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: Evaporated fuel gas from a canister is introduced into an intake path of an internal combustion engine. A target air-fuel ratio is changed to a value on the fuel rich side during the introduction of purge gas in accordance with the purge gas concentration. This change will restrict the shift of the air-fuel ratio toward the lean side, allowing a catalyst to operate at high purification efficiency even during the introduction of purge gas. The change may be varied in accordance with the volume of the evaporated fuel gas or a ratio of the evaporated fuel gas to the fuel supplied to the engine.

Abstract: A writing implement with an ink collector is able to prevent ink soiling at the pen tip even when the writing implement has been left under an atmosphere of 0° C. or below, at which the ink inside the writing implement will begin freezing and can be assembled by a simple assembling machine with its productivity improved. This writing implement with an ink collector is a direct ink storage type writing implement having an ink chamber 2 disposed at the rear part of a barrel cylinder 1 for directly storing the ink and an ink collector 5 mounted at the front part of barrel cylinder 2 and is characterized in that ink collector 5 is formed with a passage hole 6 therein in which an ink conduit core 8 for conveying the ink from ink chamber 2 to a pen tip 10 is provided while the flank of ink collector 5 is formed with air holes 7 that communicate with passage hole 6.

Abstract: A method and apparatus for controlling the air-fuel ratio of an internal combustion engine that prevents erroneous learning while properly setting a learning frequency to thereby execute highly accurate air-fuel ratio control. Fuel vapor generated in a fuel tank is temporarily adsorbed in a canister via a tank inner pressure-regulating valve, and the adsorbed vapor is discharged to an engine intake system via a purge solenoid valve. A sensor for detecting tank inner pressure is arranged in the fuel tank, and an ECU calculates a feedback correction amount based on an oxygen concentration in exhaust gas and executes air-fuel ratio feedback control by using the feedback correction amount. The ECU prohibits the air-fuel ratio learning value from being updated when the tank inner pressure exceeds a predetermined criterion value based on the tank inner pressure detected by the tank inner pressure sensor.

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 as well, the required injection time tau is 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: In an air-fuel ratio feedback control system for engines, a feedback correction amount is calculated in response to an air-fuel ratio detected at an engine exhaust side to effect an air-fuel ratio feedback control even during an engine warm-up period. A delay time compensation amount is calculated from two basic fuel injection amounts calculated presently and previously. The previous fuel injection amount is calculated the delay time before the present fuel injection amount. The feedback correction amount is corrected with the delay time compensation amount. When the engine undergoes a transient operation condition such as acceleration or deceleration, the present fuel injection amount is corrected with the corrected feedback correction amount. When the basic fuel injection amount changes rapidly due to acceleration, the delay time compensation amount is decreased responsively and the corrected feedback correction amount is increased so that the present fuel injection amount is not reduced too much.

Abstract: An air-fuel ratio feedback control has an air-fuel ratio sensor and an oxygen sensor at an upstream side and a downstream side of a catalytic converter. A CPU feedback controls an air-fuel ratio detected by the air-fuel ratio sensor to a target air-fuel ratio, with a feedback gain being varied with an output of the oxygen sensor. The CPU further estimates an air-fuel ratio response speed based on a ratio between an exhaust gas flow amount and a capacity of the catalyst and determines a rate of deterioration of the catalyst. The CPU varies further the feedback gain based on the estimated response speed and the determined rate of deterioration.

Abstract: A water based dye ink composition for a free ink rollerball pen characterized in that white resin particles which are insoluble in an aqueous medium and have an average particle diameter of 100 to 1000 nm and a refractive index of 1.50 or more at 20.degree. C. are added to a water based ink composition for a writing instrument comprising a dye and an aqueous medium to thereby allow the visible color of the ink liquid to be approximate to the visible color of lines written on a sheet of white paper.

Abstract: An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed.

Abstract: A sensing element of an oxygen sensor is controlled to keep a target impedance for maintaining activation temperature of the oxygen sensor. As the sensing element deteriorates, its internal impedance increases and power supply to a heater for heating the sensing element increases. The oxygen sensor temperature rises excessively above an activation temperature. To restrict excessive temperature rise, the target impedance is altered when the supply power to the heater exceeds a predetermined reference. The target impedance may be increased with increase in the power supply to the heater. Alternatively, the heater supply power is limited to a predetermined maximum for restricting excessive temperature rise.

Abstract: An air-fuel ratio control using an A/F sensor which outputs a current representing an air-fuel ratio in response to a voltage applied thereto. If the A/F sensor is still in a state prior to activation and the actual air-fuel ratio is different from an air-fuel ratio represented by a current of the sensor in the state prior to activation when the engine is started, that is, if the air-fuel ratio is put on the rich side by an increased amount of fuel injected at a start of an internal combustion engine at a low temperature or other causes, for example a CPU employed in an ECU, determines whether the difference between the .lambda.-conversion value of the current of the A/F sensor and a target air-fuel ratio is equal to or greater than a predetermined value. If the determination is YES, a feedback control of the air-fuel ratio is started.

Abstract: An air/fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air/fuel ratio, based on the output of an air/fuel ratio sensor. The system may determine whether there is an abnormality in the air/fuel ratio sensor based on a comparison between a change of an air/fuel ratio correction coefficient, used to drive the air/fuel ratio to the target value, and a change of the target air/fuel ratio if the target air/fuel ratio has sharply changed.

Abstract: In an engine fuel supply system, the difference between the actual and target air-fuel ratios, an air-fuel ratio feedback correction coefficient and a learned correction amount are added as a parameter for diagnosing the fuel supply system. The diagnostic parameter is smoothed and the smoothed value is compared with a diagnosis reference value, thereby detecting a malfunction in the fuel supply system. Even if the learned correction amount is not updated, the malfunction in the fuel supply system can be promptly detected from the difference between the actual and target air-fuel ratios and the air-fuel ratio correction coefficient. The diagnosis reference value is determined variably in accordance with engine operating parameters such as the amount of intake air.

Abstract: A sensing element of an oxygen sensor is controlled to keep a target impedance for maintaining activation temperature of the oxygen sensor. As the sensing element deteriorates, its internal impedance increases and power supply to a heater for heating the sensing element increases. The oxygen sensor temperature rises excessively above an activation temperature. To restrict excessive temperature rise, the target impedance is altered when the supply power to the heater exceeds a predetermined reference. The target impedance may be increased with increase in the power supply to the heater. Alternatively, the heater supply power is limited to a predetermined maximum for restricting excessive temperature rise.

Abstract: A deterioration monitoring apparatus for an exhaust system of an internal combustion engine includes an air-fuel ratio control system and a deterioration determining circuit. The air-fuel ratio control system controls an air-fuel ratio of exhaust emissions flowing downstream of a catalytic converter disposed in the exhaust system of the engine to agree with a target downstream air-fuel ratio under feedback control based on an air-fuel ratio of exhaust emissions flowing upstream of the catalytic converter and the air-fuel ratio of the exhaust emissions flowing downstream of the catalytic converter. The deterioration determining circuit determines whether the exhaust system such as an oxygen sensor mounted downstream of the catalytic converter or the catalytic converter is deteriorated or not based on the air-fuel ratio of the exhaust emissions flowing downstream of the catalytic converter and the target downstream air-fuel ratio.

Abstract: On an exhaust pipe of an internal combustion engine, an A/F sensor is disposed at an upstream side of a three-way catalyst and a downstream side O.sub.2 sensor is disposed on a downstream side thereof. A CPU determines according to an exhaust gas temperature whether the operational state of the engine is in a high load. In an early stage of the engine operation of high load, CPU sets a "rich" side target air-fuel ratio within a range that enables the downstream side O.sub.2 sensor to make linear detection of air-fuel ratio and executes feedback control of air-fuel ratio by using the set target air-fuel ratio. Also, when the level of the load has increased, CPU sets a "rich" side target air-fuel ratio according to the exhaust gas temperature and executes feedback control of air-fuel ratio by using the set target air-fuel ratio. Further, when the "rich" width deviates from a range that enables the A/F sensor to make its detection, CPU performs open-loop control with respect to the increment in fuel.

Abstract: An air-to-fuel ratio control apparatus for an internal combustion engine includes an air-to-fuel ratio sensor of a current limiting type for detecting an air-to-fuel ratio of an air-fuel mixture from a condition of exhaust gas originating from the air-fuel mixture. An air-to-fuel ratio controlling device is operative for performing feedback control in response to an output signal of the air-to-fuel ratio sensor so that the detected air-to-fuel ratio will be substantially equal to a target air-to-fuel ratio. A gain setting device is operative for setting a feedback gain of the air-to-fuel ratio feedback control in response to an atmospheric pressure.

Abstract: The fuel ratio control system controls the supply of fuel to an internal combustion engine to achieve a target air-fuel ratio, based on the output of an air-fuel ratio sensor. The system may determine whether there is an abnormality in the air-fuel ratio sensor based on a comparison between a change of an air-fuel ratio correction coefficient, used to drive the air-fuel ratio to the target value, and a change of the target air-fuel ratio if the target air-fuel ratio has sharply changed.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air-fuel ratio sensor provided at a collecting portion of an exhaust manifold. The air-fuel ratio sensor monitors an exhaust gas and changes its output in a linear fashion relative to an air-fuel ratio represented by the exhaust gas. The air-fuel ratio sensor is arranged at a position such that, after the number of strokes, corresponding to a multiple of the number of all cylinders, from a fuel injection for each cylinder, the air-fuel ratio sensor can measure an air-fuel ratio caused by the corresponding fuel injection. The system stores a target fuel amount for each of the cylinders. The system derives a feedback correction value depending on a deviation between a fuel amount introduced into the corresponding cylinder, which is derived based on the air-fuel ratio monitored by the air-fuel ratio sensor, and the stored number-of-stroke prior target fuel amount.

Abstract: An exhaust pipe of an internal combustion engine is equipped with a three-way catalytic converter. Provided upstream and downstream the converter are an A/F sensor and a downstream O2 sensor, respectively. A CPU executes air-fuel feedback control according to the readings from the A/F sensor. When the period of air-fuel ratio inversion by the downstream O2 sensor has exceeded a predetermined time, the CPU determines that the three-way catalytic converter is activated. At that point, the CPU estimates the quantity of heat required from the start-up of the engine up to catalyst activation. The quantity of heat is obtained by accumulating the intake air quantity from the start of the engine up to catalyst activation (i.e., accumulated intake air quantity). Given the accumulated quantity of heat calculated, the CPU determines accordingly whether the three-way catalytic converter has deteriorated.