For Axle Hybrids or Fully Electric Vehicles: ZF Integrates Powerful Electric Drive in Innovative Rear Axle

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- The modular mSTARS axle system provides greater flexibility and brings ZF a step closer to zero emissions due to integrated electric drive
- The innovative passenger car axle combines driveline and chassis technology in a single system
- Can be upgraded in line with customer requirements by adding an electric or conventional drive module as well as Active Kinematic Control (AKC) rear axle steering

Friedrichshafen. ZF's Vision Zero Vehicle is helping to set the course for an accident-free and zero local emissions future. The vehicle features a 150 kW electric axle drive system for dynamic acceleration. The entire propulsion system including the integrated power electronics is housed in an innovative, space-saving modular ZF rear axle system called mSTARS (modular Semi-Trailing Arm Rear Suspension). This modular axle system makes it easier to electrify volume production vehicle platforms – even existing ones as demonstrated in the Vision Zero Vehicle.

"mSTARS provides our customers with a basis for a wide range of applications in multiple vehicle segments. The solution is suitable for hybrid, fuel-cell and battery-powered vehicles as well as in combination with conventional all-wheel modules or our AKC active rear axle steering," explains Dr. Holger Klein, head of ZF's Car Chassis Technology Division. "The Vision Zero Vehicle demonstrates how quickly it could help the industry meet the challenge of producing high-performance e-cars or hybrids." The system offers vehicle manufacturers the opportunity to respond to a diverse range of market requirements using just one car platform variant.

Scope for new drive concepts

In the Vision Zero Vehicle, which is based on a volume production platform for compact and mid-size cars, the mSTARS semi-trailing link independent suspension takes up no more installation space than the conventional rear axle installed originally. The potential of ZF's innovation is far greater however – mainly because it frees up installation space between the rear wheels as a result of its unique integral link design and separate spring damper configuration. This means that ZF's electric drive fits effortlessly into the mSTARS system axle carrier.

The compact and powerful 150 kw drive unit houses not only the electric motor but also a two-stage one-speed spur gear drive, a differential, and power electronics along with control software. "We've put our concept of an intelligent mechanical system and clean mobility into this multifunctional axle system for compact passenger cars and up," says Holger Klein.

Driving safety through and through

Even in its basic version, the mSTARS axle also boasts a high level of driving dynamics and safety – delivering the performance of more expensive, conventional multi-link axles typically used for compact premium and sports vehicles. ZF’s AKC active rear axle steering system, which can be combined with any modular axle configuration, improves agility, comfort and stability. Since it also controls the rear wheel steering, it allows advanced assistance systems to operate more reliably and effectively. mSTARS is ZF's response to the key industry megatrends: The new rear axle system not only plays a role in zero-pollution driving but also in improved safety – and therefore helps bring the company a step closer to its Vision Zero: supporting an accident- and local emission-free future.