Patent GB-1482551-A (GB)
Title: Apparatus and method relating to internal combustion engines utilizing an exhaust gas reactor
IPC: F02D41/14
Filed: 1974-10-14
Abstract: 1482551 Treating IC engine charges and exhaust gas YAMAHA HATSUDOKI KK 14 Oct 1974 [16 July 3 Sept 1974] 44380/74 Headings F1B and F1H A spark-ignition, four stroke I.C. engine, which has an exhaust gas reactor in the exhaust system and which normally operates on a leaner-than-stoichiometric mixture, is characterized in that the exhaust gas passage extending from the combustion chamber(s) to the reactor is isolated from atmosphere, so that unburnt constituents in the exhaust gas can react only with residual oxygen in the exhaust gas, and has means provided for enriching the mixture supplied to the engine if the thermal load on the reactor becomes excessive. A V-type engine has an exhaust gas reactor 7 and is fed by a carburetter 9 having a primary barrel 10 and secondary barrel 11. The barrels have main fuel nozzles 18 and 19 respectively, barrel 10 has two slow-running ports 23 and 24 and barrel 11  has a single port 26. Throttle valve 21 in barrel 11  only opens after throttle valve 20 has been fully opened. Carburetter 9 normally supplies a lean air/fuel mixture. If the throttle valve is closed suddenly there is an abrupt decrease in manifold pressure and fuel which was deposited on the intake passage wall during normal operation is vapourized, so that for a brief period an excessively rich mixture reaches the engine, leading to misfiring and post-combustion in the reactor. Subsequently, during the deceleration period the mixture becomes too lean again causing mis-firing and excessive reactor temperature. To compensate for the too-rich condition, additional air is supplied through valve 47, from the air cleaner to the intake manifold 4. Valve 47 includes valve-member 49 mechanically connected to diaphragm 48a, which is pulled downwards by the very low-pressure in the manifold. A small aperture in the diaphragm allows the pressure on opposite sides of the diaphragm to equalize after a brief period of time. In order to enrich the mixture during the remainder of the deceleration period a supplementary fuel port 27 is provided which is supplied with fuel from the slow-running system which feeds port 20. Needle valve 29 which controls port 27 is mounted on diaphragm 30 which closes one side of chamber 33 which is connected through surge tank 34 to intake manifold 4. Surge tank 34 delays opening of port 27 until valve 47 has closed. Excess temperature protection. Reactor 7 includes a temperature responsive switch 39a which closes if the reactor temperature exceeds a predetermined value and energizes a solenoid 37 which moves needle valve 29 and opens port 27. In a modification, Fig. 2 (not shown) enrichment of the mixture is achieved by using switch 39a to energize a solenoid-operated air valve which is normally open and admits part of the air which forms the leaner-than-stoichiometric mixture normally supplied to the engine. The valve closes when the solenoid is energized. In a second modification, Fig. 3 (not shown) the mixture supplied from the slow running ports is made richer by reducing the amount of air mixed with the fuel in the emulsion tube. The air supply is reduced by closing an air inlet by a needle valve actuated by a suction operated diaphragm or by a solenoid. In a third modification, Figs. 4 and 5 (not shown) the starter carburetter is used to enrich the mixture, by providing a suction-operated diaphragm connected by a linkage to a lever of the starter carburetter which is normally rotated by the manual control. Ignition advance during deceleration. The contact breaker points of the distributer 43 are rotated relative to the cam by vacuum-operated diaphragm 45b. Chambers 45c and 45d on opposite sides of the diaphragm can be selectively placed in communication with intake manifold 4 by a valve 45e which is itself actuated by a diaphragm 90a subject to intake manifold vacuum and biased by spring 90c. The manifold vacuum during idling is insufficient to displace the diaphragm 90a against spring 90c and valve 45e connects chamber 45d to the intake manifold, so that the ignition is retarded. Increased manifold vacuum reverses the position of valve 45c so that the contact breaker points are moved to advance the ignition timing to 35 to 40 degrees before T.D.C., which tends to suppress misfiring.