Abstract: An intake air amount control apparatus for an internal combustion engine is provided with: an opening control mechanism and a variable valve mechanism, which control an intake air amount; an intake characteristics change mechanism for controlling the intake air amount by adjusting a parameter or parameters different from those of the above two mechanisms; and an intake amount control device for performing a cooperative control of these mechanisms upon the occurrence of any normal condition. The intake air amount control apparatus is also provided with: an abnormality detection device for detecting an abnormal condition in these three mechanisms; and a fail-safe device for controlling the intake air amount of the opening control mechanism out of these three mechanisms and controlling the other two mechanism, so as to fix their control amounts to constant values.

Abstract: A variable valve timing apparatus rotatably receives a rotor in a housing. The rotor can rotate within a predetermined angular range. In some cases, the rotor is locked by a lock pin at an intermediate position within the angular range. In this manner, it is possible to realize a suitable valve timing even when an engine is restarted after it is stopped. In some case, the rotor is prevented from moving to the largest delay angle position by a restricting pin. In this manner, it is possible to prevent the rotor from reaching the largest delay angle position before the engine is stopped. On the other hand, while the engine is operated, it is possible to rotate the rotor to the largest delay angle position and to realize a valve timing responsive to the state of operation.

Abstract: A knock control apparatus for engine has a knock sensor for detecting vibrations of the engine. The knock control apparatus determines an occurrence of knock by using at least one of a statistical process, a waveform process and a FFT process. The knock control apparatus desirably uses at least two of the above-described process for improving the accuracy of knock determination. The knock control apparatus learns a corrective value during a stable condition of the engine. The learned value is used for determining an ignition timing when the engine is in a transitional condition. Therefore, it is possible to detect a knock accurately, and reduce a knock when the engine is in the transitional condition.

Abstract: A valve timing control apparatus has a variable valve timing actuator. The system advances the valve timing to at least a middle position before the engine is completely stopped. The middle position is appropriate to start the engine. Before stopping the engine, if the oil temperature is too high to maintain a viscosity, the system provides a control to assist the above-described advancing control. For instance, the system increases the engine speed to supply a sufficient amount and pressure of oil. The system slightly advances the valve timing while the engine is in an idling.

Abstract: A knock control apparatus has a knock sensor and a signal processor. The signal processor integrates a knock sensor signal and differentiates the integrated signal. The signal processor detects a period in which the differentiated signal exceeds a threshold, and detects a peak of the differentiated signal. The signal processor then calculates a ratio between the detected signal generation period and the detected peak to determine a knock when the calculated ratio is within a predetermined range. Alternatively, the signal processor detects a peak generation time and calculates a ratio between the detected signal generation period and the detected peak generation time. In this instance, the signal processor determines the knock when the calculated ratio is within a predetermined range and the detected peak generation time is less than a predetermined time reference.

Abstract: A knock control apparatus for engine has a knock sensor for detecting vibrations of the engine. The knock control apparatus determines an occurrence of knock by using at least one of a statistical process, a waveform process and a FFT process. The knock control apparatus desirably uses at least two of the above-described process for improving the accuracy of knock determination. The knock control apparatus learns a corrective value during a stable condition of the engine. The learned value is used for determining an ignition timing when the engine is in a transitional condition. Therefore, it is possible to detect a knock accurately, and reduce a knock when the engine is in the transitional condition.

Abstract: A valve timing control apparatus has a variable valve timing actuator. The system advances the valve timing to at least a middle position before the engine is completely stopped. The middle position is appropriate to start the engine. Before stopping the engine, if the oil temperature is too high to maintain a viscosity, the system provides a control to assist the above-described advancing control. For instance, the system increases the engine speed to supply a sufficient amount and pressure of oil. The system slightly advances the valve timing while the engine is in an idling.

Abstract: An engine control system has an ECU and a valve timing control device (VVT). The ECU keeps the engine rotation after a driver turns off an ignition switch, and drives the VVT at least a middle position appropriate for starting the engine. Then the ECU stops fuel supply and ignition. Therefore, the VVT is surely driven to the middle position before the engine is stopped. Additionally, the system may shorten an extended running time of the engine since the engine is stopped when the valve timing reaches to the middle position. Further, the engine may be forcedly stopped if the engine is still running when a predetermined time is elapsed after the ignition switch is turned off.

Abstract: A knock control apparatus has a knock sensor and a signal processor. The signal processor integrates a knock sensor signal and differentiates the integrated signal. The signal processor detects a period in which the differentiated signal exceeds a threshold, and detects a peak of the differentiated signal. The signal processor then calculates a ratio between the detected signal generation period and the detected peak to determine a knock when the calculated ratio is within a predetermined range. Alternatively, the signal processor detects a peak generation time and calculates a ratio between the detected signal generation period and the detected peak generation time. In this instance, the signal processor determines the knock when the calculated ratio is within a predetermined range and the detected peak generation time is less than a predetermined time reference.

Abstract: To ensure both responsiveness and stability of a knock determination in which a knock sensor signal is compared with a knock determining reference computed from a background value, a difference between the knock sensor signal and the background value is determined through averaging by the use of the averaging coefficient. Based on the difference, the averaging coefficient n is varied so that the more latest sensor output signals are used in the background value determination as the difference becomes larger.

Abstract: A signal processing circuit includes a signal selecting device operative for selecting and outputting one of plural input signals. A filter connected to the signal selecting device filters the signal selected by the signal selecting device with a changeable center frequency of a pass band of the filtering. A frequency changing device is operative for temporarily changing the center frequency when the signal selected by the signal selecting device is changed from one to another. The filter includes, for example, a switched-capacitor filter.

Abstract: A knock sensing apparatus for an internal combustion engine which can detect a failure in a knock sensor signal system correctly even when a changeover operation due to hardware is performed at a place between a knock sensor and a band pass filter. In this knock sensing apparatus, the failure detection by a failure detecting circuit for detecting a failure in a signal system from knock sensors is invalidated for a predetermined period after one of the knock sensors has been changed over to the other knock sensor, or one of two kinds of pass bands of a band pass filter has been changed over to the other pass band, to prevent a decrease in failure detection accuracy due to the signal delaying action of the switched capacitor filter.

Abstract: An ignition timing control system for an internal combustion engine includes a basic ignition timing calculating unit for calculating a basic ignition timing of the engine and a low limit ignition timing calculating unit for calculating a low limit ignition timing of the engine, both being calculated according to an operating state of the engine. The system includes a retardation angle calculating unit for calculating a retardation angle that is retarded from the basic ignition timing. It also includes an advance angle calculating unit for calculating an advance angle that is advanced from a value corresponding to the low limit ignition timing depending on whether knocking is occurring in the engine. An operating state predicting unit is included for predicting an operating state of the engine where knocking is likely to occur. The system also includes an ignition timing control unit for controlling the ignition timing separately depending on whether a knocking is likely to occur in the engine.

Abstract: A knock control system for an internal combustion engine derives a knock intensity indicative value Vpi from an output of a knock sensor and decides presence or absence of an engine knock by comparing the knock intensity indicative value Vpi and a knock decision level V.sub.KDi for controlling a knock control factor such as an ignition timing based on the decision. The system derives a value Si corresponding to a standard deviation of a distribution of a substantially logarithmic conversion value of the knock intensity indicative value Vpi, and a value V.sub.Mi corresponding to a median value of the above-noted distribution. The system derives the knock decision level V.sub.KDi based on the value Si and the value V.sub.Mi when the value Si is within a predetermined range. On the other hand, when the value Si deviates from the predetermined range, the system derives the knock decision level V.sub.KDi based on the value V.sub.

Abstract: The knock control apparatus for an internal combustion engine comprises a knock detecting unit, a knock intensity value detecting unit for detecting a knock intensity value from a knock detecting output signal of the knock detecting unit within a predetermined crank angle range, a unit for calculating a mean value of the knock intensity value, a unit for calculating a mean deviation between the knock intensity value and the mean value, a cumulative percentage point updating unit for updating a cumulative percentage point of the distribution of the knock intensity value, a first updated quantity calculating unit for calculating a first updated quantity based on the knock intensity value and the cumulative percentage point, a second updated quantity setting unit for setting a second updated quantity for updating the cumulative percentage point updating unit based on the magnitude relationship between the first updated quantity and the mean deviation, a knock decision level calculating unit for calculating a kno

Abstract: A knock generation control system for engines has a knock sensor for detecting a knocking phenomenon occurring in an engine, a representative value detecting unit for detecting representative values V from output signals of the knock sensor which are effective for the detection of a knock, a standard deviation detecting unit for detecting a quantity SGM corresponding to a standard deviation of a frequency distribution of logarithmic conversion values lV of the representative values V, a cumulative percentage point detecting unit for detecting a value V.sub.P of a cumulative percentage point of the frequency distribution, a knock decision level setting unit for setting a knock decision level V.sub.KD in accordance with the detected quantity SGM and the detected value V.sub.P, a knock detecting unit for detecting generation of a knock in accordance with the representative values V and the knock decision level V.sub.