Toyota Jidosha Kabushiki Kaisha

Nippondenso Co., Ltd.

Takao Ishibashi

Jiro Nakano

Takao Akatsuka

Masao Kawaguchi

Mamoru Takata

Yasumichi Hotta

Michihiro Yamakawa

An internal combustion engine has an exhaust system and an oxygen sensor fitted to the exhaust system including a sensor element and an electrically powered heater for heating the sensor element. A method is disclosed for controlling the power supplied to the heater by determining a target value therefor according to engine operational parameters, by applying a smoothing correction to the target value to produce an actual value, and by supplying power to the heater in an amount according to this actual power value. The smoothing may be done by time-smoothing, and may be done by performing the calculation repeatedly in a cycle and by setting the actual power value amount equal to a function of this target power value and of values of this actual power value amount determined in previous cycles. This function may take the form of a weighted average, and as a special case such a weighted average may use only the actual power value amount determined in the previous cycle. Accordingly it is ensured that the heater is properly operated even in the case of quick variation in the engine operational parameters, which due to system inertia will only alter the exhaust gas temperature with a certain time lag. Thus, the oxygen sensor is properly kept heated up, even in such quick engine operational state alteration conditions, and engine performance and the quality of exhaust gas emissions at such a time are ensured to be good. A system is also described for implementing this method.

Method and system for internal combustion engine oxygen sensor heating

An internal combustion engine has an exhaust system and an oxygen sensor fitted to the exhaust system including a sensor element and an electrically powered heater for heating the sensor element. A method for controlling the electrical power supplied to the heater properly and quickly heats up the sensor element after engine starting from the cold condition. At the time of starting up the engine it is determined whether or not the temperature of the engine is less than a certain value. If so, the heater is provided with electrical power to the maximum practicable amount, for a certain time interval after the engine is started up. Thereby, during engine heating up operation, the temperature of the sensor element is brought up to its minimum proper operating temperature as quickly as practicable, and accordingly it is ensured that engine performance and the quality of exhaust gas emissions at the time of such engine warming up operation are good. A system is also described for implementing this method.

The oxygen sensor has a solid electrolytic element made of an oxygen ion-conducting metal oxide. This element is formed in a cup shape, closed at one end and opened at its other end. The outer peripheral surface of the element is exposed to exhaust gas, and the inner peripheral surface of the element is exposed to the atmosphere. A first electrode is fixed to the outer peripheral surface of the element, and a second electrode is fixed to the inner peripheral surface of the element. An electrically insulating layer is formed on the outer peripheral surface of the element except where the first electrode is disposed. A metal lead of thin film, connected to the first electrode, is formed on the insulating layer. Further, a retaining lead connected to the first electrode is formed on the metal lead. This retaining lead is formed by densely sintering a conductive material and a binding material.

Oxygen sensor

An internal combustion engine has an exhaust system and an oxygen sensor fitted to the exhaust system including a sensor element and an electrically powered heater for heating the sensor element. A method is disclosed for controlling the power supplied to said heater by restricting it to be less than a predetermined value. This restriction may be done by controlling the value of a relatively steady current flowing through said heater, or alternatively may be done by supplying an intermittent voltage to said heater and by controlling the duty factor of said intermittent voltage. The power supplied to said heater may be determined by detecting the current flowing through said heater, or may be determined by detecting the voltage across said heater and the current flowing through said heater. Thereby, during engine heating up operation, the temperature of the heater element is raised as quickly as practicable, without any risk of over quick heating of the heater occurring, which might lead to damage thereto. Accordingly it is ensured that engine performance and the quality of exhaust gas emissions at the time of such engine warming up operation are good. A system is also described for implementing this method.

An oxygen sensor according to the present invention comprises a tumbler-shaped solid electrolytic element formed of an oxygen-ion-conductive metal oxide. A first electrode and a lead electrically connected thereto are formed on the outer peripheral surface of the element which is exposed to exhaust gas. A second electrode is fixed to the inner peripheral surface of the element which is exposed to the atmosphere. The element is held by a ring-shaped metallic holder. The holder and the first electrode are electrically insulated from each other. A conductive metallic pipe member is disposed between the element and the holder. One end of the pipe member is electrically connected to the lead by means of a conductive metal ring. A partition wall extends integrally from one end of the pipe member, defining between its inner surface and the other peripheral surface of the element a space for housing the conductive metal ring between the pipe member and the lead. A seal member is interposed between the outer peripheral surfaces of the pipe member and the partition wall and the inner peripheral surface of the holder. The seal member is formed by compacting a powdered electrial insulating material.

An internal combustion engine has an exhaust system and an oxygen sensor fitted to the exhaust system including a sensor element and an electrically powered heater for heating the sensor element. A method is disclosed for controlling the air/fuel ratio of the air-fuel mixture supplied to the engine, by, when the voltage of the power supply to the heater has dropped below a first predetermined value and thereafter has remained below a second predetermined value higher than the first predetermined value for longer than a predetermined time period, controlling the air/fuel ratio according to engine operational parameters by an open loop form of control with no account being taken of the output signal of the oxygen sensor, and otherwise controlling the air/fuel ratio according to these engine operational parameters by a closed loop form of control taking into account the output signal of the oxygen sensor so as to obtain an optimum air/fuel ratio for the engine by a feedback control process. Accordingly it is ensured that the air/fuel ratio of the engine is kept appropriate, even if the voltage of the battery drops so low that it can no longer properly power the oxygen sensor heater, which causes the output signal of the oxygen sensor to be no longer reliable for indicating the amount of oxygen in the exhaust gases of the engine. A system is also described for implementing this method.

Engine air/fuel ratio control method and system selectively providing

An internal combustion engine has an exhaust system and an oxygen sensor fitted to the exhaust system including a sensor element and an electrically powered heater for heating it. The power supplied to the heater is controlled by determining a target value for it according to operational parameters of the engine, and by controlling the mean power in a time interval as follows: the voltage applied to the heater and the current flowing through it are detected, an intermittent voltage is supplied to the heater, and the duty ratio of the intermittent voltage is controlled so that the product of the heater voltage and the heater current is substantially equal to the target power, with the detection of the voltage supplied to the heater synchronized with the energization of the heater. A system is also described for implementing this method.

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Toyota, Japan

Takao Ishibashi