Fluid flow meter having a fluorine-containing sealant which maintains silicon-containing filler in installation recess

An air flow meter for intake air of an automotive internal combustion engine, comprising:

• a casing installed to an intake air pipe in which intake air flows, said casing comprising a main body section defining a board installation recess, and a peripheral wall section projecting from the main body section and surrounding the board installation recess, a part of the peripheral wall section being cut out to form first and second end portions which are separate from each other to define therebetween an installation plate insertion groove, the part abutting to an inside of the conduit, the first and second end portions having respectively first and second edges which face each other and parallel with each other;
• an installation plate comprising a board installation section disposed in the board installation recess, and an element installation section extending from the board installation section through the installation plate insertion groove to an outside of the board installation recess;
• a circuit board disposed on the board installation section of said installation plate, electronic parts being provided to said circuit board;
• an air flow sensor element disposed on the element installation section of said installation plate, said air flow sensor detecting a flow amount of intake air, said air flow sensor element comprising a temperature sensing resistor;
• a silicon-containing filler disposed in the board installation recess of said casing to cover the circuit board, said silicon-containing filler being formed of a material containing silicon;
• a fluorine-containing sealant disposed in the board installation recess at a portion close to the installation plate insertion groove, said fluorine-containing sealant sealing the installation plate insertion groove so as to maintain said silicon-containing sealant inside the board installation recess, said fluorine-containing sealant being formed of a material whose major component is a polymer containing fluorine;
• and
• a plate-shaped stopper member connected to said casing and inserted in the installation plate insertion groove of said casing and fitted between the first and second edges of the respective first and second end portions of the peripheral wall section of said casing, said stopper member having a tip end in contact with said air flow sensor element, the temperature sensing resistor of said air flow sensor element and said silicon-containing filler being located respectively on opposite sides of said stopper member.