GB572350A - Improvements in or relating to ignition timing control devices for internal combustion engines - Google Patents

Abstract

572,350. Ignition timing control. UNITED AIRCRAFT CORPORATION. Dec. 24, 1943, No. 21680. Convention date, Dec. 23, 1942. [Class 7 (iv)] [Also in Group XXIX] An ignition timing control device for an internal combustion engine 26 has servo motor means, responsive to the pressure rise across the supercharger 10, for retarding the ignition at low or high values of the pressure rise and advancing it at intermediate values of the pressure rise. The two magnetos 12, 13 are driven from an engine shaft 32 through a shaft 36 carrying bevel-gears which drive loose compound bevel gears 46, 50, Fig. 2, on each magneto shaft 52. From gear 50 the drive is transmitted to a bevel gear 60 keyed to the .magneto shaft by bevels 54 carried by a cage which is movable around the shaft 52 to alter the timing by means of arms 76 pivoted to the bar 72 of a yoke operated by the piston 64 of the servo motor. The latter comprises cylinders 66, 68 fitted with plugs provided with piston stops 82, 80, the piston being normally urged against the stop 80 to give retarded ignition by spring 78. The servo control valve 104 is actuated by a spring-urged diaphragm which is subjected on its upper and lower sides to the outlet and inlet pressures, respectively, of the 'supercharger. At moderate engine power corresponding to cruising speed the diaphragm is in the intermediate position shown in Fig. 1, thus applying pressure fluid from line 94 through line 84 to cylinder 68 to give advanced ignition timing. When -the diaphragm is raised by fall in the supercharger pressure rise fluid flow is along line 86 to cylinder 66 to cause retarding of the ignition. Also when the diaphragm is lowered when engine operates in upper part of its power range pressure fluid enters line 86 and again produces retarded ignition.