一种基于坐标图解法的机械尺寸精度设计方法

A Design Method for Mechanical Dimensional Precision Based on Coordinate Graphical Method

提出了一种基于坐标图解法的机械尺寸精度设计方法,该方法利用了几何思维,建立坐标系模型,将孔轴配合的尺寸公差带和配合公差带在直角坐标系内表示,通过直线方程和可行域将机械尺寸精度指标在坐标系内进行了转换、整合与统一,结合了一些孔轴尺寸公差配合的具体算例,说明了这种方法在描述尺寸公差带与配合公差带时具有直观简明的优点。同时,该方法通过孔轴各自的实际尺寸偏差分布规律求得两尺寸分布的联合概率密度函数,通过对某区域进行二重积分从而得到该区域对应配合种类概率。该方法可以对孔轴加工尺寸不规则分布的配合情况进行描述,不再受制于将尺寸分布归纳为一些常规分布。坐标图解法使得机械尺寸精度指标间的关系更加直观明晰,便于对尺寸进行描述与分析设计,为机械尺寸精度设计提供一个新的思路。

A design method for mechanical dimensional precision based on the coordinate graphical method is put forward in this paper.This method uses geometrical thought to establish a coordinate system model,and represents the dimensional tolerance zone and the fit tolerance zone of the hole shaft in the rectangular coordinate system.By using the linear equation and feasible region in coordinate,the mechanical dimensional precision indexes can be transformed,integrated and unified in the coordinate system.Some examples for tolerance and fit of hole and shaft are attached in this paper,which demonstrate strength for conciseness and simplicity in describing the dimensional tolerance zone and fit tolerance zone.Meanwhile,the joint probability density function of dimensional deviation distributions of hole and shaft is obtained through corresponding practical dimension distributions from them.Then,the probabilities to the fits of each kind are obtained by calculating the double integral of corresponding integral regions.This method has its advantages in describing fit of hole and shaft with irregular distributions in dimension,which can avoid the limitation of referring dimension distributions as some specific regular distributions.Coordinate graphical method presents an intuitive and explicit relationship between mechanical dimensional precision parameters,and also,it is convenient for description,analysis and design to dimension,which provides a new idea for design of the mechanical dimensional precision.