Abstract: An abnormality detecting system and method detect an abnormality in an oxygen sensor provided on a downstream side of a catalyst for purifying exhaust gas released from an internal combustion engine. An upstream side sensor is provided on an upstream side of the catalyst, and produces an output corresponding to an exhaust air-fuel ratio. A theoretical oxygen storage capacity of the catalyst is obtained, for example, by determining an amount of oxygen in the exhaust gas flowing into the catalyst during a period in which the oxygen sensor produces a rich output and the upstream side sensor produces a lean output. An abnormality in the oxygen sensor is detected to exist when the theoretical oxygen storage capacity has exceeded a maximum oxygen storage amount of the catalyst.

Abstract: In an abnormality detection system that detects abnormality in an oxygen sensor including a detection element for outputting a current value corresponding to an oxygen concentration upon receipt of a voltage application, a negative value is applied to the oxygen sensor so as to obtain an impedance of the detection element. Then a difference between the obtained impedance of the oxygen sensor upon application of the negative voltage and the impedance of the oxygen sensor upon application of a positive voltage prior to the negative voltage application is calculated. It is determined whether there is abnormality in the oxygen sensor based on the calculated difference.

Abstract: A fuel injection system for diesel engines, capable of carrying out a control operation for varying a mixing ratio of a fuel to water (inert material) arbitrarily in accordance with the magnitude of an engine load in a short period of time, and holding down the formation of nitrogen oxides to a level equal to that in a related art fuel injection system using an aqueous emulsion fuel, by uniformly mixing the fuel in the same manner as an aqueous emulsion fuel used in a related art fuel injection system, with water (inert material) in the combustion chamber. A fuel is injected from a fuel injection nozzle toward the water (inert material) held in water holding portions, or a fuel is injected from a fuel injection nozzle into the water (inert material) supplied from water supply passages.

Abstract: A deterioration detection apparatus for an oxygen sensor is able to detect an abnormality of the oxygen sensor constantly with high precision, without being affected by the temperature characteristic of the element impedance. The apparatus applies a voltage V to the oxygen sensor, and calculates an element impedance real value Rsr=V/1 of a sensor element based on the applied voltage and the current I caused to flow by the voltage. The apparatus calculates an element temperature estimated value Tex of the oxygen sensor from a factor that affects the temperature of the oxygen sensor. The apparatus determines whether the oxygen sensor has an abnormality on the basis of whether the relationship between the element impedance real value Rsr and the element temperature estimated value Tex can be regarded as a relationship that agrees with a normal temperature characteristic.

Abstract: An element impedance detection apparatus for an oxygen sensor is provided with a first switching device, a second resistor, first resistor, and a first condenser for application of a sweep voltage to the oxygen sensor. The first switching device is switched to ON and the sweep voltage applied; a sensor current I that flows in the oxygen sensor along with application of the sweep voltage is then detected. Element impedance is calculated based on the sweep voltage and the sensor current. The second resistor, the first resistor and the first condenser are connected to the oxygen sensor such that a time constant of the sweep voltage increases as the element impedance becomes larger.

Abstract: An object of the present invention is to achieve a highly flexible current detection circuit for an A/F sensor, that can readily provide for a change to an A/F sensor having a difference characteristic. To achieve the above object, the A/F sensor current detection circuit of the invention comprises: an operational amplifier for generating a voltage to be applied to the A/F sensor; a current-measuring first resistor connected between the operational amplifier and the A/F sensor; voltage-dividing second and third resistors connected in series with each other with one end thereof connected between the operational amplifier and the first resistor; a first output terminal provided between the operational amplifier and the first resistor; a second output terminal provided between the first resistor and the A/F sensor; and a third output terminal provided between the voltage-dividing second and third resistors.