Abstract: An simplified structure of an air-fuel ratio control system for an internal combustion engine includes an upstream and a downstream catalytic device installed in an exhaust pipe of the engine and a first, a second, and a third air-fuel ratio sensor installed in upstream or downstream side of the exhaust pipe. The system also includes a first feedback controller working to bring a value of the air-fuel ratio, as measured by the first air-fuel ratio sensor, into agreement with a target one and a second feedback controller working to sample values of the air-fuel ratios, as measured by the second and third air-fuel ratio sensors, to correct a predetermined controlled parameter in the feedback control of the first feedback controller.

Abstract: An air-fuel ratio deviation calculated by an air-fuel ratio deviation calculation part is inputted to a cylinder-by-cylinder air-fuel ratio estimation part. A cylinder-by-cylinder air-fuel ratio is estimated in the cylinder-by-cylinder air-fuel ratio estimation part. In the cylinder-by-cylinder air-fuel ratio estimation part, attention is paid to gas exchange in an exhaust collective part of an exhaust manifold, and a model is created. In this model, a detection value of an A/F sensor is obtained by multiplying histories of the cylinder-by-cylinder air-fuel ratio of an inflow gas in the exhaust collective part and histories of the detection value of the A/F sensor by specified weights respectively and by adding them. The cylinder-by-cylinder air-fuel ratio is estimated on the basis of the model.

Abstract: A control duty is obtained, which asymptotically makes the output of a control subject consistent with an output of a reference model. The output of the control subject simulates a dynamic characteristic of a variable valve timing controller, and the output of the reference model simulates an ideal input-output characteristic of the variable valve timing. The control duty makes a difference between the output of the reference model and an actual valve timing small enough. A parameter of a controller is consecutively corrected to make the difference small by means of a parameter correcting mechanism when the dynamic characteristic of the variable valve timing controller is varied due to a variation of an operating environment thereof so that the difference becomes large.

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: 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: An simplified structure of an air-fuel ratio control system for an internal combustion engine includes an upstream and a downstream catalytic device installed in an exhaust pipe of the engine and a first, a second, and a third air-fuel ratio sensor installed in upstream or downstream side of the exhaust pipe. The system also includes a first feedback controller working to bring a value of the air-fuel ratio, as measured by the first air-fuel ratio sensor, into agreement with a target one and a second feedback controller working to sample values of the air-fuel ratios, as measured by the second and third air-fuel ratio sensors, to correct a predetermined controlled parameter in the feedback control of the first feedback controller.

Abstract: When the output of the AFR ratio sensor is stable in a steady operating state, the amount of fuel is increased by step inputting to detect a point where the gradient of change in the sensor output exceeds a threshold value as a point of start of change. The time from the timing of increasing the fuel until the point of start of change is detected as a dead time. A response time is calculated until the amount of change in the sensor output reaches a predetermined ratio of the amount of change (AA?BA) of up to the steady value AA of the sensor output after the amount of the fuel is increased from the steady value BA of the sensor output before the amount of the fuel is increased. The fail condition in the AFR ratio sensor is determined based on the dead time TA and the response time TB.

Abstract: A required valve timing change rate Vreq is calculated so as to make a deviation D between a target valve timing VTtg and an actual valve timing VT small and then a required speed difference DMCRreq between a motor 26 and a camshaft 16 is calculated on a basis of the required valve timing change rate Vreq. When the deviation D is larger than a predetermined value, a required motor speed Rmreq is calculated by adding the required speed difference DMCRreq to a camshaft speed RC and a motor control value is calculated so as to control the motor speed RM to the required motor speed Rmreq. When the deviation D is not larger than the predetermined value, the camshaft speed RC is set as the required motor speed Rmreq and the motor control value is calculated so as to control the motor speed RM to the camshaft speed RC.

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: A catalyst for purifying exhaust gas is provided in an exhaust pipe of an engine. When air-fuel ratio dither control is performed, an ECU calculates a requested torque to be generated by combustion of the engine based on an accelerator opening angle or the like operated by a driver. An MBT estimated torque corresponding to MBT (Minimum advance for the Best Torque) in each case is calculated, and a spark timing retard limit estimated torque corresponding to a spark timing retard limit in each case is calculated. An air-fuel ratio amplitude amount in the air-fuel ratio dither control is calculated based on the calculated requested torque, the MBT estimated torque, and the spark timing retard limit estimated torque. An early activation of a catalyst is realized.

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 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.

Abstract: A catalyst for purifying exhaust gas is provided in an exhaust pipe of an engine. When air-fuel ratio dither control is performed, an ECU calculates a requested torque to be generated by combustion of the engine based on an accelerator opening angle or the like operated by a driver. An MBT estimated torque corresponding to MBT (Minimum advance for the Best Torque) in each case is calculated, and a spark timing retard limit estimated torque corresponding to a spark timing retard limit in each case is calculated. An air-fuel ratio amplitude amount in the air-fuel ratio dither control is calculated based on the calculated requested torque, the MBT estimated torque, and the spark timing retard limit estimated torque. An early activation of a catalyst is realized.

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 air-fuel ratio deviation calculated by an air-fuel ratio deviation calculation part is inputted to a cylinder-by-cylinder air-fuel ratio estimation part. A cylinder-by-cylinder air-fuel ratio is estimated in the cylinder-by-cylinder air-fuel ratio estimation part. In the cylinder-by-cylinder air-fuel ratio estimation part, attention is paid to gas exchange in an exhaust collective part of an exhaust manifold, and a model is created. In this model, a detection value of an A/F sensor is obtained by multiplying histories of the cylinder-by-cylinder air-fuel ratio of an inflow gas in the exhaust collective part and histories of the detection value of the A/F sensor by specified weights respectively and by adding them. The cylinder-by-cylinder air-fuel ratio is estimated on the basis of the model.

Abstract: A writing implement includes a cylindrical shaft member, a pen tip member which is fixed to one end of the shaft member and from which colored ink seeps out, liquid for ink which is stored in the shaft member and which comprises a part of the colored ink seeping out from the end of the pen tip member, and colorant to be added to the above described liquid for ink to be the colored ink. Moreover, at least a part of a cylindrical side surface of the shaft member corresponding to the storing part of the liquid for ink is formed to be transparent. Between the liquid for ink and the colorant-storing part storing the colorant is provided a colorant-adsorbing core which introduces the liquid for ink into the colorant-storing part while capturing the colorant diffusing toward the storing part of the liquid for ink.

Abstract: A writing implement includes a cylindrical shaft member, a pen tip member which is fixed to one end of the shaft member and from which colored ink seeps out, liquid for ink which is stored in the shaft member and which comprises a major component of the colored ink seeping out from an end of the pen tip member, colorant to be added to the liquid for ink, and a valve member for isolating the colorant from the liquid for ink. In the writing implement, at least a part of a cylindrical side surface of the shaft member corresponding to a part where the liquid for ink is stored is formed to be transparent, the valve member is positioned between the storing part of the liquid for ink and the colorant, and the storing part of the liquid for ink is provided with a pressure-regulating part.

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: 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: 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.