I think you need to see this.

You should modify file ../addons/web/http.py at line 450 (last_week = time.time() - 60*60*24*7), and replace 60*60*24*24*7 by the value you want (Idle Time = Timeout - in seconds ) (e.g for 15 minutes = 60*15, for one day = 60*60*24, for 2 days = 60*60*24*2 ...). And restart the server if needed.

https://www.odoo.com/forum/help-1/question/how-to-implement-automatically-signout-in-odoo-8-or-openerp-7-human-resource-module-if-the-pc-is-idle-or-sleep-condition-68076

This is the easiest solution, however I tested it and it works but quiet often i was getting some errors.