sun planet gear

Ever-Power new sun planet gear planetary reducers employ a floating sun gear rather than a fixed position one.
The word ”There’s nothing new beneath the sun’ certainly pertains to planetary reducers. And, while floating sun gears have already been around quite a while, some engineers may not be aware of the benefits this unusual gear style can offer.
Traditionally, planetary reducers have used a set sun gear, where in fact the centre gear is attached to or machined in to the shaft. When this set sun gear revolves, it turns the earth gears to create motion and/or power. Ever-Power new planetary reducers, however, are employing a floating sun gear rather than a set position sun gear.
Why a floating sun equipment? ‘In the planetary idea, the sun is the driver, or pinion, in the gear set,’Ever-Power style engineer Scott Hulstein said. ‘Because the sun gear is in constant connection with the planets, it’s important that it’s flawlessly centred among the three planets to be able to provide equal load sharing among itself and all three planets.’
Due to normal manufacturing tolerances however, a sun gear which is securely fixed on a shaft will intermittently have more load on one planet gear than on another equipment Hulstein explained. ‘By enabling the sun gear to float, it centres itself among the three planets and generates constant, equal load sharing.’
Equal load posting is just one of the advantages of this design. The floating sunlight gear provides ‘accurate involute action,’ according to Hulstein. True involute action takes place when the rolling movement between your mating gears is as complete as possible. The benefit of this complete meshing of gears is usually longer reducer lifestyle, since less internal gear slippage means fewer broken gear teeth.
That does mean lower noise levels. When the sun gear is allowed to completely roll into the planet gears, there’s less ‘rattling’ as one’s teeth mesh. In effect, the Ever-Power product offers ‘designed out’ the apparatus mesh noise by allowing the sun gear to float into place.
So why use a fixed sun gear at almost all? ‘Fixed sun gears tend to be used in true servo applications,’ Greg Pennings, Ever-Power Customer Advocate, explained. ‘A set sun gear is essential when precise positioning and low backlash are an intrinsic part of the app.’ Ever-Power engineers, however, were less worried about low backlash and more interested with higher torque and/or lower noise applications.
Our planetary reducers with floating sunlight gears were designed to compete with parallel shaft reducers, where backlash was less critical,’ Pennings said.
By using the floating sun gear concept, the Ever-Power planetary reducers are able to exceed the torque ratings of similar sized and larger sized parallel shaft reducers, yet maintain a lower noise levels.
Sun, Ring and Planet
The most basic kind of planetary gearset is proven in the figures above. The figure at still left shows a three-dimensional watch while the figure at right offers a cross-section. In this geartrain, inputs and result can be extracted from the carrier, ring and sun gears, and just the earth experiences epicyclic motion. This is the the majority of common kind of planetary gearset (with the exception of the differential) and it discovers application in acceleration reducers and automatic transmissions. If you take apart a cordless drill, you will most probably find this type of planetary gearset right behind the drill chuck.
Two Suns – Two Planets gearset
Cross-sectional view
Two Suns, Two Planets
The gearset shown above has two sunlight gears, and the two planet gears (the yellow gears) rotate as a single unit. The sun gears (green and brownish) can rotate independently of 1 another. The inputs and output can be chosen from either sun gear and/or the carrier. High speed reductions may be accomplished with this unit, nonetheless it can suffer from low efficiency if not really designed correctly.
Reddish colored sun input – purple sun fixed
Purple sun input – reddish sun fixed
The animations above show the ‘two suns – two planets’ gearset with one sunlight as input and the other sunlight fixed. Remember that the carrier rotates clockwise in the computer animation at left and counterclockwise in the animation at right – even though sunlight rotates counterclockwise in both cases.
The Differential
The gearset demonstrated above is different from the preceding gearsets in that it is composed of miter gears rather than spur (or helical) gears. The ‘sun’ gears are the ones that do not go through the epicyclic motion experienced by the planet. And the differential can be utilized to gauge the difference in speed between two shafts for the purpose of synchronization. Furthermore, the differential is often used in automotive drive trains to overcome the difference in wheel velocity when a car encircles a corner.