Patent GB-1217948-A (GB)
Title: Improvements to carburettors for internal combustion engines
Inventor: ZAHR KARL-HEINZ
IPC: F02M1/00
Filed: 1968-10-11
Abstract: 1,217,948. Spray carburetters for I.C. engines. SOC. INDUSTRIELLE DE BREVETS ET D'ETUDES. Oct. 11, 1968 [Oct. 19, 1967], No.48340/68. Heading F1B. The invention relates to a carburetter for an I.C. engine which comprises an air intake 14, a Venturi 21 and a main duct 12 connected to the engine, a throttle valve 13 being disposed in the duct 12, being shown in the closed position in which it substantially closes the duct. A main jet system 20 is indicated. The carburetter comprises also an idling duct 1 which is connected through orifice 4 to atmosphere and through orifice 3 to a source of fuel 2 by way of an orifice 24. The idling duct is connected at its downstream end by way of an orifice 5, which is regulatable, with the main duct 12 downstream of the throttle valve 13. The carburetter comprises also an air duct 8 which is connected to atmosphere through an orifice 9 which is regulatable and at its downstream end with the main duct 12 downstream of the throttle valve 13. The duct 8 has a portion 8b upstream of the variable orifice 9 which is connected to atmospheric pressure in the duct 14 by way of a fixed orifice 15. In accordance with the invention the idling duct 1 is connected to atmosphere by means of a duct 26 which is connected to the portion 8b of the air duct 8 upstream of the variable orifice 9. At idling the suction pressure in the duct 12 downstream of the throttle valve 12 induces flow of fuel and air mixture through the idling duct 1 also air through the air duct 8. The connection of the idling duct 1 to the air duct 8 upstream of the variable orifice 9 ensures that the orifice 3 through which fuel is supplied to the idling duct is subjected to suction pressure which varies in the same sense as the air flow through duct 8. The throttle stop 18 engages a screw 17 which would be pre-set; the position of the needle controlling the variable orifice 5 would also be pre-set. The idling duct 1 is also connected to the main duct 12 by an orifice 16 which is disposed upstream of the throttle valve 13 when the latter is in the closed position. In Fig. 3 the carburetter again has an idling duct 1 and an air duct 8, the idling duct 1 communicating through orifice 4 directly with the portion 8b of the air duct upstream of the variable orifice 9. A further air duct 28, 29 is provided, being connected upstream to atmospheric pressure and downstream to the main duct 12 downstream of the throttle valve 13. A shut-off valve 27 is disposed in the duct 28, 29 being arranged to be opened when the engine speed is slightly higher than idling speed. The duct 28 upstream of the valve 27 is connected by way of a duct 30 to the idling duct 1, a non-return valve 35 being disposed in the duct 30. Pre-set needles 31 and 33 are provided in the ducts 28 and 30. The arrangement is such that the suction pressure created or increased by the flow of air through the auxiliary duct 28, 29 induces a further flow of fuel/air mixture from the idling duct 1 during deceleration, i.e. when the throttle valve 13 is closed and the engine speed is greater than idling speed. In Fig. 4 is shown the assembly of two carburetters such as shown in Fig. 3. A duct 30a is connected to the idling ducts 1 of the two carburetters, the duct 30a being connected through a non-return valve 35 to the auxiliary duct 28, 29a, the portion 29a of the latter being connected to a balance pipe 39 which interconnects the main ducts 12 of the two carburetters. In Fig. 5 the portion 8b of the air duct 8 upstream of the variable orifice 9 is extended at 8c into a chamber 41 which communicates through an orifice 44 with the main duct 12 downstream of the throttle valve 13. The orifice 44 is controlled by a valve 27a mounted on a diaphragm 42, the valve being normally urged by spring 43 to the closed position. The chamber 45 above the diaphragm 42 is connected by line 46 to a chamber 47 which may communicate with the main duct 12 by way of orifice 48 which is controlled by valve 40. The valve 40 is arranged to be opened by the devices 37, 38 when the engine speed during deceleration (i.e. when the throttle valve 13 is closed) is somewhat greater than idling speed. Under these conditions the suction pressure prevailing in main duct 12 downstream of throttle valve 13 is communicated through line 46 to the chamber 45, whereby the valve member 27a is caused to open against the opposing force of spring 43. Thus air from duct 8b, 8c may pass through orifice 44 into the main duct 12. If the valve 40 were opened when the throttle member 13 was in an open position the suction pressure communicated through orifice 48 to chamber 45 would not be such as to cause the valve 27a to lift from its closed position. In Fig. 6 the assembly of two carburetters in accordance with Fig. 5 is shown, the main ducts 12 of the two carburetters being inter-connected by duct 39, and the line 46a inter-connects the chambers 45 of the two carburetters. Only one valve assembly 40, 48 is required as shown, the line 46a being connected by way of chamber 47 and orifice 48 to the main duct 12 of the left-hand carburetter when the valve 40 is opened when the speed of the engine is slightly above idling speed and the throttle member 13 is closed for deceleration. In Fig. 7 (not shown) means are provided to prevent the adjustable needle 9, Fig. 1, from being closed an excessive amount. A passage (9b) containing a fixed orifice (52) is disposed in parallel with the passage (9a) containing the variable orifice (51) so that if the needle 10 is closed air may still pass through the orifice (52) and passage (9b) to air duct 8. In Fig. 9 (not shown) the needle valve (10a) is formed with an axial bore (53) and transverse bore (54) so that if the needle (10a) completely engages against the seating (51) air can still pass from duct portion 8b to air duct 8. In Fig. 10 the idling duct 1 communicates with the main duct 12 by way of an adjustable orifice 55 and bore 65, the bore 65 being formed in a screw plug 60 and the orifice 55 being controlled by an adjustable needle 56. The air duct is indicated at 58 and communicates with the main duct 12 through orifice 58a, the adjustable orifice of the air duct being formed at 59 between the conical end of the screw plug 60 and the conical seat of the carburetter body 63. The portion of the air duct upstream of the variable orifice 59 is indicated at 58b and communicates with the air inlet 14 at 15; the portion 58b communicates directly with the idling duct 1 through orifice 4. The fuel inlet orifice to the idling duct is indicated at 3. A seal device 66 is disposed around the plug member 60 to prevent communication between the idling duct 1 and the air duct 58. The screw adjustment 56 for the needle of the variable orifice 55 is made relatively inaccessible to prevent interference.