Patent GB-1509075-A (GB)
Title: Process and device for regulating the operational behaviour of an internal combustion engine
IPC: F02D45/00
Filed: 1975-04-08
Abstract: 1509075 Automatic control of I C engines ROBERT BOSCH GmbH 8 April 1975 [9 April 1974] 14266/75 Heading G3R The fuel/air mixture supplied to an internal combustion engine, or the amount of exhaust gas which is re-circulated, is controlled in response to a comparison of successive values which represent instantaneous values of mean combustion chamber pressures. The object is to operate the engine at as lean a mixture as possible, and it is explained that the leaner the mixture the greater are the cylinder pressure variations between successive cycles Fig. 3 (not shown). These variations are measured as variations in speed or torque and compared with a reference, any difference being used to effect adjustment of the fuel supply or recirculated exhaust gas. As shown, pulses from a speed transducer 30, 35 are shaped at 36 and applied to "store" 39, where the pulse width is converted into a speed dependent voltage on a capacitor. At 180 intervals, detected by 29, 34, this voltage is transferred to a second store 40 whose output is then compared with the succeeding value in 39. The difference is transferred to an analogue shift register 42...45, clocked by the 180‹ pulses, connected through a diode network 46 to a differential amplifier circuit 55. This arrangement detects the difference between the maximum and minimum values stored in the shift register and this difference is compared at 57 with a reference from a function generator 59, the reference being varied as a function of engine speed and inlet air-flow. The output of 57 lengthens the time that fuel is injected at 26, using an integrating regulator 58 and a transistor circuit 25, also Fig.6, (not shown) in which a minimum time is established which depends upon inlet air flow and engine temperature. It is mentioned that a carburetter could be controlled instead of a fuel injector. More or less fuel is supplied according to whether the measured value is above or below the reference. In Fig.7 (not shown) an additional, digital shift register is used which stores 1 and 0 signals according to whether the speed fluctuations exceed a second reference or not. The average value in this register is used for control if it exceeds the analogue register. This arrangement is said to increase the speed of response in certain circumstances. In Fig.8 (not shown) the arrangement of Fig.4 is combined with a known system for controlling the fuel in response to an exhaust gas sensor; this provides a richer mixture and a changeover switch brings it into use when rapid acceleration is called for. In an alternative embodiment, Fig. 10 (not shown) the time duration of successive or alternate 180‹ rotations is measured and the difference between successive measurements is compared with a nominal value obtained by triple integration of each of the measured periods. (It is stated that the nominal value should be the cube of the time period). Correction to the fuel injected is made only when the "actual value" exceeds the nominal. An additional, integrating, stage may be inserted to ensure the mixture is the leanest possible even during acceleration.