Ever-Power new planetary reducers employ a floating sun equipment rather than a fixed position one.
The saying ”There’s nothing new under the sun’ certainly pertains to planetary reducers. And, while floating sun gears have been around a long time, some engineers might not be aware of the benefits this unusual gear design can offer.
Traditionally, planetary reducers have used a set sun gear, where in fact the centre gear is mounted on or machined in to the shaft. When this fixed sun equipment revolves, it turns the earth gears to create movement and/or power. Ever-Power new planetary reducers, however, are employing a floating sun equipment rather than a set position sun gear.
Why a floating sunlight equipment? ‘In the planetary idea, the sun may be the driver, or pinion, in the gear set,’Ever-Power style engineer Scott Hulstein said. ‘Because the sun gear is in continuous connection with the planets, it’s important that it is properly centred among the three planets to be able to provide equal load sharing among itself and all three planets.’
Due to normal manufacturing tolerances nevertheless, a sun gear which is securely set on a shaft will intermittently have more load on one planet gear than on another equipment Hulstein explained. ‘By permitting the sun equipment to float, it centres itself among the three planets and creates continuous, equal load sharing.’
Equal load sharing is merely one of the advantages of this design. The floating sunlight gear provides ‘true involute action,’ according to Hulstein. Accurate involute action occurs when the rolling motion between the mating gears is as complete as possible. The advantage of this complete meshing of gears is definitely longer reducer life, since less internal gear slippage means fewer damaged gear teeth.
That does mean lower noise levels. When the sun gear is allowed to completely roll into the world gears, there’s much less ‘rattling’ as the teeth mesh. In effect, the Ever-Power product has ‘designed out’ the gear mesh noise by allowing the sun equipment to float into place.
So why make use of a fixed sun gear at most? ‘Fixed sun gears tend to be used in accurate servo applications,’ Greg Pennings, Ever-Power Customer Advocate, explained. ‘A fixed sun gear is necessary when exact positioning and low backlash are an intrinsic part of the app.’ Ever-Power engineers, nevertheless, were less concerned with low backlash and more interested with higher torque and/or lower noise applications.
Our planetary reducers with floating sun gears were made 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 can exceed the torque ratings of similar sized and larger sized parallel shaft reducers, yet maintain a lesser noise levels.
Sun, Ring and Planet
The most basic type of planetary gearset is demonstrated in the figures above. The figure at still left shows a three-dimensional view as the figure at right offers a cross-section. In this geartrain, inputs and output can be extracted from the carrier, ring and sun gears, and only the earth experiences epicyclic motion. This is the the majority of common type of planetary gearset (apart from the differential) and it discovers application in acceleration reducers and automated transmissions. If you take apart a cordless drill, you will most probably find this kind of planetary gearset directly behind the drill chuck.
Two Suns – Two Planets gearset
Cross-sectional view
Two Suns, Two Planets
The gearset shown above has two sun gears, and both planet gears (the yellow gears) rotate as an individual unit. The sun gears (green and brownish) can rotate independently of 1 another. The inputs and result can be chosen from either sun gear and/or the carrier. Very high speed reductions can be achieved with this unit, but it can suffer from low sun planet gear efficiency if not designed correctly.
Red 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 sun fixed. Note that the carrier rotates clockwise in the animation at left and counterclockwise in the animation at right – despite the fact that sunlight rotates counterclockwise in both cases.
The Differential
The gearset proven above differs from the preceding gearsets in that it is composed of miter gears instead of spur (or helical) gears. The ‘sun’ gears are those that do not undergo the epicyclic movement experienced by the earth. And the differential can be used to measure the difference in speed between two shafts for the purpose of synchronization. Furthermore, the differential is frequently used in automotive drive trains to conquer the difference in wheel quickness when a car encircles a corner.