Motorola Corporation

Rupin J Javeri

Adelore F Petrie

A method and apparatus are disclosed for electronically processing a variable frequency input signal and a reference input signal to develop an output signal representative of the frequency difference between the two input signals. The state of the variable frequency signal is sampled upon the occurrence of each leading edge of the reference signal to produce a first output signal. The state of the variable frequency signal is also sampled upon the occurrence of each trailing edge of the reference signal to produce a second output signal. The two output signals are preferably ORed to develop the final output signal.

Frequency subtractor

Sensor inputs as from an engine load sensor alter the frequency of a pulse providing circuit, the output of which adds counts to those counts provided as a function of engine velocity. The total number of counts is used for determining the instantaneous advance angle in a distributorless ignition system.

Ignition advance circuit with sensor inputs

Information is derived from two given sets of sensor output pulses relating to crankshaft position for use in determining the proper cylinder to be fired, the spark time and the dwell. The spark is enabled only after the crankshaft position is known, and noise, including the spark itself, is prevented from interfering with the system operation.

Electronic ignition input logic

The circuit determines which cylinder is to be fired and continually updates the determination so that the circuit recovers immediately from any false detect and responds to any change of engine condition. The dwell timing is derived from sensors adjacent the flywheel and, to achieve the widest possible range of advance angles, the use of certain sensor-derived signals is delayed until after spark.

Ignition spark timing circuit

Digital dwell circuitry for a spark and dwell ignition control system is disclosed. Maximum advance and reference sensors are utilized to produce pulse transitions which determine positions of maximum and minimum possible advance for spark ignition with respect to the position of the engine crankshaft. For each maximum advance sensor pulse transition a main counter starts a sequential running count of speed independent clock pulses wherein the maximum count obtained by the counter is related to engine crankshaft speed. The running and maximum counts of the main counter are utilized by dwell circuitry to determine the time prior to the next maximum advance pulse at which spark coil excitation should occur. The main counter running count also determines several inputs to a read only memory (ROM) circuit whose output controls a rate multiplier. The rate multiplier receives input clock signals, provides selective frequency division for these clock signals in accordance with the ROM output, and the output of the rate multiplier is coupled to an accumulator means whose accumulated count is utilized to determine the occurrence of spark ignition by terminating spark coil excitation.

Dwell circuitry for an ignition control system

An ignition spark timing circuit with switchable hysteresis for an internal combustion engine is disclosed. A crankshaft sensor produces a periodic input sensor signal, having a predetermined period, which initiates the action of a programmable voltage slope generator that produces a predeterminedly varying signal. This varying signal serves as an input to a comparator which also receives a switching threshold input, and the comparator output is utilized to determine the time occurrence of spark ignitions. A switchable feedback path is provided between the output of the comparator and its switching threshold input such that hysteresis for the comparator threshold input is provided during critical portions (T.sub.C) of the time period of the crankshaft position sensor signal when the comparator is expected to produce output signal transitions that determine the occurrence of spark ignitions. At other portions (T.sub.N) of the time period of the crankshaft position sensor signal, the comparator output cannot affect the threshold input of the comparator.

Ignition spark timing circuit with switchable hysteresis

Electronic signal processing circuitry for use in the ignition system of an internal combustion engine is disclosed herein. A signal generator which receives crankshaft position pulses from a sensor and produces periodic outut pulses which have durations equal to a constant percentage of the period of the input sensor pulses is disclosed. The generator includes a crankshaft position sensor feeding a bistable flip-flop which controls a dual slope integrator circuit having its output coupled to a comparator with the comparator output coupled back to the reset terminal of the flip-flop. The generator produces pulses at the output of the flip-flop which have durations equal to a constant percentage of the period of the crankshaft position sensor pulses. An engine speed monitoring circuit receives the periodic varying ramp signal produced by the dual slope integrator and via sampling circuitry produces an output signal related to engine speed whose magnitude is updated during each cycle of the crankshaft position pulses.

Periodic engine speed monitoring circit utilizing sampling circuitry

Electronic signal processing circuitry for use in the ignition system of an internal combustion engine is disclosed herein. A signal generator which receives crankshaft position pulses from a sensor and produces periodic output pulses which have durations equal to a constant percentage of the period of the input sensor pulses is disclosed. The generator includes a crankshaft position sensor feeding a bistable flip-flop which controls a dual slope integrator circuit having its output coupled to a comparator with the comparator output coupled back to the reset terminal of the flip-flop. The generator produces pulses at the output of the flip-flop which have durations equal to a constant percentage of the period of the crankshaft position sensor pulses. The dual slope integrator circuit produces a periodic ramp (sawtoothed) signal which is processed by a clamping circuit and a comparator to produce an ignition dwell pulse which occurs a fixed time before the occurrence of the crankshaft position sensor pulses. An engine speed monitoring circuit also receives the periodic varying ramp signal produced by the dual slope integrator and via sampling circuitry produces an output signal related to engine speed whose magnitude is updated during each cycle of the crankshaft position pulses.

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Elk Grove Village, IL, United States of America

Rupin J Javeri