Turbocharger with reduced coking
A turbocharger including means for preventing or reducing coking, particularly following engine shutdown, without noticeably increasing weight or volume of the turbocharger. The turbocharger bearing housing ( 14 ) has defined therein a lubrication flow path for bearing lubricant and a lubricant drain gallery ( 40 ) below a shaft ( 20 ), and in accordance with the invention at least a portion of a wall ( 42 ) of the lubricant drain gallery ( 40 ) is coated with an oil repellant and/or heat insulating coating ( 44 ).
1. A turbocharger comprising:
a bearing housing ( 14 ) journaling an elongate shaft ( 20 ) therein,
a turbine wheel ( 22 ) carried at one end of said shaft ( 20 ),
a compressor wheel ( 24 ) carried at the opposite end of said shaft ( 20 ),
a turbine housing ( 28 ) defining an exhaust gas inlet ( 30 ) to said turbine wheel ( 22 ) and an exhaust gas outlet ( 32 ) therefrom,
a compressor housing ( 34 ) defining an air inlet ( 36 ) to said compressor wheel ( 24 ) and an air outlet ( 38 ) therefrom, and
said bearing housing further defining a lubrication flow path for lubricant and a lubricant drain gallery ( 40 ) below said shaft,
wherein at least a portion of the lubricant drain gallery ( 40 ) is coated with an oil repelling coating ( 44 ).
2. The turbocharger as in claim 1 , wherein said coating ( 44 ) is also heat insulating.
3. The turbocharger as in claim 1 , wherein said coating ( 44 ) is a fluorocarbon coating.
4. The turbocharger as in claim 3 , wherein said fluorocarbon coating is a poly-tetra-fluoro-ethylene coating.
5. The turbocharger as in claim 1 , wherein said coating ( 44 ) is a coating containing perfluoropolyether compounds.
6. The turbocharger as in claim 1 , wherein said coating ( 44 ) is a coating comprising amide thiol compounds.
7. The turbocharger as in claim 6 , wherein said thiol compound is fluoralkyl amide thiol.
8. The turbocharger as in claim 1 , wherein said coating ( 44 ) is an organosilicon coating.
9. A turbocharger comprising:
a bearing housing ( 14 ) journaling an elongate shaft ( 20 ) therein,
a turbine wheel ( 22 ) carried at one end of said shaft ( 20 ),
a compressor wheel ( 24 ) drivingly carried at the opposite end of said shaft ( 20 ),
a turbine housing ( 28 ) defining an exhaust gas inlet ( 30 ) to said turbine wheel ( 22 ) and an exhaust gas outlet ( 32 ) therefrom,
a compressor housing ( 34 ) defining an air inlet ( 36 ) to said compressor wheel ( 24 ) and an air outlet ( 38 ) therefrom, and
said bearing housing further defining a lubrication flow path for lubricant and a lubricant drain gallery ( 40 ) below said shaft,
wherein at least a portion of the lubricant drain gallery ( 40 ) is coated with a heat insulating and oil repelling coating ( 44 ).
10. The turbocharger as in claim 9 , wherein said coating ( 44 ) is a fluorocarbon coating.
11. The turbocharger as in claim 10 , wherein said fluorocarbon coating is a poly-tetra-fluoro-ethylene coating.
12. The turbocharger as in claim 9 , wherein said coating ( 44 ) is a coating containing perfluoropolyether compounds.
13. The turbocharger as in claim 9 , wherein said coating ( 44 ) is a coating comprising amide thiol compounds.
14. The turbocharger as in claim 13 , wherein said thiol compound is fluoralkyl amide thiol.
15. The turbocharger as in claim 9 , wherein said coating ( 44 ) is an organosilicon coating.
16. A turbocharger comprising:
a bearing housing means ( 14 ) for spacing apart respective compressor housing ( 34 ) and turbine housing ( 28 ) portions and journaling an elongate shaft ( 20 ) extending between said housing portions ( 34 , 28 ),
a compressor rotor ( 24 ) and a turbine rotor ( 22 ) each connected to said shaft ( 20 ) at opposite ends thereof and rotatable within respective ones of said housing portions,
bearing means ( 18 ) carried by said bearing-housing means proximate to said turbine housing ( 28 ) portion and rotatably supporting said shaft ( 20 ),
said shaft defining a first conductive heat transfer path extending from said turbine rotor to said bearing, and
lubrication means causing lubricant to flow over said bearing ( 18 ) and to a lubricant drain gallery ( 40 ),
wherein a second conductive heat transfer path extends from said turbine housing ( 28 ) to said bearing housing ( 14 ) and from said bearing housing ( 14 ) to said lubricant drain gallery ( 40 ), and
wherein at least a part of said lubricant drain gallery ( 40 ) is coated with an oil repellant and heat insulating coating ( 44 ).