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Planetary Gear Sets. Simple Gear Set. A planetary gear set has three major components: A sun gear in the center, A planet carrier with two or more pinion gears, and A ring/internal gear. These are also called members. Carrier with Planet Pinion Gears. Sun Gear. Ring/Internal Gear.
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Simple Gear Set A planetary gear set has three major components: A sun gear in the center, A planet carrier with two or more pinion gears, and A ring/internal gear. These are also called members. Carrier with Planet Pinion Gears Sun Gear Ring/Internal Gear
Connections, Input At least one, or two, of these members will be connected to the torque converter through a multidisc clutch so it can be come an Input. This ring/internal gear can be driven by the forward clutch Front Ring/ Internal Gear Forward Clutch
Connections, Output At least one of the members will be connected to the transmission output shaft so it can transfer torque to the final drive. Splines are used to connect this front carrier to the output shaft. Note that a complete planetary gearset is shown with all three mambers. Output Shaft Front Carrier
Connections, Reaction In all of the power flows that require a change in speed/torque or direction, one of the members must be held stationary in reaction. This carrier can be held by a roller clutch or multidisc clutch. A band is also used to hold a reaction member. Roller Clutch Rear Carrier with Lo & Reverse Clutch Hub Rear Clutch Housing
Carrier with Pinions Planet Pinion Gear This carrier has four pinion gears. The carrier is constructed so that it can be held in reaction by a multidisc clutch. It can also be connected to another gearset member Hub for Lo and Reverse Clutch Splines to connect to Input Ring Gear
Planet Pinions Pinion Pin/Shaft The pinion gears are mounted in the carrier so they can rotate freely. Parts to rebuild a carrier are shown here. Thrust Washer Thrust Washer Pinion Gear Needle Bearings
Planetary Operation This chart shows how a simple planetary gearset can produce six different gear ratios depending on which member is driven (Input) or held (Reaction).
#1: Sun: Input, Ring: Reaction Sun Gear: Input If the sun gear is the input while the ring gear is held stationary, the pinion gears will walk around the stationary ring gear and drive the carrier forward at a reduced speed. Carrier: Output Ring Gear: Held in Reaction Pinion Gears: Walking Animation: PGS 1
Pinion Gear Walking Pinion Gear rotating in carrier as it walks around sun gear If the carrier rotates at a different speed than either the ring or sun gear, the pinion gears must rotate in the carrier. This is called “walking”. Rotating Carrier Stationary Sun Gear Animation: Pinion Gear Walking
#2: Sun: Input, Carrier: Reaction Carrier: Held in Reaction Sun Gear: Input If the sun gear is driven with the carrier held in reaction, the planet pinions will act as idler gears and drive the ring gear in reverse at a reduction speed. Pinion Gears: Rotating as idlers Ring Gear: Output Animation: PGS 2
#3: Ring: Input, Sun: Reaction Sun Gear: Held in Reaction Ring Gear: Input If the ring gear is driven while the sun gear is held, the pinion gears will walk around the sun gear and drive the carrier at a reduced speed. Carrier: Output Pinion Gears: Walking around sun gear Animation: PGS 3
#4: Ring: Input, Carrier: Reaction Ring Gear: Input Sun Gear: Output If the ring gear is driven while the carrier is held, the pinion gears will rotate as idler gears and drive the sun gear at a reduction speed in reverse. Pinion Gears: Rotating as idlers Carrier: Held in reaction Animation: PGS 4
#5: Carrier: Input, Ring: Reaction Ring Gear: Held in Reaction Sun Gear: Output If the carrier is driven while the ring gear is held, the pinion gears will be forced to walk around the ring gear and drive the sun gear at an overdrive speed. Pinion Gears: Walking around ring gear Carrier: Input Animation: PGS 5
#6: Carrier: Input, Sun: Reaction Sun Gear: Held in reaction Ring Gear: Output If the carrier is driven while the sun gear is held, the pinion gears will be forced to walk around the sun gear and drive the ring gear at an overdrive speed. Pinion Gears: Walking around sun gear Carrier: Input Animation: PGS 6
#7: Two Inputs, No Reaction Ring Gear & Carrier: Input Sun Gear: Output If two of the gearset members are driven, the gearset will lockup and drive the output member at a 1:1, direct drive ratio. Pinion Gears: Locked up as they rotate with the carrier Animation: PGS 7
Neutral When no gearset member is driven, no power will transfer through the gearset. The result is neutral. If no gearset member is held in reaction and only one member is driven, no power will transfer through the gearset. Again, the result is neutral.