| 摘要 |
1491884 Spray carburetters YAMAHA HATSUDOKI KK 14 Oct 1974 [24 May 1974 26 June 1974 12 Aug 1974] 44384/74 Heading F1H A carburetter of a four-stroke engine operable with a lean mixture has a low load mixture system opening adjacent the throttle valve 30b and the ratio of the diameter d o of an air bleed orifice 320 of the low load system to the diameter D of the throttle valve containing bore is in the range between 0À035 and 0À065. To permit low load operation with a lean mixture the overlap of the inlet and exhaust valves is reduced compared with the high load overlap by increasing the length of a drive chain (85), Fig. 3 (not shown), between respective cam-shaft drives and/or the carburetter throttle valve is more open and the ignition is retarded to provide the same engine speed with normal throttle valve opening and ignition timing. A multi-cylinder engine may have one carburetter (120), Fig. 8 (not shown) supplying all the cylinders or respective carburetters (20a to 20d), Fig. 2 (not shown). The carburetter may have a liquid fuel collecting groove (33b), Fig. 11 (not shown) and the engine intake passage portions (17, 228), Figs. 4 and 8 (not shown), may be operated at a temperature between 90 and 135‹C to ensure vaporization of the fuel. The carburetter includes a manually operable starting mixture system. Fig. 16 (not shown). The engine includes an exhaust gas recirculation passage (143), Fig. 8, to the intake manifold (112) or respective passages (13a to 13d), Figs. 2 and 4, controlled by a suction operated valve which prevents recirculation at low load. The respective passages contain non-return valves (208), Fig. 18 (not shown), or flow restricting orifices (209), Fig. 19 (not shown). The engine has a thermal exhaust reactor (40), Fig. 14 (not shown) in the exhaust system, the reactor having a jacket (350) for cooling air controlled by a valve (353) to provide an optimum reactor temperature. The engine ignition system may include a plate (240), Fig. 9 (not shown), carrying points (251) providing optimum ignition and points (252) providing retarded ignition which are effective when the carburetter throttle valve is minimally open or the intake passage vacuum low. |
