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1、汽车底盘构造 变速器与分动器,主讲孟庆雨,第一节 变速器的功用和类型,功用：（1）改变传动比，扩大驱动轮转矩和转速的变化范围，以适应经常变化的行驶条件，使发动机在有利的工况下工作。（2）在发动机旋转方向不变的前提下，使汽车倒退行驶。（3）利用空档中断动力传递，以使发动机能够起动、怠速，并便于变速器换档或进行动力输出。,1.变速器的功用和组成,2.变速器的类型,1）按传动比变化方式不同：有级式变速器；用齿轮传动，有若干个定值传动比无级式变速器：采用电力或液力变矩器传动，传动比可在一定的数值范围内连续变化。综合式变速器：由液力变矩器和行星齿轮式变速器组成，传动比可在几个范围内连续变化。2）按操纵方
2、式不同：强制操纵式：靠驾驶员直接操纵变速杆换档。自动操纵式：换档自动进行。半自动操纵式：常用的几个档位自动操纵；预选式,变速器组成,变速传动机构：改变转速比、改变转矩、改变方向,操纵机构：实现换档,3.变速器的组成,变速传动机构（按传动齿轮轴数）,三轴式齿轮变速传动,两轴式齿轮变速传动,第二节 变速器的变速传动机构,一、有级式变速器变速传动机构的组成、工作原理和常见的换档方式,1.变速传动机构的组成变速传动机构主要由齿轮、轴及变速器壳体等零部件组成。,第二节 变速器的变速传动机构,2.变速传动机构的工作原理 1）利用不同齿数的齿轮对相互啮合，以改变变速器的传动比；i12=n1/n2=z2/z1
3、=M2/M1z1，n1，M1为主动齿轮的参数。z2，n2，M2为从动齿轮的参数。,从动轮2,主动轮1,i,=,主动齿轮齿数,从动齿轮齿数,Gears,Gears are used to multiply either torque or speed as power is transferred from one shaft to another.In this case the gear ratio is 40 20 or 2:1.The blue gear will have twice the torque but one-half the speed as the green gear
4、.,Input:20 Teeth,Output:40 Teeth,Gear Types,The most common gear types are Spur(left)and Helical(right)gears.Spur gears have the teeth cut parallel to the shaft.The teeth of a helical gear are cut at an angle.A helical gear runs quieter,costs more,and generates a side thrust under load.,Spur Gears,H
5、elical Gears,2）通过增加齿轮传动的对数，以实现倒档。,Idler Gears,An Idler gear(orange)can be put in a gear train to reverse direction of rotation.A simple idler,as shown,will not change the gear ratio.In this case,the gear ratio is 40(blue output gear)divided by 20(green input gear)=2:1,and both the input and output r
6、otate clockwise.,Clockwise Rotation,Idler Gear,Counterclockwise Rotation,3常见的换档方式（1）利用滑动齿轮换档 冲击、噪声、损坏齿端面、舒适性降低。倒挡常用。（2）利用接合套换档 同时承受换档冲击的齿数多，轮齿不参与换档，不会发生早期损坏。不能消除换档冲击。（3）利用同步器换档 迅速、无冲击、无噪声换档；与熟练程度无关。加速性、经济性和行驶安全性提高。,二、两轴式变速器Manual Transaxle Operation,Purpose,A manual transaxle is used in many FWD veh
7、icles.It provides various gear ratios that are necessary to transfer power from the engine and clutch to the drive shafts and wheels.,To Clutch,To Drive shaft,Construction,Most transaxles have three major shafts:an input shaft that connects to the clutch disc with the driving gears,a main/intermedia
8、te shaft with the driven gears,andthe output shaft with the differential,Input Shaft,Intermediate Shaft,Output:Final Drive&Differential,Bearings,A pair of tapered roller bearings(orange)are used to support each of the two major shafts and differential.This type of bearing allows the shaft to rotate
9、freely,but eliminates any end play.Some transmissions use ball bearings for this same purpose.,优点：直径较小；宽度较大；容量大；可承受高负荷；三元件基本位置关系能使滚子正确对中，轴承可靠性和寿命提高；轴和齿轮的刚度提高，齿轮噪声降低，减少脱档可能。,Speed Gears&Synchronizers,A synchronizer assembly normally has a speed gear positioned on each side of it.The speed gears float
10、 on the shaft.The synchronizer sleeve engages the clutching teeth of the speed gear to transfer its motion to the shaft.,1st,4th 3rd,Rev.5th 2nd,Fixed Gears,One of the gears,either the driving or driven gear,for each gear ratio is fixed solidly to one of the shafts.It meshes with a speed gear to pro
11、vide the proper gear ratio.,Rev.5th 2nd 1st,4th 3rd,Shifting Gears,A rather complex mechanism connects the gear shift lever to the shift forks inside the transaxle.The shift forks move the synchronizer sleeves to make the shifts from one gear range to another.,To Shift Lever,Shift Fork,Neutral,If ea
12、ch of the synchronizers assemblies is in neutral and the reverse idler gear is not in mesh,power is not able to get from the input shaft to the intermediate shaft.The input shaft and the speed gears can rotate,but the intermediate shaft will not be driven.,All synchros.are in neutral,center position
13、,1st Gear,This is the lowest gear ratio with the smallest gear on the input shaft driving the largest gear on the intermediate shaft.In this example a 12 tooth gear drives a 42 tooth gear.42 12=3.50,1st Gear,Driving,1st Gear,Driven,1-2 Synchro.,Shifted to 1st,2nd Gear,The 1-2 synchronizer is moved t
14、o engage the 2nd speed gear.Now a 14 tooth gear drives a 35 tooth gear.The ratio is:35 14=2.50,2nd Gear,Driving,2nd Gear,Driven,1-2 Synchro.,Shifted to 2nd,3rd Gear,With the 1-2 synchronizer in neutral,the 3-4 synchronizer is moved to engage the 17 tooth speed gear.It drives a 21 tooth gear.The rati
15、o is 21 17=1.24:1.,3rd Gear,Driving,3rd Gear,Driven,3-4 Synchro.,Shifted to 3rd,4th Gear,The 3-4 synchronizer is moved to engage the 19 tooth speed gear that is drives an 18 tooth gear.The ratio is 18 19=0.95:1.Note that this is an overdrive ratio so the intermediate shaft will rotate faster than th
16、e input shaft.,4th Gear,Driving,4th Gear,Driven,3-4 Synchro.Shifted to 4th,5th Gear,The 5th gear synchronizer is moved to engage the 15 tooth 5th speed gear.It is driven by a 20 tooth gear so the ratio is 15 20=0.75:1,another overdrive ratio.,5th Gear,Driving,5th Gear,Driven,5-Rev Synchro.Shifted to
17、 5th,Reverse,The 5-Reverse synchro.is shifted into mesh with the 42 tooth Rev.speed gear.A 12 tooth Rev.Gear drives it.The idler gear is used to change the direction of rotation.The ratio is 42 12=3.50:1,Rev.Gear,Driving,Rev.Gear,Driven,5-Rev.Synchro.Shifted to Rev.,Rev.Idler Gear,Other Reverse Type
18、s,Some transaxles construct the 1-2 synchronizer sleeve with the reverse gear teeth surrounding it.The reverse idler gear is shifted into mesh with the reverse drive gear and the driven gear on the synchro.Sleeve.This is difficult to illustrate because the idler gear and shaft are positioned behind
19、the other gears.,Rev.Idler Gear,Rev.Drive Gear,1-2 Synchro.+1st&2nd Speed Gears,Rev.Driven Gear,Input Shaft,Final Drive,A 20 tooth gear on the intermediate shaft drives the 80 tooth ring gear on the differential.Power is transferred from the ring gear to the differential case and through the differe
20、ntial gears to the CV joints and front driveshafts.The ratio is 80 20=4:1,Pinion Gear,Ring Gear,Diff.Side GearDiff.Pinion Gear,CV Joint,Overall Ratios,The overall ratio between the engine and the drive wheels is effected by both gear ratios.These ratios become:1st gear:3.50 X 4=14:1 2nd gear:2.50 X
21、4=10:1 3rd Gear:1.24 X 4=4.96:1 4th Gear:0.95 X 4=3.80:15th Gear:0.75 X 4=3:1 Reverse:3.50 X 4=14:1,二、两轴式变速器,应用：FF RR 特点：输入轴与输出轴平行，无中间轴。组成：输入轴、输出轴、倒档轴、轴承、变速齿轮,桑塔纳轿车变速器结构简图,桑塔纳轿车两轴式变速器,结构分析：一轴：一、二档齿轮与轴一体；三、四档齿轮与轴通过轴承空套轴上。二轴：一、二档齿轮与通过轴承连接；三、四档齿轮与轴一体。,一、二档传动路线,三、四档传动路线,倒档传动路线,三、三轴式变速器,三轴是指汽车前进时，传递动力的轴有
22、第一轴、中间轴和第二轴，直接档除外。,换档原理,一轴,中间轴,二轴,三轴式变速器结构图,四、防止自动跳档的措施,（1）切薄齿式利用接合套换档的变速器，由于接合套与齿圈的接合长度较短，同时汽车行驶时需要经常换档，频繁拨动接合套将使齿端发生磨损。汽车行驶中可能会因振动等原因造成接合套与齿圈脱离啮合，即发生自动跳档。,（2）斜面齿式,结合齿圈,结合套齿,花键毂,结合齿圈,传动方向,接合套和接合齿圈的齿端制成倒斜面,（3）接合套的齿端制成凸肩,五、组合式变速器,5-Speed Manual Transmission,Purpose,A manual transmission is used in ma
23、ny RWD and 4WD vehicles.It provides the various gear ratios that are necessary to transfer power from the engine and clutch to the drive shafts and wheels.,Engine Clutch Transmission Driveshaft Drive Axle,Construction,Manual transmissions have three major shafts:an input shaft/main drive gear that c
24、onnects to the clutch disc,a counter shaft that is commonly called a cluster gear,and the main shaft/output shaft with the driven gears and synchronizers.,Main Shaft,Input Shaft,Cluster Gear,Bearings,The main drive gear and main shaft are each supported by a ball or roller bearing with a pilot beari
25、ng where the main shaft fits into the main drive gear.The cluster gear is supported by a pair of bearings.These bearings are colored orange.,Cluster Gear Bearings,Main shaft bearing,Pilot Bearing,Main Drive Gear Bearing,Speed Gears&Synchronizers,A synchronizer assembly normally has two speed gears,o
26、ne on each side of it.The speed gears float on the main shaft.The synchronizer sleeve engages the clutching teeth of a speed gear to transfer its motion to the shaft.,1-2 Synchro.,3-4 Synchro.,5-Rev.Synchro.,3rd Speed Gear,2nd Speed Gear,5th Speed Gear,1st Speed Gear,Reverse Speed Gear,6-Speed Main
27、Shaft,3-4 Synchro.1-2 Synchro.5-6 Driven Gear Rev.Synchro.Output,Speed Gear Journals:,3rd 2nd 1st Reverse,This mainshaft has 3 splined areas that connect to the synchronizer hubs,a set of splines for the 5-6 fixed/driven gear,1 set of output splines for the drive shaft slip joint.And 4 smooth journa
28、ls for the speed gears.,Fixed Gears,The main drive gear and cluster gears are normally made as part of their shaft.These are the driving gears for each of the gear ranges.,Shifting Gears,Most SUV and pickup transmissions incorporate the shift mechanism into the the top of the unit.Movement of the ge
29、ar shit lever will move one of the shift forks connected to the synchronizer sleeve.,Shift Lever,Shift Rail,Shift Fork,Shift Detents,Most detents are spring-loaded balls(red)that are pushed into one of two or three notches in a shift rail or cam.They are used to hold the shift rail in an exact posit
30、ion which places the synchro.sleeve or gear in an exact position.The center shift rail detents are in back of the rail.,Detent Ball Detent Spring,Shift Rail Shift Fork,Shift Interlocks,This 5-speed transmission has three shift rails that transmit motion from the shift lever to the shift forks.When o
31、ne of the rails is moved from neutral,the plugs are moved sideways to lock the other rails in place,Shift Rails,Plug Pin Plug,Neutral,If each of the synchronizers assemblies is in neutral and the reverse idler gear is not in mesh,power is not able to get from the speed gears to the main shaft.The in
32、put shaft,cluster gear,and speed gears rotate but not the main shaft.,All Synchros.In neutral,center position,Neutral,In neutral with the clutch engaged,the input shaft will spin,but there will be no power transferred.,Input from clutch,Output to drive shaft,Neutral power flow,5-Speed gearbox,Double
33、 Reduction,Manual transmission gear ratios are effected by two gear sets.The first(input)is the ratio between the main drive gear and cluster gear.The second is the ratio between the drive and driven gears for each gear range.,15 Tooth Main Drive Gear,20 Tooth Cluster Gear,1st Gears,Input reduction:
34、20 15=1.33:1 Reduction,1st Gears:3:1 1st Gear Ratio:1.3 X 3=3.9:1,1st Gear,The 1-2 synchronizer is moved to engage the clutching teeth on the 45 tooth 1st speed gear.It is driven by a 15 tooth gear on the cluster gear.The 1st gear ratio is 3.9:1.,1-2 Synchro.Shifted to 1st,1st Speed Gear,Driven,1st
35、Gear,Driving,2nd Gear,The 1-2 synchronizer is moved to engage the 40 tooth,2nd speed gear.It is driven by a 20 tooth gear on the cluster gear.The cluster to main shaft ratio is 1.3:1,and the 2nd gear ratio is 2:1 X 1.3:1=2.6:1.,2nd Speed Gear,Driven,2nd Gear,Driving,1-2 Synchro.Shifted to 2nd,3rd Ge
36、ar,The 3-4 synchronizer is moved to engage the 20 tooth 3rd speed gear.It is driven be a 15 tooth gear on the cluster gear.The gear ratio is:1.3:1 X 1.3:1=1.69:1.,3-4 Synchro.Shifted to 3rd,3rd Gear,Driving,3rd Gear,Driven,4th Gear,The 3-4 synchronizer is moved to engage the clutching teeth on the m
37、ain drive gear.Power is transmitted directly to the main shaft so the ratio is 1:1,direct drive.,3-4 Synchro.Shifted to 4th,Main Drive Gear,Main Shaft,5th Gear,The 5-Rev.synchronizer is moved to engage the 20 tooth 5th speed gear.It is driven by a 30 tooth gear that is part of the cluster gear.The r
38、atio is 0.66:1 X 1.3:1=0.86:1,5th Gear,Driving,5-Rev.Synchro Shifted to 5th,5th Gear,Driven,Other 5th Gear Types,The 5th driving gear in this transmission is a speed gear mounted on the cluster gear along with the 5th gear synchronizer.The 5th driven gear is attached to the mainshaft.,5th Driven Gea
39、r,5th Gear Synchronizer,5th Speed Gear,Reverse,The 5-Reverse synchro.is shifted into mesh with the 45 tooth Rev.speed gear.A 15 tooth Rev.gear on the cluster drives it through the Rev.idler gear.The idler gear is used to change the direction of rotation.The reverse gear ratio is 3:1 X 1.3:1=3.9:1.,5
40、-Rev.Synchro.Shifted to Rev.,Rev.Gear,Driving,Rev.Idler Gear,Rev.Gear,Driven,Rev.Gear,Driven,Other Reverse Types,Some 4&5 speed transmissions use a reverse driven gear that surrounds the 1-2 synchronizer sleeve.The reverse idler gear(mounted behind the other gears)is shifted into mesh with the rever
41、se driving gear on the cluster gear and the reverse driven gear.All three of these gears are spur gears.,Reverse Driven Gear,Reverse Drive Gear,Reverse Idler Gear,第三节 同步器,无同步器时变速器的换档过程,1、从低档换入高档脱离瞬间：V4=VJ V5VJ、V4 保持空档片刻 V5降低，VJ、V4变化不大 在VJ与V5相等时挂入五档,2、从高档换入低档,脱离瞬间：V5=VJ V4VJ、V5 抬起离合器踏板，踩一下油门踏板，V4升高，V
42、J变化不大 在VJ与V4相等时挂入四档,四档工作：V3=V4，欲换档踩离合器接合套左移处空挡,两直线的交点为同步状态，此时挂档不会产生冲击,第二节：同步器,（一）低档换高档,一、无同步器换档过程,（二）高档换低档,五档工作时：V3=V2，因V2V4V3V4,空档时：V4比V3下降得快，直线V3、V4不会有交点，不可能达到自然同步状态，驾驶员应在变速器退到空档后，立即抬起离合器，同时踩加速踏板，使发动机连同离合器和第一轴都从B点升速，让V4V3，再踩离合器等到V3=V4，可以换档。,二、同步器构造及工作原理,1、功用：使结合套与待啮合齿圈迅速同步，缩短换档时间，同时防止啮合时齿间冲击。2、结构：
43、结合套、花键榖、对应齿轮上的结合齿圈、同步装置、锁止装置。3、同步器分类：常压式、惯性式、自增力式 惯性式同步器分类：锁环式惯性同步器 锁销式惯性同步器,1.锁环式惯性同步器,r为锁止面平均半径；为锁止面锁止角;R摩擦锥面平均半径;锥面半锥角,锁环式惯性同步器,结构,滑块,锁环,结合齿圈,原理,2.锁销式惯性同步器,摩擦锥盘,摩擦锥环,定位销,结合套,钢球,定位销,锁销,直径较大的摩擦锥面，可产生较大摩擦力矩缩短同步时间。,锁销受力,锁止角,Synchronizer Operation,Synchronizers,This 5-speed transaxle has 3 synchronize
44、r assemblies.Each one has a neutral and two other gear positions.,3-4 Synchro.Assembly,1-2 Synchro.Assembly,5-Rev Synchro.Assembly,Synchronizer Components,Input Shaft,3-4 Synchro.,Blocker Rings,Speed Gears with Needle Bearings,The hub of this 3-4 synchronizer is splined onto the input shaft The 3rd
45、and 4th speed gears fit over the needle bearings and the input shaft.This input shaft also has driving gears for 1st,2nd,and reverse.,Synchronizer Assembly,Exploded View,This synchronizer assembly has been taken apart to show the major parts.Most synchronizers have 3 or 4 struts.,Energizer Springs,H
46、ub,Sleeve,Key/Strut/Insert,Synchronizer Hub,The keys(green)and energizer springs(red)fit into the hub so the springs will exert an outward pressure on the keys.Note the splines on the inside of the hub to connect with the shaft.,Synchronizer Assembly,Assembled View,The sleeve(orange)can slide on the
47、 hub(grey).The keys(green)are pushed outward,against the sleeve by the energizer springs(red).,Synchronizer Sleeve,Two important features of a synchronizer sleeve are the neutral detent notch around the center of the splines and the spline lock back taper at the ends of each spline.The neutral deten
48、t notch engages the hump on the keys.A complete shift places the back taper along side of the clutch teeth back taper.,Back Taper,Neutral Detent Notch,Speed Gears,A speed gear has teeth(blue)that drive or are driven by another gear.It also has clutching teeth(green)that engage the synchronizer sleev
49、e,a smooth cone surface(orange)for the blocker ring,and a smooth inner bore(yellow)for the gear to rotate on.,Clutching Teeth,Cone,Blocker Rings,A blocker ring is also called a synchronizer ring or stop ring.A 1-piece,metal blocker ring is used in most older transmissions.Note the grooves(circled)an
50、d threads on the inner surface to remove the lubricant from the speed gear cone.The blocker ring floats in the synchronizer assembly and is driven by the keys,positioned in the three notches(red,triple arrow).,3-Piece Blocker Rings,Outer Blocker Ring,Intermediate Cone,Speed Gear,Inner Blocker Ring,S
