Patent GB-1231474-A (GB)
IPC: F01N3/38
Filed: 1968-06-17
Abstract: 1,231,474. Purifying exhaust gases; spark plugs; diaphragm compressors. SUZUKI JIDOSHA KOGYO K. K. June 17, 1968 [June 16, 1967; Nov.24, 1967; Dec.15, 1967; Dec. 26, 1967; Dec.29, 1967], No. 28810/68. Headings F1B and F1N. Mixture escaping through the exhaust port after entering the cylinder from the scavenging port in the case of a two-stroke engine or from the inlet port in the case of a four-stroke engine is ignited by means of a spark plug disposed in the exhaust passage immediately downstream of the exhaust port and burnt to reduce harmful components of the exhaust gas. In the two-stroke engine shown in Fig. 23, scavenging gas admitted to the cylinder from the scavenging port 6 and escaping through the exhaust port 9 before the latter is fully closed is ignited by a spark plug 16 so that most of the hydrocarbons in the exhaust gas are burnt. The spark plug 16 may be operated by the same distributor and coil as the main spark plug 8 or, as shown, by a separate distributor and coil. An ignition chamber 20, Figs. 13 and 23, may be provided in the upper wall of the exhaust passage 31. Scavenging gas excaping through the exhaust port 9 immediately prior to full closure of the port by the ascending piston is ejected as a jet through the upper part of the port, entering the chamber 20 at 21 and being deflected by the wall of the chamber into a turbulent flow. The plug 16 sparks immediately after full closure of the exhaust port 9 to ignite this gas, and the resultant flame travels through the inlet 21 and outlet 22 of the chamber 20 to ignite the escaping scavenging gas existing in a stagnant state in the exhaust passage 31. As shown in Fig. 13, a passage 61 may be provided, leading from the cylinder to an annular groove 100 surrounding the spark plug 16, whereby a pilot supply of gas enters the spark plug via skewed holes 98 which impart swirl to the gas, whereby ignition is ensured. The ascending piston 5 forces the gas through the passage 61 until the latter is closed by the piston. The passage 61 may be replaced by a recess formed in the upper part of the exhaust port and the upper part of the exhaust passage. Alternatively, as shown in Fig. 23, the passage 61 may be replaced by a passage 30 supplied through a line 130 with mixture from the inlet manifold 128 (or from a separate carburetter) by means of a diaphragm pump. In addition, air for ensuring complete combustion may be supplied to the exhaust passage 31 via a passage 110 and a line 118 by means of a further diaphragm pump. Both diaphragm pumps are driven from the engine crank-shaft through gearing and a common spindle 113, Fig. 24, so that the diaphragms 112, 125 are reciprocated once per revolution of the crank-shaft. The pumping chambers 111, 126 may be supplemented by further pumping chambers 111a, 126a which may be selectively used to enable the two pumps to be either in phase on to differ in phase by 180 degrees. The timing and angular duration of the supply of air and mixture can be adjusted by selecting the diameters and lengths of the lines 118, 130 and, if necessary, installing chambers 131, 132. Instead of being supplied by a pump, the mixture fed to the passage 30 may be obtained from the crank-case under the control of rotary valves driven from the crank-shaft. The supply of mixture to the passage 30 may be controlled so as to occur only over the range of engine operation in which combustion would otherwise be incomplete. For this purpose, the supply may be controlled by a mechanically or electromagnetically actuated valve controlled by a diaphragm subjected to the inlet manifold depression, or controlled in accordance with engine speed by means of a centrifugal governor, or connected to the throttle linkage so as to be opened at small throttle openings. Cutouts (101), Figs. 19 and 21 (not shown) may be provided in the annular outer electrode (93) of the spark plug 16, whereby the annular spark gap is divided. This affords a cooling effect and facilitates sparking and correction of any eccentricity of the centre electrode (92).