気化器の空燃比応答特性に由来するエンジンの自励振動 : 第1報, リーンハンチング発生メカニズムの定式化

抄録

Carburetor engines with a mechanical governor sometimes exhibit a self-excited oscillation in rotating speed, called hunting. In this paper, two different mechanisms of hunting, mechanical hunting and lean hunting, are discussed. Through a simple system of equations, the mechanism of mechanical hunting is explained, and it is clarified that the dynamic characteristic of the mechanical governor plays a significant role in the deterioration of system stability. On the other hand, a new mathematical formulation is developed for the mechanism of lean hunting where a differential equation for time-varying air-fuel ratio is included, and the effect of the dynamic characteristic of the governor is excluded. A numerical simulation is performed to analyze the process where lean hunting is induced as the air-fuel ratio becomes larger, or as the delay in fuel evaporation becomes larger, or as the load becomes smaller. The results of the simulation agree with the experimental fact previously reported.