| Piston is the key component of internal combustion engine.The combustion of combustible gas in the cylinder produces a huge explosion pressure,which pushes the piston to move back and forth in the cylinder.Through the movement of the piston,the kinetic energy is transferred to the crankshaft to provide power for the car.The piston will be deformed by mechanical and thermal loads during the working process of the engine.In order to make the piston fit the cylinder wall after deformation,it is necessary to consider it in the piston design.At present,the outer circle of the piston is usually designed as a convex and elliptical shape,that is,the contour line(longitudinal line)of the piston axis is a complex one with the change of height The curve has a profile accuracy of 0.005-0.01mm;the transverse section(transverse profile)perpendicular to the piston axis is usually designed as an ellipse or a kind of ellipse.The ellipse will change with the piston height.The contour precision can reach 0.005 mm,and the accuracy of the longitudinal profile and transverse profile is very high.The outer circle process of fine car is the quality control point process in piston machining.This paper studies the machining technology of the outer circle of diesel engine piston,including: the processing research of piston longitudinal profile,the processing research of piston transverse profile,the processing research of verticality of piston pin hole axis and outer circle axis.Before the research of the project,the paper analyzes the technological requirements and technical means of the outer circle processing in detail,determines the important quality characteristics of piston outer circle processing,and determines the research direction of the project.The main control of piston longitudinal profile is the control of the diameter of the outer circle reference.The super difference of the outer circle reference diameter is the main source of waste in piston machining.Through the analysis of piston processing process,it is concluded that the wear and temperature change of the tool are the causes of the diameter difference of the outer circle.Through the improvement of the tool and the control of the temperature change,the combination of the diameter of the piston outer circle is improved Lattice rate.In the process of machining the outer circle,the verticality of the ellipse long axis and the pin hole axis needs to be controlled by the rotary piston,and the reliability is poor.This paper proposes the principle of air tightness detection,and effectively proves the verticality of the ellipse long axis and the pin hole axis by controlling the air outlet position of the end face of the non-stop tire to prevent the artificial rotating piston from being in place.Too much clamping force is an important factor to affect the piston ellipse qualification.In this study,the finite element analysis is used to determine the reasonable clamping force,which can reduce the ellipse deformation of piston during clamping,so that it meets the product requirements.The main reason for the difference between the verticality of the outer circle axis and the pin hole axis is too bad when the chip is stopped.According to the principle of air tightness detection and the characteristics of piston stop positioning,a set of air tight detection device is designed to replace the traditional manual control of the chip,and the process guarantee ability of verticality between the outer circle axis and pin hole axis is improved.Through the above research and improvement,the perpendicularity of the outer circle’s longitudinal profile,transverse ellipse,outer circle axis and pin hole axis can be well guaranteed,which has practical application significance for the high-precision machining of piston outer circle. |
