For decades, engine designers have kept the motto “What’s better than engine capacity? More engine capacity!” After all, increasing the engine capacity used to be almost the only way in which engineers could achieve higher output and torque from an engine. This didn’t change until the 1970s, when turbocharged gasoline engines came onto the market.
Today, the world of modern engine construction is one of infinitely greater variety. Small engines have long been able to achieve performance data that were previously thought impossible: The keyword is “downsizing”. Downsizing is more than just turbocharging, fewer cylinders, and less engine capacity, however. Efficient downsizing and downspeeding are only possible through the use of a series of interactive technologies: Technologies such as those found in Schaeffler’s extensive portfolio.
Stage one: Optimized friction through rolling bearings and coatings
Turbocharging is increasingly becoming the standard in engine construction technology today, and is a key element in engine downsizing. This in turn is a good way of positively influencing fuel consumption without having to make sacrifices in terms of performance. Whichever option is chosen, however – whether turbocharging of the combustion engine or reduction of the engine capacity, the number of cylinders, or the engine speed – engines always have to fulfill higher requirements in terms of friction minimization, combustion efficiency, material strength, and comfort with regard to vibrations. This requires both comprehensive expertise in the individual sub-areas and expertise that spans the overall system. Schaeffler’s wide product range, with solutions for engine, transmission, and chassis applications, makes the company one of the most prominent partners for implementing engine downsizing concepts that are geared toward the future. After all, many of Schaeffler’s solutions act as “enablers” for the trend towards reducing fuel consumption and emissions that is taking place in the engine construction sector.
This becomes a detailed matter even during the design of surfaces, special coatings, and bearings that minimize friction. Rolling bearings developed specially for use in turbochargers are therefore just one of the products on offer from the technology company. Rolling bearings have a significantly lower frictional resistance compared to the plain bearings that are conventionally used. The reduced level of friction additionally offers the advantage that the turbocharger responds more rapidly. In addition to the use of rolling bearing solutions, Schaeffler also has in-depth knowledge about the use of materials that minimize friction. These are used, for example, to coat valvetrain components such as bucket tappets and roller-type finger followers to minimize friction loss in the valvetrain and wear on the materials subjected to high loads. However, reducing the wear and friction in chains and belt drives in the engine is also becoming more and more important. This is not only achieved through the use of coatings, however – tensioning and damping elements that ensure optimum running characteristics for the chains and belts also play a part.
Stage two: Variability in the valve train
In addition to the minimization of friction, the requirement-based control of the engine using variability in the valvetrain is also gaining significance. The internal combustion process that takes place in the engine is also home to technologies from Schaeffler, which range from components for cylinder deactivation or valve lift adjustment (including levers, intermediate elements and tapping elements) and phasing units through to complete systems like UniAir, the first fully-variable electrohydraulic valve control system on the market. The range of solutions available for valvetrains is as broad as the range of variants on offer from the automobile manufacturers themselves. Accordingly, Schaeffler is pushing development forward in several directions – customized to suit the requirements profiles of its customers. Examples include valve control systems that use a sophisticated mechatronic system to deactivate the intake and exhaust valves and thus turn an eight-cylinder into a four-cylinder engine or a four-cylinder into a two-cylinder engine during the drive. This cylinder deactivation system is already in volume production and, because it works extremely fast, is barely noticeable for the driver.
Stage three: Vibration damping for engine and transmission
Balancer shafts with optimized mass and rolling bearing supports are another forward-looking solution. These shafts turn at twice the engine speed and allow astonishingly smooth running in engines with a small number of cylinders; thanks to their rolling bearing supports, they also generate less friction. At the same time, the rolling bearing support allows the balancer shafts to be designed with a lightweight construction.
In order to absorb the rotational irregularities and vibrations in downsized engines, Schaeffler also makes use of the installation space available on the transmission. In addition to vibration dampers such as the dual mass flywheel (DMF), one innovation must be mentioned here that has achieved a thoroughly successful market start: The centrifugal pendulum-type absorber. This speed-adaptive damper is mounted on the flange of the dual mass flywheel.
The efficient damping of the selected order of vibration excitation – for example the firing frequency – is adjusted by the Schaeffler engineers to specifically match the engine in question. Together with the basic isolation of the vibrations by the spring mass system of the DMF, this achieves isolation levels of more than 90 percent. As a result, engines can be operated even at low speeds in a very smooth and comfortable way that allows the transmission ratio to be made longer and thus designed for greater efficiency in terms of fuel consumption. This applies for both manual and double clutch transmissions. Very effective solutions also exist for drive trains with cylinder deactivation.
The centrifugal pendulum-type absorber is now also being used in torque converters for automatic transmissions. Moreover, Schaeffler recently began developing a centrifugal pendulum-type absorber for use in combination with clutch systems, which will bring with it decisive improvements in driving comfort, especially in vehicles for cost-conscious markets.
In this way, Schaeffler delivers a wide range of solutions that both support the trend towards reducing fuel consumption and emissions taking place in the engine construction sector – with individual technologies as well as technologies that are matched to one another.