GB904191A - Improvements in carburetors working by continuous injection of fuel into the intake pipe of an internal combustion engine - Google Patents

Abstract

904,191. Carburetters. SOC. INDUSTRIELLE DE BREVETS ET D'ETUDES. Jan. 24, 1961 [Jan. 29, 1960; March 4, 1960; July 18, 1960], No. 2781/61. Class 7(3) A carburetter working normally by continuous injection of fuel into the intake pipe of an internal combustion engine through at least one fuel injection orifice opening into the pipe which comprises a main air passage and an auxiliary air passage with main throttle means in the main passage and auxiliary throttle means in the auxiliary passage, the passages uniting downstream of the main and auxiliary throttle means and the respective throttle means being interconnected, a main Venturi being provided in the pipe upstream of the main throttle means and an auxiliary Venturi being provided in the auxiliary passage, the auxiliary Venturi being of smaller cross-sectional area than the main Venturi, fuel being fed to the injection orifice by a pressure regulating or reducing device capable of supplying fuel at a pressure variable in accordance with the air pressure in the intake pipe is characterized in that this fuel pressure regulating device is controlled by a single diaphragm control means subjected to the effect of the respective suctions in the throat portions of the Venturies acting either separately or simultaneously. Under conditions approximating to idling (Fig. 1) cam 32 gradually opens first only throttle member 20, the combustion air passing exclusively through passage 18 as soon as throttle member 20 is slightly opened. In view of the fact that all this air flows through Venturi 22 which is of small cross-sectional area the suction existing in this Venturi and which is transmitted to the chamber 48 under the diaphragm 11 varies in an accurate manner in accordance with the flow rate of this air stream which also accurately determines the fuel injection pressure. Then cam 32 produces the gradual opening of the throttle member 19 so that the chamber 29 and consequently chamber 48 are more and more subjected to the suction existing in the Venturi 21 (or 23). Finally when the parts are in the position corresponding to full load running both of the throttle members 19 and 20 are fully opened, and lever 42 moves slide valve 39 against the action of spring 43 so that this valve closes conduit 26 and port 31. Diaphragm 11 is then subjected exclusively to the suction existing in Venturi 21 (or 23). Instead of simultaneously closing conduit 26 and port 31 slide valve 39 might close at least partly in a different order the conduits which open into the chamber 29. Furthermore instead of a slide valve 39 actuated by a lever 42 use might be made of a rotary distributing valve actuated either in the same manner as the slide valve 39 or by elements rigid either with the spindle 67 of throttle member 19 or with that of throttle member 20. Instead of having the throttle members actuated by a cam 32 the axis 33 of which is distinct from each of the axes of throttle member 19, 20 it would be possible to act directly upon one of these axes through lever 34 and to interpose a suitable mechanical connection between the two throttle members. Fig. 3 shows a modification in which the auxiliary passage 18 starts from a portion of the intake pipe which is located downstream of the throat of the Venturi 21. The connection to the chamber 48 is controlled by a diaphragm operated valve 55. In a further modification (Figs. 5 and 6) when the main throttle member 19 is gradually opened lever 79 moves in the anticlockwise direction (Fig. 5) thus gradually releasing the valve 70, 72. Control of the amount of air flowing through the auxiliary Venturi 22 and consequently the suction acting upon the pressure regulating device may be obtained by giving the head 72 of the valve a suitable shape. The diaphragm 11 may be a differential diaphragm, that is to say diaphragm 11 may be associated with a second diaphragm of smaller area intended for instance to prevent the suction existing on the. diaphragm 11 from being transmitted to the inside of chamber 7.