Based On The Lightweight And Casting Process Optimization Design Of A Gasoline Engine Piston

In the process of engine operation,the piston makes high-speed periodic reciprocating motion,and transforming the heat generated by gas into the mechanical energy of crankshaft rotation.Reciprocating motion is not uniform,and the existence of motion acceleration will produce huge reciprocating inertia force and inertia moment.These forces and moments are important factors that causing mechanical loss and vibration of the engine.For high-speed gasoline engine,the lightweight of piston can reduce the reciprocating inertia force effectively and improve the economic,comfortable and reliability of the engine;At the same time,the redundant part of piston is reduced,means to reduce the input of manufacturing materials and reduce the cost of raw materials.Therefore,it is very important to improve the piston lightweight.Firstly,basing on the theory of piston lightweight design,this paper completes a lightweight design of a gasoline engine piston.The initial scheme of piston is optimized and improved by combining lightweight method with advanced piston design theory in actual production.This piston is made of a new type of aluminum material with better strength.In the structure,the design objectives are achieved by lightweight design of total height,top of inner cavity,back cavity of piston ring,pin hole and skirt.The weight of piston is reduced 29 g.The improvement of the wear resistance of the ring groove and skirt are achieved by adopts anodizing in the ring groove and a new wear-resistant coating in the skirt.Secondly,the piston thermodynamic optimization is carried out by ANSYS software;The piston kinetic analysis is analyzed by Pisdyn and Glide software.Better pin hole and skirt profile are selected by calculating the contact stress of pin hole and skirt.In the initial schemethe fatigue coefficient of the ring back cavityis slightly lower.By improving the smoothness of the facing window,the fatigue coefficient of the structure improved.As lightweight improvement,the piston improved its kinetic energy,swing angle and friction loss on skirt.Then,the casting process of piston is optimized by magma software casting simulation analysis,and the casting process is optimized to reduce the casting defects caused by lightweight design.In order to improve the material properties advanced CMR technology is used to refine the metallography of piston in casting process.The blank of casting is inspected and the former die and casting process are reasonable.Finally,comparison the normal piston with the lightweighted piston through the temperature field test,piston pin hole fatigue test,piston minimum clearance cylinder pulling test,piston durability test and engine vibration test.The results of the measurement of piston temperature by the method of hardness plug are consistent with the results of thermodynamic temperature field analysis.The rationality of the design of the pin hole is tested by fatigue test.Stained the tested piston,the pin hole doesn't have crack and meet the engine requirements.The piston skirt design is reasonable by the test of the minimum clearance cylinder drawing.Piston durability test is the most important test of piston development test,which combines high and low load fatigue cycle conditions to fully reflect the durability of the engine.The test data show that the wear of the key parts of the skirt,pin hole and ring groove is reduced.No cracks are found after the dye detection of the piston after the test,which proves that the strength of the piston meets the requirements.The engine vibration test shows that the lightweight improve of piston has improved the engine vibration.The main innovation points of this paper are as follows:(1)The lightweight design of a gasoline engine piston reduces the weight of piston and the input of manufacturing materials and also the cost of raw materials.And provide lightweight gasoline engine piston design scheme and basis for the followers.(2)The first combination of lightweight improvement and process improvement for the piston can provide a feasible plan for the lightweight piston actual production.(3)The temperature,strength and second-order performance of piston before and after the lightweight are calculated by thermodynamic and dynamic simulation.And the calculated results are verified by piston test.