Patent GB-1464591-A (GB)
Title: Internal combustion engine with means for compensating for air density variation
IPC: F02M7/28
Filed: 1974-01-28
Abstract: 1464591 Spray carburetters, air density compensation ACF INDUSTRIES INC 28 Jan 1974 [9 Feb 1973] 03880/74 Heading F1H An I.C. engine having at least one suction operated control device has an attachment which modifies the degree of suction applied to the device, the attachment comprising a housing 22, a bellows 30 mounted in the housing and responsive to temperature and pressure changes in the ambient air to change a dimension of the bellows, a plate 40 pivotally mounted in the housing and operatively connected to the bellows, an air metering device 44, 46 or 48 which allows ambient air to be admitted to a passage through which suction is applied to the control device, the metering device including a metering element 52, 80 or 100, the bellows acting on the plate at a position removed from the pivot, through the intermediary of adjustment means 36 and a spring having one end secured to the plate adjacent the end of the plate remote from the pivot and having its other end adjustably secured to the housing. A partially evacuated bellows 30 which expands as ambient pressure falls or ambient temperature increases, acts through an adjustable screw 36 to cause rotation of a lever 40 in which are mounted three further screws 44, 46, 48, each of which actuates a valve-member. A screw 50 adjustably anchors one end of a biasing spring, the other end of which engages a plate adjustably secured to a housing which encloses the bellows and lever. The spring tension may be adjusted by moving the lower end in accordance with an engine operating condition e.g. exhaust gas temperature. The interior of the housing is connected to atmosphere by a conduit which leads to the engine side of the carburetter air cleaner. Screw 44 acts on a metering pin 52, biased upwardly by spring 54 and which controls the flow of ambient air from passageway 53 to conduit 16 which leads to the main fuel supply system, Fig. 5. As the bellows expands the admission of air to well 56 reduces the amount of fuel in the mixture admitted to the engine. A similar metering pin 80 controls the supply of additional air to the idling fuel system through a conduit 18, Fig. 6 (not shown). Screw 48 acts on a third metering pin 100, which is shaped to cause a decrease in the flow of air through conduit 20 as the bellows expands. Fig. 7 shows the accelerator pump which includes a diaphragm 91 defining a chamber 90 connected by a passage 86 to the carburetter intake pipe downstream of the throttle valve 88. A cavity 94 contains fuel which is supplied to the engine when the intake pipe vacuum suddenly decreases. As the bellows expands a smaller amount of air is supplied to passage 86 and this compensates for the reduced degree of vacuum which exists in the intake pipe when air density decreases. A spindle 92 attached to diaphragm 91 supports a metering rod 66 which co-operates with jet 64 to partially control the main jet fuel supply. When the accelerator pump operates, rod 66 is raised to allow a greater flow of fuel to the main fuel supply system. Fig. 7 also shows a diaphragm actuated motor 112, biased by compression spring 116 and having an actuating arm 118 which may be connected to an ignition advance mechanism or to an automatic transmission. In an alternative construction the housing is integral with the body of a four barrel carburetter and in this arrangement the metering rod 66 is also acted on by a cam and lever mechanism so that it is raised to provide mixture enrichment at full throttle.