Patent GB-723982-A (GB)
Title: Improvements in internal combustion engines
IPC: F02D19/10
Filed: 1951-11-16
Abstract: 723,982. Convertible gas and diesel engines ; starting and stopping regulating. GENERAL MOTORS CORPORATION. Nov. 16, 1951 [Dec. 9, 1950], No. 26889/51. Classes 7 (2), 7 (3), 7 (5) and 7 (6). [Also in Groups XXVI, XXVIII and XXIX] An engine operable alternatively on oil fuel alone or on gaseous fuel supplemented by oil injection to cause ignition has a gas control valve movable in opposite directions towards closed position from an intermediate fully open position, an oil injection pump of which the delivery may be varied by a control element which, from an intermediate position in which the pump supplies an injection of oil for gas ignition, is movable in one direction to vary the timing of that injection and in the other direction to increase the quantity of oil injection, a governor which maintains engine speed by adjustment of said valve or element and is capable of effecting automatic transition between gas operation and operation on oil fuel alone according to the availability of gas, and an interconnection between said valve and element such that they move in unison and both occupy their intermediate positions substantially simultaneously. Engine construction. In a multi-cylinder two stroke engine, each cylinder 5, Fig. 1, has an oil injection pump 51, a gas injection nozzle 25, one or more poppet exhaust valves 50 and a ring of inlet ports 21 supplied by an enginedriven Roots blower 8, the valves 50 and pumps 51 of all the cylinders being mounted in a single head block 43 and actuated from a camshaft 110. Oil injection means. The pumps 51 are held in head block seatings by clips 125, and each pump comprises a plunger 87, Fig. 6, reciprocable to force oil intermittently from a chamber 88 through one-way valves 83, 75 and openings 67 in an injection nozzle 65 into the combustion space 45. The injected oil is drawn from an annular chamber 93 through which a constant circulation is maintained between inlet and outlet ducts 89, 91, part of the flow being by-passed via a port 95, plunger groove 127, radial and axial plunger bores 129, 130, the chamber 88 and a port 97 when the plunger 87 is in the raised position shown. As the plunger moves down, oil injection commences when passage of the upper edge of the groove 127 past the port 95 traps the oil in the chamber 88, and ceases when passage of the lower edge of the groove past the port 97 releases the oil in the chamber. The plunger 87 is rotatable by a rack and pinion 117, 113, Fig. 1, to vary the duration and timing of oil injection as described below. Gas supply means. The gas nozzle 25, which injects through a port 27<SP>1</SP>, is pressed against the cylinder 5 by a spring 37 in a feed chamber having appropriate openings 41 in the side flanges 40, Fig. 8, thereof, a plug 159 and flexible hose connections 157 serving to connect all the feed chambers to a feed line 149 via valves 143, 145 and 147. The valve 143, Fig. 9, ensures that the gas pressure always exceeds that of the blower delivery, air from which is applied through a pipe 299 above a flexible diaphragm 285 to act in conjunction with a spring 289 against the gas pressure admitted beneath the diaphragm through a conduit 270, the action being such that increase or decrease of air pressure tends to open or shut a valve 275 in the gas line 273, 281, 279 and so cause a counterbalancing increase or decrease in gas pressure. The spring 289 may be adjustably set by a hand-screw 295. The valve 145, Fig.8, is opened only when the engine lubricating oil system attains a safe working pressure. The gas control valve 147, Fig. 3, comprises a rotatable body 209 having diametrically opposed slots 247 co-acting with bores 246 leading through a surrounding sleeve 213 into a gas inlet chamber 245. The slots 247 communicate through both ends thereof with a gas outlet 217, the valve being thus axially and radially balanced in respect of gas pressure. Engine operation. Conjoint control of the oil injection pump plungers 87 and gas control valve 147, acting as control elements, is effected by a floating lever 171, Fig. 3, fulcrumming about the end of an arm 169 on the shaft 165 of an engine-driven governor and pivoted at one end to an arm 179 on the shaft of a manual throttle lever 191 normally located by a detent plate 192 in one of three positions corresponding respectively to engine shut down, idling and full speed. The other end of the lever 171 is pivoted both to a rod 197, Figs. 1 and 3, operating the racks 117 and to a quadrant 201 actuating the valve 147 through a pinion 207. Movement of the rod 197 and quadrant 201 in the direction of increased fuel delivery can be limited by turning an axially adjustable shaft 250 to bring a stop lever 249 controlled by a spring-loaded detent 253 into the path of a quadrant extension 201, and this is effected when operation only on gaseous. fuel supplemented by oil injection is desired. When the extension 201 is against the stop lever 249, the valve 147 and the plungers 87 are in the above-mentioned intermediate positions, the valve 147 being fully open and each plunger in the angular position shown in Fig. 7 (a developed view). On starting the engine with the stop lever 249 operative the throttle lever 191 is moved to its full speed position causing the valve 147 and plungers 87 initially to take up their intermediate positions, the governor then acting as engine speed increases to move the extension 201 away from the stop lever 249 until equilibrium is reached. The governor then acts to maintain a uniform speed at varying load by changing the equilibrium point, the ports 95, 97 co-acting with mutually similarly inclined edges 131, 140 of the groove 127 so that the timing but not the duration and amount of oil injection varies, the timing being advanced or retarded as the load increases or decreases respectively. Upon the stop lever 249 being rendered inoperative the governor is allowed to move the valve 147 and plungers 87 past their intermediate positions if engine speed falls due to gaseous supply failure. The ports 95, 97 thereupon co-act with edges 131, 139 and the duration and amount of oil injection is increased sufficiently to restore engine speed. Upon gaseous supply resumption the original working supervenes. Using gaseous fuel, the engine may by movement of the throttle lever 191 be operated between the full speed and idling positions thereof in the latter of which the ports 95, 97 co-act with edges 131, 141 and the engine idles under governor control. On movement of the lever 191 to its shutdown position the valve 147 closes and the ports 95, 97 co-act with edges 137, 141 sufficiently separated to prevent oil injection.