1,721,036 research outputs found
Realizzazione banco di prova per l’analisi del gear-rattle di una coppia di ingranaggi di una trasmissione automobilistica e sviluppo della metodologia di misura
No full textGear Rattle during a start-up transient in a driveline equipped with a tuneable torsional Vibration Damper with Magneto-Rheological Elastomers
No full textThe paper reports a numerical investigation on the dynamic behaviour of a vehicle driveline, equipped with a Torsional
Vibration Damper (TVD) based on Magneto-Rheological Elastomeric (MRE) spring elements, during the start-up transient
considering an abrupt manoeuvre of clutch engagement. The TVD device consists of a flywheel and a damper disk, with
interposed some elastomeric samples which react for relative angular displacements of the two disks. The dynamical parameters of the TVD can be properly tuned by varying the magnetic field surrounding the MRE springs to mitigate the torsional oscillations of the flywheel, causes of many undesired inconveniences as critical speeds or vibro-acoustic issues.
The present study promotes the use of the MRE torsional vibration damper to reduce the annoying vibroacoustic phenomenon of “gear rattle” arising in the unloaded gear pairs of the gear box, during and after the rapid clutch engagement
transients in the vehicle start-up phase and is conducted on a simplified automotive driveline equipped with a dry clutch.
The possibility of quickly tuning the mechanical properties of the MRE-TVD, makes this device particularly eligible for
suppressing the above disturbance, adapting to the various operative conditions of the automotive driveline. Results of
the analysis, by the help of a Gear Rattle Index (GRI), demonstrate the effectiveness of the proposed device in reducing
the vibroacoustic phenomenon during the transient phases of the vehicle start-up, until the vehicles speed conditions are
reached
Determinazione delle caratteristiche operative di cuscinetti porosi di dimensioni finite
No full textA feasibility study on elastokinematic parameters identification for a multilink suspension
No full textDeterminazione delle caratteristiche operative di cuscinetti porosi di dimensioni finite
No full textExperimental investigations about the influence of oil lubricant between teeth on the gear rattle phenomenon
No full textThe article describes an experimental investigation into the "gear rattle" phenomenon in automotive manual transmissions with a special focus on the influence that lubricant oil may have in reducing this undesirable event. The experimental analysis has been conducted in order to validate a theoretical model developed by the authors that accounts for the presence of oil between the meshing gear teeth of unloaded gear pairs during the no-contact phase. An original measurement technique has been adopted for the tests that consists of the acquisition of the angular relative motion of a gear pair by two high resolution encoders. The experimental test rig designed for this analysis offers the possibility of varying the distance between the wheel axes so that the influence of the backlash variation on the rattle phenomenon can be investigated. The paper presents the results of a series of experiments conducted on helical gear pairs from an automotive gear box in the "idle gear rattle" condition by varying the lubrication mechanism. The experimental results show good agreement with the expectations provided by the theoretical model
Gear rattle reduction in an automotive driveline by the adoption of a flywheel with an innovative torsional vibration damper
No full textAn innovative device consisting of a flywheel equipped with a torsional vibration damper, based on the magnetorheological
effect in elastomeric spring elements, is proposed in this paper. The feasibility study reports the dynamic
behaviour of an automotive driveline equipped with the device aiming to explore the effectiveness of the damper in
reducing the torsional oscillations of the flywheel, at low-speed regime, responsible for the vibro-acoustic phenomenon
known as ‘‘gear rattle’’. The spring elements of the device are constituted by magneto-rheological elastomeric samples,
interposed between the flywheel and the damper disk, working for shear strains. Their dynamical characteristics can be
properly tuned by varying the magnetic field surrounding the springs in order to mitigate the forced vibration causes of
gear tooth impacts. The good attitude of the device in mitigating the rattle phenomenon is demonstrated by comparing
the results provided by a numerical drive line model, equipped with a ‘‘monolithic’’ flywheel, with those obtained by
adopting the present innovative vibration damper. The angular accelerations, resulting from the collisions between the
teeth during the operation under ‘‘idle’’ conditions at different angular speeds, are thus compared
On the recognition of anomalies in gears by means of the discrete wavelet transform
No full textStatic transmission errors and engine torque fluctuations are two major issues that characterize the dynamic behaviour of gears.
Torque fluctuations are typical, as an example, in internal combustion engine. Static transmission errors, such as tooth profile errors, tooth “spalling” defects, or wheel assembly eccentricity, are present in every actual gear pair.
This paper introduces a technique that uses a wavelet-based signal processing procedure, applied to the signal coming from two meshing gears. Discrete wavelet transform (DWT) is used to decompose the meshing signal, and the wavelet coefficients variations are analyzed to describe the dynamic behaviour of gears.
Some examples of application of the proposed technique are described adopting, as input data, the meshing signals acquired by two high resolution incremental encoders on a gear pair test rig.
The ability of DWT in detecting either gear defects or torque fluctuation is shown.
The analysis demonstrates that, by means of wavelet transform, it is possible to identify and evaluate the presence of specific anomalies in the meshing signal. The analysis also suggests the possibility of adopting such DWT based technique in an on-line control context.
Finally, in the field of gear rattle, the technique can have also a practical relevancy in the definition of new rattle indices useful to the NVH departments of automotive industries
“Determinazione sperimentale dei coefficienti dinamici di un rotore su cuscinetti radiali a pattini oscillanti
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