Hi Mauro,

You have to overwrite name_get function of product.product object for this.You Can check the sample,

class ProductProductInherit(models.Model):
    _inherit = 'product.product'
    
    def name_get(self, cr, uid, ids, context=None):
        res = super(ProductProductInherit, self).name_get(cr, uid, ids, context=context)
#write the code to here
        #then you can return the product name
        return res

i get a code from another user but i think it refer to odoo 9 because the odoo 8 code is little different.

class PurchaseOrderLine(models.Model):
    _inherit = 'purchase.order.line'

    def onchange_product_id(self, cr, uid, ids, pricelist_id, product_id, qty,
                            uom_id, partner_id, date_order=False,
                            fiscal_position_id=False, date_planned=False,
                            name=False, price_unit=False, state='draft',
                            context=None):
        res = super(PurchaseOrderLine, self).onchange_product_id(
            cr, uid, ids, pricelist_id, product_id, qty, uom_id, partner_id,
            date_order=date_order, fiscal_position_id=fiscal_position_id,
            date_planned=date_planned, name=name, price_unit=price_unit,
            state=state, context=context)
         product_id = res['product_id']
         res['name'] = product_id.name + product_id.default_code
         # for addind  "x_IDfornitore" and x_IDfornitore2 fields
          res['name'] = product_id.name (if needed,) + product_id.x_IDfornitore + IDfornitore2
return res