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Felmodsanalys av lastbilskoppling
KTH, School of Industrial Engineering and Management (ITM).
KTH, School of Industrial Engineering and Management (ITM).
KTH, School of Industrial Engineering and Management (ITM).
2019 (Swedish)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesisAlternative title
Failure mode and effect analysis of a truck clutch system (English)
Abstract [sv]

Detta kandidatexamensarbete syftar till att finna felmoder på Scanias kopplingssystem för framtida självkörande lastbilar. Detta görs genom att fokusera på ECA (Electronic Clutch Actuator), hävarm och lager. FMEA är en riskanalys som används för att kartlägga felmoder, felorsaker och deras feleffekter. Med en 10-gradig skala görs en bedömning med avseende på tre parametrar: felsannolikhet, allvarlighetsgrad och upptäckbarhet. Ett riskprioteringstal, RPN, fås genom att multiplicera dessa. Metoder som vi använt i vår studie är ett studiebesök på SCANIA, litteraturstudier och FEM-analys av hävarmen.

De sex vanligaste felmoder som identifierats för lagret är utmattning, nötning (adhesiv och abrasiv), korrosion, plastisk deformation, elektrisk korrosion och sprickbildning/brott. De vanligaste orsakerna till lagerfel kan klassificeras till områdena smörjning, montering, hantering, design och driftförhållanden. Där innefattas bl.a. främmande partiklar (smuts, nötningspartiklar), monteringsfel, linjeringsfel, otillräcklig smörjning och överbelastning. All hantering av lager är viktig då lagerfel är en kombination av flera orsaker.

Enligt experter är hävarmen välkonstruerad med hög säkerhetsfaktor. Den största orsaken till fel är på grund av intilliggande komponenter som exempelvis lager och ECA. Hög temperatur ökar spänningar och deformationer väsentligt. Bristande smörjmedel i lagren vid hävarmen har identifieras som en huvudorsak till funktionsfel.

Enligt experterna från reparationsverkstaden fungerar ECA enheten smidigt med väldigt lågt fel sannolikhet.

Abstract [en]

This bachelor thesis aims at finding the failure modes at Scania's clutch system for future selfdriving trucks. The examined components are the ECA (Electronic Clutch Actuator), the fork and the release bearings. The FMEA- tool was used for the mapping the failure modes, their causes and effects. This assessment is made using a 10-grade scale with respect to three parameters: occurrence, degree of severity and detectability. A risk priority number RPN, is calculated by multiplying the aforementioned numbers. The methods that we used are a study trip to SCANIA's facilities, the relevant literature on the subject, and the FEM-analyses of the fork.

The six most frequent failure modes identified at the release bearing are (fatigue), wear (adhesive and abrasive), corrosion, plastic deformation, electrically induced corrosion and fractures/crack formation. The most common causes for release bearing failures are classified into smearing, assembly, handling, design and runtime circumstances. They include among others exogenous particles (dirt, wear particles), assembly errors, misalignment, insufficient (grease) and excessive loads. All handling of the release bearings is important because release bearing errors have several causes.

According to experts, the clutch fork is well-designd with a high safety factor. The most common failure mode causes are a result of interactions with neighbouring components e.g. release bearing and ECA. High temperatures increase the stresses and the deformation of the components substantially. Insufficient amount of lubricant in the release bearing is identified as the main reason of failure.

According to experts from the repair workshop, the ECA unit works smoothly and with a low probability of error.

Place, publisher, year, edition, pages
2019. , p. 54
Series
TRITA-ITM-EX ; 2019:173
Keywords [en]
Clutch, Clutch fork, ECA, FMEA, Release bearing
Keywords [sv]
ECA, FMEA, Hävarm, Koppling, Lager
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-264429OAI: oai:DiVA.org:kth-264429DiVA, id: diva2:1373503
External cooperation
SCANIA CV AB
Supervisors
Examiners
Available from: 2019-11-27 Created: 2019-11-27 Last updated: 2019-11-27Bibliographically approved

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