My research supervisors want to patent an idea I made and I get a minority part of the invention
You should read your university's intellectual property policy.  If this matter is important to you, you should also consult a lawyer.  

I think you are probably confusing the concepts of credit and ownership.  The inventors get credit for creating the invention, but the owners have the right to exploit the patent.  Most likely the university owns all of the patent and the inventors who are employees or students own none if it.  The university may assign a portion of any profits to the inventors as an incentive.  This would be entirely at the university's discretion, and would typically be described in a published policy.