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在投影仪上检验小模数圆柱齿轮时,必须以很大的放大倍数画出齿轮的渐开线齿形。被检齿轮的精度愈高,放大倍数应愈大。要得到精确的齿形样板时,必须先以500:1或300:1的放大倍数画出齿形,然后再借照相把它缩小到投影仪的影屏尺寸(缩小到100:1或50:1)。用普通制图工具画渐开线齿形的方法通常有两种:一种是作图法;另一种是直角座标法。作图法比较简单,但由于必须在图纸上画出圆心,故放大倍数不能取得很大。直角座标法的优点是放大倍数不受齿轮直径的限制。
When inspecting small module spur gears on the projector, the involute profile of the gear must be drawn at a very large magnification. The higher the accuracy of the gear being examined, the larger the magnification should be. To obtain a precise profile, the profile must be drawn at a magnification of 500: 1 or 300: 1 and then reduced to a projector screen size (reduced to 100: 1 or 50: 1). There are usually two ways to draw involute tooth profiles with common drawing tools: one is the drawing method; the other is the Cartesian coordinate method. Drawing method is relatively simple, but because of the need to draw a circle on the drawings, so magnification can not get great. The advantage of Cartesian coordinates is that the magnification is not limited by the diameter of the gear.