In the past, so-called mild hybrids could only briefly support the combustion engine in its consumption-intensive phase during acceleration, but future systems of a similar design will not only be able to operate significantly more intelligently, but also significantly more efficiently. at Continental you can see great potential for fuel savings compared to a conventionally powered gasoline engine with an automatic start-stop. "In inner-city driving this can be 21 percent, it would be around 13 percent in the NEDC profile," says Dr. Oliver Maiwald, Head of Technology & Innovation at Continental, Powertrain Division, sure. The prerequisites for this, however, are 48 volts. The higher voltage enables the transmission of greater powers. In addition, the e-machine can be made more compact and provided with a higher power density.
All major suppliers are currently developing solutions for future 48-volt hybrid architectures. "The higher voltage is the key to efficiency and higher performance," says Peter Gutzmer, Technology Director at Schaeffler AG. It works on the basis of a Continental 48-volt generator on a module that is designed for side mounting between the combustion engine and transmission (BSG, Belt Starter Generator).
In addition to this axially parallel solution, a 48-volt module is also being developed, which is arranged between the motor and the transmission. This solution, called ISG (Inline Starter Generator), enables fuel savings of a further two percent because there is no friction loss due to the belt. "By 2025 at the latest, the module will sit entirely between the engine and the transmission," says Gerhard Gumpoltsberger, Head of Innovation Management and Testing at ZF. Continental plans to present a novelty in this direction at the end of April at the Vienna Motor Symposium.
The ISG architecture could also put new high-current consumers on the 48-volt side. Audi practices this in its SUV flagship SQ7, but the power SUV still has a 12-volt generator. The voltage is converted and the current is then sent to a lithium-ion battery. It supplies - for the first time in the industry - an electrical compressor and also an electrical roll compensation with electricity. It would also be possible to operate other consumers, such as the air conditioning compressor, more efficiently with 48 volts than currently with twelve volts, which would further reduce consumption in real operation. Renault also plans to put the 48-volt technology in series production next year.
There is no doubt that these systems are coming. The driver is fleet emissions, which is forcing car manufacturers to massively electrify. The belt generators with the higher voltage are seen as the most cost-effective addition to the plug-in hybrid. “The system is much easier to implement,” says Gumpoltsberger. While the expensive plug-in technology is reserved for the upper class, BSG and ISG will prevail in the segments below, according to the development departments. “For at least the next 10 to 15 years we will not say electric motor or combustion engine, but rather “and,” says Rolf Bulander, chairman of the Mobility Solutions division at automotive supplier Bosch.
By 2020 alone, Bosch will see a market of 3,1 million vehicles with 48-volt systems. Customers in Asian markets and the USA are particularly interested here. The Swabians bring another aspect into play. In their view, the topic of 48 volts is also an ideal addition to the diesel engine - since it not only saves fuel, but can also provide very efficient support in reducing emissions - also in the direction of real driving emissions (RDE). Here, the 48-volt boost recuperation system from Bosch is intended to reduce raw nitrogen oxide emissions by up to 20 percent, especially when accelerating and under high loads.
The new hybrid drive only becomes really intelligent when it is digitized. In January, Continental presented a networked 48-volt mild hybrid with so-called “connected energy management” (cEM) at the CES in Las Vegas. From the data cloud, cEM knows the real-time traffic situation and knows exactly when it makes sense to let go of the gas. If the driver does this, the software automatically activates the most efficient combination of sailing (engine switched off) and recuperation. Decelerate with a minimum of wheel brake use, if need be, exactly to the stop line in front of the traffic lights. "Applying the wheel brakes only converts kinetic energy into heat," says Maiwald, "this should be avoided as far as possible." According to Continental, the cEM could save another three to four percent in consumption.
However, intelligent powertrains are not only seen as a means of increasing efficiency. "If problems arise, you can send the necessary information directly to the nearest workshop in the future," says Schaeffler Chief Technology Officer Peter Gutzmer. "The navigation system would send the driver there without detours, the team would be prepared, and the repairs completed as quickly as possible."
Author: Michael Specht / SP-X