Fuel is a significant portion of the operating cost for an on-highway diesel engine and fuel economy is important to the economics of shipping most goods in North America. Cat® ACERT™ engine technology is no exception. Ball bearings have been applied to the series turbochargers for the Caterpillar heavy-duty, on-highway diesel truck engines in order to reduce mechanical loss for improved efficiency and lower fuel consumption.
Over many years of turbocharger development, much effort has been put into improving the aerodynamic efficiency of the compressor and turbine stages. Over the same span of time, the mechanical bearing losses of a turbocharger have not experienced a significant reduction in power consumption. Most turbochargers continue to use conventional hydrodynamic radial and thrust bearings to support the rotor. While these conventional bearings provide a low cost solution, they do create significant mechanical loss. The challenge was to develop a cost effective solution that would make a step change in mechanical efficiency without sacrificing reliability or durability.
By replacing a sliding action with a rolling action, angular contact ball bearings were developed to accomplish that goal. Honeywell Turbo Technologies (HTT) has successfully adapted their field proven Aerospace product into the high volume automotive marketplace. Caterpillar and HTT have partnered to apply ball bearing technology for the first time in the North American on-highway truck market.
Reliability is also a critical customer requirement that cannot be sacrificed when introducing a new product. A truck that is down for repair is not generating revenue. Fortunately, the ball bearing system also offers the opportunity for improving the robustness of the turbocharger. The ball bearing system provides higher load capacity, improved rotordynamics, reduced oil flow through the turbocharger, and has proven more robust to contaminated and/or marginal lubricant conditions.