建立了变位齿轮渐开线的直角坐标方程，为变位齿轮的参数化建模提供了理论基础。分析了转向器摇臂轴变厚齿扇结构特点，基于CATIA建立变位齿轮渐开线参数化方程，详细介绍了变厚齿扇的参数化三维建模方法，并对转向器电子样机进行了空间分析和运动仿真。该方法建模精度高，非常方便，只需改变相关参数就可以快速获得准确的变厚齿扇模型，为转向器的数字化装配和数控加工提供了依据。

The modified gear involute equation under Cartesian coordinates system is established and the theory foundation is provided for parameterization modeling of modified gear. The character of drop arm thickened-tooth segment of steering gear is analyzed. The modified gear involute parameterization equation is established based on the CATIA and the method of parameterization three-dimensional modeling of the thickened tooth segment is detailed. Then the space analysis and motion simulation are implemented for the Digital Mock-Up of steering gear. This method is high modeling accuracy, it is very convenient and the accurate thickened-tooth segment models can be obtained quickly by changing the relevant parameters, which provide the basis for digital assembly and NC machining.