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1、,机电技术专业英语,2,Lesson Seventeen,Text,Gear Planning The shape of the space between gear teeth is complex and varies with the number of teeth on the gear as well as tooth module, so most gear manufacturing methods generate the tooth flank instead of forming. Gear Shaping Gear shaping is inherently simila
2、r to gear planning but uses a circular cutter instead of a rack and the resulting reduction in the reciprocating inertia allows much high stroking speeds1; modern gear shapers cutting car gears can run at cutting strokes per minute. The shape of the cutter is roughly the same as an involute gear but
3、 the tips of the teeth are rounded2.,Gear Manufacturing Methods,Lesson Seventeen,Gear Hobbing Gear hobbing, the most used metal cutting method, uses the rack generating principle but avoids slow reciprocation by mounting many “racks” on a rotating cutter4. The “racks” are displaced axially to form a
4、 gashed worm. Gear Broaching Gear broaching is not usually used for helical gears but is useful for internal spur gears; the principle use of broaching in this context is for internal splines which cannot easily be made by any other method. As with all broaching the method is only economic for large
5、 quantities since setup cost are high. Gear Shaving Gear shaving is used as finishing processes for gears in the “soft” state. The objective is to improve surface roughness and profile by mating the roughedout gear with a “cutter” which will improve form.,Lesson Seventeen,Gear Grinding Gear grinding
6、 is extremely important because it is the main way hardened gears are machined. When high accuracy is required it is not sufficient to precorrect for heat treatment distortion and grinding is then necessary.,Lesson Seventeen,New Words and Expressions,Lesson Seventeen,Lesson Seventeen,Lesson Seventee
7、n,Lesson Seventeen,Notes,1.Gear shaping is inherently similar to gear planning but uses a circular cutter instead of a rack and the resulting reduction in the reciprocating inertia allows much high stroking speeds. 插齿加工在本质上与刨齿加工类似，只是采用了圆形刀具来取代齿条刀。其结果是减少了往复运动惯性，在加工过程中可以实现比刨削高得多的速度。 句中Gear shaping意为“插
8、齿”, inertia 意为“惯性”。 2. The shape of the cutter is roughly the same as an involute gear but the tips of the teeth are rounded. 插齿刀的形状与渐开线齿轮大致相同，但是其齿顶是圆的。 句中involute gear意为“渐开线齿轮”。 3. A great advantage of gear shaping is its ability to cut annular gears such as those required for large epicyclic drive
9、s. 插齿加工的一大优点是能够加工诸如行星齿轮传动所需要的内齿轮。 句中annular gears意为“内齿轮，内齿圈”, required for做后置定语修饰those（annular gears）。,Lesson Seventeen,4. Gear hobbing, the most used metal cutting method, uses the rack generating principle but avoids slow reciprocation by mounting many “racks” on a rotating cutter. 滚齿是常见的金属切削方法。它采
10、用展成原理，但是通过安装在旋转刀具上的许多“齿条”来避免缓慢的往复运动。 句中Gear hobbing意为“滚齿”, by mounting在句中做方式状语。 5. Only single start worms are cut on the wheel but gear rotation speeds are high, 100 rpm typically, so it is difficult to design the drive system to give accuracy and rigidity. 砂轮只能被切削成单头蜗杆形，由于齿轮的转速通常高达100 r/min，因此设计具有
11、所需要的精度和刚度的驱动系统是困难的。 句中single start worms意为“单头螺纹螺杆”。,Lesson Seventeen,Lesson Seventeen,参考译文,刨齿 齿轮齿间的空间形状复杂，且随着齿轮的齿数和模数的不同而变化，因此大多数的齿轮制造方法采用展成齿廓而不是成型加工。 插齿 插齿加工在本质上与刨齿加工类似，只是采用了圆形刀具来取代齿条刀。其结果是减少了往复运动惯性，在加工过程中可以采用比刨削高得多的行程速度。现代插齿机在加工汽车齿轮时可以达到每分钟2000次切削行程。插齿刀的形状与渐开线齿轮大致相同，但是其齿顶是圆的。 滚齿 滚齿是常见的金属切削方法。它采用展成
12、原理，但是通过安装在旋转刀具上的许多“齿条”来避免缓慢的往复运动。这些“齿条”轴向排布，形成了有缝的蜗杆。,齿轮制造方法,Lesson Seventeen,拉齿 通常不采用拉削的方式加工斜齿轮，但是在直齿轮加工中拉削是适用的。在这种情况下，拉削主要被用来加工其他方法不容易加工的内花键。同所有的拉削加工一样，因为设备的费用很高，齿轮拉削方法只是应用在大批量生产时才经济。 剃齿 采用剃齿方式可以对处于“软”状态的齿轮进行精加工。其目的是通过采用具有较高齿形精度的“刀具”与经过粗加工的齿轮进行啮合来降低齿面粗糙度和改善齿廓形状。 磨齿 磨齿是非常重要的。因为它是加工淬硬齿轮的主要加工方法。当对于热处理变形的预先校正达不到齿轮所要求的高精度时，就必须采用磨削加工。,谢谢观赏,,Thank You !,
