Patent GB-574669-A (GB)
Title: Improvements in means for regulating the scavenging and charging in two-stroke injection internal combustion engines
IPC: F02B25/00
Filed: 1944-07-10
Abstract: 574,669. Two - stroke engines. SOC. ANON. A. SAURER. July 10, 1944, No. 13166. Convention date, July 12, 1943. [Classes 7 (ii) and 7 (vi)] In a two-stroke, fuelinjection, internal -combustion engine having a directly driven charging and scavenging blower 18 and having an engine-driven valve 8 arranged to close the exhaust passage 7, the instant of closing of this valve is simultaneously varied by two operational magnitudes, one of which, such as the speed, blower pressure, or external air pressure tends to maintain a maximum charging pressure in the full load range and the other, such as the amount of fuel injection tends to produce in the partial load range, the minimum scavenging and charging pressure required for adequate scavenging so as to minimise the power absorbed by the blower at light loads. In Fig. 1, the cylinder has pistoncontrolled inlet ports 2 ,and exhaust ports 3 and the rotary valve 8 in the exhaust passage is driven from the crank-shaft through spur gearing 9, 10, spiral gears 11, shaft 13, sliding sleeve 14, shaft 15 and bevel gearing 17. The sleeve 14 is connected to shaft 15 through helical key-ways so that by moving this sleeve axially the timing of the valve 8 is varied. In order to maintain the full blower pressure in the cylinder for different speeds in approximately full load conditions, the instant of closure of the valve 8 is made progressively later as the speed of the engine rises. For this purpose a speed governor 21 actuates a lever 24 connected by rod 26 to a second lever 27 actuating the sleeve 14 so as to give later closing of the valve as the speed rises. In ,Fig. 2, the exhaust ports open and close at Eo, Ec respectively and the inlet ports at Io and Ic respectively. In full load conditions, the valve 8 is closed at KsI at low speed and at KsII at high speed. To reduce the blower delivery pressure at low loads, the closing of the valve 8 is made progressively later as the fuel injection of the engine decreases and occurs at the point KsIII at low speeds and at KsIV at high speed. For this purpose, the fuel pump lever 31 is connected to the fulcrum of lever 24 so that at constant speed the fulcrum is moved downwards with decreasing fuel injection, thus imparting upward movement to the sleeve and retarding the closing instant of valve 8. In a modification, Fig. 5, the blower pressure itself acts through a piston 34 against spring pressure to operate the sleeve 14. In this form, if the blower pressure falls under full load conditions, the piston 34 moves downwards and the valve member 8 closes earlier, thereby increasing the charging pressure. Under partial and no load condition the fuel pump lever acts as before to retard the closing of valve 8 and reduce the charging pressure. In another modification used when the engine is mounted in an aircraft, a barometric capsule is employed, so that as charging pressure tends to fall at increasing heights the capsule operates to produce earlier closing of the valve 8 and thus increase the charging pressure. In this case also the fuel pump lever acts to retard the valve closure'to lower the charging pressure at light loads.