Patent GB-1429961-A (GB)
Title: Digital engine control apparatus and method
IPC: F02D41/24
Filed: 1973-05-16
Abstract: 1429961 Engine control systems ESSEX INTERNATIONAL Inc 16 May 1973 [29 Dec 1972]  23351/73 Heading G3N [Also in Division F1] An operating signal for actuating a control system in an I.C. engine is controlled by generating first and second engine condition digital numbers having values representing first and second operating characteristics of the engine, storing in a data memory each of a plurality of control digital words representing a plurality of control requirements, selecting one or more of the control digital words depending on the values of the first and second engine condition digital numbers to produce a resultant control digital word representing the engine control requirement, storing the resultant control digital word, and generating a position signal for controlling the operating signal as a function of the value of the resultant control digital word, the operating signal being produced by means responsive to the position signal at a predetermined time. The disclosure describes a multi-cylinder I.C. engine Figs. 1 and 2 (not shown) having sparkplugs that are fired in response to an electrical fire signal, and having fuel injectors that are opened to admit a quantity of fuel in response to an electrical fuel signal having a duration determined by the engine speed and the throttle position. The data memory 170 stores 256 fuel digital words each representing a discrete engine fuel requirement at a particular engine speed and throttle position, and 256 ignition digital words each representing a discrete engine spark timing requirement at a particular engine speed and throttle position. Each digital word is stored at an address represented by two digital numbers. These are stored before the apparatus begins to control the engine. The  apparatus also includes a program memory 250 for storing operating instructions. As the engine operates, circuitry 210, 190 converts the engine speed and throttle position into digital signals representing the condition digital numbers. Selection circuitry 240 compares the address numbers with the condition numbers in order to select the addresses most nearly approximating the actual engine speed and throttle position. An arithmetic unit 300 then interpolates between digital words stored at the selected addresses in order to produce the resultant fuel digital word and the resultant ignition digital word, and these are stored respectively at 324 and 326, Fig. 3A. An operative digital word is also stored at 332 to determine the time at which each injector opens; The position signal is generated by a device attached to the engine crankshaft when the engine is in a predetermined position. In  order to operate the number one cylinder, the position signal initiates additional signals by which the open-time digital word is loaded into an opentime counter 330, and the counter is stepped until a predetermined count is reached. At this instant, the electrical fuel signal is produced via logic circuit 333 and output logic circuit 363 to open number one injector. In response to the production of the fuel signal, the resultant fuel digital word, to which is added a correction digital word from a register 351 to take into account the particular fuel requirement of number one cylinder, is loaded into a counter 343 and the counter is stepped by a clock 366 until a predetermined count is reached. The fuel signal is terminated at this instant. The resultant ignition digital word is then loaded into a counter 368 in response to another position pulse. After the counter is stepped and reaches a predetermined value, the fire signal is produced and the number one spark-plug is fired. These techniques are used to individually fire all spark-plugs and to individually operate all injectors of the engine. Other operating parameters of the engine e.g. intake manifold pressure, ambient air-pressure, ambient temperature, and engine temperature, may be utilized. Starting and idling conditions may be sensed to appropriately adjust the quantity of fuel injected.