可以尝试更改:

<form name="form1" action="<?php echo JRoute::_('index.php')?>" method="get">

到

<form name="form1" action="<?php echo JRoute::_('index.php')?>" method="get">
<input type="hidden" name="option" value="com_mycomponent">
<input type="hidden" name="task" value="search">