Application of magneto-elastic sensors to the measurement of fluid flow rates in the automotive domain

The monitoring of several vehicle and engine operation parameters has been a key factor for the successful introduction of electronic control of the most important car performances. Among the several measured quantities, the measurement of fluid mass flow still requires sophisticated and expensive transducers, no convenient and low cost technologies having been available so far. The recent invention of the concept of bi-layer ribbons, has allowed to adjust the sensitivity of magneto-elastic sensing elements to be employed in the construction of bending sensors, in order to match their metrological properties to the wanted application. Due to their low production cost, small size and good reliability, magneto-elastic bi-layer sensors proved to be a promising technology for the large scale production of fluid flowmeters, which can be used in the automotive industry and are operated in a very wide temperature range, with temperatures spanning from -25 to 115°C. In the present research, two main application domains have been taken into consideration namely the flow metering of the air streaming into engine air intake manifolds and the measurement of the flow rates of refrigerant fluid in the cooling loop of car air conditioning systems (HVAC). The technical feasibility of agglutinated bi-layer flow sensors, has been investigated and evaluated, by means of experimental testing under real like operating conditions. The present paper briefly describes the manufacturing process and the experimental methodologies. Preliminary results are given and future developments are foreseen, while further research guidelines are established.