WP_QUERY() to XML File

Hello,

i want to export a WP_Query result to an xml File:

$type = 'product';
$args= array(
   'post_type' => $type,
   'post_status' => 'publish',
   'posts_per_page' => -1
   );	

$array_in = new WP_Query($args);

I need a function to parse this into an xml output file.

regards