Asking to collaborate with a professor on a research project

[ppspnn20100]

Hi to all, 

I am a 2nd year PhD student in Hispanic Linguistics at a university in the United States, and my department is very research oriented. I have noticed that many fellow graduate students have been asked to collaborate with certain professors on research, which usually turns into conference presentations and an article for publication. My faculty mentor is no longer teaching and is not producing as much research as they were a few years ago, which is what originally interested me about the program. I have multiple ideas about research projects, but as you know it takes a lot of time to pursue, but I wanted to ask my faculty mentor to collaborate with me on a project, but I do not know if this is looked down upon in academia. I feel like I need to be more assertive since I tend to work independently. Any opinions or thoughts would be greatly appreciated!