关 键 词：

戴晓 cad

资源描述：

078105206戴晓思带CAD图,戴晓,cad

内容简介：

单级圆柱齿轮减速器复合形法fortran优化源程序C = PROGRAM COMPLEC = DIMENSION X(25),GX(50),XCOM(1250) COMMON /ONE/ ITE,IXE,ILI,NPE,NFX,NGR READ(*,*) N,KG,K WRITE(*,10001) N,KG,K10001FORMAT(25X,= PRIMARY DATA =/5X, 1 N=,I4,5X,KG=,I4,5X,K=,I4) CALL MAISUB(N,K,KG,X,GX,XCOM) STOP ENDC = SUBROUTINE MAISUB(N,K,KG,X,GX,XCOM)C = DIMENSION X(N),GX(KG),XCOM(N,K),FXK(50),XR(25) DIMENSION XO(25),XH(25),XL(25),BL(25),BU(25) COMMON /ONE/ ITE,IXE,ILI,NPE,NFX,NGR COMMON /TWO/ ISE READ(*,*) (X(I),I=1,N) READ(*,*) EPS READ(*,*) KWR,ISE READ(*,*) (BL(I),I=1,N),(BU(I),I=1,N) WRITE(*,1010) (BL(I),I=1,N) WRITE(*,1015) (BU(I),I=1,N) WRITE(*,1020) EPS1010FORMAT( BL:/(5X,5E15.6)1015FORMAT( BU:/(5X,5E15.6)1020FORMAT(5X,EPS=,E10.2) ITE=0 NFX=0 IXE=0 RM=2657863.01025CALL PRICOM(N,K,KG,X,GX,XCOM,FXK,BL,BU,RM) IF(KWR.LT.0) GOTO 1041 WRITE(*,1030)1030FORMAT(/25X,= PRIMARY COMPLEX =/) WRITE(*,1080) K DO 1031 L=1,K WRITE(*,1085) L,(XCOM(I,L),I=1,N)1031CONTINUE WRITE(*,1035) (FXK(I),I=1,K)1035FORMAT(4X,FXK:/(5X,5E15.6)1041WRITE(*,1042)1042FORMAT(/25X,= ITEATION COMPUTE =/)1045ITE=ITE+1 CALL FXSEGU(N,K,XCOM,FXK) DO 1050 I=1,N1050XL(I)=XCOM(I,K) FXL=FXK(K) SDX=0.0 DO 1055 I=1,K-11055SDX=SDX+(FXL-FXK(I)*2 =SQRT(SDX/FLOAT(K-1) IF(SDX.LE.EPS) GOTO 1210 IF(KWR.GT.0) GOTO 1056 IF(ITE/10*10.NE.ITE) GOTO 10901056WRITE(*,1060) ITE,FXL IF(KWR.LT.0) GOTO 1090 WRITE(*,1065) (XL(I),I=1,N) WRITE(*,1070) FXL WRITE(*,1075) (GX(I),I=1,KG) WRITE(*,1035) (FXK(I),I=1,K)1060FORMAT(/1X,* ITE=,I4,5X,FXL=,E15.7)1065FORMAT( X :/(5X,5E15.6)1070FORMAT( FX:/(5X,5E15.6)1075FORMAT( GX:/(5X,5E15.6)1080FORMAT( XCOM: (K=,I3,)1085FORMAT(2X,I2/(5X,5E15.6)1090LH=11095DO 1100 I=1,N1100XH(I)=XCOM(I,LH) FXH=FXK(LH) CALL XCENTE(N,K,K,LH,XO,XCOM) CALL FFX(N,XO,FXO) CALL GGX(N,KG,XO,GX) DO 1105 J=1,KG IF(GX(J).GE.0.0) GOTO 11701105CONTINUE1140PHI=1.31145DO 1150 I=1,N1150XR(I)=XO(I)+PHI*(XO(I)-XH(I) CALL FFX(N,XR,FXR) CALL GGX(N,KG,XR,GX) DO 1151 J=1,KG IF(GX(J).GE.0.0) GOTO 11521151CONTINUE GOTO 11551152PHI=0.5*PHI GOTO 11451155IF(FXR.LT.FXH) GOTO 1160 IF(PHI.LE.1E-10) GOTO 1195 PHI=0.5*PHI GOTO 11451160DO 1165 I=1,N1165XCOM(I,LH)=XR(I) FXK(LH)=FXR GOTO 10451170DO 1175 I=1,N BL(I)=XL(I) BU(I)=XO(I)1175CONTINUE DO 1180 I=1,N1180X(I)=XL(I) ISE=1 GOTO 10251195LH=LH+1 WRITE(*,1200) LH1200FORMAT(1X,* LH=,I2,*) IF(LH.LE.K/2) GOTO 1095 WRITE(*,1205)1205FORMAT(/25X,* ITERTION ABORTIVE */) GOTO 12201210WRITE(*,1215)1215FORMAT(/25X,= OPTIMUM SOLUTION =/)1220WRITE(*,1225) ITE,NFX,IXE1225FORMAT( ITE=,I5, NFX=,I5 IXE=,I5) WRITE(*,1065) (XL(I),I=1,N) WRITE(*,1070) FXL WRITE(*,1075) (GX(I),I=1,KG) RETURN ENDC = SUBROUTINE PRICOM(N,K,KG,X,GX,XCOM,FXK,BL,BU,RM)C = DIMENSION X(N),XO(25),BL(N),BU(N),GX(KG),XCOM(N,K),FXK(K) COMMON /TWO/ ISE2020IF(ISE) 2025,2050,20752025WRITE(*,2019)2019FORMAT(5X,READ XCOM (FORMAT: * ) READ(*,*) (XCOM(I,J),I=1,N),J=1,K) DO 2045 L=1,K DO 2030 I=1,N2030X(I)=XCOM(I,L) CALL FFX(N,X,FXK(L) CALL GGX(N,KG,X,GX) DO 2031 J=1,KG IF(GX(J).GE.0.0) GOTO 20752031CONTINUE2045CONTINUE RETURN2050CALL FFX(N,X,FXK(1) CALL GGX(N,KG,X,GX) DO 2051 L=1,KG IF(GX(L).GE.0.0) GOTO 20752051CONTINUE GOTO 20952075DO 2080 I=1,N CALL RANDOM(RM,Q)2080X(I)=BL(I)+Q*(BU(I)-BL(I) CALL FFX(N,X,FXK(1) CALL GGX(N,KG,X,GX) DO 2081 L=1,KG IF(GX(L).GE.0.0) GOTO 20752081CONTINUE2095DO 2100 I=1,N2100XCOM(I,1)=X(I) DO 2110 L=2,K DO 2105 I=1,N CALL RANDOM(RM,Q) XCOM(I,L)=BL(I)+Q*(BU(I)-BL(I)2105CONTINUE2110CONTINUE LH=0 DO 2155 LL=1,K-1 LL2=LL CALL XCENTE(N,K,LL2,LH,XO,XCOM) CALL FFX(N,XO,FXO) CALL GGX(N,KG,X,GX) DO 2111 L=1,KG IF(GX(L).GE.0.0) GOTO 20752111CONTINUE2115CONTINUE LL1=LL+1 DO 2120 I=1,N2120X(I)=XCOM(I,LL1)2125CALL FFX(N,X,FXK(LL1) CALL GGX(N,KG,X,GX) DO 2126 L=1,KG IF(GX(L).GE.0.0) GOTO 21452126CONTINUE DO 2140 I=1,N2140XCOM(I,LL1)=X(I)GOTO 21552145DO 2150 I=1,N2150X(I)=XO(I)+0.5*(X(I)-XO(I)GOTO 21252155CONTINUERETURN ENDC =SUBROUTINE FXSEGU(N,K,XCOM,FXK)C =DIMENSION X(25),XCOM(N,K),FXK(K)DO 3010 L=1,K-1KL=K-LDO 3005 LP=1,KLLP1=LP+1IF(FXK(LP).GT.FXK(LP1) GOTO 3005W=FXK(LP)FXK(LP)=FXK(LP1)FXK(LP1)=WDO 3000 I=1,NX(I)=XCOM(I,LP)XCOM(I,LP)=XCOM(I,LP1)3000XCOM(I,LP1)=X(I)3005CONTINUE3010CONTINUERETURNENDC = SUBROUTINE XCENTE(N,K,LL,LH,XO,XCOM)C = DIMENSION XO(N),XCOM(N,K) COMMON /ONE/ ITE,IXE,ILI,NPE,NFX,NGR IXE=IXE+1 DO 4015 I=1,N XS=0.0DO 4000 L=1,LL IF(L.EQ.LH) GOTO 4000XS=XS+XCOM(I,L)4000CONTINUEIF(LH) 4010,4010,40054005XO(I)=XS/FLOAT(LL-1)GOTO 40154010XO(I)=XS/FLOAT(LL)4015CONTINUERETURNENDSUBROUTINE RANDOM(RM,Q) C =C =RM35=2.0*35RM36=2.0*RM35RM37=2.0*RM36RM =5.0*RMIF(RM.GE.RM37) RM=RM-RM37IF(RM.GE.RM36) RM=RM-RM36IF(RM.GE.RM35) RM=RM-RM35Q=RM/RM35RETURN END学士学位论文原创性声明本人声明，所呈交的论文是本人在导师的指导下独立完成的研究成果。除了文中特别加以标注引用的内容外，本论文不包含法律意义上已属于他人的任何形式的研究成果,也不包含本人已用于其他学位申请的论文或成果。对本文的研究作出重要贡献的个人和集体，均已在文中以明确方式表明。本人完全意识到本声明的法律后果由本人承担。作者签名： 日期：学位论文版权使用授权书本学位论文作者完全了解学校有关保留、使用学位论文的规定，同意学校保留并向国家有关部门或机构送交论文的复印件和电子版，允许论文被查阅和借阅。本人授权南昌航空大学科技学院可以将本论文的全部或部分内容编入有关数据库进行检索，可以采用影印、缩印或扫描等复制手段保存和汇编本学位论文。 作者签名： 日期：导师签名： 日期：一、选题的依据及意义：随着社会的发展和人民生活水平的提高，人们对产品的需求是多样化的，这就决定了未来的生产方式趋向多品种、小批量。在各行各业中十分广泛地使用着齿轮减速器，它是一种不可缺少的机械传动装置. 它是机械设备的重要组成部分和核心部件。目前，国内各类通用减速器的标准系列已达数百个，基本可满足各行业对通用减速器的需求。国内减速器行业重点骨干企业的产品品种、规格及参数覆盖范围近几年都在不断扩展，产品质量已达到国外先进工业国家同类产品水平，承担起为国民经济各行业提供传动装置配套的重任，部分产品还出口至欧美及东南亚地区，推动了中国装配制造业发展。圆柱齿轮减速器是一种使用非常广泛的机械传动装置。减速器是用于原动机与工作机之间的独立的传动装置，用来降低转速和增大转矩，以满足工作需要。在现代机械中应用极为广泛，具有品种多、批量小、更新换代快的特点。目前生产的各种类型的减速器还存在着体积大、重量重、承载能力低、成本高和使用寿命短等问题，与国外先进产品相比还有较大的差距。对减速器进行优化设计，选择最佳参数是提高承载能力、减轻重量和降低成本等各项指标的一种重要途径。 目的： 通过设计熟悉机器的具体操作，增强感性认识和社会适应能力，进一步巩固、 深化已学过的理论知识，提高综合运用所学知识发现问题、解决问题的能力。学习机械设计的一般方法，掌握通用机械零件、机械传动装置或简单机械的设计原理和过程。对所学技能的训练，例如：计算、绘图、查阅设计资料和手册，运用标准和规范等。学会利用多种手段(工具)解决问题，如：在本设计中可选择CAD等制图工具。了解减速器内部齿轮间的传动关系。意义： 通过设计，培养学生理论联系实际的工作作风，提高分析问题、解决问题的独立工作能力；通过实习，加深学生对专业的理解和认识，为进一步开拓专业知识创造条件，锻炼动手动脑能力，通过实践运用巩固了所学知识，加深了解其基本原理二、国内外研究概况及发展趋势（含文献综述）：1、国外减速器技术发展简况齿轮减速器在各行各业中十分广泛地使用着，是一种不可缺少的机械传动装置。当前减速器普遍存在着体积大、重量大，或者传动比大而机械效率过低的问题。国外的减速器，以德国、丹麦和日本处于领先地位，特别在材料和制造工艺方面占据优势，减速器工作可靠性好，使用寿命长。但其传动形式仍以定轴齿轮传动为主，体积和重量问题，也未解决好。最近报导，日本住友重工研制的FA型高精度减速器，美国Alan-Newton公司研制的X-Y式减速器，在传动原理和结构上与本项目类似或相近，都为目前先进的齿轮减速器。当今的减速器是向着大功率、大传动比、小体积、高机械效率以及使用寿命长的方向发展。因此，除了不断改进材料品质、提高工艺水平外，还在传动原理和传动结构上深入探讨和创新，平动齿轮传动原理的出现就是一例。减速器与电动机的连体结构，也是大力开拓的形式，并已生产多种结构形式和多种功率型号的产品。目前，超小型的减速器的研究成果尚不明显。在医疗、生物工程、机器人等领域中，微型发动机已基本研制成功，美国和荷兰近期研制的分子发动机的尺寸在纳米级范围，如能辅以纳米级的减速器，则应用前景远大。2、国内减速器技术发展简况国内的减速器多以齿轮传动、蜗杆传动为主，但普遍存在着功率与重量比小，或者传动比大而机械效率过低的问题。另外，材料品质和工艺水平上还有许多弱点，特别是大型的减速器问题更突出，使用寿命不长。国内使用的大型减速器(500kw以上)，多从国外(如丹麦、德国等)进口，花去不少的外汇。60年代开始生产的少齿差传动、摆线针轮传动、谐波传动等减速器具有传动比大，体积小、机械效率高等优点?。但受其传动的理论的限制，不能传递过大的功率，功率一般都要小于40kw。由于在传动的理论上、工艺水平和材料品质方面没有突破，因此，没能从根本上解决传递功率大、传动比大、体积小、重量轻、机械效率高等这些基本要求。90年代初期，国内出现的三环(齿轮)减速器，是一种外平动齿轮传动的减速器，它可实现较大的传动比，传递载荷的能力也大。它的体积和重量都比定轴齿轮减速器轻，结构简单，效率亦高。由于该减速器的三轴平行结构，故使功率/体积(或重量)比值仍小。且其输入轴与输出轴不在同一轴线上，这在使用上有许多不便。北京理工大学研制成功的内平动齿轮减速器不仅具有三环减速器的优点外，还有着大的功率/重量(或体积)比值，以及输入轴和输出轴在同一轴线上的优点，处于国内领先地位。国内有少数高等学校和厂矿企业对平动齿轮传动中的某些原理做些研究工作，发表过一些研究论文，在利用摆线齿轮作平动减速器开展了一些工作。二、平动齿轮减速器工作原理简介,平动齿轮减速器是指一对齿轮传动中，一个齿轮在平动发生器的驱动下作平面平行运动，通过齿廓间的啮合，驱动另一个齿轮作定轴减速转动，实现减速传动的作用。平动发生器可采用平行四边形机构，或正弦机构或十字滑块机构。本成果采用平行四边形机构作为平动发生器。平动发生器可以是虚拟的采用平行四边形机构，也可以是实体的采用平行四边形机构。有实用价值的平动齿轮机构为内啮合齿轮机构，因此又可以分为内齿轮作平动运动和外齿轮作平动运动两种情况。外平动齿轮减速机构，其内齿轮作平动运动，驱动外齿轮并作减速转动输出。该机构亦称三环(齿轮)减速器。由于内齿轮作平动，两曲柄中心设置在内齿轮的齿圈外部，故其尺寸不紧凑，不能解决体积较大的问题。?内平动齿轮减速，其外齿轮作平动运动，驱动内齿轮作减速转动输出。由于外齿轮作平动，两曲柄中心能设置在外齿轮的齿圈内部，大大减少了机构整体尺寸。由于内平动齿轮机构传动效率高、体积小、输入输出同轴线，故由广泛的应用前景。? 三、本项目的技术特点与关键技术? 1.本项目的技术特点,本新型的内平动齿轮减速器与国内外已有的齿轮减速器相比较，有如下特点：(1)传动比范围大，自I=10起，最大可达几千。若制作成大传动比的减速器，则更显示出本减速器的优点。(2)传递功率范围大：并可与电动机联成一体制造。(3)结构简单、体积小、重量轻。比现有的齿轮减速器减少1/3左右。(4)机械效率高。啮合效率大于95%，整机效率在85%以上，且减速器的效率将不随传动比的增大而降低，这是别的许多减速器所不及的。 (5)本减速器的输入轴和输出轴是在同一轴线上三、研究内容及实验方案：研究内容： 1.采用复合形法，以体积最小为目标进行减速器优化设计；2.与常规设计结果进行比较分析，3.绘制减速器装配图及主要零件图。实验方案：1. 收集有关资料写开题报告 2. 以减速器体积最小为目标函数建立优化设计的数学模型 3采用复合型法编写优化设计程序、计算 4. 计算减速器各项尺寸，并进行结果分析 5. 运用UG绘制减速器装配图及主要零件图 6. 翻译外文资料7.撰写毕业设计论文 四、目标、主要特色及工作进度目标：本课题以减速器体积最小为目标函数，设计减速器的最优参数， 绘制减速器装配图及主要零件图。主要特色：减速器体积小，重量轻，承载能力提高，降低成本工作进度：1. 收集资料、开题报告、外文翻译 3，01-3.212. 建立优化设计的数学模型 3.22-4.043编写优化设计程序、计算 4.05-5.094. 减速器常规设计计算、结果分析 5.09-5.235. 绘制减速器装配图及主要零件图 5.24-6.136. 撰写毕业设计论文 6.14-6.277. 答辩准备及论文答辩 6.28-7.02五、参考文献【1】璞良贵，纪名刚主编.机械设计.第八版.北京：高等教育出版社，2007【2】孙靖民主编.机械优化设计.第三版.北京：机械工业出版社，2005【3】方世杰，綦耀光主编.机械优化设计.北京：机械工业出版社，1997.2【4】王昆等主编. 机械设计课程设计手册.北京：机械工业出版社，2004【5】刘瑞新，洪远征等编著.Visual Basic 程序设计教程.第二版. 北京：机械工业出版社，2006【6】杨黎明主编.机械零件设计手册.北京：国防工业出版社，1996【7】刘瑞新，洪远征等编著.Visual Basic 程序设计教程上机指导及习题解答.第二版. 北京：机械工业出版社，2006【8】郑贞平，喻德主编.UG NX5中文版三维设计与NC加工实例精解. 北京：机械工业出版社，2008【9】Carrol, R., and Johnson, G.,“Optimal design of compact spur gear sets”, ASME Journal of mechanisms, transmissions and automation in design. Vol.106, No.1, March 1984, pp.95-101复合形法减速器优化设计学生姓名: 戴晓思 班级: 078105206指导老师: 朱保利摘要：圆柱齿轮减速器是一种使用非常广泛的机械传动装置。减速器是用于原动机与工作机之间的独立的传动装置，用来降低转速和增大转矩，以满足工作需要。在现代机械中应用极为广泛，具有品种多、批量小、更新换代快的特点。目前生产的各种类型的减速器还存在着体积大、重量重、承载能力低、成本高和使用寿命短等问题，与国外先进产品相比还有较大的差距。对减速器进行优化设计，选择最佳参数是提高承载能力、减轻重量和降低成本等各项指标的一种重要途径。单级圆柱齿轮减速器优化设计主要是通过计算机辅助设计，利用fortran语言进行编程优化。本课题以减速器最大尺寸最小或重量最轻为目标函数，设计减速器的最优参数，研究内容：采用复合形法，以体积最小为目标进行减速器优化设计，与常规设计结果进行比较分析，绘制减速器3d装配图及主要零件图此次设计的减速器与常规设计比较具有体积小，重量轻，结构紧凑，成本低等问题。编程方法简单，能够很好的达到优化效果，能够运用到工程实际中去。关键字： 单级圆柱齿轮减速器、优化设计、fortran、复合型法、体积、 3d设计指导教师签名：optimal design of reliability for the single-stage helical cylinder gear reducerStudent name: Dai Xiaosi Class：0781052Supervisor: Professor Zhu BaoliAbstract: The wheels gear is a very extensive use of automatic transmission. gear is used for the original motion and the work of the independence of the transmission that is used to reduce speed and torques increase in turn, need to work. in modern machinery used in a wide variety and quantity of small and fast. the upgrading of the production of various kinds of gear have a great volume and weight bearing ability, heavy and low cost and high and use a shorter life span, And advanced product compare there is a large gap. the gear design and optimize the choice of the parameter is to improve the bearing ability, lighten the weight and reduce costs for all the way.This column with the main gear design is a computer-aided design and optimize the use of fortran programming language. this subject in order to gear the maximum size to the weight or the light of objective function, the design of gear and study the contents of a composite image ：, to save the goal of gear design and optimize the conventional design a comparative analysis, gear and main parts of the assembly drawingThe design of gear and conventional design are a small volume, light weight, compact structure, low cost etc. a programming method is simple to very good to achieve the effect can be applied to the actual.Keyword: A homopolar bevel gear speed reducer optimizing design fortran complex method volume 3d designSignature of conductor: ELEMENTS OF CAM DESIGNHow to plan and produce simple but efficient cams for petrol engines and other mechanismsCams are among the most versatile mechanisms availableA cam is a simple two-member deviceThe input member is the cam itself，while the output member is called the followerThrough the use of cams，a simple input motion can be modified into almost any conceivable output motion that is desiredSome of the common applications of cams areCamshaft and distributor shaft of automotive engine Production machine toolsAutomatic record playersPrinting machinesAutomatic washing machinesAutomatic dishwashersThe contour of high-speed cams (cam speed in excess of 1000 rpm) must be determined mathematicallyHowever，the vast majority of cams operate at low speeds(less than 500 rpm) or medium-speed cams can be determined graphically using a large-scale layoutIn general，the greater the cam speed and output load，the greater must be the precision with which the cam contour is machinedCams in some form or other are essential to the operation of many kinds of mechanical devices. Their best-known application is in the valve-operating gear of internal combustion engines, but they play an equally important part in industrial machinery, from printing presses to reaping machines. In general, a cam can be defined as a projection on the face of a disc or the surface of a cylinder for the purpose of producing intermittent reciprocating motion of a contacting member or follower. Most cams operate by rotary motion, but this is not an essential condition and in special cases the motion may be semi-rotary， oscillatory or swinging. Even straight-line motion of the operating member is possible, though the term cam may not be considered properly applicable in such circumstances. Most text books on mechanics give some information on the design of cams and show examples of cam forms plotted to produce various orders of motion. Where neither the operating speed nor the mechanical duty is very high, there is a good deal of latitude in the nermissible design of the cam and it is only necessary to avoid excessively steep contours or abrupt changes which would result in noise, impact shock, and side pressure on the follower. But, with increase of either speed or load, much more exacting demands are made on the cam, calling for the most careful design and, at very high speed, the effect of inertia on the moving parts is most pronounced, so that the further factors of acceleration and rate of lift have to be taken into account and these are rarely dealt with in any detail in the standard text books. The design of the cam follower is also of great importance and bears a definite relation to the shape of the cam itself. This is because the cam cannot make contact with the follower at a single fixed point. Surface contact is necessary to distribute load and avoid excess wear, thus the cam transmits its motion through various points of location on the follower, depending on the shape of the two complementary members. The cams for operating i.c. engine valves present specially difficult problems in design. In the case of racing engines, both the load and speed may be regarded as extreme, because in many engines the rate at which the valves can be effectively controlled is the limiting factor in engine performance. In some respects, cam design of miniature engines is simplified by reason of their lighter working parts (and consequent less inertia) but on the other hand, working friction is usually greater and rotational speeds are generally considerably higher than in full-size practice.In the many designs for small four-stroke engines which I have published, I have sought to simplify valve operation and to provide designs for cams which can be simply and accurately produced with the facilities of the amateur workshop. Numerous engine designs which have been submitted to me by readers have contained errors in the valve gear and particularly in the cams and in view of prevalent misconceptions in the fundamental principles of these items, I am giving some advice on the matter which I trust will help individual designers to obtain the best results from their engines. There have been many engines built with cams of thoroughly bad design but which, in spite of this, have produced results more or less satisfactory to their constructors. It may be said that within certain limits of speed one can get away with murder but in no case can an engine perform efficiently with badly designed cams, or indeed errors in any of its working details. This article is concerned mainly with the design of cams for operating the valves of i.c. engines and, in order to avoid any confusion of terms, Fig. 1 shows the various parts of a cam of this type and explains their functions. The circular, concentric portion of the cam, which has no operative effect, is known as the base circle: the humy of the cam (shown shaded) is known as the lobe, and the flanks on either side rise from the base circle to the nose, which is usually rounded.Lift may be defined as the difference between the radius of the base circle and that of the nose. the anele enclosed between the points where the flanks join the base circle is termed the angular period, representing the proportion of the full cycle during which the cam operates the valve gear. In Fig. 2, typical examples of cams used in i.c. engines are illustrated. The tangent cam, A, has dead straight flanks-which as the name implies form tangents to the base circle. This type of cam is easy to design and produce, the simplest method of machining being by a circular milling process forming a concentric surface on the base circle and running straight out tangentially where the flanks start and finish. It can also be produced by filing and I have in the past described how to make it with the aid of a roller filing rest in the lathe, in conjunction with indexing gear to locate the flank angles. Tangent cams can only work efficiently in conjunction with a convex curved follower, as this is the only way in which the flank can be brought progressively and smoothly into action. Some time ago an engine was described having tangent cams in conjunction with flat followers. This was not intended for extremely high speed and very likely produced all the power required of it, but it is quite clear that the flat face of the tangent cam. On engaging the flat tappet-over the full length of the flank all at once, must produce an abrupt slapping action which is noisy, inefficient and destructive in the long run. Rollers are often used as followers with tangent cams and are satisfactory in respect of their shape, but the idea of introducing rolling motion at this point is not as good as it seems at first sight, because it merely transfers the sliding friction to a much smaller area-that of the pivot pin. It is possible in some cases, however, to use a ball or roller race for the follower and this, at any rate, has the merit of distributing and equalizing the wearing surface.Tangent cams have been used with a certain degree of success for high-performance-engines and were at one time popular on racing motorcycle engines, though usually with some slight modification of shape-often “ designed ” by the tuner with the aid of .a Carborundum slip! Their more common application, however, has been on gas and oil engines running at relatively slow speeds, where they work well in contact with rollers attached to the ends of the valve rockers. Cams with convex flanks are extensively used in motor cars and other mass-produced engines. One important advantage in this respect is that they are suited to manufacture in quantity by a copying process from accurately formed master cams. The fact that hat-based tappets can be used also favours quantity production and they can be designed to work fairly silently. The contour of the flank can be plotted so that violent changes in the acceleration of the cam are avoided and, more important still, the tappet will follow the cam on the return motion without any tendency to bounce or float at quite high speeds. In such cases, it may be necessary to introduce compound curves which are extremely difficult to copy on a small scale, but cams made with flanks formmg true circular arcs will give reasonably efficient results, and are very easily produced in any scale: Concave-flanked cams. Comparatively few examples of concave-flanked cams (Fig. 2c) are to be seen nowadays, though they have been used extensively in the past with the idea of obtaining the most rapid opening and closing of the valves. Theoretically, they can be designed to produce consant-acceleration, but in practice they render valve control very difficult at high speed and their fierce angle of attack produces heavy side pressure on the tappet. The concave flank must always have a substantially greater radius than the follower, or a slapping action like that of a tangent cam on a flat follower is produced. The shape of the nose in most types of cams is dictated mainly by the need to decelerate the follower as smoothly as possible. It is one thing to design it in such a way that ideal conditions are obtained, and quite another to ensure in practice that the follower retains close contact with the cam. If the radius of the nose is too small, the follower will bounce and come down heavily on the return flank of the cam and,. if too great, valve opening efficiency will be reduced. Of the three types of cams, A, B and C, which all have identically equal lift and angular period, the lobe of B encloses the smallest area, and on first sight it might appear that it is the least efficient in producing adequate valve opening, or mean lift area, but owing to the use of a flat based tappet, its lift characteristics are not very different from those of a tangent cam with round-based tappet, and not necessarily inferior to those of a concave-flank cam. Unsymmetrical cams It is not common to make the two flanks of a cam of different contours to produce some particular result which the designer may consider desirable. In some cases, the object is to produce rapid opening and gradual closing, but sometimes the opposite effect is preferred. When all things are considered, however, most attempts to monkey about with cam forms lead to complications which may actually defeat their own object, at least at really high speeds. In many engines, particularly those of motorcycles, the cams operate the valves through levers or rockers which move in an arc instead of in a straight line, as in the orthodox motor car tappet. This may be mechanically efficient, but it modifies the lift characteristic of the cam, as the point at which the latter transmits motion to the follower varies in relation to the radius of the lever arm, (Fig. 3). With the cam rotating in a clockwise direction, the effective length of the lever will be greater in the position. A during valve opening than in position B during closing, as indicated by dimensions X and Y. This amounts to the same as using an unsymmetrical cam, and in the example shown, would result in slow opening and rapid closing of the valve, or vice versa if either the direction of rotation of the cam, or the relative “ hand ” of the lever, is reversed. The shorter the lever, the greater the discrepancy in the rate of movement, Neither the unsymmetrical cam form nor the pivoted lever is condemned as bad design, but I have sought to avoid them in most of the engines I have designed because they are a complicating factor in what is already a very involved problem, and by keeping to fairly simple cams and straight-line tappets, one can be assured that there are not too many snags. The employment of cams with flanks of true circular arc has enabled me to devise means of producing them on the lathe without elaborate attachments and, what is more important still, to produce an entire set of cams for a multi-cylinder engine in correct angular relation to each other by equally simple means. There is no doubt whatever that these methods have enabled many engine constructors (some without previous experience) to tackle successfully a problem which would otherwise have been formidable, to say the least. Many designers have attempted to improve valve efficiency by designing cams which hold the valve at maximum opening for as long a period as possible. This is done by providing dwell or, in other words, making the top of the lobe concentric with the cam axis over a certain angular distance in the centre of its lift. To do this, however, it is necessary to make the flanks excessively steep, thus producing heavy side thrust on the tappet, and making control at high speed more difficult, (Fig. 4A). A little consideration, however, will show that the same result can be achieved, with much less mechanical difficulty, by lifting the valve somewhat higher at an easier rate, as shown at B. This avoids the need for sudden acceleration and deceleration of the tappet and promotes flow efficiency of the valve. The shaded portions of the two cams show the differences in the area of the lobe, showing that nothing is really gained by the dwell. Factors in efficiency High valve lift is a desirable feature, but only if it can be obtained without making extra dificulties in controlling the valve. The maximum port area of a valve is obtained when the lift is equal to one-fourth of the seat diameter, but owing to the baffling effect on the valve head, a higher lift is better for flow efficiency-if it is practicable. Large diameter valves will obviously release and admit gas efficiently but they are more difficult to control and keep cool at high speed than smaller valves. Another point is that the exhaust valve is required to open against a high cylinder pressure, and the larger it is the more the load imposed on the cam, quite apart from the spring load.凸轮设计的基本内容如何为汽油发动机和其他机械设计和生产简单而有效的凸轮 凸轮是被应用的最广泛的机械结构之一。凸轮是一种仅仅有两个组件构成的设备。主动件本身就是凸轮，而输出件被称为从动件。通过使用凸轮，一个简单的输入动作可以被修改成几乎可以想像得到的任何输出运动。常见的一些关于凸轮应用的例子有：凸轮轴和汽车发动机工程的装配专用机床自动电唱机印刷机自动的洗衣机自动的洗碗机高速凸轮(凸轮超过1000 rpm的速度)的轮廓必须从数学意义上来定义。无论如何，大多数凸轮以低速(少于500 rpm)运行而中速的凸轮可以通过一个大比例的图形表示出来。一般说来，凸轮的速度和输出负载越大，凸轮的轮廓在被床上被加工时就一定要更加精密。在多种机械装置的操作中凸轮在某种形式下是必不可少。他们最有名的应用是在内燃机阀门操作装置中，但在工业机器中，从印刷机到收割机械，凸轮机构也是一个相当重要的一部分。 一般来说，一个凸轮可以被定义为一个圆盘面或一个为产生接触间歇往复运动的零件或从动件。大多数凸轮的运动是旋转运动，但这不是一个必要条件，在特殊情况下，它的运动是半旋转，振动或摆动。即使原动件可能是直线运动，但在某种情况下凸轮也可能会适当地被考虑，。 在机构学大多数文本书籍中给了关于凸轮设计和凸轮类型的实例设计的一些信息，产生各种规定的运动。在某种情况运行速度和机械的性能不是非常高，有一个规律是凸轮机构设计很好的协议，只需要避免过于陡峭的轮廓或从动件产生噪声，影响冲击，并侧压力的突然改变。 然而，凸轮速度或负荷增加或具有更严格的要求，寻求更精细的设计，并以极高的速度，在惯性运动部件上的作用最明显，因此，对举升的加速度和速度因素都必须考虑，这些很少在任何详细的标准教科书中得到处理。凸轮从动件的设计也是非常重要的，并且关系到凸轮自身的形状。这是因为凸轮与从动件不能在一个固定点上接触。表面接触需要分配负荷，避免过度磨损，凸轮传送运动通过从动件各点位置，这都取决于两个互补零部件形状。目前凸轮在发