《汽车理论》课程教学课件（英文讲稿）第1章 汽车动力性 Acceleration Performance 1.2 Driving Mechanics of Vehicle 汽车驱动力和行驶阻力

1.2 DrivingMechanics of Vehicle汽车驱动力和行驶阻力Transmission Courses ofAutomobile（汽车动力传递路线）：. To analyze theEngine发动机balancebetweenClutch离合器Driving Resistance(行驶阻力)andGearBox(orTransmission)变速器Tractive Force(驱AssistantGearbox副变速器一动力)along onePropellerShaft传动轴一→degree offreedom(Final Drive主减速器自由度)that isDifferential差速器longitudinaldirection(纵向)HalfAxle半轴WheelRetarder轮边减速器一DrivingWheel驱动车轮Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance 1.2 Driving Mechanics of Vehicle 汽车驱动力和行驶阻力 Transmission Courses of Automobile(汽车动力传递路线) : Engine发动机→ Clutch离合器→ Gear Box(or Transmission)变速器→ Assistant Gear box副变速器→ Propeller Shaft传动轴→ Final Drive主减速器→ Differential差速器→ Half Axle半轴→ Wheel Retarder轮边减速器→ Driving Wheel驱动车轮 • To analyze the balance between Driving Resistance (行驶阻力)and Tractive Force(驱 动力) along one degree of freedom( 自由度) that is longitudinal direction(纵向). 1

1.TractiveForce（驱动力）TTgigioN,=T一TorqueofEngineFlyingWheel（发动机转矩）T一一NumericalRatiooftheGearbox（变速器传动比）lo一NumericalRatiooftheFinaldrive（主减速比）nT—Totalefficiencyofdriveline（传动系机械效率）T，一TorqueofDrivingWheel（驱动轮转矩）2Chapter1 Acceleration Performance

Chapter 1 Acceleration Performance 1. Tractive Force（驱动力） Ttq ig i T Tt     0 Ttq — Torque of Engine Flying Wheel (发动机转矩) — Numerical Ratio of the Gear box(变速器传动比) — Numerical Ratio of the Final drive (主减速比) — Total efficiency of driveline (传动系机械效率) — Torque of Driving Wheel (驱动轮转矩) 0 i g i T Tt Tt 2

令:F,=IWTaigionrL-F,TFF1F7F, ~ Fo此图非严格意义的受力图！TractiveForce（汽车驱动力）3Chapter1 AccelerationPerformance

Chapter 1 Acceleration Performance Tractive Force（汽车驱动力） a u Ft F0 FZ W Tt Ft  F0 tq g T 0 t T i i F r   : t t T r 令 F  此图非严格意义的受力图！ r 3

(1)TorqueofEngineEngine maybe characterized by its torque and power curve as a function ofrotate speed. Figure shows typical curves for gasoline enginePemaxtqmaxTorquePowernnnnminmax01ExternalCharacteristic(FullThrottlePerformance)Curveofgasoline汽油发动机外特性曲线4Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance Pemax Ttqmax tq n p n min n nmax External Characteristic (Full Throttle Performance) Curve of gasoline汽油发动机外特性曲线 Torque Power 4 （1）Torque of Engine • Engine maybe characterized by its torque and power curve as a function of rotate speed. Figure shows typical curves for gasoline engine

Full performance andFull performance with all the accessories(外特性与使用外特性）PowerDTorqueFullPerformanceFull Performancewith all.theaccessoriesn(rated rpm)speed(r/min)5Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance Full performance and Full performance with all the accessories (外特性与使用外特性) 5

Useful formulasfor Power calculationUnit:T.:n发动机功率P。[kW]taP。9550发动机转矩Tta[N·m]发动机转速n[r/min]Clew :P,=T.n, Unit: P。[W] ; Ttq [N-m]; n[rad/s]radian：弧度1T..n2元tq1000P =Tn=pX9550, Unit: P。[kW] ; Ttq[N-m]; n[r/min]。tq606Chapter1 AccelerationPerformance

Chapter 1 Acceleration Performance Useful formulas for Power calculation Unit： 发动机功率Pe [kW] 发动机转矩Ttq [N·m] 发动机转速n[r/min] 9550 tq e T n P   Clew : ，Unit：Pe [W] ；Ttq [N·m]；n[rad/s] radian：弧度 , Unit：Pe [kW] ；Ttq[N·m]； n[r/min]。 P T n e tq    2 1000 60 9550 tq e tq e T n P T n P       6

(2)EfficienciesofDriveline(Transmission)传动系统机械效率The necessity of the introduction of nr :The inefficiencies due to mechanical and viscous losses inthe driveline components (gear box, propeller shaft; finaldrive:differential and axles).Theseacttoreducetheenginetorqueinproportiontotheproductsofthe efficienciesoftheindividualcomponents传动系统部件的机械和液力损失是造成的效率降低主要原因。各部分效率的乘积即总的传动系统机械效率。nr (combined efficiency of driveline）consists of four primary parts:Nr = NclutchN final-drivegear-boxpropeller-shaft离合器变速器传动轴主减速器GenerallyNr equal to 0.9~0.92 for a car.nr equal to 0.82~0.85 for a truck or a bus.7Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance （2）Efficiencies of Driveline(Transmission) 传动系统机械效率 • The necessity of the introduction of : The inefficiencies due to mechanical and viscous losses in the driveline components（gear box; propeller shaft; final drive; differential and axles）. These act to reduce the engine torque in proportion to the products of the efficiencies of the individual components. • 传动系统部件的机械和液力损失是造成的效率降低主要原 因。各部分效率的乘积即总的传动系统机械效率。 • （combined efficiency of driveline） consists of four primary parts: 离合器 变速器 传动轴 主减速器 t T clutch propeller sha         gear box final driv    ft e T T Generally, equal to 0.9~0.92 for a car. equal to 0.82~0.85 for a truck or a bus. T T 7

(3) Tire RadiusDefinition:NominalRadius（名义半径、自由半径）：theradiusoftirewithoutload（sparetire备胎radius)StaticLoadedRadius（静力半径）一r：thedistancefrom the center of static tire to the contact point withground under vertical load only.RollingRadius（滚动半径）一r.：theradiuswhichismeasured by S(distance passed by vehicle) and n (rollingnumbers).S=2元r, nC.~r~rn-the total rollingnumbers of this一tireradius.统称车轮半径Cdistance8Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance （3）Tire Radius Definition: • Nominal Radius（名义半径、自由半径）：the radius of tire without load (spare tire 备胎 radius). • Static Loaded Radius（静力半径）— ：the distance from the center of static tire to the contact point with ground under vertical load only. • Rolling Radius（滚动半径）— ： the radius which is measured by S (distance passed by vehicle）and n (rolling numbers). 2 r S r n    s r r r s r r r r   r——tire radius,统称车轮半径 8

（4）GraphofTractiveForce（驱动力图)F～ua. How to make tractive force~vehicle speed characteristicsgraph:1)Mathematical conversionbetween n(Engine revolutionspeed [r/min]) and ua (Vehicle speed [km/h])1n×60×2元r×uu1000LOT22r.nu.=0.377.iog019Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance （4）Graph of Tractive Force(驱动力图) • How to make tractive force～vehicle speed characteristics graph： 1）Mathematical conversion between n (Engine revolution speed [r/min]) and (Vehicle speed [km/h]) 1000 1 60 2 0      r i i n u g a  a u 0 0.377 i i r n u g a    Ft ~ ua u r Tt  9

2) Make the graphTwobasicformulasformakingthegraphTaigionrr·n=0.377uigioMakethetractiveforcelineofeachgear（givenig）ofthevehicle(giveni &givenrandgivennr):.oc Taαnua10Chapter1AccelerationPerformance

Chapter 1 Acceleration Performance 2）Make the graph • Two basic formulas for making the graph: • Make the tractive force line of each gear （given ） of the vehicle（given & given r and given ）：               0 0 0.377 i i r n u r T i i F g a tq g T t  g i 0 i T t tq a F T u n      10