Abstract: Calculation of a present air-fuel ratio correction coefficient correction value &Dgr;FAF (i) is based on a control parameter calculated by an ECU, a change in air-fuel ratio detected by an air-fuel ratio sensor, a deviation of an actual air-fuel ratio from a target air-fuel ratio and an immediately preceding air-fuel ratio correction coefficient correction value &Dgr;FAF (i−1) Then, a present air-fuel ratio correction coefficient FAF (i) is found by adding the present air-fuel ratio correction coefficient correction value &Dgr;FAF (i) to an immediately preceding air-fuel ratio correction coefficient FAF (i−1). As a result, the air-fuel ratio correction coefficients is not be thrown into confusion and no phenomenon of the air-fuel ratio being thrown into confusion occurs even if the control parameter is changed in accordance with operating conditions of the engine.

Abstract: In detecting a deterioration of an air-fuel ratio sensor, a sensor output change speed integrated value is calculated when an element temperature of a solid electrolyte is stabilized at a low temperature. Successively, a sensor output change speed integrated value is calculated when the solid electrolyte element is stabilized at a high temperature. Finally, a deviation between the change speed integrated values is calculated. By comparing the deviation amount with a predetermined determinant, presence or absence of the deterioration is determined.

Abstract: An exhaust gas cleaning system has two catalysts and three sensors. The target voltage of a second sensor arranged upstream of a downstream catalyst is set according to the output voltage of the second sensor and the output voltage of a third sensor. Thus, even if the output voltage of the second sensor shows a stoichiometric condition and the output voltage of the third sensor shows a rich condition, it is possible to restrict the unnecessary correction of the target voltage and to optimize the cleaning rate of the downstream catalyst. Therefore, it is possible to reduce emission from being impaired by an expected variation in the air-fuel ratio.

Abstract: The present invention is directed to provide a controller for an internal combustion engine, capable of suppressing deterioration in drivability of an engine. A controller for an internal combustion engine has lean control means for calculating a torque margin from a reference engine speed and an actual engine speed and setting a combustion air-fuel ratio of an internal combustion engine to the lean side on the basis of the torque margin. In addition to correction of a fuel injection amount by the lean control means, the fuel injection amount is further corrected on the basis of a final correction value for reducing deterioration in drivability. The final correction value is set by selecting either a correction value which is set on the basis of an engine speed fluctuation amount or a final correction value of last time, which suppresses deterioration in drivability more. Thus, the operation of setting the air-fuel ratio to the lean side while considering deterioration in drivability can be performed.

Abstract: A first oxygen sensor is mounted on an exhaust pipe. An ECU determines an electric power to be fed to a sensor heater, by a heater control quantity calculating block, in accordance with a difference between an actual impedance and a target impedance calculated by a running condition determining block and a specific gas sensitivity priority determining block. As a result, the detection sensitivity of the oxygen sensor to a rich component or a lean component is improved according to the running condition. This improved output is detected by an output detecting block and reflected on the air/fuel ratio control so that an air/fuel ratio is controlled thereby.

Abstract: An engine control system has a self-diagnosis function of an exhaust system. The self-diagnosis function includes a first mode for detecting a failure or abnormality of the exhaust system as a whole, and a second mode for determining and locating a specific failed component in the exhaust system. The first mode is executed during the engine is operated under a normal condition. Therefore it is possible to detect the failure of the exhaust system without lowering a drive performance or increasing emissions. In case of detecting any failure in the first mode, the second mode is activated in response to a command signal that can be entered via a service tool. In the second mode, the engine is operated in order to determine the failed component. In the second mode, determining the failed component takes priority over keeping the drive performance or reducing emissions.

Abstract: An occluded oxygen quantity in a catalyst is estimated when fuel cut is executed. Then, upon return from the fuel cut, a target air-fuel ratio is set to significantly richer value. When it is detected on the basis of an output of an oxygen sensor that oxygen occluded by an upstream-side catalyst has been consumed, the target air-fuel ratio is switched to slightly richer value. Lastly, when the occluded oxygen quantity has become 0, a return is made to a normal air-fuel ratio feedback control. It is possible to consume the oxygen occluded by the catalyst quickly, and simultaneously it is possible to diminish emission released to the atmosphere even if an estimated value of the occluded oxygen quantity is deviated from an actual value.

Abstract: An engine has an upstream catalyst and a downstream catalyst in an exhaust system. An air-fuel ratio control apparatus has an oxygen sensor that outputs signal indicative of an oxygen storage amount in the downstream catalyst. The apparatus has an air supply device for supplying the air into upstream the downstream catalyst. When the signal of the oxygen sensor indicates a shortage of the oxygen storage amount in the downstream catalyst, the air supply device is activated to supply the air to the downstream catalyst. Thus, the downstream catalyst can recover the oxygen storage amount sufficient to keep its catalysis.

Abstract: An emission control apparatus for an engine has a plurality of catalysts disposed in series in an exhaust passage. An HC absorbent catalyst is utilized for at least one of the catalysts. An ECU controls an A/F ratio in an upstream side of the HC absorbent catalyst at a target value. The target value is corrected to a leaner value when the HC absorbent catalyst is in a desorbing condition. The leaner value is leaner than the target value during the HC absorbent catalyst is in an absorbing condition or an activated condition. The leaner atmosphere provides sufficient of oxygen to purify desorbed HC from the HC absorbent catalyst itself.

Abstract: The ignition timing is sustained at an initial value during a predetermined time beginning at a start of an engine, and is retarded after the predetermined time is elapsed to heat a catalyst at an early time. The predetermined time ends when the negative pressure of an intake pipe or the negative pressure of a brake booster reaches to a predetermined value. That is, the predetermined time is a period, which begins at a start of the engine and ends when a proper negative pressure can be sustained in the brake booster. As a result, it is possible to assure a negative pressure in the brake booster at an early time and to reduce exhaust emission at a start of the engine simultaneously.

Abstract: Liquid-for-ink 50 and a main part of colorant 60 for coloring the liquid-for-ink 50 are separately stored within a writing implement. The writing implement is so fabricated that the colorant 60 is added to the liquid-for-ink 50 while the liquid-for-ink 50 is introduced to a writing tip 70.

Abstract: An emission control system has a catalyst and a sensor responding to a component of exhaust gas. In order to speed warming up the catalyst, the emission control system increases the amount of heat dissipated by exhaust gas. A diagnosis of the emission control system is carried out by determining whether the amount of heat dissipated by exhaust gas is sufficient or insufficient. The amount of heat dissipated by exhaust gas is represented by the length of time to an activated state of the sensor. In the diagnosis, the amount of heat generated by a heater provided in the sensor is taken into consideration. The diagnosis can also be carried out before and after the warming up the catalyst. The heater can also be deactivated. Detection of an abnormality of a secondary air control system can be based on a component of exhaust gas. If the amount of heat dissipated by exhaust gas is found insufficient, additional control can be executed.

Abstract: An upstream catalyst and a downstream catalyst are disposed in series in an exhaust pipe, and first through third sensors for detecting the air-fuel ratio or an adsorption amount of hazardous components on the rich/lean side of exhaust gases are disposed on the upstream and downstream sides of the upstream catalyst and the downstream side of the downstream catalyst, respectively. An ECU for controlling an engine controls the air-fuel ratio so that when the adsorption amount of the hazardous components on the rich side of the downstream catalyst is large, that of the hazardous components on the lean side of the upstream catalyst is large. Similarly, the ECU controls the air-fuel ratio so that when the adsorption amount of the hazardous components on the lean side of the downstream catalyst is large, that of the hazardous components on the rich side of the upstream catalyst is large.

Abstract: A required injection time tau is calculated at intervals of 60° CA, and an injection start timing is determined according to the required injection time tau at that time at intervals of 180° CA so that fuel is taken in the cylinder by a first injection end regulation value (ATDC 60° CA). After that, at the injection start timing, the fuel injection for the (latest) required injection time tau calculated just before the start of injection is started. During the fuel injection, the required injection time tau is also calculated at intervals of 60° CA. When the calculated required injection time tau is different from the value of last time, the fuel injection time is extended or shortened according to the change amount.

Abstract: Exhaust gas sensors are provided at the upstream side and the downstream side of a catalyst, respectively. An intermediate target value is set on the basis of the output of the downstream-side exhaust gas sensor of preceding computation time and a final target value that is a final downstream-side target air-fuel ratio. The compensation amount of the upstream-side target air-fuel ratio is calculated on the basis of the deviation between the present output of the downstream-side exhaust gas sensor and the intermediate target value. At least one of an update amount and an update rate of the intermediate value, a control gain, a control period and a control range of a sub-feedback control is varied.

Abstract: The present invention is directed to provide a controller for an internal combustion engine, capable of suppressing deterioration in drivability of an engine. A controller for an internal combustion engine has lean control means for calculating a torque margin from a reference engine speed and an actual engine speed and setting a combustion air-fuel ratio of an internal combustion engine to the lean side on the basis of the torque margin. In addition to correction of a fuel injection amount by the lean control means, the fuel injection amount is further corrected on the basis of a final correction value for reducing deterioration in drivability. The final correction value is set by selecting either a correction value which is set on the basis of an engine speed fluctuation amount or a final correction value of last time, which suppresses deterioration in drivability more. Thus, the operation of setting the air-fuel ratio to the lean side while considering deterioration in drivability can be performed.

Abstract: A control unit employed in a variable valve timing apparatus vibrates a control signal for controlling an oil-pressure control valve. If the vibration center of the duty value of the control signal for driving the oil-pressure control valve lies in a dead band, the vibration takes the duty value to the outside of the dead center temporarily. Thus, even if the center value of the control signal lies in the dead band, the valve timing of the oil-pressure control valve changes with variations in control signal. As a result, the width of the dead band appears small or to have a value of zero. Accordingly, the response characteristic of variations in valve timing to the variations in control signal is improved. The vibration of the control signal is also effective for detection of a width of the dead band.

Abstract: Exhaust gas sensors are provided at the upstream side and the downstream side of a catalyst, respectively. An intermediate target value is set on the basis of the output of the downstream-side exhaust gas sensor of preceding computation time and a final target value that is a final downstream-side target air-fuel ratio. The compensation amount of the upstream-side target air-fuel ratio is calculated on the basis of the deviation between the present output of the downstream-side exhaust gas sensor and the intermediate target value. At least one of an update amount and an update rate of the intermediate value, a control gain, a control period and a control range of a sub-feedback control is varied.

Abstract: An emission control apparatus for an engine has a plurality of catalysts disposed in series in an exhaust passage. An HC absorbent catalyst is utilized for at least one of the catalysts. An ECU controls an A/F ratio in an upstream side of the HC absorbent catalyst at a target value. The target value is corrected to a leaner value when the HC absorbent catalyst is in a desorbing condition. The leaner value is leaner than the target value during the HC absorbent catalyst is in an absorbing condition or an activated condition. The leaner atmosphere provides sufficient of oxygen to purify desorbed HC from the HC absorbent catalyst itself.

Abstract: Calculation of a present air-fuel ratio correction coefficient correction value &Dgr;FAF (i) is based on a control parameter calculated by an ECU, a change in air-fuel ratio detected by an air-fuel ratio sensor, a deviation of an actual air-fuel ratio from a target air-fuel ratio and an immediately preceding air-fuel ratio correction coefficient correction value &Dgr;FAF (i−1) Then, a present air-fuel ratio correction coefficient FAF (i) is found by adding the present air-fuel ratio correction coefficient correction value &Dgr;FAF (i) to an immediately preceding air-fuel ratio correction coefficient FAF (i−1). As a result, the air-fuel ratio correction coefficients is not be thrown into confusion and no phenomenon of the air-fuel ratio being thrown into confusion occurs even if the control parameter is changed in accordance with operating conditions of the engine.