汽车底盘构造—变速器2012.ppt
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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
2、化。 2)按操纵方式不同: 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
3、; i12=n1/n2= z2/z1= M2/M1 z1 ,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-hal
4、f the speed as the green gear.,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 generate
5、s a side thrust under load.,Spur Gears,Helical 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 (gre
6、en input gear) = 2:1, and both the input and output rotate 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 O
7、peration,Purpose,A manual transaxle is used in many FWD vehicles. 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 connect
8、s to the clutch disc with the driving gears, a main/intermediate shaft with the driven gears, and the 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 sha
9、fts and differential. This type of bearing allows the shaft to rotate 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 nor
10、mally has a speed gear positioned on each side of it. The speed gears float 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
11、 ratio is fixed solidly to one of the shafts. It meshes with a speed gear to provide 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
12、the shifts from one gear range to another.,To Shift Lever,Shift Fork,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 input shaft to the intermediate shaft. The input shaft and the speed gears can rotate, but t
13、he intermediate shaft will not be driven.,All synchros. are in neutral, center position,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,
14、Driving,1st Gear, Driven,1-2 Synchro., Shifted to 1st,2nd Gear,The 1-2 synchronizer is moved to 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 neut
15、ral, the 3-4 synchronizer is moved to engage the 17 tooth speed gear. It drives a 21 tooth gear. The ratio 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
16、ratio is 18 19 = 0.95:1. Note that this is an overdrive ratio so the intermediate shaft will rotate faster than the 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 toot
17、h gear so the ratio is 15 20 = 0.75:1, another overdrive ratio.,5th Gear, Driving,5th Gear, Driven,5-Rev Synchro. Shifted to 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 ro
18、tation. 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 Types,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
19、drive gear and the driven gear on the synchro. Sleeve. This is difficult to illustrate because the idler gear and shaft are positioned behind 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 intermed
20、iate shaft drives the 80 tooth ring gear on the differential. Power is transferred from the ring gear to the differential case and through the differential gears to the CV joints and front driveshafts. The ratio is 80 20 = 4:1,Pinion Gear,Ring Gear,Diff. Side Gear Diff. Pinion Gear,CV Joint,Overall
21、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 4 = 10:1 3rd Gear: 1.24 X 4 = 4.96:1 4th Gear: 0.95 X 4 = 3.80:1 5th 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:
22、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
23、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 many RWD and 4WD vehicles. It provides the various gear ratios that are necessary to transfer power from the engine an
24、d 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 connects to the clutch disc, a counter shaft that is commonly called a cluster gear, and the main shaft/output sha
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