Nissan Motor Company Limited

Tsuyoshi Kitahara

Kohki Sone

Masaaki Uchida

Hatsuo Nagaishi

Kenji Okamura

Koyo Nakamura

A device detects an air-fuel ratio of a fuel mixture by causing an electric current to flow through an oxygen ion-conductive solid electrolyte to cause migration of oxygen ions between an atmospheric air and a gas receiving portion into which the exhaust gases resulting from combustion of the fuel mixture are diffused via gas diffusion restricting means. The device includes means for detecting the electric current.

Device for detecting air-fuel ratio of mixture over wide range from

In order for increased precision control of air/fuel ratio, a pump electric current indicative voltage and a pump electric voltage are selectively used as an air/fuel ratio indicative signal in such a manner that the pump electric voltage is used at the stoichiometry, while the pump electric current indicative voltage is used as the air/fuel ratio indicative signal at an air/fuel ratio other than the stoichiometry. According to another aspect of the invention, the pump electric current indicative voltage is offset in response to step change in the pump electric voltage to generate an air/fuel ratio indicative signal which changes rapidly at the stoichiometry.

Air/fuel ratio detecting device and control system using same

An air/fuel ratio monitoring system in an IC engine, using an oxygen sensor of the concentration cell type which has an inner electrode layer, a microscopically porous layer of oxygen ion conductive solid electrolyte, and an outer electrode layer to be exposed to the exhaust gas and exhibits a sharp change in the level of output voltage in response to a change in the air/fuel ratio in the engine across the stoichiometric ratio. To ensure accurate monitoring of the air/fuel ratio even though an average level of the sensor output changes for various reasons such as aging of the sensor, the monitoring system produces a variable reference voltage. The output of the oxygen sensor is compared with this reference voltage by first adding or subtracting a fixed voltage to the output voltage of the sensor, depending on the result of comparison between the sensor output. The resultant reference voltage and voltage is then smoothed in an RC circuit. To prevent misjudgement of the air/fuel ratio by unintentional intersection of the sensor output voltage attenuating after responding to a change in the air/fuel ratio across the stoichiometric ratio and the reference voltage, the system includes a control means for varying the time constant at the voltage-smoothing operation according to the manner of a change in the sensor output voltage.

Air/fuel ratio monitoring system in IC engine using oxygen sensor

A system for detecting the concentration of oxygen in a gas which comprises an oxygen sensor having a first solid electrolyte cell, which produces an electrical output representing a difference between oxygen partial pressures on the opposite two sides of a solid electrolyte layer, and a second solid electrolyte cell which acts as an oxygen ion pump by application of a current thereto and is used to control the oxygen partial pressure in a fraction of the gas admitted into the sensor. The current is controlled so as to render the output of the oxygen sensor equal to a target value. The system includes means for continuously making a judgement whether the gas under inspection is equivalent to the air or not. When the atmospheric condition of the gas is established the target value is varied so as to avoid undesirable increase in the current intensity. This is favorable for durability of the oxygen sensor. A provisional output signal representing the current intensity is corrected based on the output value obtained under the atmospheric condition. This system is suitable for use in detecting the air/fuel ratio in an internal combustion engine by detecting oxygen concentration in the exhaust gas.

Oxygen concentration detecting system using oxygen sensor including

A feedback control is effected during warming-up operation so as to adjust an actual air-fuel ratio to a target value. A sensing element is used to probe exhaust gases to detect an air-fuel ratio of a fuel-rich mixture that is required for warming up the engine. The amount of fuel injection is corrected so that the actual air-fuel ratio is adjusted to a target value displaced to the rich side from the stoichiometric ratio.

Air-fuel ratio control apparatus

A control system for a motor vehicle is disclosed wherein the parameters for optimum operation for an engine are determined based upon an acceleration position and a vehicle speed, and a continuously variable transmission is operated to vary a drive ratio in such a manner as to cause the engine to operate according to those parameters.

Control system for motor vehicle

An air/fuel ratio monitoring system in an IC engine, using an oxygen sensor of the concentration cell type which has a laminate comprising an inner electrode layer, a microscopically porous layer of oxygen ion conductive solid electrolyte and an outer electrode layer exposable to exhaust gas and which exhibits a sharp change in output voltage level in response to a change in the air/fuel ratio in the engine across a stoichiometric ratio. To ensure accurate monitoring of the air/fuel ratio even when the engine is operated under conditions which cause a large rise or fall in an average level of the output of the oxygen sensor, the monitoring system has a signal treatment means for producing a variable reference voltage, with which the sensor output is compared, by first adding a definite voltage to or subtracting a definite voltage from the output of the oxygen sensor depending on the result of comparison between the sensor output and the reference voltage and then smoothing the voltage resulting from the addition or subtraction of the definite voltage.

An air/fuel ratio detection system for an IC engine, using an oxygen sensor element of the concentration cell type which has a laminate of a measurement electrode layer exposed to the exhaust gas, a porous layer of oxygen ion conductive solid electrolyte and a reference electrode layer and requires the supply of a small DC current thereto to produce a reference oxygen partial pressure at the reference electrode by a balance between migration of oxygen ions to the reference electrode and diffusion of oxygen molecules therefrom. To prevent excessive rise in the reference oxygen partial pressure even when the engine continues to discharge exhaust gas high in the content of oxygen, the detection system has a control circuit which controls the intensity and flow direction of the current for the sensor element with reference to a voltage which is produced by adding a definite voltage to, or subtracting the definite voltage from, the sensor output voltage depending on the level of oxygen content in the exhaust gas indicated by the sensor output voltage and smoothing the voltage resulting from the addition or subtraction.

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Yokohama, Japan

Tsuyoshi Kitahara