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On synchronization of heavy truck transmissions
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). Scania CV AB, Transmission Development, Sweden.ORCID iD: 0000-0002-6644-7441
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Gear shifts are becoming more and more important as engines are adapted to low speed high torque working conditions. Synchronizers are key components for successful gear shifts. To adapt the synchronizers to new working conditions due to adaptations to new engines, improved development tools are needed. The presented thesis describes the development of two types of numerical models for the synchronization process, namely fluid-structure interaction to simulate the pre-synchronization phase and thermomechanical FE models to simulate the main synchronization phase. A methodology for developing friction models based on a combination of physical testing and numerical simulations is presented. Additionally, a comprehensive gear shift and synchronizer frame of reference section is presented.

In paper A, two numerical fluid-structure interaction simulation models for assessing the pre-synchronization phase are presented. Simulations show that the synchronizer functionality is highly dependent on the gear shift maneuvering system, and that grooves in the synchronizer surface have a positive effect on the oil evacuation during the pre-synchronization phase.

Paper B describes the development of a numerical thermomechanical model for simulating the main synchronization phase. Two parameter studies were performed, one based on external loads and one based on synchronizer geometry. The effect on the temperature increase from differences in thermal properties between molybdenum and carbon friction linings are presented.

In paper C, a verification and validation methodology for highly transient thermomechanical processes was presented. Numerical verification, bulk temperature measurement, surface temperature measurement and qualitative visual inspection were combined to verify and validate the simulation model presented in paper B.

In paper D, a methodology combining physical testing with an thermomechanical simulation model to develop a friction model was exemplified by a molybdenum coated synchronizer. A simplified thermal model was developed to remove the dependence of full finite element thermal models. The friction models shows good agreement with measured data.

Abstract [sv]

Betydelsen av växlingar i en växellåda har ökat, och synkroniseringsenheter är viktiga komponenter för snabba och robusta växlingar. För att anpassa synkroniseringsenheterna till nya arbetsförhållanden och laster krävs nya utvecklingsverktyg. Denna avhandling innehåller två typer av numeriska modeller för att simulera synkroniseringsförloppet. Multifysikmodeller som kopplar samman oljeflöde och solida kroppar används för att simulera försynkroniseringsfasen. En termomekanisk modell används för att simulera synkroniseringsfasen. En metod för att utveckla friktionsmodeller under synkroniseringsfasen genom att kombinera fysisk provning med numerisk simulering presenteras. Dessutom finns ett utförligt kapitel om synkroniserings- och växlingsteori.

I artikel A presenteras två olika "Fluid-Structure interaction" ("Interaktion mellan vätskeflöde och solida kroppar") för att simulera försynkroniseringsfasen. Simuleringarna visar att synkroniseringsenheter är väldigt beroende av de aktuatorer de är kopplade till, samt att oljedräneringsspår i kontaktytan har en positiv effekt för försynkroniseringsförloppet.

Artikel B beskriver utvecklingen av en termomekanisk modell för att simulera synkroniseringsförloppet. Två parameterstudier utfördes, en där de externa lasterna utvärderas, och en där geometrin på synkroniseringsenheten utvärderas. Effekten av skillnaden i termiska egenskaper hos molybden och kolfiber utvärderas också.

Artikel C beskriver metodik för verifiering och validering av termomekaniska simuleringar av starkt transienta förlopp. En kombination av numerisk verifiering, temperaturmätning i materialet, yttemperaturmätning samt kvalitativ visuell bedömning används för att verifiera och validera simuleringsmodellen som utvecklades i artikel B.

I artikel D beskrivs en metodik för att kombinera fysiska prover med en uppdaterad termomekanisk simuleringsmodell för att beskriva friktionsbeteendet under synkronisering. Metoden exemplifieras med en molybdenbelagd synkroniseringsenhet. En förenklad termisk modell utvecklas för att kunna beskriva friktionsbeteendet utan att använda tidskrävande finita elementmodeller. Den nya friktionsmodellen överensstämmer väl med uppmätt data.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2016. , ix, 38 p.
Series
TRITA-MMK, ISSN 1400-1179 ; 2016:02
Keyword [en]
synchronization, synchronizers, gear shift, gearbox
Keyword [sv]
synkronisering, växling, växellåda
National Category
Other Mechanical Engineering
Research subject
Machine Design
Identifiers
URN: urn:nbn:se:kth:diva-181108ISBN: 978-91-7595-851-4 (print)OAI: oai:DiVA.org:kth-181108DiVA: diva2:898709
Presentation
2016-03-08, Sal Gladan, Brinellvägen 85, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20160218

Available from: 2016-02-18 Created: 2016-01-29 Last updated: 2016-02-18Bibliographically approved
List of papers
1. Robust pre-synchronization in heavy truck transmissions
Open this publication in new window or tab >>Robust pre-synchronization in heavy truck transmissions
2014 (English)In: International Gear Conference 2014: 26th–28th August 2014, Lyon, Woodhead Publishing Limited, 2014, 914-923 p.Conference paper, Published paper (Refereed)
Abstract [en]

Transmission performance directly influences vehicle behaviour, energy efficiency, and perceived quality. A modern transmission is an aggregate of interacting sub-systems, e. g. gears, bearings, synchronisers and other shifting elements. New transmission trends ask for increased shift performance with higher loads for the synchronising components. Synchroniser development has traditionally required exhaustive physical testing and few analytical methods exist. A numerical method for assessing pre-synchronisation performance, using a multi-physics FEM software, is presented. Simulations show that grooves in the synchroniser surface have a positive effect on pre-synchronisation, and that the presence of grooves seems to be more important than the groove design.

Place, publisher, year, edition, pages
Woodhead Publishing Limited, 2014
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-160811 (URN)10.1533/9781782421955.914 (DOI)000348383200092 ()978-1-78242-195-5 (ISBN)978-1-78242-194-8 (ISBN)
Conference
International Gear Conference 2014, 26th–28th August 2014, Lyon, France
Note

QC 20150227

Available from: 2015-02-27 Created: 2015-02-27 Last updated: 2016-02-18Bibliographically approved
2. Parameter study of the thermomechanical performance of heavy duty synchronizers
Open this publication in new window or tab >>Parameter study of the thermomechanical performance of heavy duty synchronizers
2015 (English)In: 15th International VDI Congress, 2015Conference paper, Published paper (Refereed)
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-182214 (URN)
Conference
15th International VDI Congress–Drivetrain for Commercial Vehicles 2015, June 16-17, Friedrichshafen, Germany
Note

NQC 20160218

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2016-02-18Bibliographically approved
3. A Verified and Validated Model for Simulation-Driven Design of Heavy Duty Truck Synchronizers
Open this publication in new window or tab >>A Verified and Validated Model for Simulation-Driven Design of Heavy Duty Truck Synchronizers
2015 (English)In: ASME Proceedings | ASME 2015 Power Transmission and Gearing Conference, ASME Press, 2015, Vol. 10, V010T11A045Conference paper, Published paper (Refereed)
Abstract [en]

The strong market trend toward lower fuel consumption for heavy road transports requires more frequent gear shifting and increased gear shift performance, i.e. shorter shift time. Increased shift performance means higher loads for the synchronizer which brings component and shifting process optimization more into focus.

Traditionally, synchronizer development has relied on physical testing of complete synchronizers in general gearbox test rigs or in specialized synchronization test rigs leaving much of the causes of the observed effects unclear. This paper presents a generalized FE-based thermomechanical simulation model to be used for model-based synchronizer analysis and design. The model is targeted for studies of how different external loads and the values of different synchronizer design parameters affect the temperature transient in the friction lining. Recommendations of how major modeling complications should be treated are presented. The developed simulation model is verified and validated with a combination of analytical means and transient temperature measurements of bulk and surface temperatures. The applicability of the presented model, as well as its limitations, are discussed and exemplified with different design cases.

Place, publisher, year, edition, pages
ASME Press, 2015
Keyword
Atmospheric temperature, Gears, Optimization, Reliability analysis, Stress analysis, Synchronization, Temperature measurement
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-182350 (URN)10.1115/DETC2015-47318 (DOI)000380413500045 ()2-s2.0-84979008641 (Scopus ID)978-0-7918-5720-5 (ISBN)
External cooperation:
Conference
ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference, IDETC/CIE 2015, Boston, United States, 2 August 2015 through 5 August 2015
Note

QC 20160218

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2016-09-07Bibliographically approved
4. Predicting friction in synchronizer systems
Open this publication in new window or tab >>Predicting friction in synchronizer systems
2016 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 97, 89-96 p.Article in journal (Refereed) Published
Abstract [en]

The coefficient of friction in synchronizers is important from both a performance and a functional point of view. The synchronization process is highly transient, and the parameters affecting the coefficient of friction have strong mutual dependences, making analysis highly complex. A new friction model for a lubricated molybdenum-steel contact has been developed based on integrating results from physical rig tests and FEM simulations. A simplified thermal model has also been developed, with the purpose to quickly assess the coefficient of friction based on transient force and synchronizer dimensions. The results show good correlation with measured data except at very low sliding speed.

Place, publisher, year, edition, pages
Elsevier, 2016
Keyword
Friction, Sliding contact, Boundary lubrication
National Category
Tribology
Identifiers
urn:nbn:se:kth:diva-182346 (URN)10.1016/j.triboint.2015.12.038 (DOI)000374194900011 ()2-s2.0-84956892595 (Scopus ID)
Note

QC 20160218

Available from: 2016-02-18 Created: 2016-02-18 Last updated: 2017-11-30Bibliographically approved

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