CAD Of The Valve Cam Of Internal Combustion Engine

Valve gear is an important part of internal combustion engine and its stand or fall has great influence to the performance of internal combustion engine. While valve gear is drove by valve cam and its performance is decided by the shape and structure of cam. So the design of valve cam has great effect to the performance of internal combustion engine. Valve gear is regarded as stiffness in the traditional design and its elastic deformation in motion is neglected. This method is called static design. However, in fact, cam has elastic deformation and all parts from follower to cam also have deformation. So elastic deformation of Valve gear must be considered in design. This method is called dynamic design In this paper, according to the characteristics of the function and structure of valve gear, by use of single dof mass-spring vibration model, the dynamic design method of valve cam is discussed and method to calculate the contact stress between cam and tappet regarding the valve gear as rigidity or elasticity, on the basis of general design for the high-speed cam mechanism.The design of valve cam is mainly to design cam profile curve and is carried out in "dynamics correction method" in this paper. Before design cam, the tappet displacement curve has to be design. While according to dynamics correction method, the valve displacement curve has to be design, which can be acquired by boundary condition and calculation method. Then by dynamics analysis, the tappet displacement curve equation can be obtained based on the dynamics differential equation. Thus, the design of cam profile can be carried out based on the tappet displacement curve equation.According to the tappet displacement curve, the design of cam profile can be carried out by "reversal method" theory. But this curve is only academic profile of cam. While actual profile lies on the type of cam mechanism, this paper take example for three kind of typical cam gear that is spire handspike disk cam mechanism, roller handspike disk cam mechanism and flat-bottomed handspike disk cam mechanism, and the design of cam actual profile is carried out.With the extensive application of computer and development of applied software, the computer-aided design is regarded increasingly. The paper's design mainly includes two parts. Fist part is the tappet displacement curve's design, and many dynamics calculation has to be done based on the dynamic design. Second part is to design cam profile curve. Above tasks are finished by Matlab and VB. According to their respective advantages, dynamics calculation and design are carried out by use of powerful calculation function of Matlab and cam profile is designed by use of the advantage of VB in the aspect of figure interface development. By two kinds of language mix programming, the CAD software of the valve cam about internal combustion engine based on Object-Oriented Programming (OOP) has been developed and is used in actual example with desirable result. Mix programming technology and interface method are discussed between Matlab and VB, and no gap integration of application system is implement, which can be utilized in CAD/ACM project of the valve gear cam.