Flow rate detecting element and flow rate sensor using same

A flow rate sensor comprising:

• a measuring conduit having a cylindrical shape and arranged in a path of a measured fluid with an axial direction thereof substantially coincident with the flow direction of the measured fluid;
• a flow rate detecting element having a flat substrate provided with a gap opening on at least one side surface thereof, a sensor section including a heating resistance element and a pair of temperature detecting resistance elements arranged on opposite sides of said heating resistance element, and wrapped by an insulating supporting film and an insulating protecting film from above and below, wherein said sensor section is arranged on a plane substantially parallel with a surface of said flat substrate and at least one end of said supporting film is held by said flat substrate to locate said sensor section over said gap, whereby a major portion of said sensor section is disposed in a non-contact state with said flat substrate, and a thermal conduction promoting member in the form of a thin film disposed in a heat transmitting path of said sensor section between said heating resistance element and said pair of temperature detecting resistance elements, said thermal conduction promoting member having a substantially higher thermal conductivity than said supporting film and said protecting film;
• a control section which maintains said heating resistance element at a prescribed temperature by controlling power fed to said heating resistance element;
• and
• a temperature measuring section which measures temperature of said pair of temperature detecting resistance elements.