ZF presents new electric 2-speed drive for passenger cars
17 July 2019
ZF has introduced a new 2-speed electric drive for passenger cars that integrates an advanced electric motor with a shift element and appropriate power electronics. The improvement in energy conversion efficiency compared to previous e-drives extends the driving range for each battery charge.
The compact design also makes this new drive system of interest for passenger cars in the compact class. The modular design of this unit can also be fine-tuned and scaled up for use in sports and performance vehicles.
For electric vehicles in everyday use, it is important to obtain as much range as possible from each battery charge. Every percent of improvement in energy conversion efficiency translates into two percent more range.
—Bert Hellwig, Head of System House at ZF’s E-Mobility division
To increase the performance rating of the new electric axle drive system, ZF leveraged its expertise in systems to develop a new electric motor with a maximum power rating of 140 kW paired with a two-stage shift element.
Vehicles with the new 2-speed drive consume less energy, which in turn extends range by up to five percent when compared to a one-speed unit. Shifts take place at 70 km/h.
By connecting to the vehicle’s CAN communication it is also possible—if the customer so wishes—to devise other shift strategies, possibly linked to digital map material and GPS. For example, the vehicle could identify from the GPS route programming how far it is to the next charging station, enabling it to respond predictively by switching into Eco-mode.
More effective shifts would also be possible in accounting for topography on the interstate, and on inter-city journeys. The software in the drive can also be updated via the network link to Cloud services via over-the-air updates.
For vehicle manufacturers, the new 2-speed drive offers two options for using improved energy conversion efficiency. The Original Equipment Manufacturer (OEM) could either go for an extended range while retaining the same size of battery, or utilize a smaller batter.
The 2-speed concept also offers benefits for OEMs pursuing performance.
Until now, with electric motors, vehicle manufacturers have had to choose between high initial torque and a high top speed. We are now resolving this conflict and the new drive will be compatible for performance and heavier vehicles—for example for passenger cars towing a trailer.
—Bert Hellwig
ZF’s modular approach combines the 2-speed gearbox with even more powerful electric motors rated for up to 250 kW. This delivers enhanced acceleration and, potentially, faster top speeds. With its modular concept, the new drive can meet a variety of requirements.
Should give better motorway cruising for EVs,
They don't say how much better it makes things, however.
Posted by: mahonj | 17 July 2019 at 03:16 AM
For overall performance, two gears are better than one; three gears would be even better. A tranny not only matches the revs of the motor to the speed of the vehicle, it also functions as a torque converter. The higher the gear reduction the higher the resulting torque will be at the tranny output. It does not matter too much if only one occupant is in the vehicle. However when the vehicle is fully occupied, the mass to be accelerated increases considerably. The electric motor itself, with or without a tranny will draw the current from the battery necessary to overcome the mass resistance of the total load. The higher the mass to be accelerated the higher the current burden will be.
It's not exactly beneficial for the battery to endure high current peak-draws even if only for short durations. IOW, a tranny is beneficial for the life duration of a battery. If a trailer should be hitched to an EV, the beneficial impact will be even greater. For anyone driving his EV only solo can disregard a tranny with ease of mind.
Posted by: yoatmon | 17 July 2019 at 04:38 AM
“Vehicles with the new 2-speed drive consume less energy, which in turn extends range by up to five percent when compared to a one-speed unit.”
5% though not entirely meaningless is not a game changer. This is a bit less than the Mild hybrid gains by ICE proponents but this requires a fraction of the commitment. If the 3-10% gains reported for MH are the best they can manage then they are doomed.
Posted by: Gasbag | 17 July 2019 at 06:51 AM
Two speed DCT seems like a good idea.
You have city then highway gears.
Posted by: SJC | 17 July 2019 at 07:04 AM
The tradeoffs: more weight; more maintenance cost, increased complexity, increased initial cost. And the question; Do you really need this for a street car designed for point to point transportation? If you are using it as a track car, that's different.
Posted by: Lad | 17 July 2019 at 08:43 PM
@ Lad
The additional weight is negligible; the last diesel I had ( over 200,000 mi. never needed oil exchange, merely had to check the oil level in the transmission; complexity and increased cost is more than balanced with the benefits for the battery.
"Do you really need this for a street car designed for point to point transportation?"
You probably don't but I and plenty others would.
Posted by: yoatmon | 19 July 2019 at 06:58 AM