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On Transmission Error, Shuttling Forces and Friction Forces as Gear Noise Excitation
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.ORCID iD: 0000-0002-9632-8398
(English)In: International Journal of Acoustics and VibrationArticle in journal (Other academic) Submitted
Abstract [en]

Traditionally, transmission error (TE) has been used to asses the noise propertiesof gears. Measurements of gear noise for a complete truck gearbox have been used tocorrelate noise from a gear pair with calculated static transmission error, shuttling forceand friction forces. Two gear pairs with very similar macro geometry but differentmicro geometry was used. The measurement results show that there is a limitationif transmission error is considered as the only excitation mechanism when designingquiet gears. Often TE is multiplied with the gear mesh stiffness in order to calculatean excitation force. For gear not operating above the critical gear mesh resonance,this often overestimates the importance of TE, thus underestimating the importance ofother sources such as shuttling and friction forces.

National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-11856OAI: diva2:285658
QS 20120326Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2012-03-26Bibliographically approved
In thesis
1. On Noise Generation and Dynamic Transmission Error of Gears
Open this publication in new window or tab >>On Noise Generation and Dynamic Transmission Error of Gears
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Noise from heavy trucks is an important environmental issue. Several sources contribute to the total noise level of a vehicle, such as the engine, gearbox, tires, etc. The tonal noise from the gearbox can be very disturbing for the driver, even if the noise level from the gearbox is lower than the total noise level. The human ear has a remarkable way of detecting pure tones of which the noise from loaded gears consists of. To be allowed to sell a heavy truck within the European Union, the so called pass-by noise test must be completed successfully. The maximum noise level permitted is 80dB(A) and undercertain conditions, the gearbox can be an important contributor to the total noise level. Gear noise is therefore an important issue for the automotive industry.

In this thesis gear noise and dynamic transmission error is investigated. Traditionally, transmission error (TE) is considered to be the main excitation mechanism of gear noise. The definition of TE is ”the difference between the actual position of the output gearand the position it would occupy if the gear drive were perfect”. Measurements of dynamic transmission error (DTE) and noise have been performed on a gearbox. The measurement object was a commercial truck gearbox powered by an electrical motor. The torque used was in the normal operating range of the gearbox and the correlation between gear noise and DTE, when the torque is changed, is investigated. The result differs for different gear pairs and for the first gear stage, located close to the housing, the correlation is high for most speeds. The measured DTE and noise show a poor correlation with calculated transmission error. A minimisation of TE therefore does not necessarily mean a minimisation of gear noise.

A transfer function can be employed to calculate the relationship between DTE and noise. The general trend of the gear noise is an increase of 6dB per doubling of the rotational speed together with fluctuations around the mean due to resonances of the system. The magnitude of the transfer function can be estimated using the amplitudesof the gear mesh orders and harmonics.

Two gear pairs with similar macro geometry but different profile modifications are investigated. Although the gear pairs have similar transmission error, the noise level display a significantly different trend, further strengt hening the position that transmission error is not the single most important gear noise excitation mechanism. Further analysis concludes that shuttling forces and friction forces can be more important than what is often suggested. A dynamic model including transmission error and shuttling forces is used to investigate the two gear pairs. The bearing forces show that for some frequency regions shuttling forces can be of the same order of magnitude as the forces caused by transmission error.

This work highlights the importance of considering other excitations of gear noise besides transmission error when designing quiet gears. The influence of transmission error can not be determined by investigating the gears only. A deeper knowledge of the gear system is needed in order to minimise gear noise for a specific gear design.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 17 p.
Trita-AVE, ISSN 1651-7660 ; 2009:89
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
urn:nbn:se:kth:diva-11858 (URN)978-91-7514-537-2 (ISBN)
Public defence
2010-01-29, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
QC 20100719Available from: 2010-01-13 Created: 2010-01-12 Last updated: 2010-07-19Bibliographically approved

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