Nissan Motor Company Limited

Kohki Sone

Kenji Okamura

Tsuyoshi Kitahara

Masaaki Uchida

Hatsuo Nagaishi

Kenji Masaki

Sadao Takase

Toyoaki Nakagawa

Hidehiro Minami

Koyo Nakamura

Shigeo Isitani

Okamura Kenji

Yoshitaka Kitagasaki

Thuyoshi Kitahara

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 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.

A gas sensor, e.g. oxygen sensor of the solid electrolyte concentration cell type, having a gas-sensitive element comprising a plate-shaped substrate fixed to an end portion of the sensor body and a laminate of relatively thin layers. A hollow cylindrical protective hood is attached to the sensor body to enclose the sensitive element therein, and two or more openings are formed in the cylindrical wall of the hood to allow a gas subject to measurement to flow into the interior of the hood and flow out. To avoid direct exposure of the sensitive element, which exhibits directionality in its output characteristics with regard to the gas flow through said openings, each of said openings is located between the sensitive element and the free end of the hood such that a cross-sectional plane intersecting the openings does not intersect the sensitive element.

Gas sensor with sensitive element enclosed in perforated hood

A temperature control system is disclosed wherein a heater of a gas sensor and a plurality of reference resistors cooperate to form a bridge circuit. The temperature control system comprises a comparator means for monitoring a balancing voltage of the bridge circuit and generating a control signal indicative of the balancing voltage and an electric power amplifier means responsive to the control signal for varying a voltage applied to the bridge circuit in such a manner to reduce the balancing voltage. The gas sensor has mounted therein at least one of the plurality of reference resistors, which reference resistor having a resistance resulting from multiplying the resistance of the heater with a constant.

Temperature control system

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.

System for detection of air/fuel ratio in IC engine by using oxygen

An air/fuel ratio control system including an oxygen sensor disposed in the exhaust gas to provide a feedback signal. The oxygen sensor is of the solid electrolyte concentration cell type having a heater and is operated with supply of a DC current to the concentration cell to maintain a reference oxygen partial pressure therein. A fuel feed control circuit in this system shifts its closed-loop control function to open-loop aiming at a lower air/fuel ratio if the output of the oxygen sensor continues to indicate that actual air/fuel ratio remains on one side of the intended air/fuel ratio due to breaking of the heater. To prevent the engine from stalling or operating unstably due to excessive increase in the air/fuel ratio before the shift to open-loop control, the system includes means for detecting breaking of the heater and immediately interrupting the current supply to the concentration cell in the oxygen sensor thereby forcing the sensor to put out an output which is indicative of a very high air/fuel ratio and, hence, causes the control circuit to lower the air/fuel ratio before the interruption of the closed-loop control.

System for feedback control of air/fuel ratio in IC engine with means to

A system for feedback control of air/fuel ratio in an IC engine, utilizing an oxygen-sensitive device which is provided with a heater and disposed in exhaust gas to provide a feedback signal. This device has a porous solid electrolyte layer with a measurement electrode layer on the outside and a reference electrode layer on the inside facing a substrate. The control system includes a sub-system to apply a voltage to the heater and force a DC current to flow through the solid electrolyte layer to cause migration of oxygen ions therethrough to thereby establish a reference oxygen partial pressure on the inner side of the solid electrolyte layer. To prevent great changes in the reference oxygen partial pressure by the influence of the exhaust gas temperature, the sub-system comprises sensors to detect the engine operating condition and control means for gradually varying both said voltage and said current according as the detected operating condition varies. For example, the voltage and current may be varied each by using a combination of a variable resistor and a stepping motor or a combination of fixed resistances and electrically controllable switches connected respectively in parallel with the resistances.

A system for feedback control of air/fuel ratio in an internal combustion engine, utilizing an oxygen-sensitive air/fuel ratio detector disposed in an exhaust gas to provide a feedback signal is disclosed. The detector has a flat and microscopically porous solid electrolyte layer with a measurement electrode layer on one side and a reference electrode layer on the other side facing a substrate. The control system includes a current supplying circuit to force a DC current to flow in the solid electrolyte layer between the two electrode layers to cause migration of oxygen ions through the solid electrolyte layer from the measurement electrode toward the reference electrode to thereby establish a reference oxygen partial pressure at the interface between the reference electrode layer and the solid electrolyte layer. To preclude an undesirably great rise of this reference oxygen partial pressure in the case of a large increase in the amount of oxygen in the exhaust gas resulting from interruption, or great reduction, of the feed of fuel to the operating engine, the control system comprises sensor means to detect the existence of such a condition and means for temporarily decreasing the intensity of the current being supplied to the air/fuel ratio detector.

System for feedback control of air/fuel ratio in IC engine having means

A feedback control system using an oxygen-sensitive air/fuel ratio sensor which is disposed in induction passage for an IC engine downstream of a fuel supply device with the provision of an ignition means to burn a fractional portion of an air-fuel mixture in the induction passage such that the oxygen-sensitive sensor is exposed to a resultant combustion gas. The sensor is of the concentration cell type having a layer of solid electrolyte such as zirconia provided with two electrode layers, and constant DC current is supplied to this sensor to cause migration of oxygen ions through the solid electrolyte layer, whereby this sensor exhibits a slope output characteristic and can detect air/fuel ratios either above or below a stoichiometric ratio or exhibits an on-off characteristic and can detect the stoichiometric ratio depending on the intensity and flow direction of the current. Owing to reduced overall length of the closed-loop, this control system can accomplish correction of a deviated mixing ratio in a shortened period of time.

System for feedback control of air-fuel mixing ratio in intake system of

A system for feedback control of air/fuel ratio in an IC engine, utilizing an oxygen-sensitive device which is provided with a heater and disposed in exhaust gas to provide a feedback signal. This device has a porous solid electrolyte layer with an outer electrode layer on one side and an inner electrode on the other side facing a substrate. There is a circuit to supply a heating current to the heater and also force a DC current to flow in the solid electrolyte layer to cause migration of oxygen ions therethrough toward the inner electrode to thereby establish a reference oxygen partial pressure on the inner side of the solid electrolyte layer. This circuit is provided with current intensity regulation means to temporarily decrease the intensity of the current flowing in the solid electrolyte layer by a predetermined value while the oxygen-sensitive device is not sufficiently heated to thereby preclude undesirable rise of the basic level of the output voltage of the oxygen-sensitive device by the effect of an increased internal resistance of the not sufficiently heated element.

A system for feedback control of air/fuel ratio in an IC engine, utilizing a recently developed oxygen-sensitive device which is provided with a heater and disposed in exhaust gas to provide a feedback signal. This device has a porous solid electrolyte layer with a measurement electrode layer on one side and a reference electrode on the other side facing a substrate. There is a circuit to supply a heating current to the heater and force a DC current to flow in the solid electrolyte layer to cause migration of oxygen ions through the solid electrolyte toward the reference electrode to thereby establish a reference oxygen partial pressure on the reference side of the solid electrolyte layer. To prevent lowering of this oxygen partial pressure while the engine is operated under a high-load condition and the feedback control is discontinued to feed the engine with a fuel-enriched mixture, the control system includes operating condition sensor means and switching means to interrupt the supply of the current to the heater in response to a command signal from the sensor means and, optionally, current regulating means to increase the intensity of current flowing in the solid electrolyte also in response to the command signal.

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Tokyo, Japan

Kohki Sone