Автомобилестроение - 2012-09-21
The latest-generation bearings and steering systems
NSK is showcasing some of its latest product developments for the automotive industry at the IZB suppliers’ fair (Hall 5, Stand 313). They include highly efficient electric steering systems and reduced-friction, lightweight bearings for chassis, drivetrain and powertrain. With these new products, the Japanese automotive supplier is responding to current hot topics: energy efficiency, reductions in CO2, lightweight design and safety. The additions on show go way beyond the company’s current product portfolio and include an electric drive system and a wheel hub motor for cars, both of which are fitted with innovative NSK components.
The products are presented so as to clearly illustrate the role which components produced by NSK play in the relevant systems and vehicles. Section models of complete drive systems offer trade show visitors an insight into the new solutions which NSK has developed for almost all kinds of car drives.
Transmissions: numerous newly developed products
NSK is presenting numerous newly developed products for car transmissions using the concept model of a hybrid IVT (infinitely variable transmission) for vehicles with front-wheel drives.
The concept features an extremely compact, highly efficient toroidal variator twinned with a light, high-speed electric motor. This combination offers a wider spread of gear ratios than conventional systems. It enables higher energy regeneration and therefore lower fuel consumption and CO2 emissions.
This transmission also uses ultra long-life ball bearings: NSK has succeeded in making the bearings more compact and up to 50% lighter by taking various steps, such as optimising the rolling elements. As a result, the bearing’s friction level has fallen by up to 12%.
Other new additions include tapered roller bearings with a plastic cage which are designed to reduce oil swirling, thereby improving lubrication within the bearing and slashing friction by around 20%. In addition to this, the concept model features low-friction ball bearings for hybrid drive systems and ball bearings developed specially for ultra-high speeds.
Dual-clutch transmissions: extensive expertise
Over the past few years, NSK has gathered a great deal of experience in developing bearings for dual-clutch transmissions (DCTs), partly thanks to its in-depth collaboration with carmakers. As well as the seven-gear DQ500 Volkswagen Group DCT, the company will show a section model of Daimler’s seven-gear dual-clutch transmission, the 7G-DCT, as a current example of its work. Fitted in the Mercedes B-Class and the new A-Class, this DCT makes extensive use of bearing technology from NSK.
Engine bearings: smaller and smaller components, higher and higher speeds
Using an engine section model as an example, NSK is also showcasing its latest-generation bearings for combustion engines. These include needle roller bearings for camshafts and balance shafts, which reduce friction by over 50%. Ball bearings developed specially for exhaust gas recirculation with a nanoparticle-based lubricant are capable of stabilising the bearing torque at a much faster rate and also reduce friction torque.
Downsizing is a key trend in engine technology. A smaller cubic capacity often goes hand in hand with a supercharged engine. NSK is presenting ball bearings which are designed for the rapidly growing turbocharger market. The bearings work with speeds in excess of 180,000 rpm and can even reach up to 290,000 rpm effortlessly in a laboratory setting. Highly pure SHX steel is used for the rings to give the bearings a much longer service life, while mechanical losses are some 50% lower than in plain bearings.
Bearings for ancillary units: minimising noise
The drive systems for ancillary units such as air conditioning compressors are expected to run increasingly quietly. This is partly due to the growing importance of driver and passenger comfort, but also stems from the fact that ambient noise is not masked by a combustion engine in hybrid and electric vehicles. NSK responded to this requirement early on – for example, by developing needle roller bearings for auxiliary drives which generate approximately 33% less noise than conventional bearings for this area of use.
Wheel bearings: lightweight design and improved seals
As one of the world’s leading manufacturers of car wheel bearings, NSK is also presenting new bearings at the IZB trade fair which were developed with high-growth automotive markets in mind (BRICS). These bearings boast even better seals and a new lubricant for an extended service life. This makes them ideal for bad and unsurfaced roads.
In addition to this, NSK is displaying reduced-weight wheel bearing units with aluminium housings, thereby demonstrating its expertise in the use of various lightweight materials. The use of light metal here shaves 20% off the units’ weight.
Electric vehicles: a wealth of experience
NSK has been developing and producing bearings for electric vehicles and the electric part of hybrid drives for more than ten years. For instance, both the drive system of the Toyota Prius and the rear axle of the world’s first diesel hybrid car (developed by PSA Peugeot-Citroën) use NSK bearings.
NSK is presenting two different electric drives for cars at the IZB show. The first drive system combines a high-speed electric motor (up to 40,000 rpm) – featuring a reduction gear to boost efficiency and reduce noise – with a dual-speed transmission. This system is hallmarked by its high efficiency and outstanding performance.
The second concept is an innovative wheel hub drive. In this system, the final gear reduction is integrated into the hub bearing, new miniature needle roller assemblies are used in the planetary gear and a compact free-wheel clutch was developed to make the system – which can be built into standard 16-inch rims – as small as possible. Gear changes are ensured by changing the direction of rotation of two small motors. This enables high torque and high speeds to be combined with compact dimensions.
Compact, highly efficient electric steering systems
NSK’s Steering Business Unit has produced some 25 million steering systems since 1988 and is amongst the market leaders for electric power steering (EPS). The company is focusing on the fast-growing segment of column EPS – a strategy which has proved successful.
It is easy to explain why carmakers were so interested in the EPS systems right from the start: the systems only draw energy when the power steering is actually in use. This means that there is no need to store the kind of energy reserves that are crucial for hydraulic power steering systems. In practice, this considerably reduces fuel consumption: when used instead of a conventional hydraulic steering system, an EPS system can reduce a compact car’s average consumption by 0.2 to 0.4 l/100 km.
The latest generation of EPS systems from NSK has been optimised with the aim of providing the driver with the best possible feel for the road and the steering behaviour. The company’s intensive development work, which took place largely at the software level, was a resounding success: the EPS steering systems which NSK manufactures for current vehicle models are unanimously praised by testers for their directness and the gentle way in which the assisted steering kicks in.
Visitors to the IZB exhibition will be able to see the most compact EPS system currently available worldwide, which features in the Toyota iQ. By integrating the electric motor, steering gear, ECU and torque sensor technology, the vehicle developers were able to optimise the packaging and further reduce the car’s front overhang. The weight of the steering module was also slashed by 12%, while its energy consumption was cut by 6%.
An EPS system with an integrated steering angle sensor will also be on show. This recognises unstable vehicle behaviour and triggers appropriate countermeasures as an active safety feature.
The steering systems used for the VW up! and the VW Polo Global will also be on display at the NSK stand in Volkswagen’s home town of Wolfsburg. NSK won a Volkswagen Group Award 2010 for its work on the VW Polo Global’s system.
NSK at the IZB trade fair: Hall 5, Stand 313