Engine Timing Geartrain Concepts and Proposals for Gear Rattle

Engine Timing Geartrain Concepts and Proposals for Gear Rattle Noise Reduction in Commercial Vehicles Master of Science Thesis in the Master Degree Programme, Automotive Engineering MILAD ESMAELI ASHWIN SUBRAMANIAM Department of Product and Production Development Division of Product Development CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden, 2011 II CHALMERS, Product Development, Masters Thesis 2011 Engine Timing Geartrain Concepts and Proposals for Gear Rattle Noise Reduction in Commercial Vehicles MILAD ESMAELI ASHWIN SUBRAMANIAM Department of Product and Production Development Division of Product Development CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden, 2011 CHALMERS, Product Development, Masters Thesis 2011 III Engine Timing Geartrain Concepts and Proposals for Gear Rattle Noise Reduction in Commercial Vehicles MILAD ESMAELI ASHWIN SUBRAMANIAM Master Thesis 2011 Department of Product and Production Development Division of Product Development Chalmers University of Technology SE-412 96 Göteborg Sweden Telephone + 46 (0)31-772 1000 Cover: Volvo engine timing gears. See chapter 4.2 for more information. Reproservice 2011 IV CHALMERS, Product Development, Masters Thesis 2011 Engine Timing Geartrain Concepts and Proposals for Gear Rattle Noise Reduction in Commercial Vehicles Masters Thesis in the Masters Programme in Automotive Engineering Milad Esmaeli, Ashwin Subramaniam Department of Product and Production Development Division of product development CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden, 2011 Abstract The engine timing gears which govern the camshaft and injection are a vital set of components in an engine and are constantly subjected to heavy loads. In recent years, imposition of firm emission legislations has forced engineers to increase the injection pressure which has a severe impact on the geartrain noise. Noise from the geartrain, distinctly gear rattle has been a main concern for the truck industry. Additionally, Volvo Powertrain also wants to focus on developing future geartrains that can be optimized from a noise point of view to meet the noise legislations. The aim of the thesis work was to propose future engine timing gear concepts for the Volvo 11, 13 and 16 liter engines. The concepts proposed are from a material selection and a layout optimization perspective. It is also focused on lowering production cost, weight and assuring sustainability. All the concepts are deduced with the main goal to reduce geartrain noise. It was found that the material choice had an influence on the component weight and adds certain valuable physical properties. The choice of material also offered a potential for cost reduction linked to its manufacturing process. Moreover, the current Volvo geartrain layout was shown to have a scope for improvement. Various layout considerations are proposed for the optimization of the geartrain based on available research in the field. For further analysis a detailed competitor benchmarking had to be conducted to study other existing geartrains and the technology utilized. The ideas from the competitors were listed and studied in order to analyze the competitive heavy duty market trend. It was found that several technologies proposed for noise reduction have been implemented by competitors to Volvo. The benchmarking study gave an insight on the current and future timing geartrains. The task was diverse in many fields of technology, with limited boundaries. Thereby a structured and systematic approach had to be followed to cover the vast topics and deliver the result. The proposed solutions based on material, layout and recent developments in power transmission technology could have an immense potential to reduce noise. The conclusions that are drawn from this pre-study sets a platform for the development of future timing gears. CHALMERS, Product Development, Masters Thesis 2011 V Table of contents Abstract .............................................................................................................................. V Table of contents ...................................................................................................................... VI Acknowledgements .................................................................................................................. IX 1 Introduction .......................................................................................................................... 1 1.1 Background .................................................................................................................... 1 1.2 Objective ........................................................................................................................ 2 1.3 Limitations ..................................................................................................................... 2 2 Methodology ........................................................................................................................ 3 3 Research questions ............................................................................................................... 5 4 Theory .................................................................................................................................. 7 4.1 Gears .............................................................................................................................. 7 4.1.1 Spur gears ........................................................................................................... 7 4.1.2 Helical gears ....................................................................................................... 7 4.1.3 High contact ratio spur gears .............................................................................. 8 4.2 Geartrain ......................................................................................................................... 8 4.3 Backlash in gears.......................................................................................................... 11 4.4 Gear rattling phenomenon and hammering noise ........................................................ 12 4.4.1 Gearbox rattle ................................................................................................... 12 4.4.2 Modeling of gearbox rattle ............................................................................... 13 4.4.3 Engine geartrain rattling phenomenon and hammering noise .......................... 14 4.4.4 Modeling of engine timing geartrain rattling and hammering ......................... 14 4.5 Noise and vibration generation .................................................................................... 16 4.6 Noise and vibration isolation ....................................................................................... 16 4.7 GearMaterials ............................................................................................................... 17 4.7.1 Steel .................................................................................................................. 18 4.7.2 Austempered ductile iron ................................................................................. 19 4.7.3 Powder Metallurgy ........................................................................................... 27 4.7.4 Austempered Gray Iron (AGI) ......................................................................... 43 4.7.5 Plastic gears ...................................................................................................... 43 5 Results and Discussions...................................................................................................... 45 5.1 Component oriented concepts ...................................................................................... 45 5.1.1 Utilization of scissors gears.............................................................................. 45 5.1.2 Concept description .......................................................................................... 45 5.1.3 Torsion spring system ...................................................................................... 46 5.1.4 Radially arranged springs ................................................................................. 46 5.1.5 Gears with an elastomeric material .................................................................. 47 5.1.6 Seeger rings ...................................................................................................... 47 5.1.7 Advantages and disadvantages of scissors gears .............................................. 48 5.1.8 Engines in which scissors gears were used ...................................................... 49 5.1.9 Future prospects of scissors gears .................................................................... 49 VI CHALMERS, Product Development, Masters Thesis 2011 5.2 Material Concepts ........................................................................................................ 50 5.2.1 Austempered ductile iron gears ........................................................................ 50 5.2.2 Powder metallurgy concept .............................................................................. 56 5.3 Redesigned layout concepts ......................................................................................... 64 5.3.1 Eccentric/Elliptic drive mechanism ................................................................. 64 5.3.2 Bevel gear timing system ................................................................................

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