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1、Gear trains review,n1=-n3=120 rpm,nH=600 rpm,Determine nH,Differentials,Direction of rotation,Gear trains Differential,adding machine,Differentials,A differential is a device that allows a difference in velocity between in two elements,Gear trains differentials,Driving power form Z5 z1 and z3 rotate
2、 uniformlyb)If resistance is met in z1 z3 will be faster than z1,Gear trains Differentials,Gear trains Differential,Gear trains Differentials,Gear trains Differentials,Construction differentials,Gear trains powertain,Case 1:A=1（离合器工作）,B=0nH directly output=?n3=0Case2:A=0,B=1n30,n3 Arm,input n4=n1 is
3、 given,n4=n1,Gear trains powertrain,Gear trains powertain,3-speed automobile transmission1st:z5,z6 meshing z3,z4 separation A,B separation2nd:z3,z4 meshing z5,z6 separation A,B separation3th:A,B meshing z3,z4 separation z5,z6 separation4thBack z6,z8 meshing A,B separation z3,z4 separation z5,z6 sepa
4、ration,Power in,output,Transmission in automobile,Better choice that spur gears are used in the case,Gear trains powertrain,Gear trains powertrain,1,8,Consider:Speed ratio in the first case and the second case?,Cam Design Gears in machine tool,Power transmission system in machine tool,Cam Design Gea
5、rs in machine tool,Speed ratio diagram of power transmission system in machine tool,Cam Design Gears in machine tool,Gear trains APPLICATIONS,Cam Design Efficiency,The general definition of efficiency is=output power/input power Efficiency of a conventional gear train is very high.power loss per gea
6、rset 12%1)the external gearset；=0.982)An external-internal gearset:=0.993）two stages gearset=1*24)Loss estimation,Efficiency of gear trains,For epicyclic trains,the efficiency is dependent on design,f is the friction coefficient,5)Helical gearset=9698%,cross helical gearset=5090%,Cam Design efficien
7、cy,Efficiency of epicycle gearTorques balance T1+T2+TH=02)Power in=power out from shaft1 to shaft2（=+1）E0T1(1-H)+T2(2-H)=0,Obtain the torques ratio through(1)(2),Cam Design efficiency,Let gear 2 is fixed,2=0,the from gear1 to arm HThe efficiency is that,because,and,therefore,See case 5,Cam Design ef
8、ficiency,b)from ARM to shaft1（=-1）,If 2=0 the gear 2 is fixed，power from H to 1,Because,See the case 6,Cam Design efficiency,Determine the efficiency form gear2 to arm,Because 1=0,therefore,1,=-1,case7,Cam Design efficiency,=+1,Efficiency from gear1 to arm,=-1,Cam Design efficiency,1,2,H,Z1=99,Zg=25
9、,Zg=25,z2=100E0=0.98Determine the overall efficiency,solution,H1,=-1,Cam Design Gear train,Example in p.308Consider the same Fergusons paradox train as the following figure,which has the following tooth numbers and initial conditionsSun gear#2 N2=100Sun gear#3 N3=99Sun gear#4 N4=101Planet gear N5=20
10、Input to sun gear#2 0 prmInput to arm 100 prm counterclockwise,Cam Design Gear train,Cam Design Gear train,-.,2=0,solution,=,Cam Design Gear train,4,SOLUTION,Two teeth difference,but output will big difference,Cam Design HOME WORK,Give z1=z3=17,z2=z4=39,z5=18,z7=152,n1=1450 rpmA is loosing,B is brak
11、ing(switch on)Determine rotation speed nH,2)Give n1=3549 rpm,Z1=36,z2=60,z3=23,z4=49Z4=69,z5=31,z6=131,z7=94,z8=36,z9=167Determine output speed nH,Cam Design HELICAL GEAR,3)Write calculation velocity formula in the epicycle train in Figure 9-35(l-k),Gear trains home work,3-speed automobile transmiss
12、ion1st:z5,z6 meshing z3,z4 separation A,B separation2nd:z3,z4 meshing z5,z6 separation A,B separation3th:A,B meshing z3,z4 separation z5,z6 separation4thBack z6,z8 meshing A,B separation z3,z4 separation z5,z6 separation,Power in,output,Write all speed ratio(1st4th)in the transmission,4),Cam Design HOME WORK,5)Give a pair of helical gear parameters z1=20,z2=40,mn=8,n=20,=15oDetermine the distance between gear and pinion,the diameter of addendum circle.,
