The simplest planetary gear train has one degree of freedom and one fixed sun gear. In a compound epicyclic gear train as shown pdfinancialcorp com in the figure, has gears. The angular speed of the planet carrier can be found since we know. Planetary kinematics note that point 1 on the planet gear is stationary zero velocity due to noslip assumption note that point 2 on the planet gear has the same velocity as point 2 on the sun gear also due to noslip assumption, which is given by. In each case, one of the two inputs is fixed, and the other input makes one full rotation. They are great speed variation mechanisms, and are often. The outermost gear, the ring gear, meshes with each of the planet gears. The properties and capabilities of such planetary gear trains depend largely on the sign of the gear ratio of the simple trainthat is, the train in which the carrier is stopped and the gear train becomes an ordinary mechanism with fixed wheel axles. The grabcad library offers millions of free cad designs, cad files, and 3d models.
F gear units are usually applied in the transmission of a. A typical application is the automatic transmission system of car. The driven gear is the gear that is driven or rotated by the drive gear. Typically, the arm and the sun gear will each be driven in some direction at some velocity. Example 2 a compound epicyclic gear train overdrive has sun, small planet and large planet gears with 21, 15 and 24 teeth respectively. Now, industrial applications demands high torque in compact a high. Structure and analysis of planetary gear trains prof. This demonstration simulates a planetary gear train with cycloidal gears a typical planetary gear train has three components the ring gear the sun gear and the planet carrier connecting the two togetheryou can see a wide range of reductions by holding stationary any one of these components and using the remaining ones as inputs and outputs. Pinion gear 8 pitch diameter 4 planet carrier 11 planetary gear set 11 power transfer unit 16 rearwheel drive rwd ring gear 11 spiral bevel gear 6 spur gear 5 sun gear 11 torque 2 torque converter 11 transaxle transfer case 16 transmission 8.
All three are attached to a plate the planet carrier, and they engage the inside of the blue gear the ring instead of the outside. The sun gear is located at the center, and transmits torque to the planet gears. A model for predicting churning losses in planetary gears. O e of the prime and biggest use of a planetary gearbox is for running the armature of a wind turbine. The computeraided design cad files and all associated content posted to this website are created, uploaded, managed and owned by third party users. How to derive and calculate epicyclic gear ratio equations in. James watt patented a sun and planet gear arrangement used in one of his early engines. Free body diagrams of gear trains american society for. Planetary gear train article about planetary gear train by.
You could rearrange things again, and this time hold the sun gear stationary, take the output from the planet carrier and hook the input up to the ring gear. There would be numerous applications of planetary gearbox, but i will anser with the one which im sure about. Epicyclic gear trains are powerful when used correctly, but are often misunderstood. Planetary gear train article about planetary gear train. Notice how the planet gears roll on and revolve about the sun gear. Figure 5 shows the ravigneaux gear train, a combination of one simple and one compound planetary gear set, which has dual sun and planet gear sets with a single ring and common carrier holding two planetary gear sets. Solid mechanics tutorial gear systems this work covers elements of the syllabus for the edexcel module 21722p hncd mechanical principles outcome 3. Sun 1 long planet ring sun 1 long planet short planet sun 2 kinematics of planetary gear trains angular velocity relations in a planetary train, the sun, carrier and ring rotate on coaxial shafts. Typically, the planet gears are mounted on a movable arm or carrier, which itself may rotate relative to the sun gear. Design of machinery an introduction to the synthesis and. Fbd of a planetary gear train a planetary gear train is a gear train that allows the input and output shaft to be coaxial. Figure 23 forces on the planet gears figure 24 the carrier of a planetary gear train with the sun gear and ring gear hidden figure 25 forces on the carrier. Each of these three components can be the input, the output or can be held stationary. In the solar system the planets revolve around the sun.
Planetary gear with two sun gears and two planet gear sets. Introduction planetary gear systems normally consist of a centrally pivoted sun gear, a ring gear, and several planet gears found between the sun gear and ring gear. 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. A carrier connected to a drive shaft holds the planet gears. The sun and planetary gear arrangement, sometimes also called as epicyclic gear train, is a gear train, where typically few smaller gears rotate and revolve by meshing around a bigger sun gear. Epicyclic gear trains are generally used for automatic transmission, overdrives, and final drives. Planetary gear trains are one of the main subdivisions of the simple epicyclic gear train family. The planetary gear set, also known as the epicyclic gear train, is one of the most important and interesting inventions in engineering. Most of the automatic transmissions use this kind of gear train. Driven gears the drive gear is the gear that is the source of the engine torque and rotation. How to derive and calculate epicyclic gear ratio equations. The sun gear is twice the diameter of the planet gear, and the ring gear is twice the diameter of the sun gear.
Illustrated below is a typical epicyclic gear train. All the components are modelled in catia to check the assembly and the. Feb 28, 2017 the planetary gear set, also known as the epicyclic gear train, is one of the most important and interesting inventions in engineering. In many cases, one of these inputs will be zero velocity, i. The ravigneaux gear block represents a planetary gear train with dual sun and planet gear sets. Introduction to gear trainsintroduction to gear trains. Introduction planetary gear trains, also referred to as epicyclic gear trains, are those in which there is one or more gears orbit about the central axis of the train. Sun gear is located at the center that transmits torque to planet gears orbiting around the sun gear. Planetary gear design a planetary gear system, also referred to as epicyclic gearing, consists of three elements a sun gear, one or more planet gears, and a ring gear. Subcategories this category has the following 4 subcategories, out of 4 total. The sun gear is located at the center, and transmits torque to the planet gears that orbit around it. Free body diagrams of gear trains shihliang sid wang.
However, advances in internal gear manufacturing did not parallel. Sun gear p planet gear r ring gear a a r m ex ampl e. With the motion of the beam, this revolved around, and turned, the sun, a second rotating cog fixed to the drive shaft, thus generating rotary motion. As we turned the planet gear it traversed the sun gear and imparted more rotation to the carrier. Choosing which piece plays which role determines the gear ratio for the gearset. Planetary gear ratio calculations this article also available in spanish. The solution of differential governing equation of motion is determined by applying the fourier series method. From our study of normal 2 gear interactions we know that the amount of traversal is determined by the number of teeth on each gear. Because there are three red gears instead of one, this gear train is extremely rugged. The inputand output shaftsare coaxial andthe inputand output 1 torques are assumedto be coaxialwith these shafts. Dynamic load sharing characteristics and sun gear radial. One of the planetary gearsets from our transmission has a ring. We know that for each turn of the planet tp the planet will travel around the sun npns times taking the carrier with it in the process where np planet gear teeth and ns sun gear teeth. The planetary gear set is the device that produces different gear ratios through the same set of.
This has become an epicyclic train with a sun gear and a planet gear orbiting around the sun, held in orbit by the arm. Planetary gears, gear train, is 4460, torque density. In this video solve numerical problem related to epicyclic and sun and planet gear train. Zoltan levai received 9 february 1968 abstract both compound and internal or external planet gears are considered as well as the paired planet gears. Gear train with sun, planet, and ring gears matlab. The sun and planet gear is a method of converting reciprocating motion to rotary motion and was used in the first rotative beam engines it was invented by the scottish engineer william murdoch, an employee of boulton and watt, but was patented by james watt in october 1781. Planetary gears are common in transmission systems, where they provide high gear ratios in compact geometries. Since the planetary gear train pgt is an assembly of. That is to say, the number of teeth in the ring gear is equal to the number of teeth in the middle sun gear plus twice the number of teeth in the planet gears. Determine the following if the engine drives the input planet carrier at 4000 revmin. This is because the planet carrier circled the sun gear once in the same direction as it was spinning, subtracting one revolution from the sun gear. A gear train is two or more gear working together by meshing their teeth and.
How epicyclic sun and planet gear box train works youtube. Other uses for gears how gear ratios work howstuffworks. Stick diagram for simple planetary gear train mesh path. Planet gears are just idle gears from the force perspective, and the fbd is shown in fig. A question that i often get is how to work out planetary gears using the gear template generator working out the tooth counts for planetary gears is actually not that complicated, so. It is stated that the simple planetary gear train consisting. Lecture 8 planetary gear train planetary gear trainspgt simple planetary trains structure carrier ring carrier gear sun gear ring gear planet planet. In the toothed formation sun and planet gears are externally mesh and ring gear internally meshes. A typical planetary gear train has three components. The animations shown below are designed to help you gain some insight into the behavior of planetary gearsets. From our study of normal 2gear interactions we know that the amount of traversal is. A new nonlinear bendingtorsional coupled model for doublerow planetary gear set was proposed, and planets eccentricity error, static transmission error, and timevarying meshing stiffness were taken into consideration. The train will end up being reverted gear 1 and 3 will be in line and gear 2.
The smaller of these gears engages an inner planet gear set, which in turn engages an outer planet gear set. Lecture 8 planetary gear train planetary gear trainspgt. Simple compoundgear train n n n n t t t t r nn nn rr rr 26 tttt 16 15 14 15 14 12 23 34 45 56 4 23 4 5 34 56. The gear ratios in the transmission and drive axle are used to match the engine speed and torque output to the vehicle speed and torque requirements. Join the grabcad community today to gain access and download. Lightweight design for planetary gear transmissions. Dec, 2016 epicyclic gear trains are generally used for automatic transmission, overdrives, and final drives. Gears 4 and 1 are in line, and gears 2 and 3 are on the same shaft. On completion of this short tutorial you should be able to do the following.
In the first three types of gear trains, the axes of the shafts over which the gears are mounted are fixed relative to each other. Epicyclic gearing systems also incorporate the use of an outer ring gear or annulus, which. Such a gear configuration has useful applications, but the overall gear ratio. Sun planet ring s r p r c r r r pitch radius of the sun. For concepts b and c the center distances of both gear pairs must be equal, thus enabling both planet gears to be connected to one stepped planet gear shaft assuming the same normal module for both gear pairs. The two sun gears are centrally located and separated longitudinally along a common rotation axis. Figure 22 a planetary gear train with the sun gear and ring gear hidden 11. The sun and planet gear of james watt, actually invented by william murdoch, as a non patentinfringing alternative to the crankshaft for his rotative beam engines. In a planetary gear train the sun gear is at the center. The article will discuss the sun and planet gear arrangement of a typical epicyclic gear train and its applications. Planetary gear train wolfram demonstrations project.
From a kinematic point of view, what sets this mechanism apart is the kinematic constraint set between gear pairs. In this gear system, the yellow gear the sun engages all three red gears the planets simultaneously. Planetary gear trains are common in industrial, automotive, and aerospace systems. The epicyclic gear train family in general has a central sun gear which meshes with and is surrounded by planet gears. A planetary gear train is very much like our own solar system, and thats how it gets its name. The sun and planet gear converted the vertical motion of a beam, driven by a steam engine, into circular motion using a planet, a cogwheel fixed at the end of the connecting rod connected to the beam of the engine. They are more difficult to analyze because they are a two degree of freedom system. This planetary gear train consists of a sun gear yellow, planet gears blue supported by the. This block models a gear train with sun, planet, and ring gears. Planet gear for each planet gear, we can write nslr as follows. Intro planetary gears also refer as epicyclic gearing consisting three elements sun gear, planet gear and ring gear. Pdf by using the poincarelike celltocell mapping method and shooting method, the global characteristics of a planetary gear train are studied based. Following are the different types of gear trains, depending upon the arrangement of wheels.