Abstract: An inductive load driver circuit including first and second switches and high and low impedance current decay paths. For the duration of a load actuation signal the first switch is responsive to the magnitude of the load current to complete and interrupt a first current path to the inductive load to cycle the load current between first and second levels. The second switch is enabled for the duration of the load actuation signal to complete a slow current decay path to the load when the first switch means interrupts the first current path. When completed the slow current decay path comprises a low impedance allowing the load current to decay slowly from the first current level to the second level to provide during such slow decay a load current sufficient to maintain actuation of the inductive load. The end of the load actuation signal disables the second switch to interrupt the slow current decay path and thereby require the load current to decay rapidly through the high impedance decay path.

Abstract: An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit has an open loop calibration for regulating the air/fuel ratio that is corrected with a closed loop correction signal developed by an integral controller. The open loop calibration is a speed-density based schedule which is combined with corrections for special conditions to account for the operating parameters of the engine at any instant. Included in these special condition corrections are provisions for increasing the air/fuel ratio upon a deceleration sufficient enough to cause a rich air/fuel ratio breakthrough because of the EGR valve lag time. A deceleration detector senses decelerations in excess of this predetermined amount by measuring the rate of change of the pressure in the intake manifold of the engine. A fixed percentage increase in air/fuel ratio is switched into the open loop calibration when the deceleration exceeds the amount required for breakthrough.

Abstract: An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit has an open loop calibration for regulating air/fuel ratio that is corrected with a closed loop signal developed by an integral controller. The integral controller bases the closed loop correction signal on a signal from an exhaust gas composition sensor located in the engine exhaust manifold. Various conditions of the system are sensed by a closed loop sensor condition detector to provide information on whether the sensor is up to operating temperature and is operative. If the exhaust gas sensor is functioning and the operating system parameters indicate the system operation should move to closed loop control, the loop is closed by the condition detector. Included in the condition detector circuit is a timer whose cycle is RPM dependent.

Abstract: An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit includes an injector driver circuit which regulates the timing of the opening and closing operations of a plurality of electromagnetic solenoid injectors which input fuel to the engine. The injector driver circuit controls the injection with a pulse width modulated signal to supply an amount of fuel calculated from the operating parameters of the engine. The injector driver circuit is further provided with an energy dissipation circuit to assist in the rapid de-energization of the solenoid injectors. The energy dissipation circuit drains the energy stored in the rapidly collapsing magnetic field of a de-energized injector through a power device whose energy dissipation is controlled by the breakdown voltage of a Zener diode connected to the control terminal of the power device.

Abstract: An economy throttle body for a single point fuel injection system is disclosed. The throttle body is formed from two integrally molded throttle body members. An upper member contains provision for the mounting two electronic solenoid injectors and an arrangement of fuel control passages while a lower throttle body member is utilized to mount the throttle body onto an engine manifold and contains the air induction bores and throttle assemblies of the system. Hot fuel handling capability is provided by a heat resistant thermal isolation seal separating the upper and lower throttle body members. Upwardly canted fuel delivery passages further enhance the hot fuel handling capability of the upper throttle body member.

Abstract: An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit has an open loop calibration for regulating air/fuel ratio that is corrected with a closed loop signal developed by an integral controller. The integral controller bases the closed loop correction signal on a signal from an exhaust gas composition sensor located in the engine exhaust manifold. Various conditions of the system are sensed by a closed loop sensor condition detector to provide information on whether the sensor is up to operating temperature and is operative. If the exhaust gas sensor is functioning and the operating system parameters indicate the system operation should move to closed loop control, the loop is closed by the condition detector. Included in the condition detector circuit is a timer whose cycle is RPM dependent.

Abstract: An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit has an open loop calibration for regulating the air/fuel ratio that is corrected with a closed loop correction signal developed by an integral controller. The open loop calibration is a speed-density based schedule which is combined with corrections for special conditions to account for the operating parameters of the engine at any instant. Included in these special condition corrections are provisions for an altitude compensation feature. The altitude compensation feature includes circuitry to modify the intake manifold pressure portion of the speed density schedule with two variables which depend on altitude.

Abstract: A hybrid electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit is divided into two functionally distinct parts including an analog function generator and a digital function generator. The analog function generator receives analog signals to process efficiently by analog scaling, amplification, multiplication, and division while the digital function generator receives digital and logic inputs to process efficiently by addition, subtraction, and comparison. The analog function generator interfaces with the digital function generator by an analog signal from a D/A converter and other unconverted digital output signals from the digital function generator. Preferably, the analog function generator provides an open loop air/fuel ratio calibration based upon a speed density calculation including special condition corrections to the base calibration.

Abstract: An electronic control unit for regulating the air/fuel ratio of an internal combustion engine is disclosed. The electronic control unit has an open loop calibration for regulating air/fuel ratio that is corrected with a closed loop correction signal developed by an integral controller. The open loop calibration is a speed-density based schedule which is combined with corrections for special conditions to account for the operating parameters of the engine at any instant. Included in these special condition corrections are provision for start and warm-up features. The start feature includes an enrichment pulse generator whose pulses have a duration dependent upon the engine operating temperature and speed which are inhibited while the engine is above a predetermined RPM. The warm-up feature includes a time and temperature dependent enrichment which is linearly multiplied by an engine load factor.

Abstract: A self-adaptive system for optimizing ignition timing in an internal combustion engine wherein a signal representing engine manifold absolute pressure is multiplied by a signal representing engine speed to provide a product signal. The product signal is differentiated and applied as the numerator in a divider. The quotient output of the divider is fed back to the divider input as the denominator. The quotient output of the divider is further integrated and the integrated quotient is used as a command signal for setting the spark timing.

Abstract: A closed loop control circuit for regulating the response of an automatic temperature control system is disclosed. The temperature control system provides automatic regulation of the temperature for the passenger compartment of a vehicle by positioning a blend air door in response to three control parameters. Two of the control parameters, the actual temperature of the passenger compartment and the desired temperature of the passenger compartment, are serially combined in one leg of a bridge circuit and compared against another leg of the bridge presenting the third control parameter, the position of the blend door. An unbalanced condition in the bridge circuit is corrected by the repositioning of the blend door until the error between the two legs is nulled. Repositioning is accomplished by a pair of differential amplifiers which detect the sense of the error and thereafter provide an interrupter control function to a vacuum modulator.

Abstract: An acceleration enrichment feature for a closed loop fuel management system controlling the air/fuel mixture delivered to an internal combustion engine to regulate the roughness of the engine at a predetermined level. The enrichment feature provides increased fuel to the engine for operator induced transient conditions proportionately by sensing the rate of change of throttle angle. A throttle angle position signal is modified by circuitry providing a transfer function that introduces a lag term into the throttle angle position signal which differentiating the signal to determine the rate of change of throttle angle. The modified throttle angle position signal is additionally corrected by the amount of roughness sensed by the closed loop control and enriched for rough operations of the engine beyond a threshold and leaned for smooth operations of the engine.

Abstract: An electronic fuel injection system wherein fuel injectors are turned on by electrical pulses whose time periods are controlled in accordance with information received from various engine condition sensors. A primary pulse is transmitted for each revolution of the engine and this pulse is used to turn on the fuel injectors for the controlled time period. Auxiliary pulses for acceleration enrichment are also used to turn on the same fuel injectors for a time period that is controlled by throttle conditions. A pulse time addition circuit is provided so that the time period of an acceleration enrichment pulse is added to the time period of a primary pulse even when the acceleration enrichment pulse occurs during the period of the primary pulse thereby insuring that the desired total amount of fuel is added to the engine regardless of the sequence of occurrence of the control pulses.

Abstract: Comparator means respond to the current levels through an inductive load to generate HIGH and LOW level outputs causing first switch means to connect and disconnect power to the load. When the load current initially exceeds a peak load actuation level, flip-flop means responsive to the corresponding change in comparator output levels change the current through an auxilliary sense resistor coupled to the sense input of the comparator means. In one embodiment, a one-shot multivibrator prevents a change in the current to the auxilliary sense resistor for a fixed period after the commencement of a load actuation signal. The subsequent HIGH and LOW comparator output levels are fed back to the comparator reference input to switch the reference voltage thereat so as to represent first and second levels of the current sufficient to maintain actuation of the load.

Abstract: A dual mode control system for operating an electronic fuel injection system for an internal combustion engine so as to achieve an optimal compromise between engine emissions, fuel economy and driveability. A closed loop control circuit is provided which senses the amount of oxygen in the engine exhaust and normally drives an integrator in a closed loop mode of operation to operate the electronic fuel injection system at the stoichiometric air/fuel ratio at which the best conversion efficiency of hydrocarbons, carbon monoxide and nitrous oxides occur. An open loop control circuit senses high speed operation where hydrocarbons and carbon monoxide conversion are normally high and where nitrous oxide emission is not critical and clamps the output of the integrator to a predetermined value which operates the electronic fuel injection system at a nonstoichiometric, relatively lean, air/fuel ratio for improved fuel economy.

Abstract: A closed loop integral control system for the air/fuel management of an internal combustion engine is disclosed. An oxygen sensor positioned in the exhaust gas of the internal combustion engine is biased with a constant current source to provide a signal indicative of the oxygen content of the exhaust gas over a significant range of air/fuel ratios. The signal waveform from the sensor is compared to a threshold value of a comparator to produce level changes in the comparator output depending on whether the output of the sensor is above or below the threshold. An integrator, receiving these level changes as commands to increase or decrease the fuel pulse widths, controls the air/fuel ratio of the engine in a limit cycle around a scheduled value. By changing the current bias on the sensor and thus modifying the unbiased waveform of the sensor to intercept the threshold value at various points different average air/fuel ratios are obtainable from the system.

Abstract: A signal conditioning circuit for the output of a magnetic position sensor is disclosed. The magnetic sensor generates a total output signal that increases as a function of the rotational velocity of the sensor with a spurious noise component that is a relatively constant percentage of the actual signal voltage over the speed range. In a preferred embodiment, the signal conditioning circuit discriminates between the noise component and the signal component by comparing the total signal to a variable threshold only after a positive going zero cross. The variable threshold is generated as a function of the peak amplitude of the total signal. In a second embodiment the signal conditioning circuit includes gain control means which varies the amplitude of the total output signal as a function of its peak to maintain the threshold above the noise component.

Abstract: A closed loop programmable EGR control system is disclosed. The EGR control system comprises a first read only memory having a look up table of base EGR pulse widths as a function of engine speed and absolute manifold pressure. This base EGR pulse width is corrected to a total desired pulse width by adding a correction pulse width obtained from a second read only memory. The second ROM stores values of the correction pulse width in a look up table as a function of engine speed and engine coolant temperature. This desired value of EGR pulse width is then compared to the actual EGR flow as sensed directly by a differential pressure transducer located in the exhaust gas recirculation conduit and an error signal is generated therefrom.

Abstract: A closed loop integral control system for the air/fuel management of an internal combustion engine is disclosed. An oxygen sensor positioned in the exhaust gas of the internal combustion engine is biased with a constant current source to provide a signal indicative of the oxygen content of the exhaust gas over a significant range of air/fuel ratios. The signal waveform from the sensor is compared to a threshold value of a comparator to produce level changes in the comparator output depending on whether the output of the sensor is above or below the threshold. An integrator, receiving these level changes as commands to increase or decrease the fuel pulse widths, controls the air/fuel ratio of the engine in a limit cycle around a scheduled value. By changing the current bias on the sensor and thus modifying the unbiased waveform of the sensor to intercept the threshold value at various points different average air/fuel ratios are obtainable from the system.

Abstract: A fuel injection control system and technique for an internal combustion engine is disclosed having at least one controlled offset fuel injector valve and only one controlled trim injector valve. The offset injector valves produce a constant quantity of fuel by being energized for a fixed pulse duration each injection cycle while the difference between that constant quantity and a desired fuel injection quantity calculated from a fuel schedule is supplied by the variable trim injector. The fuel supply schedule is determined by the engine variables of the operating system by an electronic fuel scheduler circuit which further supplies fuel injection timing pulses for triggering the beginning of the injection cycle.