Patent ID: 6633646
Filing Date: 2003-10-14
Classification: G10K

Abstract:
An apparatus for controlling exhaust noise from an internal combustion engine, comprising:a main exhaust pipe; a first bypass pipe having a length which is variable and connected to said main exhaust pipe at both ends thereof so that a first bypass section is defined in the passage of said main exhaust pipe, and two air delivering passages each passing through each of the two connection points for said main exhaust pipe and the first bypass pipe are formed thereby; a second bypass pipe having a length which is variable and connected to said main exhaust pipe at both ends thereof so that a second bypass section is defined in the passage of said main exhaust pipe, and two air delivering passages each passing through each of the two connection points for said main exhaust pipe and the second bypass pipe are formed thereby; first and second actuators adapted to be actuated to vary the length of said first and second bypass pipes, respectively; a controller for controlling said first actuator to select the length of said first bypass pipe so that the lengths of said two air delivering passages passing through said two connection points of said main exhaust pipe and said first bypass pipe differ from each other by a half wavelength of a main noise component occurring in said internal combustion engine, and for controlling said second actuator to select the length of said second bypass pipe so that the lengths of said two air delivering passages passing through said two connection points of said main exhaust pipe and said second bypass pipe differ from each other by a half wavelength of a noise component having a frequency of two times the frequency of the main noise component occurring in said internal combustion engine; a lower back pressure muffler installed downstream of said main exhaust pipe; and a higher back pressure muffler provided separately from said lower back pressure muffler; such that when the engine revolutions per minute are higher than a predetermined value, said main noise component and said noise component having a frequency of two times the frequency of said main noise component are eliminated at said two connection points of each of said main exhaust pipe and said first and second bypass pipes, and the remaining noises of other wide frequencies pass through said lower back pressure muffler, and when the engine revolution per minute is lower than the predetermined value, the exhaust noise passes through the higher back pressure muffler.