A planetary gearbox is a type of gearbox with the goal of lowering the torque or speed of a rotating input shaft. It does so using the system after which it is named, a system of gears that revolve around a central gear. To further flesh out the analogy, the three main components of a planetary gearbox are known as the sun gear, the planet gears and the ring gear. A few of the applications that are matched with planetary gearboxes include: automatic transmissions, sprinklers, electric screwdrivers and any other applications that need multiple or large reductions from a compact mechanism. It should be noted, however, that the primary application for which planetary gearboxes are used is in automatic transmissions and motor vehicles. Automatic transmission systems contain two complete planetary gearsets placed together in one component. They rely on a combination of brake bands, clutches and planetary gearboxes to change the inputs and outputs, which in turn allows for corresponding speed changes.
Quick links to Planetary Gearbox Information
Design of Planetary Gearboxes
A planetary gearbox is usually constructed from a heavy duty metal, such as steel or a steel alloy, that can help it react well to large shock loads. It may be custom designed for different applications with unique torque, load and speed requirements. However, in all forms, because of the varying planet gears that revolve around the sun gear, a planetary gearbox is capable of producing a number of different reduction ratios. In more detail, any of the three components of the planetary gearbox may be the input, the output or be held stationary in an application, which allows for a greater range and more possibilities of reduction ratios. For example, in many planetary gearbox designs, the sun gear is held stationary as the ring gears are the input and the planet gears are the output. Meanwhile, in some configurations, the central position of the sun gear allows the planet gears to rotate in the same direction, as well as for the ring gear to rotate in the same direction as the sun gear. Furthermore, in other configurations, the sun gear is designed to simultaneously turn all the planets while they still engage the ring gear. Also note that the gears are attached to the ring gear, which is the planet carrier that has teeth on the inside, and that planetary gearbox reduction ratios are, in addition to what components are engaged, partially dependent upon the number of teeth in the gears.
Types of Gearboxes
As a rule, the load capability and the torque increase as the number of planets in the system increase. This is due to the fact that the load is evenly distributed among the gears. As a result, planetary gearboxes suffer very little energy waste, instead enjoying an efficiency that averages between 96% and 98%. This is one of the many advantages of planetary gearboxes. It is important, however, that the right gearbox be selected for a job. Planetary gearboxes are just one of many different types of speed reducers, so it is important to discuss your specifications with a manufacturer that can determine if planetary gearboxes are right for you. In some cases, manufacturers will even design speed reducer systems that combine planetary gearboxes with other gearbox types in order to produce the best possible results. Most commonly, the gearbox types with which they are combined are inline gear reducers, helical reducers and worm gear reducers.
Things to Consider When Purchasing Planetary Gearboxes
Planetary gearboxes are highly customizable. They are available with a variety of mounting options, optional housings and electrical or mechanical preload options. They can also be designed with different sizes, different reduction ratios, different input speeds, different torque ratings and densities, different angle arrangements, different output bearings designs and more. In addition, most manufacturers can and will construct planetary gearboxes that meet ISO standards. Planetary gearbox design is complex and comprehensive. Another reason that it is important to select the right design is the fact that, if it is the wrong design, users will find that, once installed, the gearbox is difficult to access. So, it is not easy to make repairs or perform maintenance checks. Unfortunately, that comes with the territory and there is little that can be done about that other than being proactive and finding the best planetary gearbox for the best price. To figure out what you need and to get what you need, talk to an experienced manufacturer about your application. Narrow down your search to the best and brightest by browsing the list of quality manufacturers and suppliers listed here on this page.