Patent GB-624075-A (GB)
Title: Control mechanism for supercharged internal combustion engines
IPC: F02D9/00
Filed: 1945-10-06
Abstract: 624,075. Fluid-pressure servomotor - control systems, GENERAL MOTORS CORPORATION. Oct. 6, 1945, No. 26064. Convention date, Sept. 7, 1944. [Class 135] [Also in Group XXVII] Control mechanism for a supercharged internal-combustion engine comprises an auto. matic throttle valve regulator for maintaining a selectee pressure in the intake manifold, a further automatic regulator responsive to the outlet pressure of a variable speec supercharger and to the alti tude impact pressure so as to maintain the said outlet pressure at a selected value, and manually operated means for varying the two selected pressures conjointly. The manually operated means also varies the engine-governed speed setting and the point at which an additional altitude pressure control operating on the supercharger regulator becomes effective. The manual limitation of the latter control permits the rated speed of the supercharger to be exceeded in the emergency power range and also limits the supercharger speed in the low power range to prevent surging. Each automatic regulator comprises a fluid-pressure servomotor. The servomotor controlling the variable speed super-charger has follow-up means which re-set the selected or datum pressure to a lower value when the actual supercharger outlet pressure falls below the selected value and this prevents over-speeding of the supercharger when a leak occurs on its outlet side. Higher intake and supercharger outlet pressures may be selected when the engine is operating with water injection and automatic stop means are provided to prevent the selection of such higher pressures except when operating with water injection. Automatic means are provided to byepass an intercooler between the supercharger and the throttle when operating with water injection. The point at which the altitude control becomes effective on the supercharger regulator is also subject to modification under water injection. As shown, air entering a scoop 19, Fig. 1, is forced by an auxiliary supercharger 20 driven by an exhaust gas turbine 21 under the control of a waste gate 25, through a pipe 27, an intercooler 28, and a pipe 29 to a throttle 31 adjacent an engine driven supercharger 34 supplying the intake manifold 35. The throttle 31 is operated manually. from a pilot's lever 40 through a linkage 42, 43, 44, 45, 47, 49, 32a of which the main control shaft 44 carries a cam 77 operating through a lever 79 on the propeller pitch governor (not shown), thereby to select the engine speed. A short arm 45 on the shaft 44 carries a floating lever 47, 48 of which one arm 47 is connected to the throttle and the other 48 is connected to the servopiston 52 of the throttle valve regulator 50. The piston 52 is controlled by a pilot valve 57 connected to a floating lever 66 of which the upper end is normally maintained against a pressure selecting cam 71 by a spring 72. The lever 66 is pivoted on a pin 67 on a bridge 68 between opposed bellows 69, 70 of which the former 69 is evacuated and contains springs 69a, 69b. The inside of the other bellows 70, which contains a spring 70a is connected through a passage 323 and pipe 70x with the intake manifold 35. In the emergency pressure range the bellows 70 acts against a spring 280 located between a fixed cup 281 and a rod 283 fixed to the bellows and bearing a lock-nut 282. The bellows 69 is adjustable by a slotted screw 211 locked by a nut 213 which may be slackened for adjustment purposes on removal of a screw 210 entering the bellows shank 215 and holding a guard 212 in place. The cam 71 is adjusted from the main control shaft 44 through a linkage 73, 74, 75. The waste gate 25 is operated through a linkage 83, 85, 86, 86a, 86b by a servopiston 82 under the control of a pilot valve 87, Figs. 1, 11, connected to a floating lever 96 pivoted at an intermediate point between two opposed bellows 99, 100, generally similar to the bellows 69, 70. The bellows 99 containing springs 99a, 99b is evacuated whilst the inside of bellows 100 which contains a spring 100a is connected by a pipe 101 to the outlet of the supercharger 20. The bellows 99 is adjusted by an eccentric pin 205 operating in a slot 207 in the head of a screw 208. The pin 205 may be locked in its adjusted position by a nut 204, Fig. 15. The lever 96 is connected by a link 131 to a further floating lever 127 maintained against a pressure selecting cam 110 by a spring 126. The lever 127 is pivoted at 128 on a rod 154 guided in a spring abutment member or cup 157 and pressed by a spring 155 against a cup-shaped member 153 forming one end of an evacuated altitude pressure control bellows 150 the exterior of which is subjected through a pipe 161, Fig. 1, and a chamber 160 to the impact pressure in the scoop 19. The abutment 157 is adjustable by the lower end of a lever 170 pivoted on a pin 171 and having a cam slot 172. The lever 170 engages a fork formed between flanges 157a, 157b, Fig. 15C on the abutment 157. A pin 173 on a lever 174 is maintained against the right-hand side of the slot by a spring 175. The lever 174 and hence the position of the abutment 157 is adjustable from the main control shaft 44 through a shaft 115 and a linkage 114, 116, 117. The cam 110 is adjustable from the shaft 44 through the same linkage, the lever 114 being linked at an intermediate point to a lever 112 on the end of a hollow shaft 111 surrounding a shaft 110a bearing the cam 110. A spring 110c, Fig. 15, connecting the shafts 110a, 111 and a cross-pin 111c, operating in slots 111b, Fig. 15B provide for spring lost motion between the two shafts to enable the shaft 111 to be adjusted counterclockwise after the cam 110 engages a stop 255, Fig. 11, restraining the cam 110 from selecting pressures above a certain value. The shaft 111 is itself eccentrically mounted in a hollow shaft 145, Fig. 15, connected by a lever 144 and a bent link 141 to the end of the piston rod 83. When therefore the pressure in the bellows 100 deviates from the value selected by the cam 110, the piston 82 not only operates on the waste gate to check such deviation but also through the link 141 and the cam 110 restores the pilot valve 87 to its neutral position and re-sets the datum pressure to a higher or lower value according as the deviation was above or below the selected pressure. The change in datum pressure over the whole travel of the piston 82 would normally be about four inches of mercury for a selected pressure of about 30 inches of mercury. This reduction of selected pressure or " droop " tends to prevent over-speeding when the pipe 27 leaks or is punctured. The pivot pin 171 of the lever 170 may be adjusted horizontally to make a porportionate adjustment of the altitude pressure at which the cam lever 170 exercises effective control of the supercharger for each position of the pilot's lever 40. Such adjustment is effected by a conical ended screw 184, Fig. 14, acting cam-wise on a slidable block 180 with a conical recess 183. The block 180 supports the pivot pin 171 and is acted on by a spring 182. The screw 184 may be locked in its adjusted position which may be indicated by a pointer. The highest selectable pressures in the intake manifold 35 and in the pipe 27 are only permissible when the water injection system is in operation. Such a system comprises a tank 300, Fig. 1, containing water or a water-alcohol mixture which is delivered by a pump 302 past a metering device 303 to a nozzle 305 where it is entrained with fuel from the carburetter 30. When the water injection system is in operation pressure fluid acts through pipes 306, 307 on spring- loaded diaphragms 233, Fig. 2 and 243, Fig. 6 respectively. The diaphragm 233 acts through levers 224, 227 on a spring-pressed stop 220 to withdraw the latter from the lever 66 which may then follow the cam 71 in the highest pressure selection range.. The other diaphragm 243, Fig. 6, acts through a rod 246 on a member 252 which has a lower arm 254 supporting the stop 255 and an upper arm 253 engaging a second fork 157d, 157e on the abutment 157. During water injection, both arms 253, 254 are moved to the right in Fig. 6, so that higher pressures can be selected by the cam 110 and so that the abutment member 157 can be acted on by the pilot's lever through the lever 170 in the highest power range. A flap valve 260 which is normally in. the position shown in Fig. 1, is moved to the dotted line position 260a to byepass the intercooler 28 when water injection is in operation. The valve 260 is operated by a servopiston 262 controlled by a pilot valve 268 operated through a linkage 270, 271, 273, 224 by the diaphragm 233. All the servomotors are supplied with pressure oil from a pipe 310. Springs 52a, 92 are provided to return the servomotors to their normal positions in case of pressure fluid failure. Typical power and other curves are shown and described in the Specification.