Abstract: When a vehicle state is detected during an engine is stopped, a sampling cycle of a detection signal indicating the vehicle state and a clock frequency of a CPU are changed, according to a change speed of the detection signal or an elapsed time after the engine is stopped.

Abstract: When a vehicle state is detected during an engine is stopped, a sampling cycle of a detection signal indicating the vehicle state and a clock frequency of a CPU are changed, according to a change speed of the detection signal or an elapsed time after the engine is stopped.

Abstract: Before starting an air-fuel ratio feedback control utilizing an air-fuel ratio sensor, activation of a wide-range air-fuel ratio sensor in an internal combustion engine is diagnosed by calculating heat transferred to and from the air-fuel ratio sensor, the output value of the wide-range air-fuel ratio sensor varies in response to oxygen concentration in exhaust which varies according to the air-fuel ratio of an intake air-fuel mixture of the internal combustion engine. The activation time from the starting of the engine until the air-fuel ratio sensor is activated is estimate based on the calculated result of the heat transfer. Alternatively, activation of the sensor is diagnosed under the condition that an output voltage of the oxygen concentration detecting unit of the sensor is fixed to a value either equal to or above a rich-side set voltage or equal to or under a lean-side set voltage, before starting the air-fuel ratio feedback control.

Abstract: Before starting an air-fuel ratio feedback control utilizing an air-fuel ratio sensor, activation of a wide-range air-fuel ratio sensor in an internal combustion engine is diagnosed by calculating heat transferred to and from the air-fuel ratio sensor whose output value varies in response to oxygen concentration in exhaust which varies according to the air-fuel ratio of an intake air-fuel mixture of the internal combustion engine, and estimating the activation time from the starting of the engine until the air-fuel ratio sensor is activated, based on said calculated result of the heat transfer. Alternatively, activation of the sensor is diagnosed under the condition that an output voltage of the oxygen concentration detecting unit of the sensor is fixed to a value either equal to or above a rich-side set voltage or equal to or under a lean-side set voltage, before starting the air-fuel ratio feedback control.

Abstract: Before starting an air-fuel ratio feedback control utilizing an air-fuel ratio sensor, activation of a wide-range air-fuel ratio sensor in an internal combustion engine is diagnosed by calculating heat transferred to and from the air-fuel ratio sensor, the output value of the wide-range air-fuel ratio sensor varies in response to oxygen concentration in exhaust which varies according to the air-fuel ratio of an intake air-fuel mixture of the internal combustion engine. The activation time from the starting of the engine until the air-fuel ratio sensor is activated is estimate based on the calculated result of the heat transfer. Alternatively, activation of the sensor is diagnosed under the condition that an output voltage of the oxygen concentration detecting unit of the sensor is fixed to a value either equal to or above a rich-side set voltage or equal to or under a lean-side set voltage, before starting the air-fuel ratio feedback control.

Abstract: Discrimination is effected as to which of low-pressure and high-pressure conditions the pressure of fuel to be fed to a fuel injection valve is in. If in the low-pressure condition, the fuel injection pulse widths are corrected by assuming that the fuel pressure is a predetermined reference pressure, since the detection errors of a fuel pressure sensor are large. If in the high-pressure condition, the fuel injection pulse widths are corrected based on an actual fuel pressure detected by the fuel pressure sensor.

Abstract: The timing for opening the exhaust valve is advanced by an angle that varies depending upon the load exerted on an engine and the rotational speed of the engine at the cold starting of the engine during a predetermined period of time after the complete combustion. The heat of combustion is positively discharged into an exhaust system and, hence, an oxygen sensor and a catalytic converter disposed in the exhaust system of the engine are activated more quickly.

Abstract: In an apparatus and method for actively reducing air intake noise of an air intake system of a vehicular internal combustion engine, a sound wave having approximately the same amplitude, and a phase shifted by 180.degree. from the air intake sound wave, is generated from a sound wave generator to cancel the air intake sound, which is unpleasant to vehicular occupants.

Abstract: The present invention relates to a circuit for processing internal combustion engine crank angle sensor signals. The construction is such that an output side circuit of a crank angle sensor outputs a crank angle signal with a high level pulse generated in response to the switching on and off of a switch element connected in series to a power source. Moreover, an input side circuit of a signal processing circuit includes a voltage reducing circuit which pulls down a power source voltage applied at the time of pulse generation, to a predetermined voltage and supplies this to an arithmetic processing section. Consequently, the output signal at the time of no pulse generation becomes a low level so that influence from noise is minimized. Also, since the input signal at the time of momentary disconnection of terminals connecting between the crank angle sensor and the processing circuit is a low level, then erroneous recognition of pulse generation is prevented.

Abstract: An apparatus for detecting pressure in an engine cylinder comprises a cylinder pressure sensor inserted between an ignition plug screwed into an engine cylinder head and a bearing surface on which the ignition plug is mounted. The sensor outputs a detection signal depending upon a change in the sensor load corresponding to a change in the pressure in the cylinder, to detect the pressure in the cylinder based on a detection signal from the cylinder pressure sensor. The detection signal from the cylinder pressure sensor is invalidated for only a predetermined period based on an ignition signal that controls the ignition of the ignition plug so that the S/N ratio in the sensor output will not be deteriorated by the ignition noise.

Abstract: The heavy/light grade of fuel supplied to an internal combustion engine is detected, for example with a sensor or by detecting fluctuations in combustion pressure, and a retard angle correction amount for control of an ignition timing retard angle for activating an exhaust gas purification catalytic converter during a predetermined interval after engine start-up, is set based on the detected properties of the fuel. The time required for activating the exhaust gas purification catalytic converter can thus be shortened by retarding the ignition timing, corresponding to the heavy/light grade of the fuel, to increase the exhaust temperature while maintaining combustion stability.

Abstract: Combustion pressure is detected using a cylinder pressure sensor, and a crank angle position corresponding to a centroid of combustion during a combustion period is obtained as a combustion centroid position, based on the detected combustion pressure. Combustion conditions are then detected based on the detected combustion centroid position. On the other hand, depending on operating conditions, a crank angle position corresponding to a centroid of combustion during a combustion period for the case where desired combustion conditions are obtained, is set as a target centroid position, and an engine control quantity then feedback controlled so that the combustion centroid position becomes the target centroid position.

Abstract: A rate of change in the combustion pressure in each of the cylinders is calculated based upon a result detected by a combustion pressure sensor provided for each of the cylinders. The air-to-fuel ratio is increased and/or the ignition timing is retarded for each of the cylinders so that a rate of change in the combustion pressure approaches a value corresponding to the combustion stability limit in each of the cylinders.

Abstract: A pull-down resistor is connected to a power source line between power source connectors and a detector circuit in an apparatus in which a power source is connected via the power source connectors to the detector circuit, which includes a temperature-sensitive resistor and which outputs a voltage signal to a control unit via signal connectors. The pull-down resistor increases current flow to the power source connectors thus to suppress oxide formation thereon. A pull-up resistor or a pull-down resistor is connected to a signal line between the signal connectors and a filter circuit in the control unit, in order to increase an electric current that flows into the signal connector terminals thereby to prevent the formation of an oxide film on the signal connector terminals.

Abstract: In an internal combustion engine equipped with a mechanism for improving combustion such as a swirl control valve, the air-to-fuel ratio of the combustion mixture gas is increased until the stability of the engine reaches an allowable limit under the condition where the combustibility is to be improved by the mechanism for improving combustion. When the air-to-fuel rate at the allowable limit is equal to or smaller than a reference air-to-fuel ratio, whether or not the mechanism for improving combustion is defective is diagnosed.

Abstract: Within a predetermined time immediately after start up, ignition timing is retarded within a range wherein the output fluctuations do not exceed a predetermined permissible limit. Subsequently under conditions after elapse of the predetermined time but when warm up has not yet been completed, air-fuel ratio is weakened within a range wherein the output fluctuations do not exceed a predetermined permissible limit. Then after warm up an exhaust gas recirculation amount is increased within a range wherein the output fluctuations do not exceed a predetermined permissible limit.

Abstract: Engine output fluctuations are detected based on combustion pressure, and a fuel supply quantity amended so that the output fluctuations approach a permissible limit value. The properties of the fuel being used, can be estimated based on the amendment level, using characteristics that the limit air fuel ratio for stable combustion becomes leaner as the fuel being used is more volatile. Then when the fuel being used is volatile, the target air-fuel ratio in the air-fuel ratio feedback control is made leaner, thereby improving fuel consumption and exhaust gas properties.

Abstract: The present invention is able to detect the intake air quantity which has been discriminated into flow direction by detecting the engine intake air quantity at two locations separated in the direction of flow of the intake air, comparing the detection values and detecting the flow direction of the intake air based on for example the advance or delay of the phase of the intake air pulsations. As a result, when the flow is reversed, the detection value is subtracted so that a normal flow direction averaged intake air flow quantity is detected, thereby enabling improvement in for example the setting accuracy for the fuel supply quantity of an engine.

Abstract: A fuel vapor treatment apparatus controls fuel vapor produced in a fuel tank supplied to an engine intake system to prevent dispersion into the atmosphere. It involves adjusting a purge air quantity to a high accuracy, to thereby avoid the occurrence of air-fuel ratio fluctuations between cylinders due to the purge air. More specifically, with a construction wherein the purge air quantity is adjusted by duty controlling the opening/closing of a purge passage, the purge air quantity is set based on the engine load and engine rotational speed, and the control frequency used in the duty control is increasingly changed corresponding to an increase in purge air quantity. Moreover, the opening/closing of the purge passage is duty controlled based on the purge air quantity and the control frequency.

Abstract: Engine intake air flow rate is detected as a mass flow rate, using a thermal type air flow meter, and engine intake air flow rate is also detected as a volumetric flow rate based on throttle valve opening and rotational speed. The mass flow rate is converted to volumetric flow rate based on the current intake air temperature, and a ratio of, the volumetric flow rate obtained by the conversion and the volumetric flow rate based on throttle opening and engine rotational speed is output as a value corresponding to atmospheric pressure.