米其林低滚动阻力轮胎技术

Rolling Resistance Basic FoundationRandall CLARKRolling ResistanceBasic Foundation•Definition and Origins•Relative magnitude–Cars–Trucks–Buses•External VariablesWhat is Rolling ResistanceRolling Resistance •FRR-Tire drag on vehicle montionHow can you fell Rolling Resistance?•If you ride a bicycle withtires at low pressure,youhave to work harder toovercome the increasedrolling resistance.So is it Energy or Force?Both!•Rolling Resistence–=tire rolling energy consumed per unit distance –=work/distance–=[Newstons x meters]/msters•Rolling Resistance–=resistance force of the tires–=force–=NewtonsWhat causes Rolling Resistance?•The main three physical causes of rolling resistanceWhere is most of the energyconsumed in the tire?•Computer Modeling of Energy LossThe Role of Rubber Compounds•Positive: provide grip, resilience, toughness, wear •Negative: waste heat generated when tire flexes; lost energy comes form fuel tankChoosing Rubber Compounds •There are rubber compounds that can redece rolling resistance•The choice depends on many design requirements:–wear; grip; cut resistance….•Some new high tech compounds can reduce rolling resistance with few compromisesTread Pattern Effectsexamples: truck tiresLower Rolling ResistanceSmooth rib tires Higher Rolling Resistance lug tiresChoice of Rubber Compounds & Tread Patterns affect Rolling Resistance & Heat GenerationTruck tire images taken with infrared camera while tire rolling;both tires running under identical load and pressureComparing low rolling resistanceto high rolling resistance•You can see the difference in tread pattern and compoundBy placing differentbrands/types of tireson similar positionson the vehicle, youcan see the heat andtherefore RRdifferences by usingan infrared camera atnight…Cooler tires have other benefits, also •Truck tires: tire carcass lasts longer for potential retreading–Better use of reources•Car tires: cooler tires reduce chance of failure while running–safetyDoses the tire structure play a role?Yes! Radial tires are betterThe Bias-ply Tire •A casing made ofseveral plies positionedin a criss-cross mannerThe bias-ply tireHIGH FRICTION=HIGH ROLLING RESISTANCE Bias tire: Crown and sidewalls interdependent •Sidewall flesing is transmitted tothe tread resulting in:–Distortion of ground contact area–Scissoring of casing plies thatleads to overheating–High friction with the road surfaceRadials•Casing made of oneradial ply•Crown stabilized by several steel plies •Sidewalls and tread function separatelyRadial ConstructionLOW FRICTION=LOW ROLLING RESISTANCE Radial: sidewalls and tread function independenly•Sidewall flexing is nottransmitted to the treadresulting in:–Less distortion of theground contact are–Reduced friction with theground for enhanced ridecomfort–Cool runningRadial advantages•Improved fuel economy:–from 5% to 10% better•Better puncture resistance–safety•Cooler running casing–safety and retreadabilty•Better wear –two times longer–fewer tires needed per year; fewer to dispose •Less pavement damage than biasDoes the tire size matter? Yes!! Larger tire are better.Rolling ResistanceBasic Foundation•Definition and Origins•Relative magnitude–Cars–Trucks–Buses•External VariablesRelative importance vs other factors Tire RR as a% of all fuel used: highway •Passenger car–form 8 to 20%–or for every 100 liters of fuel, 8 to 20 liters areconsumed by the tires as lost energy•Truck and bus–form 25 to 35%–or for every 100 liters of fuel, 25 to 35 liters areconsumed by the tires as lost energyGreatly depends on driving cycleRolling ResistanceBasic Foundation•Definition and Origins•Relative magnitude–Cars–Trucks–Buses•External VariablesTime of Running •Rolling Resistance drops quickly and then stabilizesEffect of temperature •Warmer days cause a tire to be More Efficient (lower RR)Effect of speed•The tire contribution(FRR) does notchange but the %contributiondecreases becausethe areodynamicdray dominates athigher speedsEffect of PressureHigher Pressure reduces Rolling ResistanceEffect of loadComplex•The tire becomesmore efficient(CRR)-BUT theactual resistiveforce (FRR)increases becausethe load in the tireincreasesRolling Resistance:key points•It consumes fuel from your fuel tank•It cannot be completely eliminated•Certain tire designs and compounds can lower rolling resistance。