If you have been following the recent posts then you know the sugya in Rosh Hashana [28a]. There Rashi says that the reason no כוונה is required for matza is because he is not a מתעסק since he is נהנה from the eating.
That is very nice. No מתעסק. But where is the כוונה לשם מצוה? Just because someone is not מתעסק doesn't mean that they have כוונה לשם מצוה. It just means that they intended to perform the action. [Unless what the gemara is saying is that in fact no כוונה is necessary and all we need is that it should not be מתעסק and the הנאה makes it that way. In contrast to שופר where the person is מתעסק when he is תוקע לשיר].
In the Shiurei Iyun Hatalmud he explains that the reason that we need כוונה for a mitzva is in order that the מעשה should be classified as a מעשה מצוה. Otherwise, it is an empty act. [And that is why in the world of kodshim we don't find any concept of מצוות צריכות כוונה. Because the very act of bringing a korban which creates כפרה bears the stamp of a מעשה מצוה]. If so - the הנאה one derives from eating the matza is the mitzva and thus nothing more is needed in order to give it a שם מעשה מצוה. That is why one doesn't need כוונה לצאת. One only needs כוונה when the מעשה is the mitzva.
I am PERPLEXED. The gemara says in Pesachim [115b] that one is yotzei if he swallows the matza without chewing it.
Where is the הנאה? How can the מצוה be the הנאה if one can be yotzei without הנאה???