362:, called the forward and rear bands. The clutches and bands are operated by hydraulic pressure. In this case, forward means closest to the engine. When applied, a clutch connects a rotational component to the engine, causing the component to turn, and a band holds the component, preventing it from turning. The forward clutch controls power to the primary sun gear. The rear clutch controls power to the secondary sun gear. Confusingly, the band that holds the rear clutch is called the front band. The rear band holds the planet carrier.
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112:, which has two complete planetary gearsets. As originally invented, the Ravigneaux puts two planetary gear trains on a single planet carrier. It has two sun gears, two ring gears, and two sets of planet gears on a single carrier. Using a single carrier makes the Ravigneaux smaller, lighter, and less expensive to make, because the carrier is usually the largest and most expensive part of a planetary gearset.
355:. The planet carrier is the central part of a planetary gear set. Not shown are the two sun gears, called primary and secondary, that rotate within the carrier. Also not shown is a ring gear, also called an annulus, having internal teeth fitting around the carrier. Input power is applied to one or both sun gears, and output power is taken from the ring gear, which turns the drive shaft.
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center of the carrier than the gear it meshes with on the left. The left and right gears turn in the opposite direction. Only the outer planet gears mesh with the ring gear. The primary sun gear (the small sun) meshes with the inner planets, and the secondary sun gear (large sun) meshes with the gears that turn with the outer planets.
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This provides for two inputs and one output. Usually, in an automatic transmission, one component is held fixed, while another component is input, and the remaining component is used for output. By choosing a set of components for held, input, and output, the planetary gear will increase or decrease
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with respect to each other. The inner planets couple with the small sun gear and co-rotate at a fixed gear ratio with respect to it. The outer planets couple with the large sun gear and co-rotates with a fixed gear ratio with respect to it. Finally, the ring gear also couples and co-rotates with the
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In general, a
Ravigneaux can be configured with each of the three gears in the set having a different number of teeth, but in the Ford FMX, all three have 18 teeth. Multiple planets, turning in the opposite direction and meshing with different sun gears, gives the Ravigneaux the ability to provide
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The output can be coupled to either one of the ring gears, with R1 being used in all forward speeds and B in the reverse speed. The input always drives M1. In all forward speeds torque must be transferred between planet gears S1 and S2, since only S1 planets engage the input M1 and only S2 planets
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A Ravigneaux gearset is like a simple planetary gear set, except that each planet gear is replaced by a set of three gears, all on the same carrier. All three gears in a set are seen inside the carrier in the left photo. The gear on the right side of this photo is in slightly farther toward the
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In reverse gear the
Ravigneaux behaves like an ordinary planetary system, with the second system just going along for the ride with no load. The ratios depend on teeth counts and are taken from the example given in the patent.
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The
Ravigneaux set has two sun gears, a large sun and a small sun, and a single planet carrier, holding two sets of planetary gears, inner planets and outer planets. The carrier is one sub-assembly but has two
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The right-most photo shows the other side of the carrier. Of the two meshing gears showing, the one on the right is slightly farther from the center of the carrier, allowing it to mesh with the ring gear.
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The opening for the sun gears is resting on a table. A dinner fork is shown for scale. An internal-tooth ring gear (not shown) meshes with three of the planet gears. The ring gear turns the drive shaft.
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Two sun gears (not shown) fit inside this planet carrier. The sun gears are powered through clutches from the engine. One of three sets of three planet gears inside the carrier can be seen.
44:, is constructed from two gear pairs, ring–planet and planet–planet. The gearset provides four forward gear ratios and reverse by braking or restraining various elements of the mechanism.
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and is called a ring gear. The carrying arm is usually called the planet carrier. Planet gears are usually not directly coupled, leaving three components that are directly coupled:
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technology was less well developed. Several years later, when the
Ravigneaux went into production at Ford Motor Company, hydraulically operated band brakes and clutches were used.
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has two concentric gears, one or more planets bridging the gap between those gears, and one arm carrying the planets. Usually, the smaller diameter concentric gear has
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to couple with the inner and outer planets, respectively. The two sets of planet gears rotate independently of the carrier but co-rotate with a fixed gear
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Illustration of a simple planetary gear train, with the sun gear in yellow, the planets in blue, and the carrier in green. The ring gear is not shown.
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multiple speeds and reverse, with just one set of planetary gears. The FMX in the photo has three forward speeds, and reverse.
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Ring R1 is coupled to planets S2, which are coupled to Sun C. Planet gears from the S1 set are pairwise coupled to S2 gears.
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The FMX transmission is controlled through two clutches called the forward and rear clutches, and two
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clutches be used in the transmission. The year of the patent was 1949, a time when pressure operated
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Drawing from patent application shown in black, with annotations for
Knowledge in blue
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The
Ravigneaux improves upon earlier planetary automobile transmissions, such as the
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399:, Ravigneaux, "Epicyclic Change-Speed Gear", issued 1953-03-17
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Ring gear B is coupled to planet gears S1, which are coupled to Sun M1.
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and is called a sun gear, and the larger concentric gear has
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outer planets in a fixed gear ratio with respect to them.
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The photos on the right show the planet carrier from a
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Ravigneaux planet carrier from a Ford FMX transmission
36:, who filed a patent application on July 28, 1949, in
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Meccano model of a
Ravigneaux Planetary Transmission
40:France. This planetary gear set, commonly used in
468:"Structure and Analysis of Planetary Gear Trains"
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445:. Vol. 13. Berlin: Springer. p. 221.
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115:The original patent application proposed that
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268:M1 -> S1 -> A -> S2 -> R1
242:M1 -> S1 -> A -> S2 -> R1
545:Automotive transmission technologies
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417:"Understand Automatic Transmissions"
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353:Ford FMX automatic transmission
73:In contrast to a Ravigneaux, a
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216:M1 -> S1 -> S2 -> R1
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466:Levai, Zoltan (1968-02-09).
441:Pfeiffer, Friedrich (2008).
100:speed and change direction.
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312:Ford FMX Ravigneaux example
104:Invention of the Ravigneaux
75:simple planetary gear train
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443:Mechanical system dynamics
477:: 131–148. Archived from
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423:. Source Interlink Media
415:Jim Smart (March 2012).
366:Inner and outer planets
42:automatic transmissions
133:engage the output R1.
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28:is a double planetary
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475:Journal of Mechanisms
397:US patent 2631476
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61:Planetary gear trains
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190:M1 -> S1 -> B
540:Epicyclical gearing
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26:Ravigneaux gearset
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521:by Alan Wenbourne
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360:band brakes
529:Categories
488:2012-11-25
427:2012-11-19
383:References
143:gear shift
519:H1 Hummer
233:free spin
210:free spin
207:free spin
187:free spin
181:free spin
149:Carrier A
121:hydraulic
92:Ring gear
253:rotating
227:rotating
89:Sun gear
517:in the
169:reverse
161:Ring R1
110:Simpson
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273:fourth
265:output
262:braked
259:braked
239:output
236:braked
221:second
213:output
201:braked
184:output
175:braked
172:-0.285
158:Ring B
152:Sun M1
535:Gears
482:(PDF)
471:(PDF)
299:fifth
288:fixed
282:input
256:input
250:0.576
247:third
230:input
224:0.429
204:input
198:0.267
195:first
178:input
155:Sun C
146:ratio
54:ratio
50:radii
447:ISBN
305:TBD
30:gear
24:The
302:1.5
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