File Upload Class: Change file name

[eluser]metamorpher[/eluser]
still having the same issue with the 1.7.1

Code:

$configuracion['upload_path']    = $this->config->item('gallery_upload_path');
        $configuracion['allowed_types']    = 'gif|jpg|png';
        $configuracion['max_size']        = '1500';
        $configuracion['overwrite']        = FALSE;
        $configuracion['file_name']        = "whatever";
        $this->load->library('upload',$configuracion);