Patent GB-678361-A (GB)
Title: Control systems for internal combustion engines
IPC: F02D9/00
Filed: 1946-05-06
Abstract: 678,361. Pumps. BENDIX AVIATION CORPORATION. May 6, 1946 [May 29, 1945], No. 13690/46. Class 7(ii) [Also in Group XXIX] An aircraft engine control system comprises pilot controlled means for selecting a desired inlet manifold pressure, a throttle valve for controlling the inlet manifold pressure, a supercharger for supplying air to the inlet manifold, servomotor means for positioning the throttle, inlet manifold pressure responsive means for controlling the servomotor means, a plurality of hydraulic couplings between the supercharger and the engine, and means for controlling flow of pressure fluid to a selected hydraulic coupling, said controlling means being regulated by said manifold pressure responsive means upon the throttle being adjusted to its fully open position whereby the supercharger is driven at a speed necessary to obtain the desired inlet manifold pressure. As shown, the supercharger 32, Fig. 1, is driven by the engine 26 through gearing and a pair of hydraulic clutches of the type in which the " slip " is determined by the quantity of liquid in the clutches. The clutch 39, for high-speed drive, is supplied with liquid through a pipe 277 and a drilling 43 whilst the other clutch 51, for low speeds, is supplied through a pipe 276 and a drilling 54, a valve 54A being provided to cut off automatically the flow of liquid when the speed of the driven member 52 of the clutch exceeds that of the driving. member, i.e. when the high-speed clutch is operative. Drains 44, 51A are provided in the housings of the clutches 39, 51, respectively. A pilot's power control lever 1 is connected by a link 2 to an arm 3 fixed to a shaft 4, Fig. 2, to which is also fixed an arm 6. The arm 6 is connected by linkage, etc. 7, 8, 13, 11, 14, 15 to a sleeve 16 carrying a pulley 17 connected to the airscrew governor 20, for varying the compression of the loading-spring 23 and, therefore, the speed of the engine. The linkage incorporates an adjustable spindle 10 on which is pivoted the arm 11, and which has an eccentric 9 on which is mounted the arm 8, whereby, by adjustment of the spindle 10, the relationship of the pilot's control lever travel to the airscrew governor control travel may be varied. An air inlet 56 to the supercharger includes the carburettor 57 and the throttle valve 59, connected by a link 60 to an arm 61, Fig. 2b, keyed to a shaft 62 in which is rotatably mounted one end of the shaft 4. Fixed to the shaft 4 is an arm 70 and fixed to the shaft 62 is an arm 69, the latter being connected by a link 68 to a servopiston 64 and by links 73, 71 and a lever 72, to the arm 70. Pivoted to the lever 72 is an arm 74 fixed to a shaft 75, whilst rotatably mounted on the shaft 75 is an arm 78 connected by a link 79 to a spring-loaded piston 80 subjected, through a conduit 82, to the pressure of the liquid used for actuating the servo-piston, whereby, upon failure of the liquid pressure, the piston 80 is moved downwardly to rotate the arm 78 such that the arm 74 is confined, with slight play, between stops 84, 86. A control valve 103, Fig. 2a, for the servo-piston 64 having a pressure liquid supply 82, an exhaust 108 and conduits 66, 67 connected respectively to the upper and lower ends of the cylinder containing the servo-piston, is actuated, through leaf springs 104, 132 connected to a lever 133, and a link 131, by a bellows assembly comprising a bellows 126 subjected internally through a conduit 129 to the inlet manifold pressure, and a spring- loaded evacuated bellows 121 anchored at 122 and separated from the bellows 126 by a partition 125. Upon a deviation from the selected manifold pressure the valve 103 is deflected to deliver pressure liquid to one end of the servo-cylinder whilst exhausting the other end, to rotate the arm 69 in a direction to adjust the throttle valve to restore the selected pressure, the arm 74 being free to move during this operation. Contraction of the bellows 126 is limited by an adjustable stop 128 whereby at low manifold pressures the throttle may be controlled manually. Should the pressure liquid supply fail, the arm 74 is confined so that by rotation of the shaft 4 by the pilot's lever, the lever 72 rocks about its connection to the lever 74 and the throttle is actuated manually. The slight amount of movement permitted the arm 74, however, causes slight rotation of the shaft 75 when the shaft 4 is rotated so that a spring-loaded plunger 100 is moved, such movement being effected by an arm 94, pivoted at 95, and connected by a pin and slot connection 93, with an arm 91 rotatably mounted on the shaft 75 but engaged by an arm 88 fixed to the shaft. This movement of the plunger 100 actuates the valve 103 in such a direction that any slight liquid pressure which may be available is directed to the appropriate end of the servo-cylinder to assist in the manual operation of the throttle. Upward movement of the valve 103 under these circumstances is effected by a spring- loaded plunger 113 normally retained in the position shown by liquid pressure from the conduit 82 acting on its upper surface. The plunger 113 also allows liquid in the exhaust passage 108, which normally escapes to the control unit housing through a port 115, to drain to a lower level through a passage 117 on failure of pressure. For varying the selected pressure, a cam 136 is fixed to the shaft 4, the cam coacting with a follower 137 carried by a lever 138 pivoted to a lever 140. The lever 140 is pivoted at 142 and carries a pin 146 which rotates a lever 135, acting, through a pin 134, on the lever 133. A spring 139 biasses the lever 138 in a clockwise direction about the follower 137 whereby the lever 138 engages a screw 145 carried by the lever 140 and the two levers 138, 140 under normal conditions, act as a single lever. A pilot's economy lever 150 is connected by a link 151 to an arm 152 fixed on a shaft 96 which carries an arm 153 connected by a link 154 to a bell-crank 155, freely rotatable on the shaft 4. Movement of the economy lever in one direction causes the bell-crank to engage the lever 138 and move it away from the cam 136 to increase the manifold pressure. To reduce this pressure when the control shaft 4 is rotated to close the throttle, i.e. in an anti-clockwise direction, an arm 160 is provided, keyed to the shaft 4 and having an adjustable screw 161 which engages an arm 163 loosely mounted on the shaft 4 and having a pin-and-slot connection with a pin 164 fixed to the lever 140. Movement of the economy lever in the other direction causes the bell-crank to engage the lever 140 and reduce the manifold pressure. For reducing the selected pressure with increasing altitude a bellows 170 is provided, subjected internally to barometric pressure, and arranged in opposition to a spring-loaded evacuated bellows 171. Movement of a partition 174 between the bellows rocks a lever 175 about a pivot 176 and moves a link 177 which abuts against a lever 179 pivoted at 180. Movement of this lever is transmitted to another lever 182, pivoted at 183, by a pin 192 carried by a link 193 pivoted to a lever 195 which rotates about a pin 196 and engages a cam 197 carried by the shaft 4. Movement of the lever 182 is transmitted to the lever 135 by a sleeve 184 fixed to the lever 182, a pin 185 fixed to an arm 186 and mounted within the sleeve, and a link 187. The cam 197 is shaped so that with movement of the pilot's lever to increase the power, the pin 192 is moved to the left as seen in Fig. 2, so as to cause a greater correction to the manifold pressure. Means for injecting into the manifold an antidetonant, e.g. water or alcohol, comprises a tank 206, a pump 207 with a byepass incorporating a relief valve 212, an electromagnetically operated valve 208 and a metering device 204, the anti-detonant being injected through a nozzle 202 through which is also injected the fuel from the carburetter 57. The valve 208 may be opened either by a switch 210 or by a switch 210A arranged to coact with the pilot's lever 1. When the anti-detonant system is in operation, the pressure of the antidetonant fluid acts through a pipe 213 on, a diaphragm (not shown) which, through linkage, moves the follower 137 away from the cam 136 to increase the manifold pressure. In addition, when the pilot's lever 1 is in a position to close the switch 210A a pin (not shown) carried by the cam 136 also acts on the linkage to increase the manifold pressure. The supply of liquid to the clutches is controlled by d piston valve 250 having lands 252, 253, 254 and to which liquid under pressure is supplied from the conduit 82, through a conduit 282, a reducing valve 280 and a passage 272. The valve 250 is loaded by a spring 257 and is restricted in its movement by adjustable stops coacting with a pin 258 carried by the valve. The valve is actuated against its spring, when, after the servo-piston 64 has reached the upper limit of its travel, i.e. when the throttle is fully open, and on the manifold pressure falling below that selected, the pressure below the piston 64 builds up to overcome the force of the spring 257. The liquid flow to the lowspeed clutch, which, up to this point was permitted to a limited extent through the valve 250 and a conduit 270 connecting with the conduit 276, is then increased, whilst on continued downward movement of the valve 250 a conduit 271, connecting with the conduit 277, is placed in communication with the liquid supply whereby the highspeed clutch becomes effective and the valve 54A closes. It is stated that variations in the back-pressure set up by the clutches give rise to errors in the quantity of liquid delivered by the valve 250, and to overcome this the reducing valve 280 is subjected at its lower end to the back pressure of the clutch in use so that the pressure of liquid supplied to the valve 250 increases as the back pressure increases. A shuttle valve 290, for conne