calibre automatically renames all files as they are imported, to the form "title - author.format" -- and this cannot be changed.
Additionally, you can set a metadata template. Preferences ==> Import/Export ==> Saving books to disk. This is preferred, since you are not supposed to touch the library copies except through calibre.
I use
Code:
{author_sort:sublist(0,1,&)}/{title}/{title} - {authors:sublist(0,1,&)}
This is basically the same as the default template, except I make sure only the first author is used, for the case of anthologies with dozens of authors.