Internal Gears are gear teeth generated in the internal diameter of a cylinder while external gears have the gear teeth generated on the outside diameter of the component. While there are several different types of gears, only two can be produced as both internal and external gears, spur and helical gears.
An internal gear can also be called a ring gear. Internal gears are used in planetary gear box applications, but can also be applied in other situations.
A common design feature utilized to combat some of the limitations of an internal gear is a profile shift in the involute gear tooth profile. There are large amounts of profile shift that can be designed into internal gears more so than what can occur in external gears.
There are large amounts of profile shift that can be designed into internal gears more so than what can occur in external gears.