The crank processes specification and
development direction
The crank processes specification
The crank specification is very high, its machine-finishing technological process different and the crank complex degree has the very big difference along with the production guiding principle, but includes following several main stages generally: Localization datum processing; Thick, lathe finishing and rough grinding each host neck and other outer annuluses; Che Lianjing; Drills the oil hole; Correct grinding each host neck and other outer annuluses; Correct grinding Lian Jing; Big, capitellum and key slot processing; Journal surface treatment; Transient equilibrium; Super finishing various journals.
May see, the main neck or Lian Jing the turning working procedure all separates with the grinding working procedure, is often middle arrangement some different machined surfaces or the heterogeneity working procedure. After the rough machining can have the distortion, therefore the normal force reduces gradually; Because simultaneously thick, the precision work working procedure carries on separately before, the latter working procedure has the possibility to eliminate the working procedure error, finally obtains the very high precision and the very low roughness. Thick, the precision work separates, and arranges the
alignment working procedure behind the cutting force big working procedure, guarantees the processing precision.
In order to reduce the distortion which the cutting force causes, guaranteed when precision work precision request, correct grinding various journals, uses the single grinding wheel in turn grinding generally.
The journal processing requests high, the main neck and the neck uses continually processes many times.
Crank machining development direction
Along with our country numerical control engine bed unceasing increase, the crank rough machining will be widespread uses in the numerical control lathe, the numerical control the milling machine, the numerical control vehicle broaching machine and so on the advanced equipment to the main journal, the connecting rod journal carries on the numerical control turning, in the milling, the vehicle - broaching processing, by will effectively reduce the amount of deformity which the crank will process. The crank precision work will be widespread uses the CNC control the crankshaft grinding to carry on the correct grinding processing to its journal, this kind of grinder will provide grinding wheel automatic function requests and so on transient equilibrium installment, center rest automatic tracking unit, automatic survey, self-compensating system, grinding wheel automatic conditioning, permanent link speed, will guarantee the grinding quality the stability.
In order to satisfy the processing request which the crank enhances day by day, set the very high request to the crankshaft grinding. The modern crankshaft grinding except must have the very high static state, the dynamic rigidity and outside the very high processing precision, but also requests to have the very high grinding efficiency and more flexibilities. In recent years, requested the crankshaft grinding to have the stable processing precision, for this, had stipulated to the crankshaft grinding process capability coefficient Cp≥1.67, this meant requested the crankshaft grinding the actual processing common difference to have the common difference which assigned compared to the crank small one half. Along with the modern actuation and the control technology, the survey control, CBN (cubic boron nitride) the grinding wheel and the advanced engine bed part application, for the crankshaft grinding high accuracy, the highly effective abrasive machining has created the condition. One kind calls it the connecting rod neck follow-up grinding craft. Has manifested these new technical synthesis application concrete achievement. This kind of follow-up grinding craft may obviously enhance the crank connecting rod neck the grinding efficiency, the processing precision and the processing flexibility. When carries on the follow-up grinding to the connecting rod neck, the crank take the main journal as the spool thread carries on revolving, and clamps the grinding all connecting rod neck in an attire. In the grinding process, the wheelhead realization reciprocation swing feed, tracks the biased rotation connecting rod neck to carry on the abrasive machining. Must realize the follow-up grinding, X axis besides must have the high dynamic performance, but also must have the enough tracking accuracy, guarantees the shape common difference which the connecting rod neck requests. The CBN grinding wheel application realizes the connecting rod neck follow-up grinding
important condition. Because the CBN grinding wheel resistance to wear is high, in the grinding process medium plain emery wheel diameter is nearly invariable, a conditioning may the grinding 600~800 cranks. The CBN grinding wheel also may use the very high grinding speed, may use generally on the crankshaft grinding reaches as high as the 120~140m/s grinding speed, the grinding efficiency is very high.
Connecting rod processing and trend of development
Connecting rod processing method
The connecting rod decomposes (also called connecting rod breaks) the technical principle uses the material break theory, first artificial has the whole forging connecting rod semi finished materials big end of hole the fissure, forms the initial break source, then expands with the specific method control fissure, achieved the connecting rod The decomposition processing process enable the decomposition the connecting rod cap, the pole adjoining plane to have the complete meshing jig-saw patterned structure, guaranteed the adjoining plane precise docking, tallies, does not need to carry on the adjoining plane again the processing, simultaneously simplified the connecting rod bolt hole structural design and the whole processing craft, has the processing working procedure few, the economical precision work equipment, the nodal wood energy conservation, the product quality high, the production cost low status merit. Main body and the connecting rod cap separate goal.
Trend of development
At present, the drop for and the die casting connecting rod host, the important status, are facing the powder to forge the steel connecting rod and a powder agglutination steel connecting rod forming craft challenge. Speaking of the domestic present situation, although the powder metallurgy forging industry had certain development, but must provide the mass and the high grade powder metallurgy forging is not mature. Moreover involves the equipment to renew, aspect expense questions and so on technical change, in next one, in long time, domestically produced connecting rod production also by drop forging craft primarily.
The connecting rod is one of internal combustion engine main spare parts, its reducing socket two sizes and the shape position errors have many requests, for example: Diameter, roundness, cylindricity, center distance, parallelism, hole and end surface verticality and so on. How does these erroneous project produce the scene in the workshop to examine, always is in the internal combustion engine profession a quite difficult question.
In the connecting rod production, domestic mainly has following several examination method at present: With the spindle survey, namely puts on the spindle in connecting rod two, with the aid of in V shape block, plate, dial guage survey. Because the spindle needs to load and unload, therefore between the hole axis has the gap, the measuring accuracy is very low.
中文翻译
曲轴加工的技术要求及发展方向
曲轴加工的技术要求
曲轴的技术要求是很高的，其机械加工工艺过程随生产纲领的不同和曲轴的复杂程度而有很大的区别，但一般均包括以下几个主要阶段：定位基准的加工；粗、精车和粗磨各主颈及其它外圆；车连颈；钻油孔；精磨各主颈及其他外圆；精磨连颈；大、小头及键槽加工；轴颈表面处理；动平衡；超精加工各轴颈。
可以看出，主颈或连颈的车削工序都与磨削工序分开，往往中间安排一些不同的加工面或不同性质的工序。粗加工后会发生变形，因此常把粗、精加工分开，并在切削力较大的工序后面安排校直工序，以保证加工精度。
为了减小切削力所引起的变形，保证精加工的精度要求，精磨各轴颈时，一般采用单砂轮依次磨削。
轴颈的加工要求高，主颈和连颈采用多次加工，使加工余量越来越小，切削力逐渐降低；同时由于粗、精加工工序分开进行，后工序就有可能消除前工序的误差，最终获得很高的精度和很低的粗糙度。
曲轴机加工发展方向
随着我国数控机床的不断增加，曲轴粗加工将广泛采用数控车床、数控内铣床、数控车拉床等先进设备对主轴颈、连杆轴颈进行数控车削、内铣削、车-拉削加工，以有效减少
曲轴加工的变形量。曲轴精加工将广泛采用CNC控制的曲轴磨床对其轴颈进行精磨加工，此种磨床将配备砂轮自动动平衡装置、中心架自动跟踪装置、自动测量、自动补偿装置、砂轮自动修整、恒线速度等功能要求，以保证磨削质量的稳定。
为满足曲轴日益提高的加工要求，对曲轴磨床提出了很高的要求。现代曲轴磨床除了要有很高的静态、动态刚度和很高的加工精度外，还要求有很高的磨削效率和更多的柔性。近年来，更要求曲轴磨床具有稳定的加工精度，为此，对曲轴磨床的工序能力系数规定了Cp≥1.67，这意味着要求曲轴磨床的实际加工公差要比曲轴给定的公差小一半。随着现代驱动和控制技术、测量控制、CBN（立方氮化硼）砂轮和先进的机床部件的应用，为曲轴磨床的高精度、高效磨削加工创造了条件。一种称之为连杆颈随动磨削的工艺。正是体现了这些新技术综合应用的具体成果。这种随动磨削工艺可显著地提高曲轴连杆颈的磨削效率、加工精度和加工柔性。在对连杆颈进行随动磨削时，曲轴以主轴颈为轴线进行旋转，并在一次装夹下磨削所有连杆颈。在磨削过程中，磨头实现往复摆动进给，跟踪着偏心回转的连杆颈进行磨削加工。要实现随动磨削，X轴除了必须具有高的动态性能外，还必须具有足够的跟踪精度，以确保连杆颈所要求的形状公差。CBN砂轮的应用是实现连杆颈随动磨削的重要条件。由于CBN砂轮耐磨性高，在磨削过程中砂轮的直径几乎是不变的，一次修整可磨削600～800条曲轴。CBN砂轮还可以采用很高的磨削速度，在曲轴磨床上一般可采用高达120～140m/s的磨削速度，磨削效率很高。
连杆的加工方法和发展
连杆的加工方法
连杆裂解（也称连杆胀断）技术的原理就是利用材料断裂理论，首先将整体锻造的连杆毛坯大头孔人为产生裂痕，形成初始断裂源，然后用特定方法控制裂痕扩展，达到连杆
本体与连杆盖分离的目的。裂解加工过程使裂解的连杆盖、杆接合面具有完全啮合的犬牙交错结构，以保证接合面精确相接、吻合，无需再进行接合面的加工，同时简化了连杆螺栓孔的结构设计和整体加工工艺，具有加工工序少、节省精加工设备、节材节能、产品质量高、生产成本低等优点。
发展趋势
目前,模锻和模铸连杆的主、重要地位,正面临着粉末铸造钢连杆和粉末一次烧结钢连杆成型工艺的挑战。就国内现状而言,粉末冶金锻造工业虽然有了一定的发展,但要提供大批量和高质量的粉末冶金锻件还不成熟。而且涉及设备更新、技术改进等方面费用问题,在今后一个比较长的时间内,国产连杆生产还将一模锻工艺为主。
连杆是往复泵的主要零部件之一,他的大小头二孔的尺寸和形位误差有多项要求,例如:直径、圆度、柱度、心距、行度、与端面的垂直度等。这些误差项目在车间生产现场如何检测,一直是内燃机行业中一个比较困难的问题。
在连杆的生产中，目前国内主要有以下几种检测方法：用心轴测量，即在连杆二孔中穿上心轴，借助与V形块、平板、百分表测量。因为心轴需要装卸，所以孔轴之间有间隙，测量精度很低。
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