Caused by downsizing of combustion engines, the torque fluctuation at the crankshaft induces torsional vibrations in the powertrain. Manual transmissions and dual clutch transmissions are particularly sensitive to gear-rattle noise. Gear-rattle noise arises from oscillations of loose parts with clearance, e.g. idler gears, synchronizer rings and gearshift sleeves. The aim of this research is the formulation of a gear oil for the application in a manual transmission to minimize gear rattling noise. Acoustic measurements on a gear-rattle noise test bench verify the noise reduction of the developed gear oils with commonly used low oil viscosity. An analysis of the transmission error proves that gear tooth impacts during rattling lead to elastic deformation of the meshing gear pairs. The main source for the intensity of gear-rattle noise is the additional presence of meshing impacts at the beginning of each gear pair meshing. Gear-rattle noise reduction can be achieved by avoiding meshing impacts, e.g. by minimizing the traction coefficient of the gear oil.
Author(s): Axel Baumann
Publisher: Springer Vieweg
Year: 2022
Language: English
Pages: 156
City: Wiesbaden
Abstract
Contents
Abbreviations and Indexes
Symbols
1 Introduction
1.1 Issue
1.2 Task and Objective of the Work
1.3 Structure of the Work
2 State of the Art in Research and Technology
2.1 Market and Development Situation of Vehicle Transmissions
2.2 Torsional Vibration Behavior of Internal Combustion Engines
2.3 Requirements and Structure of Vehicle Transmissions in Spur Gear Design
2.4 Work on Rattling Noise Behavior of Vehicle Transmissions
2.5 Measures to Minimize Rattle Noise from Vehicle Transmissions
2.6 Transmission Power Loss
3 Gear Rattling Noises from Vehicle Transmissions
3.1 Gear Rattling
3.2 Synchronizer Ring Rattling
3.3 Rattle Noise Analysis of Vehicle Transmissions
3.3.1 Test Bench Setup and Test Execution
3.3.2 Acoustic Properties of the Soundproof Cabin
4 Lubricants as Design Elements
4.1 Tasks and Requirement Profile of a Gear Lubricant
4.2 Chemical Composition of Gear Oils
4.2.1 Mineral Oil Based Base Oils
4.2.2 Polyether Oils
4.2.3 Synthetic Hydrocarbons
4.2.4 Carboxylic Acid Esters
4.2.5 Additives
4.3 Mechanical Properties of Gear Oils
4.3.1 Viscosity
4.3.2 Density
4.4 Selected Test Procedures for Testing Gear Oils
4.4.1 Contact Angle Measurement
4.4.2 Mini Traction Machine for Measuring the Coefficient of Friction
4.4.3 Flow Behavior under Shear Stress
5 Parameter Variation of Base Oils and Additives
5.1 Structure of the Manual Transmission for Front-Transverse Drive
5.2 Test Procedure
5.3 Rattle Noise Investigations
5.3.1 Standard Gear Oils, Adhesion Additive and Wetting Agent
5.3.2 Gear Oils Based on Polyalkylene Glycols
5.3.3 Base Oil Type Variation
5.3.4 Variation of VI Improvers
5.3.5 Different Concentrations of Dispersant PAMA
5.3.6 Various VI Improvers in High Concentration
5.3.7 Formulations with Ester Oils
5.3.8 Effect of Friction Modifier and Antifoam Agent
5.4 Measurement of the Drive-Side Torque Loss
5.5 Notes on formulating an optimized gear oil
6 Correlation between Oil and Geometric Parameters
6.1 Structure of the Single-Stage Test Gearbox
6.2 Test Procedure
6.3 Gear Rattle Experiments
6.3.1 Oil Level Variation
6.3.2 Variation of the Oil Sump Temperature
6.3.3 Contribution of Synchronizers
6.3.4 Influence of a Relative Speed Between Gear Shaft and Idler Gear
6.3.5 Influence of the Oil Type with Different Torsional Backlashes
6.3.6 Dependence between Axial and Torsional Backlash
6.4 Synchronizer Ring Rattling Experiments
6.4.1 Variation of Oil Sump Temperature
6.4.2 Influence of a Relative Speed between the Synchronizer Hub and Synchronizer Ring
6.4.3 Variation of the Clearance between Synchronizer Hub and Synchro-Ring
7 Mechanism of Gear Rattling Noise Generation
7.1 Rotational Path Deviation Without Torsional Vibration Excitation
7.2 Comparison of Straight and Helical Gears
7.3 Influence of Torsional Backlash with Helical Idler Gear in the Non-Shifted State
7.4 Variation of the Oil Type with Helical Gearing
7.5 Summary of the Mechanism of Rattling Noise Generation
8 Summary and Outlook
Bibliography
