Your partnership agreement is going to take precedence over the provisions of Oregon's partnership act which is found in ORS Chapter 67. Typically, partnership agreements have provisions for "winding up" business when it comes time to do so.
Your partner may be able to liquidate the business if you don't let him buy you out, but really it all depends on the partnership agreement. If the agreement is silent on the issue, then ORS Chapter 67.290 has the laws on winding up a business partnership.
If this is a valuable business, I would encourage you to seek counsel on the matter. I would be happy to sit down with you at no cost and try to give you a little direction. If you wanted my assistance beyond that I would charge an hourly rate as listed on my profile.
Anyway, good luck.