- 期刊
機車用一體型曲軸鍛件之扭轉模具設計研究與開發
The study and development of the design of the twisting die for one piece crank of motorcycle
摘要
引擎是汽車之心臟，其主要構件有汽缸，活塞，連桿與曲軸。在引擎運轉時，活塞的往復運動轉化成曲軸的旋轉運動，曲軸承受很大的應力。因此，在製程上必須使用熱間鍛造製程以提高產品之強度與耐疲勞性質。而由於一體型曲軸之凸輪間轉動時有角度之差異，在模具設計上有鍛造後再扭轉與直接鍛造成形兩種，前者之鍛造模具設計較為容易，模具壽命較長，但有文獻指出曲軸之扭轉成形時，若製程參數控制不恰當，可能會傷害曲軸進而影響強度，後者則因分模線變化太大，鍛造模具設計不易且壽命較短。現行之鍛造製程則為將曲軸上不同角度之凸輪直接鍛打成形，模具壽命差。在實際大量生產上，顧及產線之連續運轉，以模具壽命較長之鍛造後再扭轉之製程為較理想之製程，在國內尚未有人開發扭轉模具。故本計畫之目的即對於車用曲軸扭轉成形模具進行開發，建立扭轉模具設計模式與量產製程技術。首先針對廠商提供之曲軸鍛件，以DEFORM鍛造模擬軟體進行扭轉成形製程分析。確認可行後，以油壓式複動機構與螺旋式機構，進行扭轉模組設計與製作與組裝，接著進行950℃、850℃、750℃不同溫度下曲軸凸輪實際扭轉成形測試，探討模具設計可行性與扭轉後曲軸之機械性質，並建立相關製程參數，進行量產。結果顯示，本研究之扭轉模具成形時運轉順暢，扭轉後之曲軸尺寸符合圖面之要求。曲軸扭轉部位的鍛流線均為連續，且表面無裂紋。750℃∼950℃加熱後扭轉之金相組織，均為肥粒鐵＋波來鐵之混成組織，為正常之組織與原本曲軸均相同，並無明顯差異，其機械性質亦符合工件之要求。經過鍛造廠商實際量產測試後確認本計畫所開發之扭轉模具與製程可行，並可成功地應用至量產製程。
關鍵字
無資料並列摘要
Engine is the hart of automobile, which compose of cylinder, piston, connecting rod and crank. The crank undertakes big stress due to the rotation by the repeated movement of piston during working. Therefore, the hot forging process should be used to elevate the strength and the fatigue resistance of the crank. There are angle differences between cams in the crank. There are two kinds of process to forging the crank such as twisting after forging and direct forging. The former has the advantages such as easy tooling design and longer tooling life, but some literatures indicated that the strength will be injured if the process variables not suitable. The latter is simple in processing but difficult tooling design and lower tool life due to the complicate parting line. For the consideration of smooth in actual production, the former is the ideal process due to longer die life and lower die cost. But the twisting die has not developed in domestic. In this project, the design of twisting die is developed and the process is expected to be set up. First of all, the twisting process is simulated and analyzed by using DEFORM software for the crank forgings provided by the forging supplier. The mechanisms of the hydraulic multi-action and the screw are used to design the die set, and then to be manufactured after the process is confirmed available by simulation. The test is followed by twisting the crank forgings at the temperature of 950℃, 850℃ and 750℃ respectively. Finally, the feasibility of the die design and the mechanical properties of the twisted parts are investigated and the relative process variables are set up for mass production. The results show that the twisting die works smoothly, the dimensions of the part conform to the requirements of the drawings and the flow line is continuous without cracks on the portion of twisting. The metallography is the mixture of pearlite and ferrite on the portion of twisting, which is normal and the same as the original forging. The mechanical properties on the portion of the twisting confirm to the requirements of the part as well. Through the production test in forging company, the developed die and the process are confirmed feasible and can be applied successfully in mass production.