Prevent electric corrosion in variable frequency drive device and high speed performance can help improve power density.

Hybrid ceramic bearings provide solutions to current and future technical challenges. The hybrid ceramic bearing adopts steel inner and outer rings and ceramic rolling elements, which can reduce weight, reduce friction, eliminate electric corrosion, and improve reliability and speed performance at the same time.

Nowadays, the world changes with each passing day, and the global trend is changing our travel, business and lifestyle. With the advancement of urbanization, more and more people are migrating to cities. Digitalization and automation are speeding up our pace of life and work, and the whole society must deal with the challenges of a variety of environmental problems. At the same time, we also see the rapid development of electrification (especially electric vehicles) and the continuous development of globalization.

These global trends further promote the reform of the bearing field. Many emerging technologies require bearings to have special properties, such as suitable for variable frequency drives, reduced maintenance requirements, help to improve power density, reduce friction, and so on.

Hybrid ceramic bearings provide potential solutions to all these existing and future technical challenges. The combination of steel inner and outer rings and ceramic rolling elements gives the hybrid ceramic bearing unique performance, making it suitable for a variety of modern applications. SKF hybrid ceramic bearings use silicon nitride rolling elements, which are available in two types: deep groove ball bearings and cylindrical roller bearings, and can be customized according to customer needs.

Using ceramic materials in bearings is not new. From the 1960s to 1980s, ceramic materials were favored by the international aerospace industry because of their light weight and good heat resistance. This industry took the lead in adopting ceramic bearings. However, it was not until the 1980s that ceramic materials (silicon nitride) were commercially produced. Since the 1990s, modern hybrid ceramic bearings have been used in many applications, including machine tools, wind turbines, railway and electric vehicle traction motors, aerospace industry, and fluid machinery such as compressors, pumps and vacuum pumps.

Silicon nitride rolling elements used in SKF hybrid ceramic bearings have better characteristics than standard steel rolling elements. The compressive strength of silicon nitride is much higher than that of bearing steel, and its elastic modulus is about one third higher than that of bearing steel, which helps to reduce friction in rolling contact.

Importantly, the hardness of silicon nitride is more than twice that of bearing steel, making it an ideal choice under poor lubrication and other harsh working conditions. Compared with bearing steel, silicon nitride is non-conductive and its density is much lower. In addition, the thermal expansion coefficient of silicon nitride is very low, so the bearing clearance can be adjusted accurately, but the influence of some special working conditions such as ultra-low temperature applications needs to be considered.

Silicon nitride can improve the performance of rolling bearings, giving them excellent electrical insulation, weight reduction, excellent friction performance and wear resistance. In addition, it can significantly improve the speed performance of the bearing.

How do these features address the challenges posed by specific applications? Why is hybrid ceramic bearing expected to become the standard technology in many industries in the next few years?

Prevent electric corrosion in variable frequency drive device

All the advantages of hybrid ceramic bearings are fully reflected in the variable frequency drive device, which is used to optimize the control of rotating equipment such as pumps and traction motors. Due to the use of pulse width modulation technology, harmful high-frequency current will be generated. When the current passes through the bearing, it may cause damage to the inner and outer rings and rolling elements of the bearing, and affect the performance of the lubricant. Increased bearing vibration is only the least harmful consequence. Moreover, electric corrosion may greatly shorten the service life of bearings and lubricants.

The use of hybrid ceramic bearings solves this problem. Silicon nitride is an electrical insulator, which can prevent current from passing between the inner and outer rings of the bearing, and even insulate extremely high-frequency current, thus completely avoiding the bearing failure caused by it.

Extend maintenance intervals by extending grease life

The second advantage of hybrid ceramic bearings is to extend maintenance intervals and service life. The ceramic rolling element can greatly extend the service life of the lubricant, which means that the bearing can continue to operate for a longer time without maintenance. Ceramic rolling elements can improve the lubrication state of the lubricant on the rolling contact surface. Due to the reduction of friction and electric corrosion, the thermal degradation of the lubricant is avoided, so that its lubrication performance can be maintained for a longer time.

In the test of SKF, the lubricant life of mixed ceramic deep groove ball bearings is more than twice that of all steel bearings of the same specification, and the maximum is close to seven times. In similar tests of cylindrical roller bearings, the lubricant life of mixed ceramic cylindrical roller bearings is twice to four times that of all steel bearings of the same specification.

High speed performance helps improve power density

The third advantage of hybrid ceramic bearings is that they can achieve higher speed, thereby improving power density. This is the general trend of the motor manufacturing industry, especially for motors used in trains, automobiles, engineering vehicles and other means of transportation. Simply put, power is a function of torque and speed. If the speed of the bearing increases, the motor power will also increase.

Why increase power density?

Under the same size, the motor can output higher power

With the same output power, the size of the motor can be reduced

P = M•n

The maximum speed is also limited by the size of the bearing

Because the weight of the hybrid ceramic bearing is lighter than that of the steel bearing, its speed performance can be increased by up to 25%. In addition, the friction of hybrid ceramic bearings is small, which means lower operating temperature and longer service life at high speed. More importantly, the increase of bearing stiffness helps to improve the accuracy of the equipment and reduce the risk of rotor dynamics problems.

Reduce friction

Another advantage of hybrid ceramic bearings is the reduction of friction. Reducing bearing friction helps to reduce energy consumption, which is an important consideration in modern industry. Ceramic rolling elements in hybrid ceramic bearings have a direct effect on the friction between rolling and sliding torque. For hybrid ceramic bearings, the high Young's modulus makes the contact elliptical surface smaller, which reduces the energy loss caused by rolling torque. In addition, due to the better surface quality of ceramic rolling elements, the sliding friction torque is also reduced.

The test conducted by SKF shows that the friction torque of hybrid ceramic bearings at high speed is 5% to 8% lower than that of all steel bearings. At the same time, the test also shows that the hybrid ceramic bearing can also deal with the working conditions of insufficient lubrication and reduced viscosity, which is helpful to reduce friction. The adjustment of these lubrication factors improves the application conditions, and the friction can be reduced by 50% at most without affecting the service life of the bearing.

Hybrid ceramic bearings -- from solving problems to leading industry standards

Industry and automobile manufacturing are trying to increase production to meet the challenges of global sustainable development and keep pace with social and technological trends. Hybrid ceramic bearings with ceramic rolling elements and steel inner and outer rings are expected to solve many problems in design and maintenance, so as to improve reliability. In addition to solving technical problems, hybrid ceramic bearings can also achieve more economical operation and higher power output. Therefore, hybrid ceramic bearings are likely to become the standard bearing solution for many applications and industries in the next few years.

Innovative cage design helps achieve higher speed

Compared with all steel bearings, the main advantage of hybrid ceramic bearings is that they can achieve higher speed. For manufacturers who want to further improve the speed, advanced bearing cage technology will be of great use. SKF has introduced an innovative cage design for hybrid ceramic bearings. This new two-piece cage is made of light polymer material polyether ether ketone (PEEK), which can adapt to high-speed operation and reduce the phenomenon of heating and lubricant performance degradation at high speed. The rotating speed it can bear is 60% higher than that of brass cage and 100% higher than that of traditional nylon cage.

More about FRC Ceramic Self Aligning Bearings：

Ceramic self aligning bearings, China, manufacturers, suppliers, factory, specifications, dimensions, high quality, buy, price.

A Full Ceramic Self Aligning Bearing has two rows of balls and one, concave spherical raceway in the outer ring. As a result the bearing is self-aligning and insensitive to misalignments of the shaft in relation to the housing.

Self Aligning Ceramic Bearings have high temperature resistance, low cold resistance, high-pressure resistance and corrosion resistance, but have no magnetism and power insulation and oil lubrication. They are suitable to be used in special environments where mixed ceramic ball bearings and steel bearings cannot work.