Order post by subcategory – display each in one row

Hi!
I’m trying to display my post ordered by child category
Example:
subcategory1 –> post1 – post2 – post3
subcategory2 –> post1 – post2 – post3
subcategory3 –> post1 – post2 – post3
ecc…
This is my query…doesn’t work and display every post of every category:

<?php $cats = array(
	'type'                     => 'post',
	'child_of'                 => 71,
	'orderby'                  => 'name',
	'order'                    => 'ASC',
);?>
 <?php 

  query_posts('$cats&posts_per_page=45' );

  if ( have_posts() ) while ( have_posts() ) : the_post(); ?>

Anyone can help me?
I suppose it should not so difficult but now drives me crazy! ??

thanks!