why is the $this->db not available in a certain module?

In my controller I am using $this->load->database(); which gives me access to $this->db in that controller. I have a php file at /app/assets/MyExport6765.php. But I have no access to $this->db in it. I can see $this in my debugger, but the db is not in there. Is there someway that I can share the same dbase handle from my controller with MyExport6765.php? I need to do some dbase manipulations of a table in that module. 

proof that an old dog can learn new tricks