Research On Connection Technology And Connection Strength Of Assembled Camshaft Hot Gas Hydro-forging

In recent years,lightweight has become an inevitable trend in the development of automobile industry.As a key part of engine,camshaft directly affects the performance of engine.The traditional integral camshaft can not meet the requirements of modern engine in light weight and wear resistance.Because of the advantages of light structure and optimized material matching,the application range of assembled camshaft is more and more wide.At present,a variety of assembled camshaft connection technologies have been developed,mainly including welding,hydraulic expansion,knurling,etc.The hot gas hydro-forging is a new joining technology,which has the advantages of low dimensional accuracy and low cost.However,there is a lack of in-depth study on the forming method,forming quality and contact pressure.The main purpose of this paper is to get the influence rule and forming parameter range of each influencing factor on the forming quality and contact pressure of camshaft,so as to provide guidance for the industrial production of assembled camshaft connected by hot air hydro-forging.In this paper,the optimal design of cam and insert structure was carried out firstly,and the calculation formula of the ideal minimum feeding quantity related to the length of insert slope was derived according to the principle of volume invariance.Then,the finite element simulation model of temperature rise,temperature drop and hot gas hydroforging connection of the shaft and tube was established,and the connection experiment of hot gas hydro-forging was carried out.Through the combination of simulation and experiment,the influence of the inclination of the cam end face,the inclined length of the insert,the forming temperature,the internal pressure and the axial feeding amount on the forming quality was analyzed.Then,the cooling model of camshaft was established and the torque of the test piece is measured.The influences of the inclination of cam end face,forming temperature,axial feeding amount and thermal cycle on the contact pressure of camshaft were analyzed,and the forming parameter range was determined.At last,the connection experiment of multi cam assembled camshaft was carried out.In the process of hot gas hydro-forging,the deformation area of the axle tube is mainly between the cam end face and the insert slope,and the maximum strain is in the folding area of the inner wall of the axle tube.With the decrease of the inclination of the cam end face,the increase of the length of the inclined surface of the insert,the internal pressure and the axial feeding amount,the fitting length increases continuously,and the filling condition of the outer wall of the shaft tube to the cam end face becomes better and better;the fitting length is the largest and the filling condition is the best when the forming temperature is 850?.The inclination of the cam end has little effect on the folding of the inner wall of the axle tube;with the increase of the length of the inclined surface of the insert,the internal pressure and the axial feeding amount,the folding trend of the inner wall of the axle tube gradually appears and deepens;when the forming temperature is750?,the folding of the inner wall of the axle tube is the shallowest.The average contact pressure of the camshaft increases with the increase of the inclination of the cam face,the forming temperature and the amount of one side axial feeding.The static torsional strength of the test piece also increases with the increase of the feeding amount and the forming temperature,and the results are consistent with the simulation results.When the unilateral axial feeding amount is more than 5.5mm,the static torsional strength is far greater than the allowable torque of 80N·m.At 150?,with the increase of holding time,the static torsional strength decreases rapidly at first,and then tends to be gentle gradually.According to the determined forming parameter range,the double and four position multi cam assembled camshaft is trial manufactured.The test results show that the static and torsional strength of the assembled camshaft can meet the use requirements completely.