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Technology

Bearings bring better automotive fuel economy

NSK's cartridge bearing for turbochargers is made of steel materials and is resistant to high temperatures. The ball bearings inside contain ceramic balls able to withstand extreme heat.

TOKYO -- When thinking of technology able to improve automotive fuel consumption, bearings probably do not come to mind. But the performance of bearings that facilitate the turning of wheels and engine components are a key factor for better fuel efficiency.

     The global automotive market is expected to grow to support the production of more than 100 million cars annually in 2020. Keen to capture shares of the expanding market, automakers worldwide are engaged in fierce competition to develop cars with better fuel economies.

     A similar degree of heated competition is taking place among bearing manufacturers. Smoother turning and minuscule weight reductions of products can make a difference in this high-stakes game.

All kinds of bearings

The wheels on either side of cars are connected by an axel, and the bearings attached to either end of this axel transfer power from the engine. Without axel bearings, cars cannot be driven safely and smoothly. In all, the average car relies on 100-150 bearings, and this humble automotive component is now evolving in major ways.

     Japanese bearing maker NTN is developing a new type of bearing for electric vehicles and hybrid cars. High-performance sensors attached to axel bearings link tires and wheels more closely to the engine, helping to reduce wasted energy. These sensors detect tire movement with precision, providing information to prevent the engine from generating excessive power, even under adverse conditions such as rain and snow.

     NTN has developed proprietary manufacturing technologies to reduce the number of parts that house bearings. To join parts, it uses as little adhesive as possible and instead interlocks the pieces. The result is that these bearings weigh 12% less than conventional products. The company expects to begin mass production in 2015.

     Meanwhile, NSK has developed a bearing with a unique cross shape resembling a ninja throwing star. Cast without waste, these bearings are 5% lighter than those with the usual rounded shape. The company has also developed a way to manufacture these bearings at a lower temperature, making them strong by extruding the steel through a die and applying pressure to harden the material. These bearings are currently being used on the Daihatsu Move minicar.

     Earlier questions about technology able to improve a car's fuel consumption may have brought thoughts of turbochargers, which boost engine efficiency by reutilizing an engine's exhaust gas. But turbochargers also use bearings, and companies are also developing new bearings for this application.

     When it comes to bearing types, sliding bearings are more durable, but ball bearings move more smoothly. These are designed as two rings sandwiching a set of balls that can rotate freely.

Ceramic balls for turbos

The bearings in a turbocharger are subjected to temperatures of 200 C and spin at speeds of 250,000 rotations per minute. "They must be durable enough to withstand heat and speed similar to a jet engine," explained NSK Executive Officer Hiroya Miyazaki. For its new turbocharger bearings, NSK uses a ceramic material for the balls, and to boost durability it adjusts the carbon component of the bearing material and covers the structure with a coating of heat-resistant steel.

     Minebea, known for its small, precision ball bearings, is also targeting the same market for automotive turbocharger bearings.

     Aiming for a 2-3% improvement in fuel efficiency, a German subsidiary of Minebea developed turbocharger bearings with high durability, based on the same material it uses for specialty bearings in jet engines. Minebea then established the manufacturing technologies for these new turbocharger bearings at its Karuizawa facility in Nagano Prefecture, using proprietary test equipment that it installed at a cost of hundreds of thousands of dollars. Now the company is mass-producing the bearings at a factory in Thailand.

     The lubricating oil used for bearings is another area of competition. Bearings turn more smoothly with less viscous oil, and by modifying oil components, NTN has developed bearings that can boost a car's fuel efficiency by 0.3%.

     Bearings are basically used in all products and machines with rotating parts, from ATMs and copiers to factory machinery. So, their importance is not just improving the fuel economy of cars.

     NSK, NTN and a third leading Japanese bearing maker, Jtekt, collectively hold more than 30% of the global market. Foreign rivals include SKF of Sweden and Schaeffler of Germany, as well as makers from emerging nations.

     The automotive bearings market is huge and growing, so the battle at the cutting edge of the technology is bound to continue as makers vie to develop bearings that are lightweight and offer higher performance.

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