Exhaust device for two-stroke internal combustion engine

#The present invention relates to a device for receiving the exhaust gas output of a reciprocating piston internal combustion engine, and more particularly discloses a muffler assembly that is particularly advantageous for use with a two-stroke gasoline engine, which assembly provides both an exhaust scavenging function and a supercharging function, and in addition, comprises a low profile and compact design.

#This invention discloses an exhaust gas handling assembly for an internal combustion engine, which is especially useful in small two-stroke gasoline engines such as in radio-controlled airplanes and wheeled vehicles for ground travel, such as motorcycles and all terrain vehicles. The device is commonly referred to as a muffler, but this is a term that is too restrictive for all the functions performed by the device. While the device does serve to muffle or dampen the noise of combustion in such internal combustion engines, it also serves at least two other critical functions, exhaust scavenging and fuel-charge densification.

#The present invention has been found to be particularly advantageous when used on a two-stroke, internal combustion, piston and crankshaft type engine which burns a volatile fuel such as gasoline and/or alcohol, and which utilizes valving consisting of ports formed through the wall of the piston cylinder, controlled by movement of the piston within the cylinder to alternately expose and cover up said ports.

#FIG. 1 is a front schematic view of the muffler device of the present invention;

#FIG. 2 is side sectional view of the invention taken at line 2—2 of FIG. 1;

#FIG. 3 is a side sectional view of the invention taken at line 3—3 of FIG. 1;

#Referring to FIGS. 1-3, and more particularly FIG. 1, the muffler device 101 is illustrated as it appears when viewing from the front of the engine 102 to which it is attached. Muffler 101 consists of three basic modules, the pipe section 103, the can section 104, and the cover plate 105. As illustrated in this embodiment, the muffler 101 is cylindrically shaped, but as illustrated in the second embodiment herebelow, this shape could just as well be any geometrical shape desired, including square and rectangular.

#FIG. 2 is a sectional end view of the pipe section 103 taken at line 2—2 of FIG. 1. The pipe section 103 consists of a cylindrical outer housing shell 106 and a helical divider wall 107 spiraling inward from the outer wall 106 to a central chamber 108. The axial height of spiral wall 107 is equivalent at all points to the height of shell 106, so that the addition of the flat inner wall 109 of can section 104 against pipe section 101 serves to seal against the entire length of divider wall 107, thereby creating a sealed spiral passage 110. The only openings to passage 110 are the inlet opening 111 communicating with the exhaust valve of engine 102, and an exhaust outlet opening 112 formed in wall 109 of can section 104. One or more mounting holes 113 are formed through the left wall 114 of pipe section 103 for mounting the muffler device 101 to the engine 102, allowing the passing therethrough of mounting screws or bolts from the wall section 114 to the engine block of engine 102.

#FIG. 3 is a side sectional view of the can section 104 of the muffler device 101, taken at line 3—3 of FIG. 1. Can section 104 consists of cylindrical housing or shell 115 which is machined for tight-fitting sealing engagement with housing 106 of pipe section 103, a flat wall section 109 adapted to seal off and create the enclosed spiral passage 110 in pipe section 103, and a chamber forming divider wall 116 which is attached to wall section 109 and is arranged to seal against cover section 105 to form an expansion and compression chamber 117. An exhaust inlet opening 112 is formed through wall 109 to communicate with passage 110 in pipe section 103, and is generally located at about the center of section 104. The opening between pipe section 103 and can section 104 must be at or near the end of the spiral passage 110 for proper operation, i.e., at the center of the pipe section, designated as outlet 112. The opening from the expansion chamber 117 to the atmosphere can be located through cover plate 105 so that it aligns with either end of expansion chamber 117. In FIG. 3 this is indicated in phantom at 118 to show the location of the exhaust port with respect to opening 112. An alternate location for the exhaust port in the cover plate 105 is also indicated in FIG. 3 at 119. Either location, 118 or 119, allows exhaust gas to be flowed out of the muffler device while still taking full advantage of the expansion/compression chamber 117. However, the exact location of this port is not critical to the operation of the invention, because changing the location serves mainly just to change the back pressure that is created within the exhaust assembly and to also vary the temperatures reached within the exhaust assembly. Also, the size of port 118 determines pressures, temperatures and mass flow effects within the entire exhaust system. One skilled in the art, with only a minimum of trial and error, will be able to vary the size and location of port 118 to optimize the particular exhaust effects desired, depending upon the application of the engine on which the system is to be installed, and depending on the RPM range at which the operator wishes power from the engine to be optimized.