Custom component strings for component without sef_ext

hello,
I created a small component with its file router.php to generate the sef url, but I can not change the component name  pippo=>pluto in the Sef Advance options.
Is not possible  change the name for a components with a file router.php?
it is better to write a file sef_ext.php instead of router.php?

thx for help and sorry for bad english.

Yes, you can change component name only if it has sef_ext.php extension.