粉末對粉末冶金件螺旋齒輪精度之影響

Abstract

螺旋齒輪為傳動系統中重要機械元件之一，常被使用於平行軸齒輪組上。一般產業常用的螺旋齒輪製造方法，可概分為切削性加工與非切削性加工兩大類。粉末冶金法製造之螺旋齒輪屬於非切削性加工，具有省料，省工、適合大量生產及成本低等優點，且機械性質良好，已被工業界所大量採用。 粉末冶金件螺旋齒輪於製造過程中，其齒面幾何誤差受到粉末、生胚密度、模具設計、燒結時間與燒結溫度等製程參數影響，幾乎難以避免。而為了提高齒輪製造精度，且不改變其機械性質，亦即在其他製程參數固定的情況下，便可透過模具齒形的修整，以補償粉末冶金件螺旋齒輪其齒面幾何誤差。 本論文將採用實際上粉末冶金螺旋齒輪的製程條件，進行試作實驗與齒輪精度的量測，以探討粉末及螺旋齒輪之節圓半徑這兩個製程參數對於齒輪精度的影響；同時應用齒輪創成原理所推導之螺旋齒輪數學模式，配合齒面變異分析，求得齒輪設計參數改變量與齒面變異量之關係。再以實驗量測結果為依據，利用電腦模擬齒面變異，計算出理想的齒輪成形模具設計參數修整量。

A helical gear is one of the important transmission elements in a machine system and often used for parallel axes gearing. The manufacture methods can be categorized into the cutting method and the non-cutting method. A powder metallurgy helical gear belongs to the non-cutting method and has great advantages of material-saving, labor-saving, fitness for mass production, cost down and good mechanical properties. It has been widely used in the industry. In the powder metallurgy helical gear manufacturing, the gear surface deviations are due to the influences of powders, green density, sintering time, sintering temperature and the design of a forming die. To improve the gear manufacture precision without changing the mechanical properties of the gears and other process parameters, correcting the shape of the forming die to compensate the metallurgy helical gear surface deviations would be feasible. This study refers to the conditions of practical powder metallurgy manufacture process, and proceeds to experiments and gear precision measurements as well as investigation on the effects of two parameters, powders and pitch circle radius, on gear precision. The relationship between gear parameters and gear surface deviations was derived from the mathematical model for the involute helical gears and the analysis of gear surface deviations. In accordance with the measurement results of experiments, an ideal correction on the parameters of a forming die could be derived from the computer simulations of gear surface deviations.