Hybrid bearings extend performance and life, having more useful features than standard bearings. Hybrid bearings have steel rings typically made from AISI52100, 440C, or Cronodur. Hybrid bearings usually have a nonmetallic retainer such as polyamide and ceramic rolling elements. The combination of steel rings, polyamide retainers, and ceramic balls are free of maintenance, have reduced friction, and are lighter in weight than standard bearings. Hybrid bearings are available as ball bearings and cylindrical roller bearings. Many times, they can be customized for most applications, and as such are used in a wide range of applications.
Hybrid bearings are used as insulating bearings. As you may know, bearings operating in environments near stray electric currents can cause havoc with bearings. In applications like electric motors and generators, the use of hybrid bearings has proved to be an easy and reliable solution. When Hybrid bearings are used in applications like variable speed drive electric motors and wind turbine generators, the ceramic material insulates the bearing.
SKF’s new cage design for hybrid deep groove ball bearings combines innovative design features with a high-performance polymer material.
A key design feature of hybrid bearings using ceramic balls is to reduce friction. When friction is reduced in the bearing, less rolling resistance results in reduced electrical draw. Ceramic balls have smaller contact ellipses resulting in less energy losses.
Industry tests have shown that friction torque is up to 8% lower using hybrid bearings. When using hybrid bearings, little to no lubrication is used in helping to further reduce internal friction.
It is possible to reduce friction by as much as 50% when applying all the features and optimizing the application.
Applications for Hybrid Bearings
Miniature hybrid ball bearings are commonly used at high speed in dental turbines, contra angle handpieces, and dental motors. These dental products reach speeds up to 500,000 rpm. Other ideal candidates for hybrid bearings are in Aviation, Aerospace, and Defense applications. The automotive industry, due to stricter emission directives, looks to increase motor efficiency. Turbochargers reach speeds of more than 250,000 rpm and can operate in temperatures from -40 to +320°C by applying hybrid bearings. In the machine tool industry, high-precision ABEC7 and ABEC9 hybrid angular contact bearings are being specified for high-speed machine tool spindles.
Ceramics was introduced in the 1960’s by the aerospace industry. Ceramics having high heat resistance properties and being light weight were a perfect solution. By the 1980’s, ceramic was becoming widely used. Hybrid bearings are used in many other applications including railway, electric vehicles, traction motors, compressors, pumps, vacuum pumps, and fluid machinery.
Silicon Nitride (ceramic) has properties that are much higher than steel. Interestingly, silicon nitride has double the hardness of AISI 52100 steel. With its coefficient of thermal elongation far lower than steel, it makes silicon nitride more accurate when calculating internal clearance values in low temperatures.
Speed ratings for hybrid bearings increase by around 10% merely by changing materials to silicon nitride versus AISI steel. In some industry tests, the lifespan of the lubricant in a hybrid deep groove ball bearing was twice to five times that of a standard steel and cylindrical bearings. The lubricant lasts longer because the heat generation in the hybrid bearing is so much lower than standard steel bearings.
There are a multitude of benefits to using hybrid bearings, and each application can be improved significantly with proper design and consideration to the operating environment. If you would like more information on hybrid bearings or full ceramic bearings, please contact Pacific International Bearing Sales Inc.