Systems that Improve Fuel Efficiency and Increase Durability

The bearing and associated seal system is vital to the long-term performance of any turbocharger. The shaft that connects the turbine to the compressor wheel runs in fully floating ring journal bearings, which are lubricated in oil and result in less friction compared to single film or semi-floating ring bearings. Less friction leads to improved fuel efficiency via improved turbocharger performance. Holset Turbocharger bearings are well proven by proprietary testing, advanced analysis techniques and operating experience, which ensures a high rate of reliability and long-lasting durability, key attributes that mark Cummins Turbo Technologies as the first choice for customers.

Fully Floating Designs that Set the Mark for Durability

Journal bearings are of the fully floating ring type, which means that the ring is free to rotate and there are two oil films, one on the outer diameter of the journal, the other on the inner. Oil is transferred from the outer to the inner film by radial holes drilled in the bearing. Predominantly, this system is used in automotive turbochargers, although some large industrial and passenger car units use rolling element bearings fed by an integral oil supply. All current Holset Turbochargers use fully floating designs.

Strategic Design that Leads to Precise Validation

The purpose of the floating ring arrangement is twofold. First, it allows the shaft to run at high speeds with controlled motion while maintaining adequate oil film thickness. Second, it minimizes power loss. The floating ring typically runs at 30% of shaft speed. The design of the bearing system is enhanced using analysis programs that calculate the oil-film thicknesses under all conditions of rotor operation and production clearance. The predicted bearing performance is confirmed during approval of a bearing system by measuring movement of the shaft at the compressor end.