Fuel heating apparatus for internal combustion engine

Claim 1

In an internal combustion engine including an intake pipe, a throttle valve provided therein, means upstream of said throttle valve for supplying liquid fuel into said intake pipe and an intake manifold for distributing a mixture of air and the fuel to respective engine cylinders, said intake manifold defining an inlet opening connected to the bottom end of said intake pipe, the improvement which comprises a fuel heating apparatus including a tubular extension member disposed substantially coaxially with said intake pipe and extending downwardly through said inlet opening into said intake manifold and having a substantially cylindrical inner peripheral surface substantially flush with the inner peripheral surface of said intake pipe, and an annular heating element disposed in said intake manifold substantially in vertical alignment with the peripheral wall of said tubular extension member and supported therefrom wherein said inlet opening in said intake manifold is substantially coaxial with said intake pipe and has an inner diameter greater than the inner diameter of said intake pipe, the part of said intake manifold below said inlet opening defining a distribution chamber from which the mixture of air and fuel is distributed through branches of said intake manifold to respective engine cylinders, said heating element including a generally annular casing disposed in said distribution chamber and spaced downwardly a distance from the bottom end of said tubular extension member, at least one stay supporting said casing from said tubular extension member, said casing having a substantially annular open top disposed beneath the bottom end of said tubular extension member so that the part of the fuel which flows in liquid phase on the inner peripheral surfaces of said intake pipe and said tubular extension member falls down therefrom into said casing, a substantially annular heating means disposed in said casing and adapted to be electrically energized to heat and vaporize the liquid part received in said casing, wherein the part of said intake manifold which defines said inlet opening has a flat top surface secured to the bottom end of said intake pipe with a heat insulating member and a gasket member being sandwiched therebetween, said flat top surface being formed with an annular recess adjacent the peripheral edge of said inlet opening, and wherein said tubular extension member has an annular flange extending radially outwardly from the upper end of said tubular extension member into said annular recess, said annular flange having a top surface substantially flush with the top surface of said intake manifold around said annular recess, wherein said heating element further includes inner and outer annular packings disposed in said casing in substantially concentric relationship with each other, said annular heating means comprising an annular heating plate of a sheet metal having inner and outer peripheral edges axially and radially supported by said inner and outer packings, an annular ceramic heater disposed in heat-conductive relationship with the underside of said heating plate and adapted to be electrically connected to an electric power source, said ceramic heater being also electrically connected to said casing.