| With the rapid development of the manufacturing industry and the continuous update of automobile engine technology,competition in the automobile engine market at home and abroad is becoming more and more fierce.The engine has higher and higher requirements for the machining accuracy of the crankshaft cylinder ring groove and longer service life.Therefore,it is of practical guiding significance to study the machining accuracy of the ring groove of the automobile crankshaft cylinder block.The ring groove of the automobile crankshaft cylinder is clamped and processed by a special fixture.The clamping accuracy and clamping stability of the cylinder-clamp system become particularly important.This paper analyzes the mechanism of vibration lines in the ring groove of the automobile crankshaft cylinder block during the machining process,finds the reason for the vibration lines in the crankshaft cylinder block ring groove,and proposes a method to solve the vibration lines of the crankshaft cylinder block ring groove.First,analyze the processing technology of the automobile crankshaft cylinder block,and determine the positioning reference and processing method of the crankshaft cylinder block ring groove.Vibration marks appear in the ring groove during the machining of the cylinder ring groove.The cause of the vibration marks is analyzed from the six aspects of system resonance,machine tool accuracy,tool wear,cutting error,fixture positioning and deformation,and workpiece deformation,and the cylinder ring is preliminarily determined.The cause of groove chattering.Then the cutting force in the process of ring groove machining is calculated through the ISCRA cutting force calculation software,and the clamping force is calculated according to the model of the fixture clamp.Perform static finite element simulation on the fixture and crankshaft cylinder,apply cutting forces at the 0°,90°,180°,and 270° positions of the crankshaft cylinder ring groove respectively,and find the fixture clamp through the finite element analysis results Deformation occurs,and the side support of the fixture cannot be clamped,causing the crankshaft cylinder to be displaced during the machining process.The modal analysis of the crankshaft cylinder block is carried out.Through the modal analysis,the first-order natural frequency of the crankshaft cylinder block is about twice the vibration ripple frequency,and the system resonates.It is determined that the ring groove vibration pattern of the crankshaft cylinder is caused by the deformation of the fixture,the displacement of the cylinder and the resonance of the system.Finally,the fixture is optimized for the above-mentioned problems,and two optimization schemes are designed with external auxiliary support and V-block clamping,and the latter is better by comparison.The clamping point position of the fixture is improved,the V-shaped block structure is designed and the response surface analysis and topology optimization are performed to reduce the deformation and quality of the V-shaped block.Reasonably re-select the clamp connecting rod clamp,reduce the clamping force,and then perform finite element simulation on the optimized clamp and the crankshaft cylinder.The maximum deformation of the clamp after optimization is 0.038 mm,which is lower than before optimization.81.55%,the maximum deformation of the crankshaft cylinder is 0.008 mm,which is 61.9% lower than before optimization,and the optimization effect is obvious.After optimization,the modal analysis of the crankshaft cylinder body shows that the first-order natural frequency is 1584.6Hz,which is not the same frequency as the vibration ripple frequency,which eliminates resonance.In this paper,the jig is optimized and improved in view of the vibration pattern of the crankshaft cylinder ring groove.After the fixture is optimized,the vibration pattern of the crankshaft cylinder ring groove is eliminated,which meets the requirements of crankshaft cylinder ring groove processing. |
