Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
1999-01-19
2001-02-13
Paschall, Mark H (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S202000, C219S501000, C219S481000, C123S689000
Reexamination Certificate
active
06188049
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an air-fuel ratio sensor for detecting an air-fuel ratio of an air-fuel mixture based on the oxygen concentration in the exhaust of an internal combustion engine, and more specifically, to the technique for controlling a heater for heating a sensor element of said air-fuel ratio sensor.
(2) Related Art of the Invention
In the prior art, there was known an electronically-controlled fuel injection apparatus of an internal combustion engine comprising an air-fuel ratio sensor for detecting an air-fuel ratio of an air-fuel mixture based on the oxygen concentration in the exhaust, wherein the quantity of fuel injection was feedback controlled so as to bring the air-fuel ratio of the air-fuel mixture close to the target air-fuel ratio (refer to Japanese Unexamined Patent Publication No. 60-240840).
The air-fuel ratio sensor mentioned above has a characteristic to vary the output thereof related to the oxygen concentration corresponding to the temperature of the sensor element. Therefore, in order to perform an accurate detection of the air-fuel ratio, it is requested that the temperature of the sensor element be maintained at the activation temperature or above.
Therefore, the apparatus disclosed for example in the Japanese Unexamined Patent Publication No. 60-235047 comprises an electric heater for heating the sensor element, and by supplying maximum power to the electric heater for a predetermined period after starting the engine, the sensor element is heated at a relatively early stage to the activation temperature or above, thereby enabling to perform an air-fuel ratio feedback control with high accuracy at an early stage. Moreover, in this the apparatus, the sensor element temperature is estimated from the temperature of the cooling water and the like of the engine, and the lower the temperature of the sensor element is, the more the period for supplying maximum power to the electric heater is increased.
In such apparatus, it was requested that the capacity of the electric heater be increased in order to activate the air-fuel ratio sensor at an early stage. However, if the capacity of the electric heater was increased and maximum power was supplied thereto from the start, there was a problem that the sensor element may experience a large temperature difference and that the sensor element may be damaged by the heat shock.
SUMMARY OF THE INVENTION
The present invention aims at solving the above-mentioned problems. An object of the present invention is to provide an apparatus and method for controlling a heater for heating a sensor element in an air-fuel ratio sensor enabling the sensor element to be activated at an early stage while preventing the damage to the sensor element caused by the heat shock.
Moreover, the present invention aims at providing an apparatus and method wherein the characteristic of the sensor element according to the temperature enables to increase the power feed quantity gradually without an influence of a change in a power source voltage.
In order to achieve the above objects, in the apparatus and method for controlling a heater of an air-fuel ratio sensor in an internal combustion engine, the temperature of a sensor element of an air-fuel ratio sensor is detected, and by a characteristic of the sensor element according to the temperature, a power feed quantity gradually is increased from the start of the power feed to an electric heater.
According to such a structure, by gradually increasing the power feed quantity to the electric heater, the occurrence of large temperature difference to the sensor element may be prevented. Moreover, by varying the characteristic of the power feed quantity variation in correspondence to the sensor element when increasing the power feed quantity gradually, the temperature of the sensor element may be raised to the activation temperature or above with maximum response while preventing the occurrence of a large temperature difference.
Here, by setting an initial power feed quantity to be provided to the electric heater at the start of the power feed according to the temperature of the sensor element, the characteristic of the power feed quantity variation may correspond to the temperature of the sensor element.
According to such a structure, if large power is provided from the start of the power feed when the temperature of the sensor element is low, a large temperature difference is likely to occur. Therefore, the lower the temperature of the sensor element is, the smaller the initial power feed quantity is set, so as to prevent the occurrence of a large temperature difference.
Moreover, it is preferable that the initial power feed quantity be corrected and set in correspondence to the power source voltage.
According to such structure, due to a change in the battery voltage working as the power source, the actual power feed quantity changes even while providing the same power feed control, thereby enabling of the prevention of the occurrence of change in the rising temperature characteristic.
Moreover, the speed of a change in the power feed quantity when gradually increasing the power feed quantity from the initial power feed quantity to the maximum quantity may be set in correspondence to the temperature of the sensor element, thereby setting the varying characteristic of the power feed quantity corresponding to the temperature of the sensor element.
According to such a structure, the temperature of the sensor element may be raised to the activation temperature or above by increasing the power feed quantity with maximum response and without generating a large temperature difference.
Moreover, the initial power feed quantity to be provided to the electric heater at the start of the power feed may be set corresponding to the temperature of the sensor element, and at the same time, the speed of the change in the power feed quantity when gradually increasing the power feed quantity from the initial power feed quantity to the maximum quantity may also be set corresponding to the temperature of the sensor element.
According to the above-mentioned structure, the power feed quantity at the start of the power feed is set to different values corresponding to the temperature of the sensor element, and at the same time, the speed of the change in the power feed quantity from the initial quantity to the maximum quantity may be set to different values as well, corresponding to the temperature of the sensor element. Therefore, the temperature of the sensor element may be raised to the activation temperature or above with maximum response speed while reducing the occurrence of a heat shock.
In the structure mentioned above of setting the initial power feed quantity and the speed of the change in the power feed quantity in correspondence to the sensor element temperature, it is also preferable that the initial power feed quantity be corrected and set according to the power source voltage.
These and other objects and phases of the present invention will become apparent from the following description on the embodiment related to the accompanied drawings.
REFERENCES:
patent: 5656190 (1997-08-01), Aoki
patent: 5782227 (1998-07-01), Abe
patent: 5816231 (1998-10-01), Inoue
patent: 60-240840 (1985-11-01), None
patent: 60-235047 (1985-11-01), None
patent: 63-51273 (1988-04-01), None
Foley & Lardner
Paschall Mark H
Unisia Jecs Corporation
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