Table of Contents
How do planetary gears work?
A planetary gear set is comprised of an outer gear ring that’s called the ring gear. As they rotate inside of the ring gear, the planetary gears create pitch circles that can be formed into a gear train that, in turn, is hooked up to input and output shafts.
What is the function of a planetary gear set?
Generally, planetary gears are used as speed reducers. They are used to slow down motors and increase the torque. Torque is the working power of the machine.
How does a planetary final drive work?
The planetary gears mesh with the sun gear and turn while rolling around the ring gear. They spin at a slower rate than the sun gear, and that speed reduction increases torque. These gearing relationships and the power they provide is known as your final drive ratio.
How does a planetary gear work as a differential gear?
An epicyclic differential can use epicyclic gearing to split and apportion torque asymmetrically between the front and rear axles. Epicyclic gears are also called planetary gears because the axes of the planet gears revolve around the common axis of the sun and ring gears that they mesh with and roll between.
What are planetary gear sets?
Overview. Epicyclic gearing or planetary gearing is a gear system consisting of one or more outer, or planet, gears or pinions, revolving about a central sun gear or sun wheel. Simple planetary gears have one sun, one ring, one carrier, and one planet set.
What is planetary gear set in automatic transmission?
The planetary gear train is a mechanical system in which the gears are connected with a set of bands and clutches. When the driver changes gears, the bands hold one gear still while rotating another to transmit torque from the engine and increase or decrease gears.
Why do automatic transmissions have planetary gear sets?
The torque converter clarifies how the engines send power to the transmission, but the planetary gear sets explain how an automatic transmission changes gear. The planetary gear set is really the heart of an automatic transmission. This one part creates all the possible gear ratios that the transmission can produce.
Where are planetary gears used?
Planetary gear train (PGT) has been widely used in the transmissions of helicopters, automobiles, wind turbine, aircraft engines, etc. The main advantages of this transmission are its high efficiency, its compactness, its large transmission ratio and its large power-to-weight ratio, etc.
Are planetary gears more efficient?
In addition to their durability, planetary gear motors also provide a higher efficiency over spur gear motors. Due to the construction of a planetary gear head, the length of a planetary gear motor is usually longer and narrower than spur gear motors.
Can a planetary gearbox be back driven?
A 10:1 is very easy to back drive. The largest ratio planetary gearbox I have back driven was a two stage 100:1. On a side note, if you are driving the gearbox with a DC or servo motor you will probably have to disable the dynamic braking to back drive it.
How many gear ratios are in a planetary gear set?
Single-stage planetary gearhead ratios range from 3:1 to 10:1. Gear ratios cannot exceed 10:1 because pinion gears can be made only so small. Gear ratios greater than 10:1 are possible with an additional planetary stage, although this normally increases length and cost.
How do planetary gears increase torque?
The planet gears are mounted on a joint carrier that is connected to the output shaft. The rotational speed of the output is lower than that of the drive, and the torque of the output is higher in reverse proportion. The more gear wheels mesh with each other, the higher the torque.
What is law of gearing?
Law of gearing states that the common normal at the point of contact between a pair of teeth must always pass through the pitch point for all positions of mating gear. This is a must condition for the two gears to perform properly.
What is planetary gear motor?
A planetary gear motor mimics a planetary rotation system, the input shaft drives the central gear, also known as the sun gear, which then turns the surrounding gears, also known as planet gears. As these Epicyclic Gear Train motors are very popular amongst Robotics designer.
Who invented the planetary gear set?
The Ravigneaux gearset is a double planetary gear set, invented by Pol Ravigneaux, who filed a patent application on July 28, 1949, in Neuilly-sur-Seine France. This planetary gear set, commonly used in automatic transmissions, is constructed from two gear pairs, ring–planet and planet–planet.
What is a planetary carrier?
The planetary carrier is a functional component that is crucial for planetary transmissions in conventional powertrains and electric powertrains. It can be described as a cage into which the planetary gears are integrated.
How many teeth are on planetary gear set?
and here it is inserted. In this case, the planet gears have 12 teeth, the sun gear has 18 and the ring gear has 42 teeth.Working out planetary gear turns ratios. T r Turns of the ring gear R Ring gear teeth S Sun gear teeth P Planet gear teeth.
How many planetary gears are in an automatic transmission?
The typical automatic gearbox has two planetary gears, with three forward gears and one reverse. 30 years ago, cars had an overdrive gearbox in addition to the main gearbox, to reduce the engine RPM and “stretch” the high gear with the idea of achieving fuel economy during highway driving.
Why do manual transmissions not use planetary gears?
Manual transmissions tend to be lighter and simpler than automatics. They use a clutch to get a more solid lock between the engine and the gears. So why can we just automate that whole process and make an automatic transmission without the need for heavier, more complicated planetary gears.
Do automatic transmissions use planetary gears?
They also form the basis of the most common type of automatic transmission, known as the hydraulic planetary automatic transmission. Most modern automatic transmissions in the automotive industry use planetary gears. Automatic transmissions of all types carry planetary gears, such as this 10-speed from Ford.
Do manual transmissions use planetary gears?
The main difference between manual and automatic transmissions is that the manual transmission uses multiple sets of gears to the drive shaft while an automatic transmission uses a planetary gear set to produce different gear ratios.
At what RPM should you shift gears?
Generally, you want to shift gears when your car reaches 2,500-3,000 RPM. Eventually, you will know when to shift by sound and feel.
What is a 3 stage planetary gear?
Instead of the drive shaft the planetary carrier contains the sun gear, which drives the following planet stage. A three-stage gearbox is obtained by means of increasing the length of the ring gear and adding another planet stage. A transmission ratio of 100:1 is obtained using individual ratios of 5:1, 5:1 and 4:1.
