4.2Machineelements inmechanical designThemachine elements commonlyfound inmechanical devices includethe following parts: the belt drives and chain drives, the gears, thewormgear drives,keys,couplings,the bearings (therolling bearing/theplain surface bearing),the screws, thefasteners, the shafts,etc在机械设备中普遍可见的机械元件包括：带传动和链传动，齿轮，蜗轮传动，键，联轴器，轴承（滚动轴承/平面轴承）螺钉紧固件，转轴等
4.2 Machine elements in mechanical design The machine elements commonly found in mechanical devices include the following parts: the belt drives and chain drives, the gears, the wormgear drives, keys, couplings, the bearings (the rolling bearing / the plain surface bearing), the screws, the fasteners, the shafts, etc. 在机械设备中普遍可见的机械元件包括：带传动和链传动，齿轮，蜗轮 传动，键，联轴器，轴承（滚动轴承/平面轴承），螺钉，紧固件，转轴等
4.2Machine elements in mechanical design 4.2.1BeltDrives and ChainDrives4.2.2 Gears and Wormgear Drives4.2.3KeysandCouplings4.2.4Bearings24.2.5Fasteners4.2.6Shaft
4.2.1 Belt Drives and Chain Drives 4.2.2 Gears and Wormgear Drives 4.2.3 Keys and Couplings 4.2.4 Bearings 4.2.5 Fasteners 4.2.6 Shaft 4.2 Machine elements in mechanical design
4.2.1BeltDrives and ChainDrivesSlacksid6AbeltisaflexiblepowerDtransmission element that seatsV,=Beltspeedtightly on a set of pulleys orDTight sidesheaves.Note:皮带是一种柔性的动力传输元件，它D,D,arepitchdiameters紧紧地固定在一组滑轮或带轮上。Fig.4-6.Basic belt drive schematic geometry
4.2.1 Belt Drives and Chain Drives A belt is a flexible power transmission element that seats tightly on a set of pulleys or sheaves . 皮带是一种柔性的动力传输元件，它 紧紧地固定在一组滑轮或带轮上
4.2.1BeltDrivesandChainDrivesAt higher speeds, dynamiceffects such as centrifugal forces, beltwhip, andvibration reduce theeffectiveness of the drive and its life.在高速情况下，动态因素如离心力，带抖动及振动会影响传动效率及寿命。Some belt designs employhigh-strength,reinforcing strands and a coggeddesignthatengages matchinggrooves inthepulleys to enhancetheir abilitytotransmitthehighforces atlow speeds:一些皮带设计采用高强度的加强带绳和嵌齿设计，该设计接合滑轮中的匹配凹槽以增强它们在低速下传递高作用力的能力。Many types of belts are available: flat belts,grooved or cogged belts.standard V-belts,double-angle V-belts, and other.许多种类的带是常用的。比如平带，凹槽或嵌尺带，标准V型带，双角V型带及其他
At higher speeds, dynamic effects such as centrifugal forces, belt whip, and vibration reduce the effectiveness of the drive and its life . 在高速情况下，动态因素，如离心力，带抖动及振动会影响传动效率及寿命。 Some belt designs employ high-strength, reinforcing strands and a cogged design that engages matching grooves in the pulleys to enhance their ability to transmit the high forces at low speeds . 一些皮带设计采用高强度的加强带绳和嵌齿设计，该设计接合滑轮中的匹配凹槽 ，以增强它们在低速下传递高作用力的能力。 Many types of belts are available: flat belts, grooved or cogged belts, standard V-belts, double-angle V-belts, and other. 许多种类的带是常用的，比如平带，凹槽或嵌尺带，标准V型带，双角V型带及其 他。 4.2.1 Belt Drives and Chain Drives
4.2.1BeltDrivesandChainDrivesThe V-shape causes the belt towedgetightly intogroove,GrooveBeltangleride-outincreasing friction and allowinghigh torques to be transmittedTypical belt sectionbefore slipping occurs.and groovegeometryGroovePitchdepthV形使皮带紧紧的楔入轮槽内，增加diameter摩擦，在打滑现象出现前传递较大Sheave的扭矩。outsidediameterFig.4-7.Cross section of V-belt and sheave groove
The V-shape causes the belt to wedge tightly into groove, increasing friction and allowing high torques to be transmitted before slipping occurs. V形使皮带紧紧的楔入轮槽内，增加 摩擦，在打滑现象出现前传递较大 的扭矩。 4.2.1 Belt Drives and Chain Drives