Exhaust system for an internal combustion engine, burn-off unit and methods therefor

In a torch means for a burn-off means for an exhaust system of an internal combustion engine which burns a hydrocarbon fuel mixture and which produces a carbonaceous particle carrying exhaust gas stream that passes through a filter means of said system that retains at least part of said particles therein, said burn-off means being adapted for periodically burning said retained particles in said filter means to tend to periodically clean said filter means of said retained particles thereof, said torch means for said burn-off means comprising means for raising the temperature of said exhaust gas stream intermediate said engine and said filter means to raise the temperature of said filter means to particle burning temperature thereof, said means for raising the temperature of said exhaust gas stream comprising means for injecting and burning a certain amount of said fuel mixture in said exhaust gas stream intermediate said engine and said filter means, the improvement wherein said means for injecting and burning comprises means for aspirating said certain amount of said fuel mixture into said exhaust gas stream intermediate said engine and said filter means and said means raising the temperature of said exhaust gas stream comprises an electrical heater means and a catalyst bed in which said injected fuel mixture is to burn, said electrical heater means and said means for aspirating said fuel mixture being disposed upstream from said catalyst bed with said heater means being disposed intermediate said means for aspirating said fuel mixture and said catalyst bed, said means for raising the temperature of said exhaust gas stream also comprising passage defining means having an inlet for receiving said exhaust gas stream from said engine and an outlet for directing said received exhaust gas stream to said filter means, said catalyst bed and said heater means being disposed in said passage defining means, said means for aspirating said fuel mixture being disposed to feed said fuel mixture to said passage defining means upstream of said heater means therein, said passage defining means having valve means disposed in said passage defining means between said means for aspirating said fuel mixture and said heater means for closing said passage defining means between said inlet and said outlet.