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Gearbox noise: Correlation with transmission error and influence of bearing preload
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The five appended papers all deal with gearbox noise and vibration. The first paper presents a review of previously published literature on gearbox noise and vibration.

The second paper describes a test rig that was specially designed and built for noise testing of gears. Finite element analysis was used to predict the dynamic properties of the test rig, and experimental modal analysis of the gearbox housing was used to verify the theoretical predictions of natural frequencies.

In the third paper, the influence of gear finishing method and gear deviations on gearbox noise is investigated in what is primarily an experimental study. Eleven test gear pairs were manufactured using three different finishing methods. Transmission error, which is considered to be an important excitation mechanism for gear noise, was measured as well as predicted. The test rig was used to measure gearbox noise and vibration for the different test gear pairs. The measured noise and vibration levels were compared with the predicted and measured transmission error. Most of the experimental results can be interpreted in terms of measured and predicted transmission error. However, it does not seem possible to identify one single parameter, such as measured peak-to-peak transmission error, that can be directly related to measured noise and vibration. The measurements also show that disassembly and reassembly of the gearbox with the same gear pair can change the levels of measured noise and vibration considerably. This finding indicates that other factors besides the gears affect gear noise.

In the fourth paper, the influence of bearing endplay or preload on gearbox noise and vibration is investigated. Vibration measurements were carried out at torque levels of 140 Nm and 400 Nm, with 0.15 mm and 0 mm bearing endplay, and with 0.15 mm bearing preload. The results show that the bearing endplay and preload influence the gearbox vibrations. With preloaded bearings, the vibrations increase at speeds over 2000 rpm and decrease at speeds below 2000 rpm, compared with bearings with endplay. Finite element simulations show the same tendencies as the measurements.

The fifth paper describes how gearbox noise is reduced by optimizing the gear geometry for decreased transmission error. Robustness with respect to gear deviations and varying torque is considered in order to find a gear geometry giving low noise in an appropriate torque range despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error, noise, and housing vibrations were measured. The correlation between dynamic transmission error, housing vibrations and noise was investigated in speed sweeps from 500 to 2500 rpm at constant torque. No correlation was found between dynamic transmission error and noise. Static loaded transmission error seems to be correlated with the ability of the gear pair to excite vibration in the gearbox dynamic system.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , viii, 20 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2008:19
Keyword [en]
gear, gearbox, noise, vibration, transmission error, bearing preload
Identifiers
URN: urn:nbn:se:kth:diva-9899OAI: oai:DiVA.org:kth-9899DiVA: diva2:145390
Public defence
2009-02-05, Sal F3, KTH, Lindstedtsvägen 26, Stockholm, 13:15 (English)
Opponent
Supervisors
Note
QC 20100923Available from: 2009-01-28 Created: 2009-01-28 Last updated: 2010-09-23Bibliographically approved
List of papers
1. Gear Noise and Vibration: A Literature Survey
Open this publication in new window or tab >>Gear Noise and Vibration: A Literature Survey
2001 (English)Report (Other academic)
Abstract [en]

This paper is a survey of the literature on gear noise and vibration. It is divided into three parts, “Transmission error”, “Dynamic models” and “Noise and vibration measurement”. Transmission error (TE) is considered to be an important excitation mechanism for gear noise and vibration. The definition of transmission error is “The difference between the actual position of the output gear and the position it would occupy if the gear drive were perfectly conjugate”. Dynamic models of the system consisting of gears, shafts, bearings and gearbox casing are useful in order to understand and predict the dynamical behaviour of a gearbox. Noise and vibration measurement and signal analysis are important tools when experimentally investigating gear noise because gears create noise at specific frequencies, related to number of teeth and the rotational speed of the gear.

Publisher
25 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2001:11
Keyword
gear, noise, vibration, transmission error, dynamic models
Identifiers
urn:nbn:se:kth:diva-9891 (URN)
Note
QC 20100923Available from: 2009-01-27 Created: 2009-01-27 Last updated: 2010-09-23Bibliographically approved
2. Gear Test Rig for Noise and Vibration Testing of Cylindrical Gears
Open this publication in new window or tab >>Gear Test Rig for Noise and Vibration Testing of Cylindrical Gears
1999 (English)In: Proceedings OST-99 Symposium on Machine Design, 1999, , 7 p.183-199 p.Conference paper, Published paper (Refereed)
Abstract [en]

Gear noise is sometimes the dominating noise in commercial vehicles. Noise testing of complete gearboxes is very time-consuming and expensive. A test rig has been designed for testing gears under controlled conditions. The test rig is of the recirculating power type. Finite element analysis has been used to predict the dynamical properties of the gear test rig. Experimental modal analysis has been carried out on the gearbox housing to verify the theoretical predictions of natural frequencies. The test rig can be used for noise and vibration testing of gears with different manufacturing errors and different design parameters. In addition to noise testing, the rig can be used for gear life testing and measurement of efficiency.

Publisher
7 p.
Series
Trita-MMK, ISSN 1400-1179 ; 1999:28
Keyword
gear, noise, vibration, test rig, modal analysis
Identifiers
urn:nbn:se:kth:diva-9892 (URN)
Note
QC 20100923Available from: 2009-01-27 Created: 2009-01-27 Last updated: 2010-09-23Bibliographically approved
3. A Study of Gear Noise and Vibration
Open this publication in new window or tab >>A Study of Gear Noise and Vibration
2002 (English)Report (Other academic)
Abstract [en]

The influence of gear finishing method and gear deviations on gearbox noise is investigated in this mainly experimental study. Eleven different test gear pairs were manufactured using three different finishing methods as well as different gear tooth modifications and deviations. The surface finish and geometry of the gear tooth flanks were measured. Transmission error, which is considered to be an important excitation mechanism for gear noise, was predicted and measured. LDP software from Ohio State University was used for the transmission error computations. A specially built test rig was used to measure gearbox noise and vibration for the different test gear pairs. The measurements show that disassembly and reassembly of the gearbox with the same gear pair can change the levels of measured noise and vibration considerably. The rebuild variations are sometimes in the same order of magnitude as the differences between different tested gear pairs, indicating that other factors besides the gears affect gear noise.

Most of the experimental results can be understood and explained in terms of measured and predicted transmission error. However, it does not seem possible to find one single parameter, such as measured peak to peak transmission error, that can be related directly to measured noise and vibration.

Shaved gears do not seem to be noisier than ground gears even if their gear tooth deviations are larger. Factors that do seem to reduce gear noise, when compared with profile ground reference gears, are threaded wheel grinding, increased face-width, decreased lead crowning, increased pitch errors and decreased lead twist. Factors that seem to increase noise are a rougher surface finish, increased lead crowning and helix angle error.

Publisher
44 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2002:8
Keyword
gear, gearbox, noise, vibration, transmission error
Identifiers
urn:nbn:se:kth:diva-9893 (URN)
Note
QC 20100923Available from: 2009-01-27 Created: 2009-01-27 Last updated: 2010-09-23Bibliographically approved
4. Gearbox Noise and Vibration: Influence of Bearing Preload
Open this publication in new window or tab >>Gearbox Noise and Vibration: Influence of Bearing Preload
2008 (English)Report (Other academic)
Abstract [en]

The influence of bearing preload or endplay on gearbox noise and vibrations was investigated using a test gearbox consisting of a helical gear pair, shafts, tapered roller bearings, and housing. Vibration measurements were carried out at 140 Nm and 400 Nm torque, with 0.15 mm and 0 mm bearing endplay, and 0.15 mm bearing preload. The results show that the bearing endplay or preload influences the gearbox vibrations. For the test gearbox, it seems that in comparison with endplay, bearing preload decreases vibrations at speeds below 2000 rpm and increases vibrations at speeds over 2000 rpm. Finite element simulations show the same tendencies as the measurements. The literature was reviewed in order to find earlier work investigating the influence of bearing properties on gearbox noise.

Publisher
15 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2008:17
Identifiers
urn:nbn:se:kth:diva-9894 (URN)
Note
QC 20100923Available from: 2009-01-27 Created: 2009-01-27 Last updated: 2010-09-23Bibliographically approved
5. Gear Geometry for Reduced and Robust Transmission Error and Gearbox Noise
Open this publication in new window or tab >>Gear Geometry for Reduced and Robust Transmission Error and Gearbox Noise
2008 (English)Report (Other academic)
Abstract [en]

Gear geometry was optimized for decreased transmission error in order to reduce gearbox noise. Robustness with respect to gear deviations and varying torque was considered in order to find a gear geometry giving low noise in the appropriate torque interval despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error as well as noise and housing vibration were measured using a gear test rig. The correlation between dynamic transmission error, housing vibration, and noise was investigated. In speed sweeps from 500 to 2500 rpm at constant torque, no correlation was found between dynamic transmission error and noise. Static transmission error seems to be the excitation of dynamic transmission error as well as housing vibration and noise, but different natural frequencies for different degrees of freedom of the dynamic system consisting of gears shafts, bearings, and housing lead to lack of correlation between dynamic transmission error and noise.

Publisher
21 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2008:18
Identifiers
urn:nbn:se:kth:diva-9895 (URN)
Note
QC 20100923Available from: 2009-01-27 Created: 2009-01-27 Last updated: 2010-09-23Bibliographically approved

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