use that 10 percent to improve EVs’ range or reduce the size, weight and cost of battery packs,” says Bill Martin, Zeroshift’s managing director.
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genuis!!!!
Proton put this in your EMAS, it should be the best hybrid in the market.
I don’t understand lor
yeah, me neither. can some1 help translate the article into english?
i always wonder why almost all electric cars have no gears.. no gear = less fun.
Good work, but the transmission will add to driveline losses. You can actually change use combination of mechanical field weakening (changing motor geometry) and advancing the phase current to achieve the same goal without having the transmission losses.
Can it be done? i wonder…
How the much different the torque, speed and efficiency compare to single transmission?
wonder how a small motor can sustain if full capacity applied…
Zeroshift makes whats called ‘seamless shift’ boxes. What this means is that unlike other fast shifting boxes with internals like a manual gearbox (Ferrari F1, BMW SMG) or dual clutch boxes (BMW DCT, Audi S Tronic, VW DSG) etc, seamless shift boxes do not have to cut engine power entirely to change gears. All the other systems mentioned have a short period where the car is ‘coasting’ because engine power is disconnected momentarily when changing from one gear to another. In racing, the car should always be accelerating or braking or taking a corner. Coasting is to be minimized or eliminated is possible.
Zeroshift’s system is ingenius because it is very simple and can be implemented in an existing manual type gearbox, making the system cheap to integrate.
Almost all F1 teams are using some type of seamless shift box though I think Williams is the one that actually collaborated with Zeroshift
Now, this is the first time I heard about optimum efficiency range of an electric motor, which I have never thought about. As you see, most of the EV prototype or not, has said that electric power has flat torque graph right from 0 rpm, give an impression of it is as efficient at 0 rpm as well as 20,000 rpm.
How many more possible technology we could develop to fine tune this existing technology like how we do to our oil burners in the pass century?
The best type of electric motor (3 phase brushless permanent magnet) typically can be designed wih max efficiency higher than 95%, typicall near the ‘knee’ region where maximum torque output starting to drop . The high efficiency region of the electric motor is flatter or more spead out. However, at low speed and low torque, the efficiency will drop to about 70% or maybe lower. In comparison, the internal combustion engine might have peak thermal efficiency of 41% (TDI diesel engine) and it looks like a small island under the peak torque area.