Denso Corporation

Nippondenso Co., Ltd.

Yasuo Mukai

Masaaki Nakayama

Noriaki Iwase

Yasuo Sagisaka

Masahiko Yamaguchi

Mikiyasu Matsuoka

Shingo Nakata

Kuniaki Ueda

Hisayo Douta

Hisashi Iida

Yukihiro Yamashita

Keiji Wakahara

Makoto Miwa

Junya Morikawa

Yuji Yamada

Yasuhito Takasu

Hisayo Dohta

Takeshi Fujimoto

Tetsuji Mitsuda

An Osensor includes a sensor element using a solid electrolyte layer and a pair of electrodes placed at a position to interpose the solid electrolyte layer, detects an exhaust gas from an internal combustion engine as an object of a detection, and outputs an electromotive force signal depending on an air-fuel ratio of the exhaust gas. The sensor element is connected with a constant current circuit supplying a constant current that is prescribed. A microcomputer conducts an abnormality diagnosis of an output response of the sensor element on the basis of a state of variation in an electromotive force output. Further, when the microcomputer conducts the abnormality diagnosis, the microcomputer restricts a supply of the constant current by the constant current circuit before conducting the abnormality diagnosis.

Gas sensor control device

An individual cylinder air-fuel ratio estimation of estimating an air-fuel ratio of an individual cylinder is performed on a sensed value of an air-fuel ratio sensor set in an exhaust gas collection part of an engine, and an individual cylinder air-fuel ratio control of controlling the air-fuel ratio of the individual cylinder is performed in such a way that a variation in the air-fuel ratio between the cylinders becomes small on the basis of an estimated air-fuel ratio of the individual cylinder. Further, it is determined whether or not a misfire of the engine is caused and when it is determined that the misfire of the engine is caused, the individual cylinder air-fuel ratio estimation and the individual cylinder air-fuel ratio control are stopped and an individual cylinder correction value by the individual cylinder air-fuel ratio control is reset. In this way, it is possible to avoid the individual cylinder air-fuel ratio control from being performed continuously as usual in a state where the air-fuel ratio of the individual cylinder cannot be controlled correctly due to the effect of the misfire.

Individual cylinder air-fuel ratio control device of internal combustion engine

An Osensor has a sensor element, which includes a solid electrolyte layer and a pair of electrodes, while the solid electrolyte layer is interposed between the electrodes. The Osensor outputs an electromotive force signal in response to an air-to-fuel ratio of exhaust gas of an engine, which serves as a sensing subject. A constant current circuit, which induces a flow of a predetermined constant electric current between the pair of electrodes of a sensor element, and a current sensing arrangement, which senses a current value of an actual electric current that is conducted through the sensor element, are provided. A microcomputer determines whether an abnormality of the constant current circuit is present based on the current value of the electric current, which is sensed with the current sensing arrangement, in a case where the constant current is induced by the constant current circuit.

An air-fuel-ratio of each cylinder is estimated based on a detection value of an air-fuel-ratio sensor. An air-fuel-ratio detection timing determination is executed to determine whether a deviation in air-fuel-ratio detection timing exists based on the estimated air-fuel-ratio while the cylinder-by-cylinder air-fuel-ratio control is performed. An observation residual is computed based on the detection value of the air-fuel-ratio sensor and the estimated air-fuel-ratio. When the observation residual is greater than or equal to a specified threshold value, the air-fuel-ratio detection timing determination is prohibited. Therefore, when the observation residual is still large before the estimated air-fuel-ratio of each cylinder is converged, or when the observation residual is still large due to a temporal deterioration in estimating accuracy of the estimated air-fuel-ratio, the air-fuel-ratio detection timing determination can be prohibited.

Cylinder-by-cylinder air-fuel-ratio controller for internal combustion engine

An ECU executes a cylinder-by-cylinder air-fuel-ratio control in which an air-fuel-ratio of each cylinder is estimated based on a detection value of an air-fuel-ratio sensor to adjust the air-fuel-ratio of each cylinder. Further, the ECU computes a learning value of a correction quantity for each cylinder, which is obtained by executing the cylinder-by-cylinder air-fuel-ratio control. Then, the ECU determines whether the estimated air-fuel-ratio has converged according to whether the estimated air-fuel-ratio of each cylinder has been closer to a target value than a specified value for not less than a specified time period. A computation of the learning value is prohibited until the estimated air-fuel-ratio has converged. Therefore, it can be avoided to compute the learning value based on the fuel correction quantity that is obtained when the estimated air-fuel-ratio has not converged yet.

A deviation amount of a downstream air-fuel ratio sensed with a downstream air-fuel ratio sensor, which senses an air-fuel ratio of exhaust gas downstream of a catalyst, from a target air-fuel ratio is integrated during a period in which the downstream air-fuel ratio continuously shows deviations from the target air-fuel ratio while main feedback control and sub feedback control are performed based on outputs of an upstream air-fuel ratio sensor and the downstream air-fuel ratio sensor respectively. The thus-calculated continuous deviation amount of the downstream air-fuel ratio (deterioration degree of exhaust gas purification rate) is compared with an abnormality determination value to determine existence/nonexistence of an abnormal state where the exhaust gas purification rate is deteriorated by an air-fuel ratio variation among cylinders (i.e., state where control center of main feedback control has shifted).

Abnormality diagnosis device of internal combustion engine

An alcohol concentration sensor detecting alcohol concentration of fuel is provided in a fuel tank or a fuel passage. An alcohol concentration detected at a previous driving of an engine is stored in a backup RAM. When a current alcohol concentration is different from the previous alcohol concentration, a procedure of an abnormality diagnosis is prohibited or invalidated until all of the fuel remaining in the fuel passage is consumed.

Abnormality diagnosis apparatus for internal combustion engine

A computer calculates an estimated cylinder-intake-air amount based on outputs from an airflow meter and a throttle position sensor, and then calculates a reference cylinder-intake-air amount based on an air-fuel ratio in an exhaust gas and fuel injection amount. An error of the estimated cylinder-intake-air amount is calculated by comparing the reference cylinder-intake-air amount with an estimated cylinder-intake-air amount base value. The error is low-pass filtered. The estimated cylinder-intake-air amount base value is corrected to obtain the final estimated cylinder-intake-air amount.

Air-fuel ratio controller for an internal combustion engine and diagnosis apparatus for intake sensors

An opening of a waste gate vale is adjusted to control an actual supercharging pressure of intake air. Abnormality in a changing characteristic of the actual supercharging pressure relative to a change in a TCV control duty value can be detected. When an engine is in a steady operation condition, the TCV control duty value is forcibly changed repeatedly by a predetermined amount from 0% to 100%. A deviation between a target supercharging pressure corresponding to the TCV control duty value and an actual supercharging pressure is calculated each time the TCV control duty value is changed by the predetermined amount. This deviation is compared with an abnormality determination value to determine presence/absence of the abnormality in the changing characteristic of the actual supercharging pressure relative to the change in the TCV control duty value.

Apparatus and method of abnormality diagnosis for supercharging pressure control system

Air-fuel ratio controller for internal combustion engine and diagnosis apparatus for intake sensors

A malfunction detection apparatus is disclosed for a forced induction system. The system includes a compressor provided on an upstream side of a throttle valve in an intake passage of an engine, an upstream intake pressure sensor that detects intake pressure between the compressor and the throttle valve, and an atmospheric pressure sensor that detects atmospheric pressure. The malfunction detection apparatus includes a malfunction detection program that makes a comparison between the atmospheric pressure detected by the atmospheric pressure sensor and the upstream intake pressure detected by the upstream intake pressure sensor. The comparison is made in an operating state of the forced induction system in which the compressor compresses an amount of air that is approximately equal to or less than a predetermined amount to thereby determine whether the upstream pressure sensor has a malfunction.

Malfunction detection apparatus for pressure sensor

In a system for detecting deterioration of an exhaust catalyst, when a catalyst temperature exceeds 150&deg; C., the changing widths of the output voltage of an oxygen sensor downstream of the catalyst are integrated for a predetermined sampling period to determine data &Sgr;V reflecting the amount of purified gas component, and the deviation of the air/fuel ratio detected by an air/fuel ratio sensor upstream of the catalyst, and a target A/F and an exhaust gas flow rate or an intake flow rate are multiplied so that data &Sgr;A/F&Circlesolid;Q of the fluctuation of the gas component flowing into the catalyst are determined by integrating the multiplied values. At the instant when the catalyst temperature reaches 550&deg; C., the data &Sgr;V, as integrated till then, are compared with a deterioration determining value, as set according to the data &Sgr;A/F&Circlesolid;Q, to determine whether the catalyst is deteriorated.

System for detecting deterioration of catalyst for purifying exhaust gas

A fuel vapor purge system has an apparatus for detecting leakage. The apparatus detects leakage based on a detected pressure in the tank. A remaining amount of fuel indicating a capacity of air in the tank and an introducing time of a negative pressure indicating an evaporated amount of fuel are taken into consideration of a detecting process. Therefore, the leakage detection is carried out accurately by compensating influences on the detected pressure by the remaining amount of fuel and an evaporated amount of fuel.

Apparatus for detecting leakage of vapor purge system

When a diagnosis execution condition is established, a canister closure valve is closed, thereafter, a purge control valve is opened, a purge control valve is closed in a state where negative pressure is introduced into an evaporated gas system to thereby maintain the evaporated gas system in a hermetically-sealed state and the hermetically-sealed state is continued until abnormality diagnosis is finished. Time period for maintaining the evaporated gas system in the hermetically-sealed state is divided into three time periods of a pressure change determining time period at a first time, an awaiting time period and a pressure change determining time period at a second time. After determining a pressure change amount DPT1 of the evaporated gas system in the pressure change determining time period at the first time, the evaporated gas system is successively maintained in the hermetically-sealed state, after the predetermined awaiting time period has elapsed, the pressure change determination at the second time is carried out by which a pressure change amount DPT2 of the evaporated gas system is determined. Further, presence or absence of leakage of the evaporated gas system is diagnosed by comparing the pressure change amount DPT1 at the first time with the pressure change amount DPT2 at the second time.

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Kariya, Japan

Yasuo Mukai