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IP屬地：廣東 上傳時間：2022-08-31 格式：PPT 頁數(shù)：110 大小：1.12MB 積分：15 舉報 版權(quán)申訴

1、第一章汽車動力性Vehicle Performance主要研究內(nèi)容: 分析受力; 建立行駛方程式; 以圖、表(或編程)形式，按照評價指標(biāo)，確定汽車的動力性。定義在平直良好路面上行駛時所能達(dá)到的平均行駛速度。Definition : At the good and straight and even track, the auto driving can reach at the average speed.Main contents:Analysis is subjected to the reactions;Establishing the motion equation of vehicl

2、e;With the form of the diagram, the table or the plait distance), press the vehicle tractive evaluation index, make sure the motion of the vehicle.汽車動力性Veh. Perf.第一章 汽車動力性1.1 汽車動力性評價指標(biāo)1.2 汽車驅(qū)動力和行駛阻力1.3 汽車驅(qū)動力附著條件以及附著力1.4 汽車驅(qū)動力行駛阻力平衡圖1.5 汽車功率平衡1.1 Traction performance evaluation index1.2 Traction forc

3、es and the resistance as vehicle driving1.3 Driving traction force , adhesive condition and its forces1.4 Balance diagram between the traction force & driving resistance1.5 Power balanceVehicle traction performance1.1 汽車動力性評價指標(biāo)最大車速 umax加速時間 t最大爬坡度 imaxIndex Evaluating Vehicle Traction Performance Ma

4、ximum SpeedAcceleration TimeMaximum grade加速時間評價方法超車加速時間 Overtaking acceleration time 以最高檔或次高檔，以amax加速至某一高速所用的時間。原地起步加速時間 The start acceleration time 由I或II檔起步，以amax，并考慮換檔時間，一般用0400m或0100km/h的時間表示原地起步的加速時間。Method evaluating acceleration time 最高車速 Max Speed最高車速，是指汽車在平直的良好道路(混凝土或柏油)上所能達(dá)到的平均最高行駛車速。Max. s

5、peed, means that the vehicle drives on the straight and even and good (concrete or asphalt) roadway can reach at the average and largest speed.汽車加速過程曲線VelocityTimeDiagram of velocity vs timevehicle acceleration history 車速Gear shifting爬坡能力的評價 以滿載、良好路面上的imax來表示: 商用車30或16.5； 越野汽車60或31。 轎車最高車速較大，且通常在良好的

6、市區(qū)道路行駛，其爬坡度很大。對其無這項要求。 有的國家要求汽車在常遇坡道上汽車必須保持的速度來表明其加速能力。The sloping ability evaluationSome nations request the MV on often meeting the road of slope the speed that the MV must keep to expresses that it accelerates the ability.發(fā)動機(jī)傳動系離合器、變速器、分動器、傳動軸、主減速器、半軸驅(qū)動輪驅(qū)動力行駛阻力滾動阻力坡度阻力加速阻力空氣阻力汽車動力傳遞路線：發(fā)動機(jī)離合器變速器副變

7、速器傳動軸主減速器差速器半軸輪邊減速器車輪1.2 汽車驅(qū)動力和行駛阻力1.2 Traction forces and resistances as vehicle driving平衡1.2 汽車驅(qū)動力和行駛阻力Traction force and resistances as vehicle driving驅(qū)動力滾動阻力空氣阻力加速阻力爬坡阻力驅(qū)動轉(zhuǎn)矩行駛阻力發(fā)動機(jī)轉(zhuǎn)矩Traction forcetraction effortdriving force圖1-2 汽車驅(qū)動力MV Traction ForceNormal reactionGravitySpeedRadiusTorque部分負(fù)荷特性

8、：節(jié)氣門部分開啟時，轉(zhuǎn)矩或功率等與轉(zhuǎn)速的關(guān)系使用負(fù)荷特性曲線：即帶有附件時的負(fù)荷特性，通常汽油機(jī)下降15，而柴油機(jī)下降10外特性曲線：節(jié)氣門(油門)全開時，轉(zhuǎn)矩或功率等與轉(zhuǎn)速的關(guān)系發(fā)動機(jī)速度特性full throttle/acceleratorrpm:revolution per minute 圖1-3 汽油發(fā)動機(jī)外特性Braking Power ,kWRevolution, rpmCharacteristic of engine speed at full throttleBraking Torque, .m發(fā)動機(jī)過渡工況的速度特性在過渡工況，功率和轉(zhuǎn)矩均下降約5%6%。Characteri

9、stic of the engine speed in transient conditionIn transient condition, power and torque all descend about 5%-6%.外負(fù)荷特性的使用和制作方法表格法（輔助插值）曲線族法數(shù)學(xué)模型法n1n2n3nnPe1Pe2Pe3PenTt1Tt2Tt3Ttnbe1be2be3benFull-load characteristic diagram methodInterpolation with tableCurvesModeling外特性及負(fù)荷特性數(shù)學(xué)描述Modeling for Full- & par

10、t-load characteristicm7 mopt5Braking Power ,kW圖1-4 汽油發(fā)動機(jī)外特性及部分負(fù)荷特性Characteristic of engine speed at full and part loadengine speed, r/minBraking Torque, N.m發(fā)動機(jī)負(fù)荷特性經(jīng)驗公式Approximation for Full- & part-load characteristic傳動系功率損失機(jī)械損失液力損失摩擦潤滑油齒輪傳動副間摩擦軸承摩擦。潤滑油的攪動潤滑油與零件表面間摩擦。傳動系機(jī)械效率T Transmissions efficienc

11、yPower lossLiquid L.Mecha. L.RubLubr.傳動系機(jī)械效率T Transmissions efficiency損失主要部件: Parts causing to lose 變速器和主減速器(含差速器)損失主要形式: Forms causing to lose 液力損失和機(jī)械摩擦損失 Mechanical loss & liquid loss液力損失,如攪動和磨擦。與潤滑油的性能、溫度、轉(zhuǎn)速、油面高度等有關(guān)。46檔變速器 4-6speed gearbox 0.9668檔變速器 6-8speed gearbox 0.95傳動軸 drive shaft 0.98離合器 C

12、lutch 0.98主減速器 differential 0.96-0.92半軸 semi-shaft 0.99汽車機(jī)械效率 MV mechanical efficiency轎車 Passenger car T=0.900.92商用車 Commercial Veh.T=0.820.85越野車(SUV) 4W drive Veh.T=0.800.85典型的傳動系效率值Typical drive system efficiency某汽車變速器的機(jī)械效率Mechanical efficiency of MV gearbox輪胎半徑r Tire radius自由半徑 r Unloaded radius靜

13、力半徑 rs Static radius with load滾動半徑 rr Dynamic radius with load rr= rs = r=s/(2nw)S行駛距離 trip，n 轉(zhuǎn)動圈數(shù) revolutions歐洲輪胎與輪輞委員會(ETRTO)推薦 rr= Fd/(2) F=3.05 radial F=2.99 bias德國橡膠工業(yè)協(xié)會推薦 CR=CR(1+ua/1000),mmCircumference length輪胎半徑r（mm)車型規(guī)格自由靜力滾動桑塔納2000195/60R1429532685286紅旗CA7228l85/70HRl431232855301奧迪100195/

14、65Rl531732915308躍進(jìn)NJl0617.00-2045244306448解放CA10919.00-2050954856492東風(fēng)EQl0929.R2050954766493黃河JNll8111.00-2054265177525大 小 中定義：用Ft-ua曲線圖來全面地描述汽車的驅(qū)動力。若已知外特性曲線、傳動系速比、傳動系機(jī)械效率、車輪半徑就可求計算驅(qū)動力。汽車驅(qū)動力圖 MV traction force diagramDefinition:Use the Ft-ua curves to describe completely the MV traction force. If on

15、e has already known the full load characteristic curve, transmission , system efficiency and rolling radius, one can calculates the traction forces.轉(zhuǎn)速速度線性變換轉(zhuǎn)矩驅(qū)動力線性變換驅(qū)動力圖制作 Drawing diagram of tractionSp ISp IISp IIITractionMV VelocityMV traction diagram驅(qū)動力汽車行駛阻力滾動阻力Ff :輪胎內(nèi)部摩擦產(chǎn)生的遲滯損失。這種遲滯損失表現(xiàn)為阻礙車輪運動的阻

16、力偶。MV driving resistanceRolling resistance Ff: the tire inner part rub causes to loss, this kind of lose performance shows the resistance moment of the wheel motion.輪胎徑向變形曲線 Tire radius deforming curveDamping loss輪胎/路面接觸輪胎變形載荷遲滯損失阻力偶loadunload從動輪Driven Wheel滾動阻力系數(shù) f rolling resistance coefficient輪胎內(nèi)

17、部因摩擦產(chǎn)生的遲滯損失表現(xiàn)為阻礙車輪運動的阻力偶.The damping loses caused by tire inner inter-rubs are shown as the resistance moment against wheel motion滾動阻力系數(shù):車輪在一定條件下，滾動所需要推力Fp1與負(fù)荷W1之比，即單位重力的推力。Rolling resistance coefficient: wheel under the certain condition rolls over with the ratio of push force Fp1 to weight W1, nam

18、ely push force for the unit gravity .阻力偶一般用滾動阻力描述roll resistance moment is depicted by rolling resistance.滾動阻力無法在受力圖上畫出。它是一個數(shù)值,在受力圖上它是切向反力。Roll resistance cant be drawn in being subjected to the reaction diagram, It is only one value. There is a longitudinal reaction in the force diagram.在實際計算時可不必考慮

19、阻力偶，而用滾動阻力描述。While computing physically need not consider the resistance pair, but use to roll resistance.試驗確定法牽引法、滑行法和轉(zhuǎn)鼓法經(jīng)驗法 通過以往試驗結(jié)果歸納的經(jīng)驗公式滾動阻力系數(shù)的確定方法室內(nèi)試驗道路試驗滾動阻力系數(shù)的影響因素1. 速度 ua 對 f 的影響creating a phenomenon of standing wave, heat, shed off, burst.Effect of velocity ua on resistance coefficient f.駐

20、波彈性輪胎在滾動時，胎面各部份都反復(fù)處于受力變形和恢復(fù)原形的狀態(tài)。這個運動過程使輪胎的變形恢復(fù)到原狀的力有彈力、胎壓和離心力等。輪胎從接地受力變形，到離開地面后恢復(fù)原狀，存在滯后時間。其長短與輪胎負(fù)荷、轉(zhuǎn)速、工作溫度和環(huán)境溫度等有關(guān)。負(fù)荷大，胎面變形大; 轉(zhuǎn)速高，胎面離心力大。離心力使胎面反向變形，這樣胎面在正、反方向力的交替作用下造成不同胎面部位半徑的波動。當(dāng)輪胎行駛速度超過輪胎的撓屈變形極限速度后，此胎面波動看上去變形移動的狀態(tài)恰似停止，稱作駐波。常發(fā)生在胎肩與胎側(cè)交界區(qū)。 2.輪胎結(jié)構(gòu)、材料、簾線對 f 的影響也很大。子午線輪胎 f 小，天然橡膠 f 低。The tire structu

21、re, material, the influence of the lines upon the f is also very big. The meridian tire f is small, the crude rubber f is low.f 經(jīng)驗公式 fit for fCommercial veh.Passenger carPassenger carCommercial veh.While turning normally驅(qū)動輪受力圖Forces reacting on drive wheel切向力Circumferential Force真正驅(qū)動車輪前進(jìn)的力是地面切向反力FX2

22、。其在數(shù)值上等于汽車驅(qū)動力Ft與滾動阻力Ff之差驅(qū)動力與地面縱向（切向）力定義：汽車直線行駛時受到的空氣阻力在汽車行駛方向上的分力。分類：壓力阻力和摩擦阻力壓力阻力由形狀阻力、擾動阻力和誘導(dǎo)阻力組成。形狀阻力主要與汽車的形狀有關(guān)，約占58?？諝庾枇rag or air resistanceCD對高速汽車動力性和燃料經(jīng)濟(jì)性影響極大! 干擾阻力：汽車上的突出部件，如后視鏡、門把手、導(dǎo)水槽、驅(qū)動軸、懸架導(dǎo)向桿等，約占14。 內(nèi)循環(huán)阻力：發(fā)動機(jī)冷卻系、車身通風(fēng)氣流等流過汽車內(nèi)部形成的，占12。 誘導(dǎo)阻力：空氣升力在水平方向的分力，占7。 摩擦阻力：9?？諝庾枇w正比于氣流相對運動的動壓力。Fw的影

23、響因素：CD和A。A由于乘坐空間的制約變化不大,CD變化較大。19501970年為0.40.6,1990年為0.250.40,概念車約為0.2,當(dāng)前 Passat 0.28。1. 前部低 2. 過渡平滑3. 后部加擾流板4. 掠背式(艙背式)5. 底部導(dǎo)流、平整化，向后應(yīng)逐步升高6. 整車俯視形狀為腰鼓式7. 改進(jìn)氣流進(jìn)、出口位置8. 商用車頂(側(cè))部安裝導(dǎo)流罩CD降低的要點降低汽車空氣阻力的基本思路Basic thought for decreasing aerodynamic drag MV坡道阻力grade resistanceRoad resistance coefficientGra

24、de angle 汽車行駛方程式MV motion formulaCorrelation of drive force and driving resistance隔離法：平面受力圖driven tireInsulation method: force diagram with two dimensionsLongitudinal forceNormal forcetangential reactioncircumferential force從動輪受力分析 reaction analysis of the moved tireVertical forceNormal reaction從動輪受

25、力分析（續(xù)）analysis of forces on the moved tire隔離法：受力圖Forces reacting on drive tireInsulation method: force diagram with two dimensions驅(qū)動輪受力分析Forces acting on the tracition tire除以r驅(qū)動輪受力分析(續(xù))Forces on the tracitive tire加速時車身受力圖Force diagram on the body while acceleration車體受力分析 forces on the body飛輪慣性矩Flywh

26、eel inertial車體受力分析 (續(xù)) forces on the body車體受力分析 (續(xù)) forces on the body車體受力分析 (續(xù)) forces pressed on the body汽車行駛方程式_總結(jié) 只是表示各個物理量之間的數(shù)量關(guān)系。 有些項并不是外力。Ft不是作用于車輪上的切向反作用力，僅為了計算方便才定義為驅(qū)動力。 滾動阻力也不是作用于汽車上的阻力，而是以滾動阻力偶矩的形式作用于車輪上。 作用在汽車上的慣性力是mdu/dt，而不是mdu/dt。飛輪慣性力矩作用在汽車的橫截面上，而不作用于車輪上。 Fj 代表慣性力和慣性力矩的總效應(yīng)。1.3 汽車行駛驅(qū)動-

27、附著條件及汽車附著力1.汽車行駛驅(qū)動附著條件Driving traction, adhesive condition and its forceDriving tractionadhesive condition驅(qū)動（行駛）的必要條件:Driving essential condition:the adhesive condition between the tire and ground tire shows the phenomenon of slide revolution on the road 后驅(qū)動汽車Fz2Reaction of ground on traction tire,

28、i.e. It is controlling the second condition that MV drives. generally is the necessary and full conditions that the MV drives.Rear drive MV2. 汽車附著力 MV adhesive force在硬路面上， 主要取決路面的種類和狀況，也與 有關(guān)。On the hard road, it depends mainly on the category and conditions of road surface, also is relevant with the

29、 velocity路面類型 混凝土（干） 混凝土（濕）附著系數(shù) 0.70.8 0.50.6路面類型 碎石 土路（干） 土路（濕）附著系數(shù) 0.60.7 0.50.6 0.20.4L=wheel baseB=wheel track前輪驅(qū)動和后輪驅(qū)動時的地面反力對后輪取矩，得到Torque received on rear tire , givenRoad Reactions on front/rear drive tire對前輪取矩，得到Torque received on front tire, given軸距增加，重心高度小，動載荷減小。良好路面Static load on axleDyna

30、mic load on axle前輪靜載荷 static load front tire 后輪靜載荷static load rear tire Getting from above formulae由此得到For rear drive對于后驅(qū)動后驅(qū)動地面附著力adhesive force of rear driveFor rear drive對于前驅(qū)動前驅(qū)動地面附著力adhesive force of front driveFor 4WD(AWD)Prior conditionThen it can make use of well前輪、后輪驅(qū)動附著利用率For RWDFor FWDUtili

31、zation of MV adhesives while front or rear axle driveUsually for front drive MV , the static load of front axle larger then that of rear axle. The position of the mass center can be determined by means of weighing.附著利用率RWDFWD4WDAdhesive factorAdhesive utilizationAdhesive utilization depending on dri

32、ve type1.4 汽車驅(qū)動力-行駛阻力平衡圖便可分析在附著良好的典型路面上汽車的行駛能力。即在油門全開時，汽車可能達(dá)到最大速度、加速能力和爬坡能力。汽車行駛方程式反映了汽車行駛時，驅(qū)動力和外界阻力之間的普遍情況；若已知1.4 balance Between Traction & driving MV resistanceThe driving equation shows the correlation between the traction and driving resistance when the MV drives. Ifare known, can analyze then

33、the driveability of MV on the good road to face, namely at full acceleration pedal, the MV may attain the max. speed, acceleration ability and grade ability. 驅(qū)動力與行駛阻力平衡圖定義：為了清晰地描述汽車行駛時受力情況及其平衡關(guān)系，通常將平衡方程式用圖解方式描述，即將驅(qū)動力Ft和常見行駛阻力 Fw 和 Ff 繪在同一張圖上。1. 最高速度和部分負(fù)荷時的平衡2. uamax3. 最大爬坡度diagram of the equilibrium

34、 between drive force and driving resistanceDefinition: For describing the automobile to drive clearly be subjected to the reaction and its balance relations, usually draw equilibrium equation to illustrate the way to carry on the description, ie draw the drive force Ft and the driving resistance Fw

35、and Ff in the same diagram.1. max speed and force balance for part load (see next page)2.uamax3. max grade climbing汽車驅(qū)動力行駛阻力平衡圖FtSpeed, ua (km/h)equilibrium between drive force and driving resistancedrive force2. 加速能力，可用aj評價,， 但不方便，常用加速時間或加速距離來評價。加速度倒數(shù)：Acceleration reciprocalAcceleration timeAcceler

36、ation travel汽車加速度速度圖Speed, ua,km/hDiagram of acceleration vs velocity MV ua is different from uAcceleration aj,m/s2加速度倒數(shù)曲線圖1/ajua,Diagram of acceleration reciprocalacceleration reciprocaltSpeed, km/h將驅(qū)動力、滾動阻力和空氣阻力計算出，就可按公式計算加速度及其倒數(shù)，從而求得加速時間或者加速距離。After computing drive force, roll resistance and air

37、resistances, it can be computed the acceleration and its reciprocal according to the formula and get the acceleration time or travel.手工計算時一般忽略原地起步過程的離合器打滑過程，即假設(shè)在最初時刻，汽車已具備起步換檔所需的最低車速。換檔時刻的確定：若I-II加速度曲線相交，規(guī)定在交點處換檔；若I-II的加速度曲線不相交，則規(guī)定在發(fā)動機(jī)最高轉(zhuǎn)速處換檔；換檔時間一般忽略不計（正態(tài)分布t=0.2-0.4s)。計算加速時間的用途：確定汽車加速能力；傳動系匹配情況；合理選

38、擇發(fā)動機(jī)的排量。注意NoticeGenerally when handicraft computes, at first ,the slide of clutch at the start process is neglected, then the assumption is in the first time, the MV has already had the lowest speed that start need when shift gear.Time of shift gear to determine: If the gear 1st- 2nd acceleration cu

39、rves is intersected, then shift gear 1st to 2nd; If the acceleration curves of the gear 1st and 2nd is not intersected, then at max engine speed shift the gear 1st to 2nd; neglect shift gear spending time. (normal distribution t=0.2-0.4 s)Use of computing acceleration time: to determine MV accelerat

40、ion ability, trade-off power-train; reasonably choose displacement of the engine.3. 利用驅(qū)動力行駛阻力平衡圖確定汽車爬坡能力Its prior condition is a road surface good, except overcoming the Fw+ Ff ,all drive force is used for overcoming a grade resistance, namely.Diagram of equilibrium of drive force - driving resistan

41、ce to determine grade ability of MV其前提條件是路面良好，汽車克服Fw+Ff后的全部力都用于克服坡道阻力，即坡度通常用i表示i represents grade usuallyMV gradient iSpeed, km/himax is max sloping gradient for 1st gear.i0max is max sloping gradient for top gear.Objective: decreasing the number of shift on normal slope, which makes the speed of MV

42、 slowly down. 二、動力特性圖評價汽車動力性unit drive force to evaluate MV tractive performanceNormalized drive forcedrive factorCharacteristic of normalized drive force and its use汽車動力特性圖及其用途To solve imax ,let While MV acceleration, the road must be flatness. i.e.1.5 汽車功率平衡 MV power balance 汽車在行駛時驅(qū)動力與阻力平衡 發(fā)動機(jī)輸出功率也與行駛阻力功率平衡定義：用縱坐標(biāo)表示功率，橫坐標(biāo)表示車速，將發(fā)動機(jī)功率與經(jīng)常遇到的阻力功率對車速的關(guān)系繪制在直角坐標(biāo)圖上，就得到功率平衡圖。The traction and resistance balances when the MV drivesThe engine power output also balances with the driving resistance power. Definition: let vertical coordinate as the power, horizontal coordinate as MV speed, draw diag