Roller bearings move the world. We take them for granted, but without them, our world would stand still. No cars, no planes, no drilling machines or washing machines would work without roller bearings. They are the invisible heroes of our everyday life. In a German household you can find around 160 of them. Roller bearings, or ball bearings, are always used when components need to be moved or rotated.
The origins of roller bearings lie in Ancient Egypt. Also the Celts knew cylindrical roller bearings about 700 BC. How excavations from the mentioned epochs show, our ancestors used wood as material, other materials followed later. Over the centuries, the system and the material have been improved up to the point when Leonardo da Vinci drew the first ball bearing draft. In his drawing, he developed the idea of incorporating the elements of separation, which are now known as cages. At all times people have been looking for motion sequences that cause as little friction as possible. Ball bearings serve as fixed or loose bearings to fix axles and shafts, taking up the radial and axial forces and simultaneously enable the rotation. At the same time, the friction and therefore the power loss and the wear should remain as low as possible. Hardly any company develops and manufactures more facets of miniature ball bearings in mass production than the Japanese company MinebeaMitsumi. Also the tiniest ball bearing in the world, which can be produced in mass production and which has an outer diameter of just 1.5 millimeters, proves the success. With a broad product range, the Group and its subsidiaries achieve a world market share of more than 60 percent of ball bearings up to 22 millimeters in diameter. The portfolio ranges from simple stainless steel ball bearings for industrial, domestic and automotive applications to bearing cartridges in the passenger car turbochargers and special bearings for aviation industry and full ceramic bearings for the food and semiconductor industries. More than 8500 ball bearing types are produced in huge production facilities around the world. Each ball bearing type has characteristic qualities which make it particularly suitable for certain arrangements.
When choosing the right bearing, several factors play an important role. In addition to load capacity and speed, other aspects such as installation, greasing, temperature, maintenance and a long service life are also of particular importance. The example of the turbocharger shows how important the bearing technology is in the automotive sector, mechanical engineering and mechatronics. The turbocharger development has been refined remarkably over the last 30 years, but the original principles still exist today. Despite all efforts, there are still weak points, which are difficult to eliminate and related with high costs. The most frequent damage to turbochargers is the bearing system of the rotor shaft, which connects the compressor wheel with the turbine wheel. Most turbochargers are equipped with hydrodynamic bearings (friction bearings), which need oil as a lubricant. Oil increases the resistance, particularly during the cold start, when engine and oil have not reached the operating temperature yet. This can be noticed during abrupt acceleration. But it takes seconds after pushing the accelerator pedal until the driver gets a feedback of the power of his vehicle. The driver tries to accelerate even more. In addition, when there is a soiling or even a short-term loss of the oil, damaged bearings are easily caused and can lead to the total failure of the turbocharger.
These disadvantages are associated with higher fuel consumption. One possibility to improve the response behavior and the dynamics of the turbocharger is the optimization of the mechanical efficiency by reducing friction. This can be achieved with the use of a bevel bearing cartridge, shortly ball bearing cartridge, with ceramic balls. A significant reduction in fuel consumption results from a reduced friction, especially during cold start and partial load operation. The transient behavior is improved. This bearing system combines the functions of support and thrust bearings in one unit. The reduced intervals ensure an increase of the turbine and compressor output. In the expected, upcoming use of motor oils with lower viscosity, the roller bearings have decisive advantages towards fluid bearings. The fluid bearing fails in the use of very low-viscosity oils but roller bearings keep working. Ball bearing cartridges are especially designed for high, dynamic rotational speeds and extreme temperatures. They are termed hybrid bearings.
The materials used, such as ceramic balls or special alloyed steels, are particularly found in aircraft engines, where high requirements for the material have always been common practice. In 2009 the development of ball bearing cartridges for extreme applications alreadybegan with the subsidiary myonic GmbH. The focus of the development was on the suitability for mass production (Engineerging to Cost). This affects the definite costs of the ball bearing cartridge for the customer. Last but not least the price determines, from an economic point of view, if the better bearing system from turbochargers is also used for smaller engines. So far, only turbochargers used in powerful engines can profit from this. Ceramic materials are very resistant to wear, corrosion and temperature. They are lightweight, stiff and electrically insulating - properties which are advantageous for roller bearings. Good Manufacturing Practice has top priority in the food industry.