《机械原理》课程PPT教学课件（Theory of Machines and Mechanisms）Chap5 Gear Trains

Chap.5 Gear Trains Chap.5.1 Introduction Chap.5.2 The fundamental law of gearing Chap.5.3 Gear tooth nomenclature Chap.5.4 Condition for Correct Meshing Chap.5.5 Contact Ratio Chap.5.6 Interference and undercutting Chap.5.7 Gear types and Application Chap.5.8 Ordinary gear trains Chap.5.9 Epicyclic or planetary gear trains Chap.5.10 Applications of gear train

Chap.5 Gear Trains Chap.5.1 Introduction Chap.5.2 The fundamental law of gearing Chap.5.3 Gear tooth nomenclature Chap.5.4 Condition for Correct Meshing Chap.5.5 Contact Ratio Chap.5.6 Interference and undercutting Chap.5.7 Gear types and Application Chap.5.8 Ordinary gear trains Chap.5.9 Epicyclic or planetary gear trains Chap.5.10 Applications of gear train

Chap.5.1 Introduction Can you give some example the gearsets? Gears are machine elements that transmit motion by means of successively engaging teeth. Gears may be classified according to the relative position of the axes of revolution. The axes may be 1. parallel 2 intersecting 3. neither parallel nor intersecting

Chap.5.1 Introduction ◼ Can you give some example the gearsets? ◼ Gears are machine elements that transmit motion by means of successively engaging teeth. ◼ Gears may be classified according to the relative position of the axes of revolution. The axes may be 1. parallel 2. intersecting 3. neither parallel nor intersecting

Gears for connecting parallel shafts 1.Spur gears external contact internal contact

Gears for connecting parallel shafts 1. Spur gears external contact internal contact

Gears for connecting parallel shafts 2.Parallel helical gears 3.Herringbone gears(or double-helical gears)

2. Parallel helical gears 3. Herringbone gears (or double-helical gears) Gears for connecting parallel shafts

Gears for connecting parallel shafts 4.Rack and pinion(The rack is like a gear whose axis is at infinity.)

4. Rack and pinion (The rack is like a gear whose axis is at infinity.) Gears for connecting parallel shafts

Gears for connecting intersecting shafts 1.Straight bevel gears 2.Spiral bevel gears

Gears for connecting intersecting shafts 1. Straight bevel gears 2. Spiral bevel gears

Neither parallel nor intersecting shafts 1. Crossed-helical gears 2.Hypoid gears 3.Worm and worm gear

Neither parallel nor intersecting shafts 1. Crossed-helical gears 2. Hypoid gears 3. Worm and worm gear

Chap.5.2 The fundamental law of gearing 1. The Fundamental Law of Gearing 2. The Involute Tooth Form 3. Pressure Angle 4 Changing Center Distance 5. Backlash

Chap.5.2 The fundamental law of gearing 1. The Fundamental Law of Gearing 2. The Involute Tooth Form 3. Pressure Angle 4. Changing Center Distance 5. Backlash

1.The Fundamental Law of Gearing Tooth profile 1 drives tooth profile 2 by acting at the instantaneous contact point K. M,N,is the common normal of the two profiles. velocities V,and V,at point K,along N,N,are equal in both magnitude and direction.Otherwise the two Otootiprofleszwould separate from each other

▪ Tooth profile 1 drives tooth profile 2 by acting at the instantaneous contact point K. ▪ N1N2 is the common normal of the two profiles. ▪ velocities V1 and V2 at point K, along N1N2 are equal in both magnitude and direction. Otherwise the two tooth profiles would separate from each other. 1. The Fundamental Law of Gearing 1 1 1 2 2 2 O N  = O N 