| The crankshaft is one of the core parts of the engine.Because of its complex shape and high working speed,the dynamic balance index of the crankshaft is very high.Usually after the machine is finished,it needs to be tested and weighed by the balancing machine to meet the requirements.The central hole at both ends of the crankshaft is the positioning datum of the whole machining process.Because there are many non machining surfaces on the crankshaft,if the centring method of the center hole is not correct,it will cause excessive weight removal or incorrect direction removal,and finally can not move balance into waste.At present,geometric centering and mass centering widely used in crankshaft production are aimed at centering of crankshaft blank,and can not directly control the weight and position before the dynamic balance.For this reason,a new method of iterative centering based on the virtual machining of crankshaft scanning forgings is proposed for the first time,that is,the position of the center hole of the forgings is reversed by the minimum unbalance quantity before the dynamic balance of the finished product,and the forward optimization design of the crankshaft forgings is studied on the basis.The flow equations were stablished by dividing cushioning process into three stages,which are local pressure loss,sharp edged throttling and variable gap throttling.And the mathematical model of cushioning process of about wedge-shaped cushioning hydraulic cylinder was established.The mathematical model was simulated and analyzed by using MATLAB.The main research contents of this research are:1)Based on the principle of double side correction balance of the rotor dynamic balance by the rigid rotor,the "crankshaft dynamic balancing analysis software" is developed with the Visual Studio software development platform and the UG Open open command,and the accuracy of the software analysis results is verified.The influence of crankshaft calculation step length on software calculation results and calculation time is analyzed.2)Taking the crankshaft model as an example,the virtual machining process of the crankshaft scanning forgings is described,including the establishment of the material removal model,the determination of the geometric axis of the forgings,and the virtual machining of finished products by Boolean operation.At the same time,the relationship between several models is explained in the form of set.3)Developing the "crankshaft dynamic balance analysis software" as the tool of analysis and calculation,explaining the forming process of iterative centering method and putting forward the iteration formula.According to the iteration formula,the best crankshaft centering position is obtained,which guides the actual crankshaft forgings to process and verifies the feasibility of the iterative centering method.4)A forward optimization method of crankshaft forgings is proposed.By decomposing the dynamic unbalance of crankshaft to multiple planes,the optimization of the structure near the plane is instruct to reduce the dynamic unbalance of the crankshaft forgings.The research of this subject can provide reference for the application of computer aided technology in machining manufacturing.It has certain theoretical value and practical engineering significance. |
PDF Full Text Request