While click on any button first the record will save (create will call) after that corresponding button action will call. 

Every time you called the create method it will generate the new record in your model and if you are making some of the object button and you clicked it the activity which you have defined on the object button will get called first and the changes which are done in the form will get save when you clicked on the save button.

@subbarao

Ok,

thank you.

Is this an odoo implicit behavior ?

What can I do if I want create a new button without this behavior? I know how to modify the view but I don't know how TO AVOID the implicit save of the record.........