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OIL-Less

 

COMP TURBO TECHNOLOGY, INC. OIL-LESS TURBO

A great deal of effort was expended in the early years of small turbocharger development to produce a bearing system that had sufficient durability to make them commercially viable. Research and development in the 1960's resulted in the perfection of shaft instability (oil-whirl) but had appreciable friction losses at their high speeds of operation.

Due to the friction losses in the floating sleeve systems that hamper the acceleration rate of the turbocharger rotating assembly, many attempts were made to use ball bearings in small turbochargers, all unsuccessful, until the TRIPLEX CERAMICball bearing system was incented. This system consists of an elongated, rotatable steel cylinder with back-to-back angular contact ball bearings, mounted in the compressor end of the cylinder, that carry axial thrust in both directions, and a single angular contact bearing slidably mounted in the turbine end that carries no thrust. The turbine end bearing outer race bears against a preload spring that allows the bearing to move with axial expansion of the shaft. A small clearance between the outside diameter of the steel cylinder and the mounting bore in the bearing housing is supplied with the lube oil that protects the bearings from shock and vibration. This triple ball bearing system has been successfully used in commercial production by Comp Turbo Technology for over three years, has out-performed competition in stringent racing applications and has produced a large number of very satisfied customers.

Historically, the use of engine oil to lubricate the floating sleeve and stationary thrust bearings in commercial turbochargers have rise to a number of operational problems. To prevent oil leakage into the compressor and turbine casings, piston ring seals are employed in commercial turbochargers. Since the piston ring seals are not positive contact seals, there is a small leak path around the piston rings and, during certain operating conditions of the engine, i.e. low idle or a vacuum in the air intake system, some oil leakage can occur. Any ail leakage into the turbocharger casings can result in the undesirable emissions in the engine exhaust.

In cold weather, there can be a significant lag in the flow of oil to the turbocharger bearings when the engine is initially started. If the lag is long, the sleeve bearings can fail on startup.

Another problem can occur when an engine is shut down quickly after being operated at high speed and load where the exhaust gas temperature is maximized. Heat transferred into the turbocharger casings can cause residual lube oil in the bearing system to carbonize. This carbonization can build up and eventually cause failure of the bearings.

Notwithstanding the fact that years of development has mitigated the above named problems, there remained a motivation to remove the use of engine oil to lubricate the bearing systems in small turbochargers. Comp Turbo Technology has responded to this challenge by developing what is believed to be the first commercial turbocharger that does not require a lubricating oil supply from the engine. Lube oil supply and drain lines are no longer necessary and the turbocharger can be mounted in a variety of positions that were not possible when lube oil had to be gravity drained back to the engine crank case.

The Comp Turbo Technology oil-less turbocharger, employs the well proven TRIPLEX CERAMIC ball bearing system, wherein the ball bearings are lubricated by high temperature grease. In the oil-less bearing system, the elongated steel cylinder is provided with axially spaces “O” rings in its outside diameter that engage the bore in the bearing housing. Cooling water is supplied from the engine to a water jacket in the bearing housing and to the space between the “O” rings. This cools the “O” rings and the bearing carrier, carrying away the heat generated in the bearings. Since the bearing system is easily removed as an assembly from the bearing housing, the bearings can be re-greased at appropriate intervals to extend their service life indefinitely.