Patent GB-603235-A (GB)
Title: Improved control for internal combustion engines
IPC: F02D9/00
Filed: 1945-04-25
Abstract: 603,235. Fluid-pressure servomotor-control systems; hydraulic clutches. GENERAL MOTORS CORPORATION. April 25, 1945, No. 10382. Convention date, Feb. 3, 1944. [Classes 69 (ii) and 135] A supercharger which is driven from an internal combustion engine through an infinitesimally variable speed gear is controlled by a servo-operated speed ratio control member which is under altitude pressure control by means of a valve member and which is adapted to restore the valve member to equilibrium position when a pre-determined relation between altitude pressure and speed ratio has been established. In an embodiment, the supercharger is driven from the engine shaft h4, Fig. 2, through a fluid coupling Hand gearing d4. The fluid in the coupling can escape through ports h5 into a chamber from which it is withdrawn by a scoop h7, the distance of the latter from the axis of the coupling being varied by the servomotor to determine the amount of fluid withdrawn from the coupling and, hence, the amount of slip in the drive. Fluid flowing out through scoop h7 is delivered by a scavenger pump T to an oil cooler and/or tank K from which it is withdrawn by a pump L and delivered past a cleaner M to a line N leading to the supercharger bearings or to a line O leading to the various servomotors. Excess oil passes a relief valve P and flows back into the axis of the coupling. The supercharger is an auxiliary supercharger from which the compressed air is delivered to a further supercharger driven directly by the engine, and liquid fuel is injected into the air passage connecting the two superchargers. Air is picked up by a scoop and delivered to the auxiliary supercharger past a throttle valve and carburetter. The fluid-coupling scoop h7 is connected to and actuated directly by a piston and cylinder servomotor with a pistontype control valve, the latter being connected to the lower end of a lever 83<SP>1</SP>, Fig. 10, which is pivoted on a bridge 85<SP>1</SP> connecting the free ends of two bellows 88<SP>1</SP>, 89<SP>1</SP>. Both bellows are fixed at their outer ends and are provided internally with loading springs ; bellows 88<SP>1</SP> is evacuated and so subject to altitude control, and the interior of bellows 89<SP>1</SP> is connected either with the air scoop or with the impact chamber of the carburetter. The upper end of lever 83<SP>1</SP> is acted upon by a loading spring 106<SP>1</SP> and also by a cam 210 when shaft 211 is connected by a lever 216, Fig. 20, and a link 213 to the servo-piston rod so that, when the servopiston moves the scoop h7 in response to a variation in the pressures acting on the bellows, the cam will be rotated to re-set the servomotor control valve. The throttle valve V, Fig. 6, is actuated by a servomotor with a control valve and control bellows 88, 89, Fig. 31, similar to the mechanism shown in Fig. 10, but in this case, bellows 89 is subject to manifold induction pipe pressure. The point at which control by bellows 88 starts is pre-set by adjusting the position of the bellows end plate by means of a screw 136 with lock nut. A manual control lever 124, 125, Fig. 6, carries a further lever 18 to the lower end of which is pivoted a floating bell crank 14, 28, and the two arms of the latter are connected, respectively, to the throttle valve V and the servo-piston 32 of the boost control. Arm 124 of lever 124, 125 is connected by a link 120 and lever 117 to a shaft 110 to which a cam 105 is secured, and the cam acts in opposition to a loading spring 106 on the end of a floating lever 83 carried by the bridge member connecting the free ends of the two bellows 88, 89. Thus, when lever 125 is actuated, the throttle valve V is moved manually and cam 105 is rotated to alter the datum of the servomotor, i.e. to select a charging pressure which is indicated on a scale 127 by a pointer carried by lever 117. The movement given to cam 105 actuates the servomotor, and the movement which the servopiston imparts to floating bell crank 14, 28, will open the throttle valve a further amount to a position to give the selected charging pressure at that particular altitude. Subsequent variations in altitude of the aeroplane will cause bellows 88, 89 to actuate the servomotor and so control the degree of opening of the throttle valve to maintain the selected charging pressure. Arm 117 has an extension carrying a roller 230 engaging with a cam surface 231 and the free end of the lever on which the cam surface is formed is connected by a link 235 and a lever 228, Fig. 20, with a shaft 212, Fig. 10, on which the cam 210 is eccentrically pivoted. When a fresh charging pressure is selected, the movement of lever 117 will cause a rotation of eccentric shaft 212, and this will rotate cam 210 to actuate the servomotor controlling the amount of slip in the fluid coupling in the auxiliary supercharger drive and so vary the speed of that supercharger. Lever 216, Fig. 20, has an extension with an adjustable stop 218 which moves in the path of lever 228 whereby, at the higher charging pressures, the action of the servomotor controlling the fluid coupling is reduced so that the rate of reduction in the slip of the coupling with increasing altitude is reduced. To allow the engine to operate at abnormally high charging pressures, a further loading spring 304, Fig. 31, is provided for bellows 89. At normal charging pressures, spring 304 has no effect, but when bellows 89 has expanded sufficiently due to an abnormal induction pipe pressure, nut 306 carried by the free end of the bellows engages the end of the spring and the bellows is thereby stiffened and has a weakened effect on the throttle servomotor for corresponding increases in the charging pressure. Where anti-detonant injection by means, for example, of water or water and alcohol mixture is employed, the anti-detonant is allowed to act on a diaphragm 311, Fig. 31. The diaphragm is connected through levers 331, 335 with a spring-loaded reciprocating rod 339 in such manner that, when the supply of anti-detonant fails and the pressure on the diaphragm is relieved, rod 339 will be moved into the path of lever 83 to prevent the actuation of the servomotor and further opening of the throttle. Simultaneously, a further lever on shaft 332 is roated to place a stop in the path of the lever carrying cam surface 231.