Unisia Jecs Corporation

Hitachi, Ltd.

Akira Uchikawa

Shoichi Sakai

Futoshi Ichiyanagi

Masao Tsukada

Yutaka Kanbara

Goji Matsumoto

Keiji Mori

Masami Kawashima

An oxygen sensor includes a base body portion; and a plurality of function layers laminated on a surface of the base body portion. The function layers includes a solid electrolyte layer adapted to conduct oxygen ions; a reference electrode layer located on a base body portion side of the solid electrolyte layer; a sensing electrode layer located on the opposite side of the solid electrolyte layer to the reference electrode layer; a heater portion adapted to activate the solid electrolyte layer by heating; and a gas diffusion layer formed between the reference electrode layer and the base body portion, and adapted to diffuse a reference gas within the gas diffusion layer. The gas diffusion layer is formed to have a porosity indicating a limit current value ranging between 60 &#x3bc;A and 200 &#x3bc;A. The limit current value is a value of a current flowing between the reference electrode layer and the sensing electrode layer when the current flowing therebetween becomes substantially constant during the process of bringing a voltage applied therebetween higher.

Oxygen sensor

An oxygen sensor includes a sensing element detecting an oxygen concentration in a measurement gas that flows in a pipe, a cylindrical protector which covers an outside of the sensing element and whose top end portion projects toward an inside of the pipe. An outside diameter D of the protector and a projection amount L of the protector inside the pipe are set so that a ratio of the product of the outside diameter D and the projection amount L (D&#xd7;L) to a cross-sectional area S of a flow passage of the pipe becomes substantially smaller than or equal to 2.5%.

An oxygen sensor includes a tubular casing; an oxygen detecting element installed in a leading end of the tubular casing; lead wires each extending from the oxygen detecting element to the outside of the tubular casing through an open base end of the tubular casing, each lead wire including a core wire of metal; a rubber bush plugged in the open base end of the tubular casing, the rubber bush having the lead wires passed therethrough; and a heat resisting structure for protecting the rubber bush from a high temperature. The heat resisting structure is constructed to satisfy the following inequality:10%&#x2266;50%,

The present invention aims at executing an air-fuel ratio feedback control making use of a wide range air-fuel ratio sensor, such that the purifying performance of an exhaust gas purification catalytic converter is exhibited to the utmost. To this end, fuel is injected from a fuel injection valve by establishing a fuel injection quantity, in consideration of a perturbation control constant for oscillating the air-fuel ratio at a predetermined period with a predetermined amplitude. Thus, even when the air-fuel ratio feedback control is executed making use of the detected result of the wide range air-fuel ratio sensor, it becomes possible to conduct a so-called perturbation control in which the air-fuel ratio of exhaust gas at the inlet portion of the exhaust gas purification catalytic converter is oscillated at a predetermined period with a predetermined amplitude. As a result, there can be effectively caused the adsorption and desorption of oxygen molecules onto and from the surface of the exhaust gas purification catalytic converter, so that the purifying performance of the catalytic converter can be remarkably improved.

Method and apparatus for controlling air-fuel ratio of internal

The present invention relates to an apparatus for diagnosing misfire of an internal combustion engine. With this invention, crank angle intervals for detecting angular velocity for each cylinder are variably set for each operation region. An average value of a predetermined number of misfire judgment values M1 set based on a plurality of angular velocities is compared with a reference value, to thereby carry out misfire diagnosis distinguishably of a misfire in a single cylinder or misfires in multiple cylinders.

Misfire diagnosis method and apparatus of internal combustion engine

An object is to carry out abnormality diagnosis of a wide range air-fuel ratio sensor to a high accuracy, with a relatively simple construction. Judgment is made as to whether abnormality diagnosis permit conditions have materialized, and if materialized, a detection value of an air-fuel ratio sensor is monitored. It is then judged if the responsiveness of a change in the detection value of the air-fuel ratio sensor subsequent to changing a target air-fuel ratio is within a predetermined range. If so, an OK judgment is given. If not, an NG judgment is given and a warning lamp is illuminated to advise the driver of the abnormality in the air-fuel ratio sensor so as to take action. With this arrangement, abnormality diagnosis of a wide range air-fuel ratio sensor can be carried out to a high accuracy with a relatively simple construction.

Method and apparatus for diagnosing an abnormality in a wide range

A system for estimating the temperature of an oxygen sensor installed in an exhaust system of an engine comprises a section for sensing a load of the engine; a section for sensing a rotation speed of the engine; and a section which, based on both the engine load and the engine rotation speed, calculates a basic estimated temperature of the oxygen sensor which would appear under a normal condition. A section is employed which senses a speed of the vehicle. A section is employed which, based on the vehicle speed, determines a first correction factor for correcting the basic estimated temperature. A section is employed which senses the temperature of outside air. A section is employed which, based on the outside air temperature, determines a second correction factor for correcting the basic estimated temperature. A target estimated temperature calculating section is employed which, based on the basic estimated temperature and the first and second correction factors, calculates a target estimated temperature of the oxygen sensor and issues an output signal representative of the target estimated temperature. A stopper section is further employed which suppresses the target estimated temperature calculating section from issuing the output signal or calculating the target estimated temperature until a predetermined time passes from a time on which energization of the electric heater starts.

System and method for estimating the temperature of oxygen sensor

A misfire diagnostic system for an Internal combustion engine comprises a crank-shaft angle sensor for monitoring a crankshaft angular velocity reflecting a combusting condition of each of engine cylinders, and a control unit for calculating an angular-velocity correction factor of each of the engine cylinders on the basis of the angular velocity in every engine operating region only under a stable engine operating condition. The control unit corrects the angular velocity by the angular-velocity correction factor of each of the engine cylinders for every engine operating region. The presence of a misfire is accurately decided on the basis of the angular velocity corrected for every engine cylinder and for every engine operating region.

Misfire diagnostic system for internal combustion engine

In an internal combustion engine equipped with electronically controlled fuel injection valves, there is provided an air-fuel ratio detecting system. The system comprises a wide range type air-fuel ratio sensor disposed in an exhaust pipe of the engine. The sensor issues an output voltage that varies continuously in accordance with an exhaust gas air-fuel ratio possessed by an exhaust gas in the exhaust pipe. The output voltage of the sensor is translated to an air-fuel ratio of air-fuel mixture with reference to a reference table. A variation characteristic of the output voltage of the sensor is decided relative to variation of the air-fuel ratio of air-fuel mixture. A correction data of the translated air-fuel ratio is formed with reference to the variation characteristic. The translated air-fuel ration is corrected with reference to the correction data.

Air-fuel ratio detecting system of internal combustion engine

Technology for diagnosing an intake air amount detection device of an internal combustion engine, wherein an operation region in which the engine is stably operating is determined, the opening degree of a throttle valve interposed in an intake system of the engine is detected, a change in the opening degree of the throttle valve is calculated when the opening degree of the throttle valve is changed in the determined stable operation region, and an intake air change amount detected by the intake air amount detection device is calculated when the opening degree of the throttle valve is changed in order to diagnose performance of the intake air amount detection device based on a relationship between the change in the opening degree of the throttle valve and the intake air change amount.

Method for diagnosing performance of intake air amount detection device

An air-fuel ratio feedback correction coefficient for correcting a fuel supply quantity to an engine is proportional-plus-integral controlled based on an output from an oxygen sensor for detecting oxygen concentration in the exhaust gases. When the oxygen sensor is in an inactive condition, deviation of an air-fuel ratio control point in the air-fuel ratio feedback control is detected, and an operating quantity in the proportional-plus-integral control is corrected so as to reduce the detected deviation.

Apparatus and method for controlling air-fuel ratio of an internal

In an air/fuel ratio control system for an internal combustion engine, having a second air/fuel ratio sensor disposed downstream of a catalytic converter, a computing type used for computing a second air/fuel ratio correction quantity in accordance with an output of the second air/fuel ratio sensor is switched in such a manner that the second air/fuel ratio quantity is set larger when the output of the second air/fuel ratio sensor is outside a reference level range than when the output of the second air/fuel ratio sensor is within the reference level range.

Air/fuel ratio control system for internal combustion engine

In a device having air-fuel ratio sensors upstream and downstream of an exhaust gas purifying catalytic converter with learning carried out based on output values from the downstream air-fuel ratio sensor, independent learning is carried out depending on whether the catalytic converter is active or not. The air-fuel ratio is then controlled based on the output value of the first air-fuel ratio sensor, the output value of the second air-fuel ratio sensor and the learned value. As a result leaning accuracy is increased and air-fuel ratio control performance enhanced.

Method and apparatus for controlling the air-fuel ratio of an internal

Fuel property detecting apparatus for internal combustion engines

In an internal combustion engine with oxygen sensors provided respectively upstream and downstream of an exhaust purification catalytic converter, the air-fuel ratio is feedback controlled based on an output of the second oxygen sensor only. When in this control situation, an output period of the first oxygen sensor becomes longer than that of the second oxygen sensor, response deterioration of the first oxygen sensor is judged to have occurred. Once the occurrence of response deterioration is determined, a proportional operating amount used in a proportional control of an air-fuel ratio feedback correction coefficient LMD for air-fuel ratio feedback control using the first oxygen sensor, is corrected in proportion to the response deterioration to thereby correct a deviation of the air-fuel ratio control point. As a result, response deterioration of the first oxygen sensor can be diagnosed, and deviation of the air-fuel ratio control point due to the response deterioration can be avoided, so that control accuracy to the target air-fuel ratio can be ensured.

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Atsugi, Japan

Akira Uchikawa