Patent GB-880196-A (GB)
Title: Improvements in and relating to carburettors for internal combustion engines
IPC: F02M1/10
Filed: 1960-08-08
Abstract: 880,196. Spray carburetters. GENERAL MOTORS CORPORATION. Aug. 8, 1960 [Aug. 27, 1959; Jan. 13, 1960], No. 27380/60. Class 7(3). In a carburetter for an internal combustion engine having an air valve 28 and a throttle valve 22 in an induction passage 14 with a metered fuel orifice 70 therebetween, the degree of opening of the air valve 28 is controlled in accordance with the pressure drop across the valve 28 by means of a servo device which also meters the fuel proportionately to the degree of opening of the air valve, and the fuel metering action of the servo device is adjustable in accordance with certain engine operating conditions. As shown, the servo device comprises diaphragm 46, which is operatively connected by levers 44, 38, 34, and 32 to air valve 28 and is adjustably connected via levers 44 and arm 78 of lever 38 to fuel metering rod 74. The lower side of the diaphragm is subject to atmospheric pressure while the upper side is subject, via duct 54 and chamber 52, to the pressure anteriorly of the air valve. The effect of the movement of the diaphragm on the metering rod is varied according to load and temperature respectively by (a) manifold suction acting on spring loaded piston 176 which by means of lever 174 and U-shaped member 166 rigid with lever 160, pivoted at 162, alters the radial position of the end of the metering rod 74 in slot 80 of arm 78, and (b) a thermostatic coil 190 which via cam 172, mounted on shaft 188, acting on stops 168, 170 on member 166 also varies the radial position of the end of rod 74. An accelerator pump 90, comprising chamber 108 connected by means of conduit 110 to fuel reservoir 50 and connected via conduit 128 to orifices 130, is provided. A diaphragm 96 has a rod 134 rigid therewith and is normally biased by spring 106 so that ball 112 is free from its seating 120, allowing fuel to enter chamber 108. The latter is connected by duct 118 to chamber 122 but fuel is prevented from passing to orifice 130 by a ball 126 pressed against its seating by spring 132. On opening the throttle the diaphragm 96 is forced upwards by the action of lever 26, spring 104, lever 100, and rod 98. Valve 120 is closed and fuel under pressure overcomes the action of spring 132 and is forced out through orifice 130. A starting enrichment device 92 is also provided. Normally the lower side of a spring loaded diaphragm 124, is subject to the pressure rearwards of the air valve by conduit 146 connected to chamber 154 by a cut away portion in piston 136 fast with diaphragm 124, which is held down by manifold suction through conduit 149. On starting the engine the manifold vacuum is not strong enough to hold the diaphragm 124 down and spring 152 forces the latter upwards which by means of a rod 150 unseats ball 126 and allows fuel to flow to orifice 130 and also allows atmospheric pressure into chamber 154 from vent 142 through a second cut away portion of piston 136. When the engine is cold the throttle stop is on the high step of a cam 196 and if the throttle is fully opened the mixture ratio will be too rich. However the end of slot 216 will engage link 218 rotating the fast idle cam in a counter-clockwise direction which through link 194 will move cam 172 and lever 160 to temporarily decrease fuel flow through the metering orifices. Idle air flow is provided by passages by-passing the air valve and throttle. The screw valve regulating the air passage by-passing the air valve indirectly controls the idle mixture. As described the induction passage divides into two anteriorly of the air valve, each being provided with a metered fuel orifice and a throttle valve. The two metering rods are connected together and the two throttle valves are mounted on a common shaft.