GB600934A - Improved control mechanism for supercharged internal combustion engines - Google Patents

Abstract

600,934. Fluid-pressure servomotor-control systems. GENEBAL MOTORS CORPORTION. April 11, 1945, No. 8998. Convention date, April 26, 1944. [Class 135] [Also in Group XXVII] A control mechanism for internal-combustion engines comprises a manually-operable member for moving the intake throttle and for selecting by means of a cam a boost pressure to be maintained in the engine intake manifold, and a device responsive to pressure in the manifold such that divergencies from the selected pressure control the throttle valve through a servomotor so as to restore the selected pressure, and means independent of the manual member for modifying the action of the pressure selector cam on the servomotor under certain conditions of operation to prevent a pressure in the manifold sufficiently high to cause detonation. As applied to an engine having a main supercharger directly driven from the engine and an auxiliary variable-speed supercharger, the boost pressure is selected by a cam 40, operated by a lever 20 from the pilots' throttle control lever, which adjusts a floating lever 45 connected to capsules 58, 50 and operating the valve 30 of a servomotor 24, controlling the throttle valve 11, the action of the cam being modified above a certain altitude when in its high boost pressure position by a capsule-controlled stop rod 70 which moves the lever 45 to the right and reduces the boost pressure to prevent detonation. Capsules 58, 50 are spring-loaded, capsule 58 being evacuated and the interior of capsule 50 being exposed to induction pipe pressure, fluctionations in which expand or contract the capsule and alter the position of lever 45, thereby opening the servo valve 30 and operating the servomotor to open or close the throttle valve 11 and maintain the selected pressure. The evacuated capsule 77 controlling the stop rod 70 is exposed to intake air pressure through duct 75. In a modification, Fig. 4, the stop rod 90 is controlled by the temperature on the outlet side of the auxiliary supercharger, which temperature rises with increasing altitude. A finned tube 94 in the engine intake manifold 93 is connected by a pipe 95a to a bellows 101 controlling the rod 90, the whole assembly being filled with a liquid of desired coefficient of expansion. When the induction temperature exceeds a certain value, the bellows 101 expands, moving rod 90 to the right and reducing the boost pressure as before. Initial adjustment of the rod 90 is obtained by means of screw 115, Fig. 5, carrying an eccentrically situated pin 111 engaging in groove 110 in the side of the casing 98. In an engine having only one directly driven supercharger, in which danger of detonation occurs at low altitudes, a similar construction to that of Fig. 4 is used, but the rod 90 holds lever 45 off the cam 40 at low altitudes and it is moved to the left to allow increased boost pressures at higher altitudes.