Joomla DB where statement not works as expected

I don’t understand the world right now. I try to make a simple query from the DB, but it fails with the message that the column is not known. I do not understand why Joomla! tries to see the value I am looking for as a column. This is my query:

            $data = new stdClass();
        try{
            $db = JFactory::getDbo();
            $query = $db->getQuery(true);
            $query
                ->select('*')
                ->from($db->quoteName('#__extensions'));
                $query->where($db->quoteName('element') . " = " . $db->quoteName('com_componentname'));
            $db->setQuery($query);
            $data->params = $db->loadObject();


        }catch(Exception $e){
            $data->query = $query->dump();
            $data->errormsg = $e->getMessage();
        }

        return $data;

    }else{
        return false;
    }

The response is:

'errormsg' => 'Unknown column 'com_componentname' in 'where clause'',

Why does Joomla! try to find the component name as a column? What I want:
Where componentname in Columns name from table extensions.

Or is there another / better way to load the parameters of a component within a module?

$query->where($db->quoteName('element') . ' = ' . $db->quote('com_componentname'));