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On Noise Generation and Dynamic Transmission Error of Gears
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. (Vibro acoustics)
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.
Series
Trita-AVE, ISSN 1651-7660 ; 2009:89
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-11858ISBN: 978-91-7514-537-2 (print)OAI: oai:DiVA.org:kth-11858DiVA: diva2:285792
Public defence
2010-01-29, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note
QC 20100719Available from: 2010-01-13 Created: 2010-01-12 Last updated: 2010-07-19Bibliographically approved
List of papers
1. Analysis of gear noise and dynamic transmission error measurements
Open this publication in new window or tab >>Analysis of gear noise and dynamic transmission error measurements
2004 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Measurements of dynamic transmission error (DTE) and noise have been performed on a truck gearbox. The DTE is related to the dynamic properties of the complete gear system. To investigate the coupling between noise and DTE, the correlation between noise and DTE is calculated for fixed speeds, as the torque is increased. The highest correlation is found for the low split gear pair, which is located closest to the gearbox housing. When the correlation is low, one of the reasons can be a resonance of the shafts, although not all resonances effect the correlation between noise and DTE. The DTE is also compared to calculated static TE for the gear teeth. Both the DTE and noise for the fifth gear increases as the torque is increased. The calculated static TE shows the opposite trend and decreases as the torque is increased.

Place, publisher, year, edition, pages
New York: ASME, 2004
Keyword
Gears, Gear noise, transmission error
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-11842 (URN)2-s2.0-19544385769 (Scopus ID)
Conference
2004 ASME International Mechanical Engineering Conference
Note
QC 20100719Available from: 2010-01-12 Created: 2010-01-08 Last updated: 2010-11-30Bibliographically approved
2. On model of gearbox noise and dynamic transmission error
Open this publication in new window or tab >>On model of gearbox noise and dynamic transmission error
2005 (English)In: Twelfth International Congresson Sound and Vibration, 2005, 3198-3205 p.Conference paper, Published paper (Refereed)
Abstract [en]

Gearbox is an important noise source in automotive industry. Dynamic Transmission Error(DTE) describes the dynamic behaviour of the complete gear system and is closely related tothe vibrations of, and hence the noise radiated from, a gearbox. The coherence between DTEand noise radiated has been investigated previously and promising results have been obtained.The paper focuses on the models of DTE and the gearbox noise and the relation betweenthem. In order to understand the behaviour of the signals, a simple model is drawn whereDTE is modelled as the excitation source of a gear system. When the speed of rotation is notextremely high, DTE is expected to be independent of the speed of rotation when theobservation points are located on the wheel. On the other hand, the radiated sound isexpected to increase at the rate of 6 dB per double of the rotation speed, although a bigfluctuation is also expected due to the influence of the shifted frequency and hence thedifferent transfer function. Experimental data is analysed. The dynamic transmission errormeasured on a truck gearbox is separated into deterministic parts and a stochastic part. Theapplied torque has little influence on the averaged DTE of the whole gear because of the highstiffness. However, when the averaged DTE of a single tooth is concerned, the influence ofthe applied torque is rather obvious. The predicted trend of the radiated sound pressure isalso seen in the measured data.

Series
12th International Congress on Sound and Vibration 2005, ICSV 2005, Volume 4
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-11854 (URN)2-s2.0-84881596980 (Scopus ID)978-162748149-6 (ISBN)
Conference
Twelfth International Congress on Sound and Vibration, 11-14 July Lisbon
Note

QC 20100719

Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2014-09-29Bibliographically approved
3. Analysis of Gear Noise and Dynamic Transmission Error Using a Recursive Kalman Filter Algorithm
Open this publication in new window or tab >>Analysis of Gear Noise and Dynamic Transmission Error Using a Recursive Kalman Filter Algorithm
(English)In: International Journal of Acoustics and Vibration, ISSN 1027-5851Article in journal (Other academic) Submitted
Abstract [en]

Measurements of dynamic transmission error (DTE) and gear noise have been usedto investigate the relation between DTE and noise. A Kalman filter order trackingmethod was used to calculate the amplitudes of the gear mesh orders. The DTE showsnon-linear behaviour with rotating speed , which decreases as the torque is increased.There seems to be a linear relationship between noise and DTE for the higher torquesmeasured. This indicates that for the higher torques measured, a linear model can beused to predict the dynamic behaviour of the gear system.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-11855 (URN)
Note

QCR 20161212

Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
4. On Transmission Error, Shuttling Forces and Friction Forces as Gear Noise Excitation
Open this publication in new window or tab >>On Transmission Error, Shuttling Forces and Friction Forces as Gear Noise Excitation
(English)In: International Journal of Acoustics and Vibration, ISSN 1027-5851Article 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
Identifiers
urn:nbn:se:kth:diva-11856 (URN)
Note

QC 20161212

Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
5. On Shuttling Forces and Transmission Error as Gear Noise Excitation
Open this publication in new window or tab >>On Shuttling Forces and Transmission Error as Gear Noise Excitation
(English)In: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001Article in journal (Other academic) Submitted
Abstract [en]

This work studies the influence of shuttling forces on gear dynamics. Dependingon the frequency range of interest, shuttling forces can induce bearing forces of thesame order of magnitude as transmission error. A dynamic model including shuttlingforces is presented and the perturbation method in the order domain is used to solvethe equations of motions. The result of the dynamic model is compared with static calculations using a commercial finite element program.

National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-11857 (URN)
Note
QS 20120326Available from: 2010-01-12 Created: 2010-01-12 Last updated: 2017-12-12Bibliographically approved
6. A dynamic gear model including transmission error and shuttling forces
Open this publication in new window or tab >>A dynamic gear model including transmission error and shuttling forces
(English)In: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001Article in journal (Other academic) Submitted
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-14140 (URN)
Note
QS 20120326Available from: 2010-07-19 Created: 2010-07-19 Last updated: 2017-12-12Bibliographically approved

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