I am not sure whether there is such a library for Inventor, but Ed Sparks does have an iGear on the FIRST cad library. The file,
http://www.firstcadlibrary.com/drawi...r(English).zip, lets you choose bore, hub, tooth, pressure angle, DP. It isnt a true involute gear but it is a very good approximation. Hope this helps.
-Rc