Patent GB-610329-A (GB)
Title: Control mechanism for supercharged internal combustion engines
IPC: F02D19/12
Filed: 1945-10-06
Abstract: 610,329. Fluid-pressure servomotor-control systems. GENERAL MOTORS CORPORATION. Oct. 6, 1945, No. 26063. Convention date, Aug. 19, 1944. [Class 135] [Also in Group XXVII] Control mechanism for a supercharged internal - combustion engine comprises means for injecting an antidetonant into the fuel mixture and a variable datum boost control for the throttle valve by which any one of a range of intake manifold pressures can be selected, the injection means and boost control being inter-connected such that for normal operation the range is limited to a safe operating value whilst the limit of the range is automatically raised consequent to injection. The Figures show a throttle valve 49 for an aircraft engine at the inlet to an auxiliary supercharger 1.2 which supplies a main supercharger 11 (Fig. 1), the throttle valve being controlled both manually and by a servomotor TC (Figs. 3 and 4). The servomotor operates to keep the induction pipe pressure at a value which is determined by a cam 1.56 interconnected with the manual throttle control and a stop 240 (Fig. 6). The stop is operated by water pressure from the water or water and alcohol injection system. When the water injection system is functioning properly the stop is inoperative and the cam can set the servomotor to control at a higher pressure than otherwise. Figs. 3, 4 and 5 placed side by side make one complete Figure. The water injection system comprises a pump 60, Fig. 5, drawing its supply from a tank 50 and delivering through a filter 98, unit 100, pipe 101 into a fuel nozzle 23 in the induction pipe in front of the main supercharger. The unit 100, Fig. 11, includes a diaphragm-operated valve 127 which is opened whenever water is flowing through the unit and allows the water pressure to pass by a chamber 129 and pipes 130 and 131 to a chamber 133 in the servomotor housing to a chamber 132, Fig. 4, of a fuel metering or carburetter unit 21 and to a pressure switch 135 which operates an indicator light 136. The pressure of the fluid in chamber 133 acts upon a diaphragm 143 (Fig. 6) and through levers 248, 243 moves the stop 240 to an inoperative position. The levers are interconnected with a stop acting on the speed control of the auxiliary supercharger. This is described later. In the chamber 132 the water pressure operates a valve 140 carried by a diaphragm 142 and reduces the fuel flow to the nozzle 23. The unit 100 meters the water delivery of the pump 60 by means of valves 111 and 114. The valve 111 is acted on by a rod 104 carried by diaphragms 103, 105. Unmetered fuel pressure from the fuel metering unit is supplied by pipe 103a to a chamber 102 where it acts on the diaphragm 103. A chamber between the diaphragms is connected to atmosphere. The pressure of unmetered fuel is thus maintained in the chamber 107. The metered fuel pressure from the nozzle 23 is maintained in the pipe 101 and this enables the metering force of the carburetter to be applied to the valve 114 since the underside of the diaphragm 112 controlling the valve 114 is connected to the chamber 107. The pump 60 is operated by an electric motor 70 which is switched on by a pressure switch 90 operating a solenoid 75 which closes the circuit of the electric motor. The pressure switch is operated by the induction pipe pressure, at the outlet side of the main supercharger 11 and the pressure at the inlet side of the throttle valve 49. The water injection system is thus switched on when the difference of these two pressures reaches a certain limit. The pressure at the outlet side of the main supercharger also controls the position of the throttle valve 49. The pressure on the inlet side of the throttle valve or the pressure in the induction pipe between the superchargers varies the fuel flow from the fuel nozzle 23 and the pressure at which a byepass for the fuel pump and the water injection pump operates. The pressure on the inlet side of the throttle valve controls the speed of the auxiliary supercharger by means of a servomotor FC, Fig. 3, operating a fluid clutch 17 (Fig. 1). In the arrangement for controlling the throttle valve 49 (Figs. 3, 4 and 6) by the induction pipe pressure at the delivery side of the main supercharger, this pressure passes by a pipe 93 and passages (not shown) in the servomotor housing to a bellows 162. Bellows 162 is connected by a bridge-piece 160 to an evacuated bellows 161. The bridge-piece carries a lever 158, one end of which is connected to a control valve 183 of the servomotor and the other end is held against the cam 156 by a spring 157. The valve 183 controls the supply of pressure fluid from an inlet 203 to a cylinder 180 housing a piston 181 having an operating rod 232. The rod 232 actuates the throttle valve 49 through a differential linkage which is also operated by a manually-controlled lever 150. The rod 232 turns a lever 220 about a pivot 221 and the lever actuates the throttle valve 49 by a link 224. The pivot 221 is carried on a lever 222 fixed to a shaft 151 which is operated by the manual lever 160. Thus, when the manual lever moves the pivot 222 the throttle valve is operated. The shaft 151 carries a lever 152 which operates the cam 156 by a link 153 and lever 154. Thus, the manual lever operates the throttle valve and at the same time sets the pressure at which the servomotor will control by turning the cam and thus moving the lever 158. The servomotor operates to keep the pressure constant at whatever pressure is selected by the cam. When the lever and cam reach a position corresponding to a predetermined high induction pipe pressure, the lever 158 contacts the stop 240 which thus prevents higher pressures being obtained. When water injection is functioning, the stop is removed and higher pressures can be obtained. The fuel pump and water injection pumps are controlled by byepass valves 31 and 31<1>. The pressure at which these valves open is determined by the pressure on the .rear of diaphragms 33, 33<1>. To maintain this pressure as near constant as possible, a selector device 41 is employed which is arranged so that the higher of the pressures at the inlet to the throttle valve 49 and the delivery pressure of the supercharger 12 is always acting on the rear of these diaphragms. One of these pressures is supplied to each side of the diaphragm 43 so that the diaphragm moves to the side of lowest pressure and shuts off the pipe supplying this pressure while the pipe from the other side is connected to an outlet pipe 46 which transmits the pressure to the diaphrams. A diaphragm 38 connected to the valve 35 of the fuel nozzle 23 is also operated on by the same air pressure. In accordance with the pressure at the inlet to the throttle valve 49 the servomotor FC is employed to control the speed of the auxiliary supercharger. This servomotor is similar to that previously described. In the interior of the housing, not shown, are two bellows corresponding to those of the servomotor previously described, one being evacuated and the other acted on by the air pressure. Variations of air pressure enable the servomotor control valve to cause pressure fluid to move an operating rod 260 which is connected to the control of the fluid clutch 17 and thus controls the supercharge speed. The operating rod is connected by a rod 262 to a cam, not shown, similar to the cam 156. An interconnection is provided between the servomotors TC and FC so that the servomotor FC raises the speeds of the auxiliary supercharger when the manual control 150 of the servomotor TC is set at pressures above a predetermined limit. The arrangement is shown in Fig. 3. The lever 154 has an arm 154a carrying a roller 275 moving in an opening in a lever 273. Lever 273 is 'linked to a lever 271 mounted on a shaft which eccentrically carries a shaft 155<1> on which the cam of the servomotor FC is carried. Lever 271 is tensioned by a spring 277. When the manual lever operates the lever 154 to select pressures exceeding the predetermined limit, a cam surface 276 on the lever 273 enables the lever 271 to move counter-clockwise and this moves the cam by the eccentric mounting so that the servomotor increases the speed of the auxiliary supercharger. To prevent supercharger speeds which will cause detonation when the inlet pressure falls to certain low values, the shaft 155<1> is moved to the left after a certain movement of the lever 260. This is effected by a stop screw 280 engaging the lever 271. When water injection is not used, the extent to which the lever 273 can move upwardly when high induction pipe pressures are selected is limited by the engagement of the lever 273 with a stop 290. When water injection is in use, a lever 291 carrying the stop is moved away from the path of the lever 273. The lever 291 is operated by a shaft 247 of the lever 248 which comprises part of the operating mechanism for the stop 240. The main supercharger 11 is driven from the engine through gearing 13 and the drive for the auxiliary supercharger 12 includes gearing 14 connected to the engine shaft, a universal joint 16, and gearing 18 on the supercharger side of the fluid clutch 17. Specifications 565,332, [Group XXVII], and 597,396 are referred to.