Gear Rattle Noise Research Articles

An experimental and theoretical investigation of the influence of backlash on gear train vibro-impacts and rattle noise

Rattling is a perennial gear noise problem observed in various powertrain components ranging from manual transmissions to engine balancers and timing gear trains. Under lightly loaded conditions, gear systems that are subjected to input and/or output torque fluctuations exhibit vibro-impacts as tooth separations and coast-side contacts take place in the presence of backlash. Experimental set-ups that can impose tightly controlled torque fluctuations to single or multi-mesh gear train are used here to determine the sensitivity of the rattling noise levels to the magnitudes of backlash within wide ranges of torque fluctuation parameters. Torsional discrete models of the experimental set-ups were used to simulate these rattling motions and to predict impact velocity-based rattle severity indexes as a function of both excitation parameters and backlash magnitudes. Single-mesh results show that the larger backlash values result in higher noise levels in most of the cases. In case of double-mesh systems, the resultant noise levels and the corresponding rattle indices exhibit different sensitivities to backlash magnitudes depending on the excitation conditions.

Dynamic behavior of an agricultural power take-off driveline for rattle noise reduction: Part 2. Experimental analysis of rattle noise effect according to spline tolerance level

Agricultural tractors comprise power take-off (PTO) drivelines, which that transmits engine power to the outside for various agricultural work, and various mechanical components are connected by spline couplings with tolerances. Dynamic behavior of the spline couplings causes a jumping phenomenon where the rotation speed fluctuation amplifies and then rapidly decreases. This paper experimentally examined the effects of spline tolerance on the dynamic behavior and PTO gear rattle noise for four different spline tolerance levels. For the fit tolerance (0.1 mm), no jumping was observed. For increasing tolerance levels of 0.5, 0.9, and 1.3 mm, the jumping rotation speed decreased to 920, 890, and 880 rpm, respectively. With increasing tolerance, both the rotation speed fluctuation and noise level immediately before jumping increased gradually. Furthermore, for the specimen with tolerance levels of 1.3 mm(type D), a transient range was observed in which the dynamic behaviors before and after jumping were mixed and rotation speed fluctuation and sound pressure level showed large deviations from their respective average values.

An experimental methodology to study engine gear rattle problems

Gear induced noise represents a major part of overall automotive drivetrain noise. Gear rattle noise is caused by strongly nonlinear dynamic behavior of the gear pair, primarily due to external torque of speed fluctuations under lightly loaded conditions. Such loading conditions cannot be generated by using the conventional gear dynamics test set-ups that employ power recirculating gearbox arrangements or conventional electric motors. In this paper, a new test set-up is introduced to emulate the actual torque/velocity fluctuations of the input and/or output members of a gear train through three-phase synchronous servo-motors. In addition to establishing backlash boundaries, a pair of absolute encoders are used to measure the relative motions of the gears as well as their impacts along the drive and coast sides flanks or gears. Torsional vibratory behavior of a gear pair is presented at different backlash values under several input/output fluctuation conditions along with the companion sound pressure measurements.

Dynamic behavior of an agricultural power take-off driveline for rattle noise reduction: Part 1. Effect of spline tolerance on the power take-off rattle noise

An agricultural tractor has a power take-off (PTO) driveline that is directly connected to the engine to improve its power transmission efficiency. The PTO driveline comprises various mechanical components coupled by a spline joint. The spline coupling tolerance causes collisions between various mechanical parts of the PTO driveline and affects gear collision, thereby causing rattle noise. Therefore, the aim of this study is to conduct a dynamic behavior analysis to predict the gear rattle noise level of a PTO driveline. The dynamic behavior of the PTO driveline was analyzed through 1D simulations, and the results confirmed that the dynamic behavior changes according to rotation speed. Experimental verification of the dynamic behavior analysis results confirmed that the dynamic behavior changes as the main engine excitation-component amplification changes and then decreases at a relatively high rotation speed. Additionally, the dynamic behavior changes of the PTO driveline resulted in a jumping phenomenon that occurs rapidly at a specific rotation speed. The amplification of the engine’s main components was reduced from 3 to 4 times to 1.2 times owing to the jumping phenomenon; the noise level of the gear rattle was also reduced by approximately 10.9 dB(A).

Investigation of gear rattle noise including visualization of vibro-impact regimes

This paper presents an experimental study of gear rattle noise induced by vibroimpacts between gear teeth. A specific experimental set-up is designed to analyse the nonlinear dynamic behaviour of a spur gear submitted to input velocity fluctuation. The drag torque, the mean drive gear rotational speed, the velocity fluctuation amplitude and frequency are controlled during experiment. The dynamic transmission error is measured thanks to high resolution optical encoders. The originality of the experimental set-up consists in using a high-speed camera in order to visualize the contact zone and to identify the occurrence of successive impacts between gear teeth. The rattle threshold is identified as a function of velocity fluctuation amplitude and frequency for various operating drag torques and mean rotational speeds. Experiments show very good agreement with the theoretical master curve. Once impacts occur, stationary nonlinear gear dynamic response and rattle noise radiated by the mechanical system are investigated. Most of the time, an almost periodic response is observed with 2 impacts per period. One impact between the active flanks alternates with one impact between the reverse flanks. A contact phase between gear teeth is observed after each impact instead of an instantaneous rebound. The number of successive tooth pairs crossing the meshing zone without any contact between gear teeth varies according to the ratio of the excitation frequency to the rotation frequency. Analytical and numerical works performed using a gear rattle model show good agreement with experiments. Finally, sound pressure emitted from the gear pair is measured. The acoustic power imputable to gear rattle is found to be proportional to the total kinetic energy transferred per second to the system by the successive impacts.

Optimization on Nonlinear Dynamics of Gear Rattle in Automotive Transmission System

Recently, gear rattle noise is gradually becoming a nonignorable issue involving comfortableness in automotive transmission for a car. Generally, the rattle noise is influenced by nonlinear dynamic of multiple pairs of idler gears in the multistage gear transmission system. Optimization methods based on nonlinear rattle dynamic analysis are worthy of further study to control the noise. In this research, an equivalent rattle dynamic model of the idler gear is proposed, and the nonlinear rattle dynamic responses are solved based on the integral method. The effect laws of key factors on nonlinear dynamic performance are investigated by using a bifurcation diagram, spectrum map, and Poincaré map. Finally, the gear backlash, equivalent mass, and rotational speed are optimized based on Kriging surrogate model (KSM) and differential evolution (DE) algorithm by taking the minimization of the maximum rattle noise as the optimal object. It can be concluded that the rattle dynamics of the idler gear show rich nonlinear characteristics as the parameters change. The proposed method can not only reduce the sound pressure level of rattle noise but also provide a viable path and reference value for the low‐noise design of the gear transmission system.

Transmission error model-based optimisation of the geometric design parameters of an automotive transmission gearbox to reduce gear-rattle noise

The optimisation of gearbox geometric design parameters to reduce gear-rattle noise in an automotive transmission based on a transmission error model is presented. Towards this aim, a four-degree-of-freedom torsional vibration model for the geared system is obtained. Differential equations of the pinion gear-wheel gear system are obtained. The state-space forms of the differential equations are obtained. The transmission error of the gear system is calculated via a state-space model. An empirical model is used for rattle noise calculation for the five-speed gearbox. The transmission error is considered as the objective function, and bending stress, contact stress and the constant distance between gear centres are considered as constraint functions. By optimising the geometric parameters of the gearbox, such as the module, number of teeth, axial clearance, and backlash, it is possible to obtain a gear structure with high bending and contact strength and to minimise the torsional vibration, transmission error and gear-rattling noise. It is concluded through optimisation that minimising the transmission errors of the gearbox leads to reduced vibration and noise levels of the gearbox. It is determined that the optimised geometric design parameters reduce the calculated rattle noise level by 10% [dB] compared with the sample five-speed gearbox. Furthermore, a 95% reduction in transmission error results in a 12% decrease in rattle noise. All optimised geometric design parameters are significant for the required constraints.

Applied research of the multi-stage torsional vibration damper on controlling the gear rattle

The gear rattle noise of automobile transmission, which belongs to broadband noise, tends to attract the driver’s increasing attention. This paper performs a test on the noise, vibration and harshness (NVH) performance of power train in a passenger car. The results of the test show that the angular acceleration of the input shaft in the transmission increases with the increase of the angular acceleration of the flywheel, and excessive fluctuations of angular acceleration lead to the generation of the gear rattle in transmission. In this paper, a mathematic model of torsional vibration under the working conditions of acceleration, constant speed and deceleration has been established by taking a pair of helical gears as an example. The solving model of the mathematic model is set up by Matlab/Simulink and numerical solution has been solved. The theoretical analyses show that the ability of the traditional single-stage torsional vibration damper to attenuate fluctuations of angular acceleration is limited, while the multi-stage torsional vibration damper can attenuate larger fluctuations of angular acceleration, and the power train can provide good comfort and low fuel consumption. The experimental results in this paper are in accordance with above theories. Dynamic model of torsional direction of helical gears built in this paper is of great significance to the analysis of dynamic characteristics of gears. The multi-stage torsional vibration damper proposed in this paper can attenuate larger fluctuations of angular acceleration effectively, which plays an important role in controlling gear rattles, meanwhile it can enhance the riding comfort of a vehicle and reduce fuel consumption.

エンジンのギアケーシングへの制振処理の適用

As the diesel engine used for the forklift and construction machineries is operated at the continuous heavy duty condition, it employs the gear train to drive the fuel injection pump and valve train. When the driving torque acting on the rotating shaft is decreased in the idling condition, separation of gear tooth and rattle noise are induced. Moreover, torsional vibration of crankshaft increases the impact vibration between the gear train. This gear train is commonly installed at the pulley side of the crankshaft and the gear casing is attached to an engine block to cover the gear train. Vibration level of this gear casing is often magnified due to the engine block vibration and consequently the engine noise is increased at the pulley side. The effects of changing the structure of gear casing and noise radiation from the gear casing are evaluated by use of the modal synthesis method which employs the vibratory characteristics of each structure and static deformation caused by the displacement of the connecting points. The rubber pasting on the gear casing is carried out to reduce engine noise. A modal damping ratio of coupled system after pasting rubber on the gear casing evaluated by use of modal analysis technique and its validity is confirmed by vibration experiment of a box model which imitates engine block and gear casing. Change of actual engine noise level by rubber pasting on gear casing is also discussed in detail.

Experimental study on transmission rattle noise behaviour with particular regard to lubricating oil

This article presents an experimental study on the gear rattle noise phenomenon of automotive transmissions. A single-stage gear transmission has been designed and applied to a gear rattle noise test bench. The gear transmission allows the variation of several parameters affecting the rattle noise level, e.g. tooth backlash variation. High resolution incremental encoders on the transmission input and output shaft, as well as on the idler gear, enable the acquisition of the angular relative motion of the gear pair within the range of tooth backlash. The angular relative motion evaluates the sequence of meshing gear teeth along the path of contact under rattling conditions.The analysis of the angular relative motion indicates that gear tooth impacts during rattling lead to elastic deformation of meshing gear pairs. High contact forces during impacts cause Hertzian flattening of gear tooth flanks and rising fluid viscosity with pressure in the contact zone (elastohydrodynamic lubrication regime). The elastic deformation of meshing gear pairs lead to deviations from the angular velocity ratio between two gears of a gear pair and thus from the Law of Gearing. The main source for the gear rattle noise level 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 using low traction gear lubricants.

클러치 동적 토크 계측에 관한 연구

Torque fluctuation of engine generate gear rattle noise of transmission and many researches have been studied to decrease rattle noise by adjusting clutch damper system. So design optimization of clutch system is very important to decrease rattle noise and need knowing clutch dynamic torque at real vehicle driving condition. This makes it possible to measure clutch dynamic torque by using a small-size magnetic sensor. We install a small-size magnetic sensor on the input shaft of the transmission and measure the relative angular displacement between clutch hub and disc plate. We can obtain the clutch torque correspond to the angular displacement in the clutch torsional characteristics test. The object of this research is to measure clutch dynamic torque on real vehicle condition. Therefore, Clutch dynamic torque is very useful for investigating operating range of clutch according to engine torque and predicting the damping performance of torsional vibration on the powertrain.