US 4,048,965 AGranted

Apparatus for determining the fuel injection quantity in mixture compressing internal combustion engines

AssigneeRobert Bosch GmbH

InventorsValerio Bianchi, Reinhard Latsch, Peter Schmidt

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Abstract

A fuel metering system of an internal combustion engine is controlled by a digital computer circuit which delivers injection pulses to actuate the fuel injection valve of the engine. The duration of these pulses is directly related to the amount of injected fuel and depends on the inherent characteristics of the engine as well as on the engine r.p.m. and the degree of throttle opening. A set of data points each of which correlates a fuel datum with a pair of numbers related to engine speed and throttle valve opening, respectively, is stored in a digital memory and can be addressed by digital signals from transducers associated with engine speed and throttle valve position. An arithmetic unit then performs an interpolation process by weighted addition of nearest neighbor values of the datum stored in the memory. The final, interpolated datum is counted down at constant or variable frequency and represents an output signal related to the fuel injection period.

Claims13

Dependent claims

In an apparatus for controlling the operation of an internal combustion engine including determination of the fuel injection quantity, said internal combustion engine including cylinders defining combustion chambers and injection valves for injecting fuel into said combustion chambers, said fuel being injected in dependence on throttle valve position and engine r.p.m. and being controlled by controlling the injection duration of said fuel injection valves on the basis of characteristic engine data, said apparatus including a system clock for providing master timing signals and a digital arithmetic circuit including a read-only memory in which said characteristic engine data is stored, first transducer means for providing a first digital datum corresponding to throttle valve position and second transducer means for providing a second digital datum corresponding to engine r.p.m., means for feeding the most significant bits (MSB) of the instantaneous values of said first and second digital datum to said read-only memory thereby selecting a digital word contained in said read-only memory, the improvement comprising:

said digital arithmetic circuit includes a shift register connected behind said read-only memory, for adding selected data from said read-only memory and for transmitting it in serial bit form to a subsequent accumulator circuit, and further includes a 1-bit full adder circuit the input of which is connected to the outputs of said shift register and said accumulator and the output of which is connected to the input of said accumulator;
whereby
said digital arithmetic circuit performs the generation of a weighted average of a number of said digital words from said read-only memory.

Dependencies are inferred from the claim text.