Transmission Gear Rattle Research Articles

Experimental investigation of gear rattle and nonlinear dynamic interaction in a dual-clutch transmission

Dual-clutch transmissions (DCT) having high efficiency and powershift are widely used in passenger cars thanks to the dual-clutch and preselection strategies. However, the dual-clutch transmission gear rattle behaviour still needs to be fully discovered, especially the influence caused by different preselection strategies. In this regard, the gear rattle sensitivity and dynamic evolution of the geartrain in a DCT were experimentally investigated on a rattle test bench and vehicle powertrain. The rattle response and instantaneous speed of all speed gears potentially contributing to the overall rattle are measured. The measured results from the DCT were compared with a similar structure six-speed manual transmission to depict its characteristics. Moreover, a multi-degree-of-freedom nonlinear torsional model was established to gain the nonlinear dynamic response along with the rising torsional irregularities; the model considers the crucial parameters affecting rattle behaviour. Two qualitative criteria were consequently given based on the numerical results and the law of the gear motion.The experimental results on the rattle test bench show that the DCT rattle behaviour varies with different preselected gears and is quite different from the manual transmission. The rattle sensitivity curves disclose an abrupt jump-up phenomenon when the excitation level reaches a certain level. The nominal input speed, preselection gear and lay-shaft configuration considerably determine the excitation level and amplitude increase of the jump-up on the rattle response. Based on the proposed qualitative criteria, a strongly nonlinear dynamic response is observed in the loaded gear pair under preselection conditions and deteriorates the rattle noise. A considerable dynamic interaction between active and passive sub-gearboxes is found. The appearance of the harmonics of the excitation frequency on the active input shaft that generates the high impact amplitude and density contributes to the jump-up and high vibration response on the rattle sensitivity. Finally, vehicle experiments reproduce the rattle jump-up and dynamic torsional interaction in the DCT powertrain are confirmed.

Manual Transmission Gear Rattle Vibration Research Based on Mathematical and Multi-Body Dynamics Co-simulation and Experiment

A method, which compares the angular acceleration and vibration spectrums of shafts and gears with physical characteristics of gearbox as tooth numbers and speed ratios, is proposed to find the source of gear rattle vibration. A mathematical and multi-body dynamics co-simulation model is built to reproduce the gear rattle phenomenon of one typical type of manual transmission. In the model, multi-body dynamics part is used for rotational motion and engagement simulation of gearbox shafts and gears, while mathematical part for control and data processing. The simulation results show that the sound source of the gear rattle from the first gear to the third gear is similar to the experimental results; different parameters like rotating damping, contact stiffness, contact damping, inertia moment and torque fluctuation making effects on gear rattle vibration strength are researched and simulated. The comparison of the simulation and experimental results shows that this method can provide recommendations for solving practical gear rattle problems.

Dynamics Modelling of Transmission Gear Rattle and Analysis on Influence Factors

Based on the vibration dynamics modeling for the single stage gear of transmission system, this paper is to understand the mechanism of transmission rattle. The dynamic model response using MATLAB and Runge-Kutta algorithm is analyzed, and the ways for reducing the rattle noise of the automotive transmission is summarized.

Effect of multi-parameters interaction on transmission gear rattle based on RBF neural network

This paper proposes a method to analyse multi-parameters interaction on transmission gear rattle. Firstly, a simulation model of manual transmission was established, and the angular velocity of each loose gear as well as the mesh force were obtained. Then the loose gear angular velocity was measured on a manual transmission gearbox to verify the model. The derivative of gear mesh force was taken as the rattle index (jerk index), and was calculated using forward difference method. A radial basis function (RBF) neural network was applied to map the relationships between the selected input parameters and rattle index. The results show that gear backlash has the largest influence on gear rattle, followed by the inertia of the loose gear, the speed fluctuation and the drag torque. This study can be easily extended to other types of transmission systems to control the gear noise and improve sound quality.

Effect of multi-parameters interaction on transmission gear rattle based on RBF neural network

Effect of multi-parameters interaction on transmission gear rattle based on RBF neural network

On the effect of multiple parallel nonlinear absorbers in palliation of torsional response of automotive drivetrain

Torsional vibrations transmitted from the engine to the drivetrain system induce a plethora of noise, vibration and harshness (NVH) concerns, such a transmission gear rattle and clutch in-cycle vibration, to name but a few. The main elements of these oscillations are variations in the inertial imbalance and the constituents of combustion power torque, collectively referred to as engine order vibration. To attenuate the effect of these transmitted vibrations and their oscillatory effects in the drive train system, a host of palliative measures are employed in practice, such as clutch pre-dampers, slipping discs, dual mass flywheel and others, all of which operate effectively over a narrow band of frequencies and have various unintended repercussions. These include increased powertrain inertia, installation package space and cost. This paper presents a numerical study of the use of multiple Nonlinear Energy Sinks (NES) as a means of attenuating the torsional oscillations for an extended frequency range and under transient vehicle manoeuvres. Frequency–Energy Plots (FEP) are used to obtain the nonlinear absorber parameters for multiple NES coupled in parallel to the clutch disc of a typical drivetrain configuration. The results obtained show significant reduction in the oscillations of the transmission input shaft, effective over a broad range of response frequencies. It is also noted that the targeted reduction of the acceleration amplitude of the input shaft requires significantly lower NES inertia, compared with the existing palliative measures.

Vibro-Impact Analysis of Manual Transmission Gear Rattle and Its Sound Quality Evaluation

Vibro-Impact Analysis of Manual Transmission Gear Rattle and Its Sound Quality Evaluation

Experimental and numerical analysis for the transmission gear rattle in a power-split hybrid electric vehicle

Experimental and numerical analysis for the transmission gear rattle in a power-split hybrid electric vehicle

Experimental and numerical analysis for the transmission gear rattle in a power-split hybrid electric vehicle

Experimental and numerical analyses are carried out for the investigation of the gear rattle issue appearing in a novel power-split hybrid transmission. The gear rattle in the transmission takes place mainly owing to engine excitations, unloaded gear pairs and gear backlashes. For the analysis of gear rattle phenomena, a non-linear dynamics model is established for the power-split hybrid driveline, and also acoustic measurements for the gear rattle in the hybrid vehicle are performed in a semi-anechoic chamber equipped with a single-axle dynamometer. It is clearly demonstrated by test results that the gear rattle occurs when electric machines are idly operated. Numerical analyses are further undertaken according to the non-linear dynamics model, and noise sources of the gear rattle of this hybrid transmission are identified with simulation results. By optimisation of the hybrid vehicle control strategies, the rattle noise is obviously reduced and the vehicle comfort is improved as well.

Driveline Torsional Analysis and Clutch Damper Optimization for Reducing Gear Rattle

This paper describes a research work on driveline modeling, torsional vibration analysis, and clutch damper parameters optimization for reducing transmission gear rattle on the vehicle creeping condition. Firstly, major driveline components, including quasi-transient engine, multistage stiffness clutch damper, detailed manual transmission and differential mechanism, and LuGre tire, are modeled, respectively. Secondly, powertrain system modeling adopting a two-stage stiffness clutch damper is constructed and analyzed. Transient responses predicted by the model show that the driveline undergoes severe torsional vibration and transmission gear rattle phenomenon. By analysis, it is concluded that the clutch damper works jumping between the first- and second-stage stiffness, which results in this problem for the creeping condition. Then, a three-stage stiffness clutch damper is proposed innovatively to solve this problem. It is shown that severe driveline vibration and gear rattle phenomenon are inhibited effectively. Finally, it draws a conclusion that clutch damper parameters could have a great effect on driveline vibration and gear rattle phenomenon and a three-stage stiffness clutch damper could be utilized to solve gear rattle phenomenon efficiently on the vehicle creeping condition.

Effect of the multi-staged clutch damper characteristics on the transmission gear rattle under two engine conditions

The scope of this article is limited to the torsional driveline system of a front-engine front-wheel type of vehicle. A reduced-order model of a manual transmission (with the third gear engaged and the fifth gear unloaded) is developed on the basis of the modal characteristics. A simplified nonlinear mathematical model is then proposed with the focus on the multi-staged clutch damper properties such as the asymmetric transition angles and the pre-loads. The drag torque is estimated under two engine conditions (wide-open throttle and coast) by assuming that the vehicle is in the steady-state condition. Finally, the gear rattle criteria are investigated, and illustrative examples for three real-life clutch dampers are described. In particular, methods for solving the real-life gear rattle phenomenon are suggested.

An investigation of manual transmission drive rattle

Manual transmission gear rattle is an NVH (noise, vibration, and harshness) concern in the automotive industry. It is induced by repetitive impacts on loose (unselected) gear wheel teeth by their corresponding driving pinions. This phenomenon occurs under various loading conditions and is classified accordingly, including ‘idle rattle’ when the transmission is in neutral and ‘creep and drive rattle’ when the transmission is in a gear with a widely open or a partially open throttle. The phenomenon is also present from drive to coast conditions, referred to as overrun rattle. Engine order fluctuations on the input shaft are considered to be the underlying cause for rattle of loose gears. However, the mechanism of transmission of vibration through lubricated contacts is not fundamentally understood. It is surmised that changes in lubricated contact conditions at different bulk oil temperatures may play a key role and, therefore, offer an opportunity to deal with rattle by a root-cause fundamental solution. This means that a detailed multi-physics approach (including dynamics, vibration, and tribology) is needed. This article provides detailed analytical models of lubricated conjunctions in a multi-body dynamics model of a transaxle seven-speed transmission system under creep rattle conditions. The results show the important role of the regime of lubrication in lightly loaded conjunctions, increasing the propensity to rattle at higher temperatures. It is also revealed that the effect of engine order vibration as an initiating source for rattle becomes significant with reduced hydrodynamic contact stiffness at rising temperatures.

Characterizing the Onset of Manual Transmission Gear Rattle Part I: Experimental Results

Characterizing the Onset of Manual Transmission Gear Rattle Part I: Experimental Results

Characterizing the Onset of Manual Transmission Gear Rattle Part II: Analytical Results

Characterizing the Onset of Manual Transmission Gear Rattle Part II: Analytical Results

Non-linear vibro-impact phenomenon belying transmission idle rattle

This paper investigates automotive transmission gear rattle. Specifically, idle gear rattle, where the repetitive impacts of teeth are subject to light loads is investigated. Hydrodynamic regime of lubrication prevails in lightly loaded impact of teeth pairs. Formation of a lubricant film is due to the combined entraining motion of the lubricant and squeeze film effect. A lumped parameter inertial dynamic model, comprising hydrodynamic impact and flank friction for pairs of simultaneous teeth pairs of loose gears is developed. The overall dynamic model includes seven loose gear pairs and rigid body lateral motions of input and output transmission shafts. Therefore, the influence of fluid film behaviour on idle gear rattle is determined, which has hitherto not attracted sufficient research studies. Gear rattle is manifested by a vibration signature, which corresponds to the bands of frequencies due to torsional engine oscillations, meshing frequencies, and impact characteristics of lubricated conjunctions. The spectral contributions are affected by lubricant rheology, specifically its bulk viscosity variation with temperature. It has been found that spectral disposition tends towards lower frequency contributions with reducing lubricant viscosity because of rising temperatures and lowering lubricant stiffness. The findings conform with the experimental results, also reported in the paper. It has also been shown that squeeze film motion plays a significant role in the propensity of transmission system to rattle.