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PLANETARY GEARS. Chapter 4 Page 61 Classroom Manual. PLANETARY GEARS & SHAFTS. Describe how different gear ratios are obtained from a planetary gear set. Identify components of a planetary gear set & their operation. Describe the different designs of compound planetary gear sets.
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PLANETARY GEARS • Chapter 4 • Page 61 • Classroom Manual
PLANETARY GEARS & SHAFTS • Describe how different gear ratios are obtained from a planetary gear set. • Identify components of a planetary gear set & their operation. • Describe the different designs of compound planetary gear sets. • Describe the construction and operation of typical Simpson gear train.
INTRODUCTION • Automatic Transmissions provide different gear ratios for performance and economy over the entire driving range. • Ratios are selected manually (driver) or automatically (hydraulically). • A planetary gear set consists of a sun gear, a planet carrier, internal gear. Page 61
SIMPLE PLANETARY GEAR SETS • Planetary gear sets are typically helical cut gears. • Sun gear is in the center. • Planet gears rotate around the sun gear. • The Ring, Annulus, or Internal gear is the outer gear of the set. Page 61
SIMPLE PLANETARY GEAR SETS Page 61
SIMPLE PLANETARY GEAR SETS • Planet gears are in constant mesh with the Sun and Internal gears. • Number of planet gears depends on the load the transmission was designed for. • A planet gear set can provide (1) gear reduction, (2) overdrive, (3) direct drive, (4) reverse, or a (5) neutral position. Page 62
SIMPLE PLANETARY GEAR SETS • When a smaller gear drives a larger gear, output speed is decreased. • When a larger gear drives a smaller gear, output speed is increased. • When a external gear drives another external gear, output direction is reversed. Page 63
SIMPLE PLANETARY GEAR SETS • When a external gear is in mesh with an internal gear, the two gears will rotate in the same direction. • Clutch packs and bands are used to hold or release the members of the planetary gear set to get the proper direction of rotation and/or ratio. Page 63
GEAR REDUCTION • When the output gear turns at a slower speed then the input gear, gear reduction has occurred and results in increased torque output. • 2 ways to get reduction • Hold sun gear, drive internal gear. • Hold internal gear, drive sun gear. Lower ratio. Page 63
OVERDRIVE • When output speed is greater than input speed, overdrive is achieved. • 2 ways to get overdrive. • Hold sun gear, drive planet carrier. • Hold internal gear, drive planet carrier. Higher ratio overdrive. Page 64
DIRECT DRIVE • Input and output speed are the same. • Drive any two members of the planet and the result is direct drive. Page 64
REVERSE • Input rotation direction is reversed. • 2 ways to get reverse. • Hold planet carrier, drive planet carrier. • Hold planet carrier, drive sun gear. This is reverse overdrive. Page 64
NEUTRAL • Input but no output. • When no member of the planetary set is held or locked to another, there will be no output regardless of which member receives the input. Page 65