With a new solution developed to volume production readiness, the Schaeffler Group offers a state-of-the-art wheel bearing that is more precise, more lightweight and at the same time more cost-efficient. The wheel bearing with spur gear teeth is characterized by a unique design variant where the wheel bearing and the axle journal are connected to each other axially instead of radially. Thus, the component can be mounted clearance-free and weighs ten percent less. In addition, the mounting outlay is reduced. While the clearance-free mounting and reduced weight directly benefit the driving characteristics, the simplified mounting process helps to reduce costs.

Previously, the gear teeth of the axle journal of the input shaft were pushed axially into the wheel bearing. In this solution, the drive torque is transferred via longitudinal gear teeth. This mounting method has proven itself many million times. However, it also involves a number of disadvantages. The relatively solid and therefore heavy component has a certain amount of clearance to make mounting easier. Loads that occur during vehicle operation involve the risk that the assembly constantly loosens way beyond the normal mounting clearance, resulting in everything from losses in comfort and uncomfortable noises right up to the failure of the bearing. Up to now, the only solution was to reduce the radial clearance to zero in the design phase. This, however, necessitated the use of expensive and complex mounting technology.

The new FAG wheel bearing module with spur gear teeth is well equipped for the forces that occur in the wheel bearing. The positive connection between the wheel bearing carrier and the input shaft is ensured by the spur gear teeth. The wheel bearing with spur gear teeth is appealing due to simple mounting methods as the self-centering axial gear teeth are simply placed on the axle journal and fixed in place by means of the central screw. The mounting requires no significant force in contrast to the insertion of radial gear teeth. The bearing remains clearance-free and securely in the gear teeth during operation, regardless of whether the vehicle travels 1,000 or 100,000 kilometers. The reduction in weight in the individual wheel bearing easily amounts to a reduction of more than a kilogram overall for all four wheels. As this weight saving reduces the unsprung masses, it directly benefits the driving characteristics. In addition, the reduced weight contributes to cutting CO2 emissions.

The idea of using spur gear teeth is not new. However, the economical manufacture of this innovative wheel bearing design was only possible with the use of the orbitally-formed shoulder as the carrier of the gear teeth. As early as 1989, FAG manufactured wheel bearings for compact and mid-size vehicles where the bearing inner ring was axially fixed with the orbitally-formed shoulder. The screw fixing common at that time was no longer required.

The new FAG wheel bearing concept with spur gear teeth was initiated in 2004. In the new wheel bearing concept, the spur gear teeth are applied onto the orbitally-formed shoulder by high-precision cold forming. The forming technology experts of the Schaeffler Group have thus found a sophisticated solution for the manufacture of this complex component that allows volume production to the highest standards of quality.

A comprehensive series of tests has shown that the torque transmission with the spur gear teeth is considerably higher compared with conventional radial gear teeth. This is mainly due to the larger diameter of the pitch circle of the gear teeth.

This Schaeffler innovation has already been transferred to volume production. Due to their significant advantages, wheel bearings with spur gear teeth will successively replace conventional radial gear teeth. “We are convinced that this groundbreaking invention will sooner or later become established with all automotive manufacturers”, said Dr. Manfred Krauss, Chief Engineer Chassis Applications of Schaeffler Group Automotive.

This acclaimed wheel bearing solution, which has won the “2008 Automechanika Innovation Award” and the “2009 NoAE Innovation Award” (Network of Automotive Excellence), is for the first time used in serial applications in the BMW X1.

The Schaeffler Group
FAG can look back on more than 120 years of tradition. In 1883, Friedrich Fischer invented the ball grinding machine. For the first time, this made it possible to grind steel balls to absolute roundness. He thus laid the foundation for the entire rolling bearing industry. Since then, FAG has been one of the leading brands for applications in mechanical engineering, the automotive industry and in aviation and aerospace technology. Accordingly, FAG has a long tradition as a renowned supplier to numerous automotive manufacturers. FAG has been part of the Schaeffler Group since 2001.

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