GB1483397A - Carburetor having cold enrichment control - Google Patents

Abstract

1483397 Spray carburetters FORD MOTOR CO Ltd 21 Feb 1975 [6 March 1974] 7457/75 Heading F1H In order to prevent stalling under 'cold run' conditions of an internal combustion engine, the fast idle cam 160 of a thermostatically choked carburetter, which cam is arranged to be operable in response to the thermal activation system 40, is not affected by the operation of an additional choke valve pull-open servo 90, Fig. 2. The choke valve 28 is spring-biased toward a closed position against a stop finger 50 via the angularly displaceable link 54, the finger 50 being positioned in response to the thermal activation system 40. This allows the servo 90, connected via rod 156 to link 54, to open the choke valve by rotating the link away from the stop 50 independently of the thermal activation system, in response to high engine vacuum. Correct idle speed is selected by the screw 178 engaging one of the faces of steps 170, 172, 174 or recess 176 on the fast idle cam the angular position of which is controlled by engagement under gravity of screw 164 with finger 50. The thermal activation system 40 Fig. 1 comprises a bi-metallic coiled spring 68, responsive to manifold heat via the passages 78, 80, or the ambient temperature in the housing 84, and operating the shaft 44 via lever 60. A piston 87 actuated by manifold vacuum allows the choke to be 'cracked' open after initial engine firing. The pull-open servo 90 is prevented from operation below a predetermed temperature by a bi-metallic disc valve 126, Fig. 4. When the valve 126 is opened air under the influence of the manifold vacuum, bleeds via a restrictor plug 105 and check valve 108 from the vacuum chamber 144 causing the diaphragm 140 to move the rod 148 inwards thus opening the choke. On the collapse of the engine vacuum the check valve unseats to allow air to flow unrestricted into the chamber 144 via slot 106, returning the rod 148 rapidly to its inoperative position. The lost motion linkage 152, 154 ensures that the operation of the thermal activation system will be independant of the servo 90 when the servo is in the inoperative position.