Abstract: The signal provided by an oxygen sensor monitoring the exhaust discharge from an internal combustion engine having a closed loop air/fuel ratio controller is compensated so that the controller is insensitive to the difference between the rich-to-lean and lean-to-rich time responses of the sensor signal. The compensated sensor signal has fixed symmetrical voltage change slopes which are set at a value smaller than the smallest of the two slopes of the sensor signal when the compensated sensor signal being clamped at rich and lean voltages that are respectively less than and greater than the sensor rich and lean voltages.

Abstract: An H-switch driver circuit includes two pairs of opposed drive transistors each pair being selectively energized to control the polarity of power applied to a load. Each pair of transistors is energized by a power current mirror that includes an NPN transistor that supplies base drive current to the remaining transistors in the power current mirror. The emitter of the NPN transistor is coupled to the load. The NPN transistor is biased off to inhibit base drive current to the circuit transistors in the event of a short to plus fault at one of the load terminals.

Abstract: A protection circuit for an output transistor includes a transistor having two discrete emitter regions and which is responsive to both the voltage across the protected transistor and its drive current to provide both short circuit and overcurrent protection for the output transistor.

Abstract: An air/fuel ratio controller for an internal combustion engine including two memories each having numbers stored at locations addressed by engine operating points with the locations addressed by the engine operating points being updated during closed loop operation in accord with the value of a closed loop adjustment of the air/fuel ratio. Each memory location in the first memory is updated during operation of the engine at the corresponding operating point in accord with an update time constant having a value so that the number stored tracks adjustment value producing the predetermined desired closed loop air/fuel ratio during varying values of engine operating parameters. Each memory location in the second memory is updated during operation of the engine at the corresponding operating point in accord with an update time constant having a value so that the number stored is the average of the values producing the predetermined closed loop air/fuel ratio during varying values of engine operating parameters.

Abstract: A high gain voltage responsive current source supplies emitter current to a lateral input PNP transistor in a monolithic integrated circuit voltage responsive switch and, in conjunction with an impedance between the voltage signal input terminal and base region of the input PNP transistor, protects the voltage responsive switch from negative voltage transients at the signal input terminal.

Abstract: An air/fuel ratio controller for an internal combustion engine including a memory having numbers stored at locations addressed by engine operating points with the locations addressed by the engine operating points being updated during closed loop operation in accord with the value of a closed loop adjustment of the air/fuel ratio. Each memory location in the memory is updated during operation of the engine at the corresponding operating point in accord with an update time constant having a value so that the number stored tracks adjustment value producing the predetermined desired closed loop air/fuel ratio during varying values of engine temperature. The update time constant is varied directly with the value of engine temperature so that the rate of adjustment of the numbers in the memory is greater during engine warmup where engine temperature increases rapidly. The memory is used during closed loop operation to preset the closed loop adjustment at least when the engine first operates at an operating point.

Abstract: A closed loop fuel control system for an internal combustion engine is responsive to the output of a sensor monitoring the air/fuel ratio of the exhaust gases in the exhaust gas passage from the engine and therefore, after a transport time delay period dependent upon engine operating conditions, to the air/fuel ratio of the mixture supplied to the intake space of the engine and generates a first signal having a value preset to zero at each change in the sense of deviation of the sensed air/fuel ratio from a stoichiometric ratio and varying thereafter at a predetermined rate dependent upon the transport time delay and a second signal having a constant value for the period of the transport time delay after a change in the sense of deviation of the air/fuel ratio from a stoichiometric ratio and thereafter varying at the predetermined rate and in a sense determined by the sense of deviation of the air/fuel ratio from the predetermined ratio.

Abstract: A diagnostic and warning system for a motor vehicle monitors the condition of a number of preselected parameters. When the condition of a parameter is representative of a fault condition, the system energizes a malfunction lamp in the vehicle compartment during the period of the detected fault and the particular fault detected is stored in a nonvolatile memory. A single counter is employed which functions to filter intermittent malfunctions for each of the monitored parameters and which imposes a minimum time duration for energization of the malfunction lamp.

Abstract: A diagnostic and warning system for a motor vehicle monitors the condition of a number of preselected parameters. When the condition of the parameters is representative of a fault condition, the system energizes a malfunction light in the vehicle compartment during the period of the detected fault. The particular fault detected is stored in a nonvolatile memory where it is stored independent of the subsequent condition of the respective parameter. The stored fault conditions may thereafter be read from memory to provide an indication of the malfunctions that have occurred in response to a diagnostic interrogation signal. The fault conditions stored in the nonvolatile memory are erased when a predetermined time period has lapsed since the occurrence of a detected fault condition so that old nonrecurring self-correcting faults are not retained in memory and accordingly not indicated in response to a diagnostic interrogation signal.

Abstract: A closed loop fuel controller for a vehicle internal combustion engine is responsive to the oxidizing/reducing conditions in the exhaust gases from the engine to provide a control signal for adjusting an air and fuel supply means and which varies in a sense tending to produce a predetermined air/fuel ratio. When the engine operation changes from one condition to another condition representing an acceleration or deceleration transient, the value of the air/fuel supply adjustment is preset to a value from a memory location addressed by the engine condition determined to produce the predetermined air/fuel ratio when the engine is accelerating and to a value from another memory location addressed by the engine condition determined to produce the predetermined air/fuel ratio when the engine is decelerating so that the air/fuel ratio adjustment is substantially instantaneously preset to the value determined to produce the predetermined ratio during engine accelerating and decelerating transient conditions.

Abstract: A closed loop air-fuel ratio controller adjusts the air and fuel ratio of the mixture supplied by a carburetor to an internal combustion engine to a predetermined ratio in response to sensed exhaust gas oxidizing-reducing conditions. An air valve is energized to bleed air into the air-fuel mixture upstream of the exhaust gas sensor and independent of the mixture supplied by the carburetor when the carburetor idle fuel system is functioning and the magnitude of the adjustment in the mixture leaning direction reaches a predetermined value in response to a sensed rich air-fuel ratio to effect a decrease in the amount of the adjustment in the lean direction. The air bleed effectively increases the lean adjustment authority of the air-fuel ratio controller and avoids a lean air-fuel ratio excursion as the carburetor operation shifts from its idle fuel circuit to its main fuel metering circuit during cold engine operation.

Abstract: A series pass voltage regulator compares the output voltage with a reference voltage and adjusts the base bias of a PNP series pass transistor coupled between an unregulated voltage source and a load to maintain the output voltage at a predetermined constant value. A current sensing resistor senses the base current of the PNP series pass transistor and limits the base current to a predetermined value indicative of a maximum allowable load current.

Abstract: A system for providing acceleration enrichment in a vehicle engine fuel injection system is enabled by a sensed transition from a transmission neutral condition to a transmission drive condition to enrich the mixture supplied to the engine to provide improved engine performance.

Abstract: A system for increasing the amount of fuel injected into an internal combustion engine in response to an increase in the manifold absolute pressure greater than a predetermined amount and greater than a predetermined rate. The amount of enrichment is equal to a first value determined by the engine coolant temperature increased by a factor that has an initial value determined by the rate of increase in the manifold absolute pressure and that is varied toward unity at a rate determined by engine temperature. The duration of acceleration enrichment is determined by the amount of change in the manifold absolute pressure and the engine coolant temperature.

Abstract: A closed loop air and fuel ratio controller is responsive to the oxidizing/reducing conditions in the exhaust gases from an internal combustion engine to provide a control signal having a value for adjusting both the idle and main fuel metering circuits of a carburetor so as to supply an air and fuel mixture to the engine at a predetermined ratio. Two memory elements are provided, each being associated with a respective one of the idle and main fuel metering circuit for storing a value of the control signal provided by the controller. During operation of each of the idle and main fuel metering circuits, the value of the control signal stored by the respective one of the storage elements is updated in accord with the average value of the control signal provided by the controller.

Abstract: An engine air and fuel controller for a vehicle internal combustion engine is described wherein the mass fuel flow rate is controlled directly in response to vehicle operater command. The engine throttle is positioned by an electronic controller in response to the fuel flow rate to achieve a mass air flow rate determined to produce a scheduled air/fuel ratio. The controller includes a circuit which is responsive to the engine speed to limit the minimum value of the commanded fuel flow rate in accord with a predetermined schedule at a rate whereat the engine throttle is controlled to a scheduled open position during engine overrun conditions to improve engine operation.

Abstract: A closed loop air/fuel ratio controller for an internal combustion engine includes a control circuit responsive to the output of an exhaust gas sensor representing at least the sense of deviation of the air/fuel ratio of the mixture supplied to the engine from stoichiometry and provides a control signal which is used to adjust the air/fuel ratio of the mixture supplied to the engine in direction tending to restore a stoichiometric air/fuel ratio. The control signal includes an integral correction term and an asymmetrical proportional correction term that abruptly shifts the value of the control signal upon a detected change in at least one direction in the sense of the deviation of the air/fuel ratio from a stoichiometric air/fuel ratio.

Abstract: In a closed loop air and fuel ratio controller for an engine, an air/fuel sensor is responsive to the engine exhaust gases to provide a signal representing the air/fuel ratio of the mixture supplied to the engine. The output of the sensor is sampled N times during each of successive sampling periods and the number of samples indicative of a rich mixture versus the number of samples indicative of a lean mixture is utilized to provide an output representing a rich or lean error input to the closed loop controller.

Abstract: An air/fuel ratio controller for an engine determines a hot restart condition by comparing the prior engine shutdown temperature with a predetermined constant and with the engine startup temperature. If the prior engine shutdown temperature exceeds the predetermined constant and the difference between the engine shutdown temperature and the engine startup temperature is within a predetermined value, a hot restart condition is indicated and the open loop air/fuel ratio otherwise determined in accord with engine operating parameters is adjusted to provide for improved hot restart engine performance.

Abstract: A processing circuit for use in an internal combustion engine closed loop air/fuel mixture controller is responsive to the output of an oxygen sensor exposed to the exhaust gas output of the internal combustion engine to provide a signal that indicates the sense of the deviation of the oxidizing/reducing conditions of the engine exhaust gases from a predetermined condition (usually stoichiometry). The processing circuit compares the output signal from the oxygen sensor with a pair of reference levels to provide the signal that indicates the sense of the deviation of the condition of the exhaust gases from the predetermined condition and which is independent of the effects of the absolute levels of the oxygen sensor and independent of the variance between the sensor response to changing air/fuel ratios in one direction and to sensor response to changing air/fuel ratios in the opposite direction.