Home Blog Schaeffler Bearings Help Cut Co2 Emissions

Schaeffler Bearings Help Cut Co2 Emissions

Release time : 2015-06-12 12:13:27
Schaeffler has developed a range of bearing solutions that are helping vehicle manufacturers produce more compact, lighter vehicles, with improved fuel consumption and reduced CO2 emissions. The latest of these solutions is the FAG wheel bearing, which is more compact and 10 per cent lighter than its predecessor. The bearing also offers simplified mounting via a self-centring, axial spur gear teeth design. First developed in 2004, the FAG wheel bearing has since moved into series production, with BMW using the unit on its X1 model. A reduction in weight of 10 per cent typically amounts to an overall weight reduction of 1kg for a four-wheel vehicle. With a spur gear teeth design, in which the wheel bearing and axle journal are connected axially rather than radially, the bearing module is lighter and can be mounted clearance free. Driving characteristics are improved and automotive manufacturers benefit from a simple mounting process and the associated cost reductions. Previously, the gear teeth of the axle journal of the input shaft were pushed axially into the wheel bearing. Here, the drive torque was transferred via longitudinal gear teeth. This mounting method has proven itself over many years; however, it has a number of disadvantages. The relatively solid, heavy component requires a certain amount of clearance to enable easy mounting. Also, loads that occur during vehicle operation can lead to the assembly becoming loose, resulting in loss of comfort and higher noise levels, as well as possible failure of the bearing. Up to now, the solution has been to reduce the radial clearance to zero in the design phase. However, this requires the use of complex, costly mounting technology. The FAG wheel bearing with spur gear teeth is better equipped to deal with the loads that occur during vehicle operation. The spur gear teeth ensure positive connection between the wheel bearing carrier and the input shaft, which simplifies mounting. The self-centring axial gear teeth are placed on the axle journal and fixed in place by using a central screw. Unlike radial gear teeth, this mounting procedure does not require significant force. The bearing remains clearance free, but securely held in place during vehicle operation. Having four lighter wheel bearings on the vehicle reduces the unsprung masses, which improves the driving characteristics and contributes to a reduction in CO2 emissions. Schaeffler also offers the INA lightweight balancer shaft and rolling bearing assembly. This is currently being used on the Mercedes-Benz OM 651, a 2.2 litre, four-cylinder diesel engine that produces up to 204ps and 500Nm torque. The weight of the INA balancer shaft and bearing assembly are optimised in order to improve engine efficiency and reduce overall fuel consumption. By replacing conventional plain bearings on the balancer shaft with rolling bearings, friction is reduced. Using needle roller bearings with a raceway directly on the shaft reduces friction by up to 50 per cent over the whole speed range. At the development stage, by analysing engine load conditions, Schaeffler was able to optimise weight distribution. This enabled the width of the bearing to be reduced, which meant that the weight of the shaft could be cut by more than a third. This equates to an engine weight saving of 0.75kg. When designing the complete drive train for the OM 651, Mercedes was then able to utilise this reduced shaft rotational inertia. The lower mass moment of inertia reduces the load in the power train, therefore improving the acoustic characteristics. In addition, the narrower raceway improves the oil mist supply to the rolling bearings, enabling a simpler system design without oil feed holes. The engine requires a lower throughput of oil, so the oil pump can also be made smaller. All of these technical improvements meant that engine fuel savings of around 0.5 per cent to one per cent were achieved. The INA lightweight balancer shaft assembly is said to offer huge potential for reducing engine fuel consumption and emissions. For example, based on an average reduction in fuel consumption of one per cent over the life of an engine, and calculated for a vehicle mileage of 250,000km, this would lead to approximately 175 litres of fuel savings. Even if only 25 per cent of all four-cylinder engines were fitted with INA lightweight balancer shaft assemblies, this would still reduce harmful CO2 emissions by around six million tonnes per year. Trucks, SUVs and light vans are also using Schaefller's bearing solutions. By replacing 'line' contact associated with conventional tapered roller wheel bearings with a new design based on 'point' contact using ball bearings, Schaeffler has developed a 'twin tandem' wheel bearing unit, which the company said reduces friction by around 50 per cent over conventional tapered roller wheel bearings. This equates to a 1.5 per cent reduction in fuel consumption. The twin tandem design is based on replacing the rows of tapered roller bearings with two rows of ball bearings in each case. A double-row tapered roller bearing therefore becomes a four-row ball bearing. Replacing the line contact of the tapered rollers with the point contact of the balls eliminates rib friction and reduces overall friction by 50 per cent. The twin tandem bearing also has a lower operating temperature compared to conventional tapered roller units, therefore improving the service life of the lubricants. Cornering stiffness is also increased. Schaeffler has also considered interchangeability of the twin tandem with conventional tapered units. The twin tandem is designed to cater for the use of sensors (such as ABS sensors) and installation in the wheel carrier is identical for conventional tapered roller wheel bearings. Assuming a vehicle emits 300g/km of CO2 over a distance travelled of 15,000km per year, the reduction in CO2 emissions resulting from the twin tandem unit will be 67.5kg per year per vehicle. Fuel consumption is also reduced by 1.5 per cent, giving a reduction of 40 litres per year for an average light truck travelling 15,000km per year. A collaborative development between Schaeffler and Fiat Powertrain has resulted in a new engine system that is claimed to reduce vehicle fuel consumption and cuts CO2 emissions by up to 25 per cent. Uniair is a fully variable hydraulic valve control system that will make its debut on Fiat's Alfa Mito 1.4 Multiair. It is the first vehicle within the Fiat Group to be equipped with this technology. As well as offering car manufacturers a more compact valve control system, Uniair can help the automotive industry meet future CO2 emissions targets for passenger cars. Uniair provides improvements in start-up, part load and acceleration behaviour of the vehicle. During the engine warm-up phase, for example, hydrocarbon (HC) emissions are up to 40 per cent less and nitrogen oxide (NOx) is reduced by up to 60 per cent. Uniair is also said to offer an improved driving experience, through more power, higher engine torques and optimised engine response.