上帝充通大￥ Shanghai Jiao Tong University Mechanical Design and Manufacturing II Power/Energy Transmission ll: Belt Drives(带传动)
1 Mechanical Design and Manufacturing II Power/Energy Transmission II: Belt Drives（带传动）
上淄克通大学 Shanghai Jiao Tong University Lectures Power/Energy Conversion (Electrical Motors) Power/Energy Transmission (Gears,Cams,Linkages, Belt Drives, Power Screws) Transmission Joints (Fasteners, Support (Bearings) Structural Connectors) Support (Frames) Tools Statics,Dynamics, Stress Analysis,etc.. 2
2 Lectures Power/Energy Conversion (Electrical Motors) Power/Energy Transmission (Gears, Cams, Linkages, Belt Drives, Power Screws) Transmission Support (Bearings) Joints (Fasteners, Connectors) Structural Support (Frames) Tools Statics, Dynamics, Stress Analysis, etc
上泽充通大学 Shanghai Jiao Tong University Basic Belt Drives2 Fo .A belt drive is a flexible power transmission element that seats tightly on a set of pulleys(带轮) >Sometimes called sheaves .When used for speed reduction,the smaller sheave is mounted on the high-speed shaft >e.g.shaft of an electric motor .Larger sheave is mounted on driven machine. .Belt is installed by placing it around the two sheaves while center distance between them is reduced. .Then the sheaves are moved apart placing the belt in high initial tension(初拉力). 3
3 Basic Belt Drives2 •A belt drive is a flexible power transmission element that seats tightly on a set of pulleys（带轮） Sometimes called sheaves •When used for speed reduction, the smaller sheave is mounted on the high-speed shaft e.g. shaft of an electric motor •Larger sheave is mounted on driven machine. •Belt is installed by placing it around the two sheaves while center distance between them is reduced. •Then the sheaves are moved apart placing the belt in high initial tension（初拉力）
上泽充通大学 Shanghai Jiao Tong University Basic Belt Drives2 .When transmitting power,the driving sheave rotates,friction causes driving sheave to grip the belt,increasing the tension on one side,called“tight side”(紧边)of drive. Opposite side of belt is still under tension,but at a smaller value,called“slack side”(松边)of drive. .The difference between the tensile forces of two sides in belt exerts a tangential force on the driven sheave and thus a torque is applied to the driven shaft via friction force. F2 Slack side Tight side Fy B2 F
4 Basic Belt Drives2 •When transmitting power, the driving sheave rotates, friction causes driving sheave to grip the belt, increasing the tension on one side, called ―tight side‖ (紧边) of drive. •Opposite side of belt is still under tension, but at a smaller value, called ―slack side‖ (松边) of drive. •The difference between the tensile forces of two sides in belt exerts a tangential force on the driven sheave and thus a torque is applied to the driven shaft via friction force
上帝充通大￥ Shanghai Jiao Tong University Basic Belt Drives2 Slack side D vo=Belt speed Tight side Note:D1.D2 are B2 pitch diameters Groove Belt angle ride-out d101/2=d202/2 Typical belt section 01/o2=d2/d speed ratio and groove geometry Pitch Groove diameter depth power=C so T1@1=T2 @2 Sheave outside diameter 01/02=T2/T1 Figure 13-4 Cross Section of V-belt and Sheave Groove d=Pitch diameter,diameter belt appears to ride without slipping Note:slip and creep present,so not exactly equal to ratio 5
5 Basic Belt Drives2 d1 ω1 /2 = d2 ω 2 /2 ω1 / ω 2 = d2 / d1 = speed ratio power = C so T1 ω1 =T2 ω 2 ω1 / ω 2 = T2 / T1 d =Pitch diameter, diameter belt appears to ride without slipping Note: slip and creep present, so not exactly equal to ratio