第六章 齿轮传动选编.ppt

第六章 Toothed gearing 齿轮传动;§6-1 General considerations 概述;一、Characteristics and applications 特点和应用 1、 Advantages 优点 ① Long service life and high reliability 工作可靠，寿命长 ②Constant speed ratio 传动比恒定 ③ High efficiency 工作效率高 ④Small overall size 结构紧凑;2、 Shortcomings 缺点 ① High cost 成本高 ② Noise in operation at considerable speeds or low precision in manufacture 制造精度低或者高速运转时，振动噪音大 ③ They are unsuitable for duty over medium and long distances 不适合大的中心距;;二、 Types of toothed gearing齿轮分类; ② Toothed gearing between intersecting shafts 相交轴齿轮传动 （ Bevel gearing 圆锥齿轮传动） ;2、 According to the difference operating conditions： 按工作条件分 ① Closed gearing 闭式齿轮传动 ② Open gearing 开式齿轮传动 ③ Partly open gearing 半开式齿轮传动 ;§3-2 Materials, types of failures and design criteria of gears 齿轮材料、失效形式和计算准则;一、 Materials of gear 齿轮材料 Requirements 基本要求： ① Enough impact toughness 一定的冲击韧性 (Ensure sufficient beam strength in bending under variable load ) （保证变载荷下，弯曲疲劳强度较高) ;② Enough hardness 一定的硬度 （ Ensure sufficient endurance of their surface layers 保证抗齿面失效的能力） ③High manufacturability and low cost 工艺性好、成本低;1、 Forged steel 锻钢 （ Wide application 常用） ⑴ Under ordinary service condition一般场合： Lower hardness of tooth surface 软齿面（HB≤350）齿轮材料 Processing procedure 工艺过程： Medium-carbon steels(45) 中碳钢 、Medium-carbon alloy steels(40Cr) 中碳合金钢 Structural improvement and normalization 调质或正火 Cutting 切齿; For gears with lower hardness of tooth surface, the hardness difference between small gear tooth surface and large gear one is required: 软齿面大小齿轮之间要求具有一定的硬度差： ΔHB＝HB1－ HB2＝30～50;⑵ Critical gears 重要应用：;3、 Cast iron铸铁 ⑴ Grey iron灰口铸铁（HT200~HT400)： Easy to manufacture and low cost 工艺性好、价格低； However, the strength and toughness is considerably less than that of steels 但冲击韧性差、强度低 F