Gear and gearbox_2018

1Gear & GearboxMotion drivingChange speed ratioReverse orientation Prepared by: Wilson Wang2018-07-30•Part 1: Classification of Gears •Part 2: Common Gearbox•Part 3: Material selection•Part 4: Measurement &Inspection •Part 5: Common Problems •Questions•Spur •Helical •Worm •Bevel •CrownSpur Gear•General Characteristic:–Majority of gears are spur.–Relatively easy to designand make.–Parallel shaft.–High efficiency.–Can back drive.Spur Gear -Internal •GeneralCharacteristic :–Similar performance tonormal spur–Results in compactdrive geometry.–Typical model : Epicycle/ Planetary gears.Spur Gear -Rack •GeneralCharacteristic:–Transit rotary motion tolinear motion.–Proportional constantvelocity.–Material select on POM(stiff); Nylon (Tough)Helical Gear•General Characteristic :–Single Helical have similarproperties to spur.–Drive results in axial thrust.–Smoother / quieter for same size / spec.–Can run high speed, highertorque / life capabilities forsame size as spur.Worm Gear•General Characteristic :–Offset shafts at 90Degree.–Very high ratiospossible in singlestage.–Low efficiency athigher ratios and lowspeed.–Cannot drive back.Bevel Gear•GeneralCharacteristic:–Drive transmissionthrough 90 degree.–Only low ratiosused. (4:1 and less)–Not used on highduty high speedapplication.Crown Gear•Battery operated motor gearbox •Mechanical Driven gearbox (Non Battery type)•Wind up type•Pull back type•Friction type•Press and go type•Battery operated gearbox•Motion Driven by Wind up mechanism•Motion Driven by Pullbackmechanism•Motion Driven by Press and Gorelease mechanism•Motion Driven by Friction Push (Flywheel) mechanism•Mechanical Driven (Non Battery type)Type ofCommon ApplicationMechanismWind up Walking, Car running, ClimbingPull back Car runningPress and Go Car runningFriction Car running•Acetal (POM)•Nylon (PA)•HytrelComparison on Material type of GearsRemarks: Best 1 to Good 3, Easy 1 to Difficult 3.•Gearbox key characteristics–Target specification(Key parameters)Setting the target before start the design1) Dimension2) Output Torque3) Noise Requirement4) Life cycle5) Current draw1Aesthetics1.1Aesthetics insepction(注件不满,齿崩,缺齿,飞边,翘曲、气泡、凹陷等)Visual/CCD2Main Dimension2.1Dimension 1:齿顶(齿根)圆直径二次元/卡尺(偶数齿)2.2Dimension 2:孔径/轴径二次元/塞规2.3Dimension 3:齿厚齿轮卡尺2.4Dimension 4:齿宽卡尺2.5Dimension 5:偏心度*啮合机3Main Gear Precision3.1Precision 1:齿轮齿形齿向误差齿形齿筋测量仪3.2Precision 2:齿轮径向跳动误差齿形齿筋测量仪或啮合机(master gear)3.3Precision 3:齿轮切向综合误差啮合机(master gear)3.4Precision 4:齿轮径向综合误差啮合机(master gear)4Reliability and function4.1play function after assembly by hand4.2gear noise db meter4.3product life homemade fixture Main inspection pointsMain Equipment齿形齿筋测量仪Main Equipment啮合机(master gear)Basic parameterM=d/zBasic parameterBasic parameterBasic parameterBasic parameter•General problems1.Noise2.Torque3.Speed4.Gear break5.Life6.Aesthetics注件不满,齿崩,缺齿,飞边,翘曲、气泡、凹陷等Points to be considered on gearbox performanceTroublePossible faultFunctionLife NoiseCurrent Torque Speed Gear break 1Alignment of centerdistanceToo loosesYes X Yes X Yes Yes Too tight Yes Yes Yes YesYes Yes 2Clutch force adjustmentToo weakX X Yes X X X Too high XX X X YesX 3Gear damagelittleYes Yes X X X Yes largeYesYesYesYesYesYes4Over loadingYesYes Yes Yes X Yes 5LubricationExcessX Yes X Yes X X Not enoughYes Yes Yes Yes Yes Yes 6Interference of gearYesYesYesYesYesYes•How to achieve an Ideal Gearbox?–Design–Tool fabrication–Injection–Inspection•Key issue: Noise and vibrationQ:How to reduce the source of noise &vibration?a.Soft material as a motor pinion, because thehigher speed over there. (reduce motor noisefirst)b.High concentricity between Shaft and gearc.Proper lubricantd.Less speed ratio between level 1 and level 2 geare.Shape of gear toothf.Center distance ,a=m(z1+z2)/2+0.3mg.Unsealed gearbox•Key issue: LubricationQ : How much viscosity is suitable?Lubrication advantage is reduce friction and noise, but the side effect is tocause the current draw get higher.Case study -1•Design toleranceCase study -1•Design Tolerance–Case is no room for make the gear larger andstrong when the torque requirement for theproduct increase 10% during the EP stage.•Actions–Redesign the gearbox and rebuild all the tooling,lost the money and project delay.•Solution for future–Reserve design allowance: reserve the room forfurther development around 30% to 50% atDFMEA.Case Study –2•Material selectionBackground:Incorrect shaftmaterial(Nylon) wasused due tounderestimated thetorque there. The gearfailed torque test ,andthen change to POMwith tightenedassembly for solution.•Design based on torqueThanks!。