Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
1999-10-13
2002-01-29
Kwon, John (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C123S697000
Reexamination Certificate
active
06341599
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates generally to a heater control system for a gas concentration sensor which may be employed in an air-fuel ratio control system for automotive vehicles for measuring the concentration of gas such as O
2
, NOx, or CO.
2. Background Art
Japanese Patent First Publication No. 61-132851 teaches one of conventional power supply systems for limiting current oxygen sensors used to measure an oxygen content in exhaust gasses of an internal combustion engine. The power supply system is designed based on the fact that an internal resistance of the limiting current oxygen sensor and a resistance value of an installed heater are usually changed with a change in surrounding temperature and determines the electric power required for activation of the oxygen sensor based on operating conditions of the engine to correct the electric power supplied to the heater as a function of the internal resistance of the oxygen sensor and the resistance value of the heater.
Japanese Patent First Publication No. 63-249046 teaches a power supply system which supplies a full power to a heater of an oxygen sensor until an internal resistance of the oxygen sensor and a resistance value of the heater each reach the value corresponding to a selected temperature and controls the power supply to the heater so as to keep the internal resistance of the heater constant.
Further, Japanese Patent First Publication No. 8-278279 teaches another type of power supply system which supplies a full power to a heater of an oxygen sensor until the temperature of the heater reaches a given initial heating temperature and controls the power supply to the heater as a function of the temperature of a sensor element after reaching a selected value.
The above described power supply systems are all designed to control the power supply to the heater so as to keep the sensing element at a given activating temperature (about 700°) regardless of operating conditions of the internal combustion engine or other preselected conditions. Specifically, a large amount of power is consumed in operating the gas sensor, which does not meet the energy saving required in automobile technologies in recent years.
For instance, the consumption of electric power in automotive vehicles usually results in an increase in fuel economy. It is, thus, known that the reduction in energy consumption in electric parts is important to increase the fuel economy of the automotive vehicles. Particularly, in the case of hybrid cars using an electric motor, the consumption of electric power increases the consumption of fuel more greatly than in gasoline-fueled automobiles.
SUMMARY OF THE INVENTION
It is therefore a principal object of the present invention to avoid the disadvantages of the prior art.
It is another object of the present invention to provide a heater control system for gas concentration sensors which is designed to allow the sensor to provide an accurate sensor output with an decreased power consumption.
According to one aspect of the invention, there is provided a heater control apparatus for controlling a temperature of a heater used to heat a solid electrolyte-made sensing element of a gas concentration sensor up to a temperature at which the sensing element is activated to provide a desired gas concentration output. The heater control apparatus comprises: (a) a power supply controlling circuit controlling an electric power supply to the heater to bring one of a temperature of the sensing element of the gas concentration sensor and a temperature of the heater into agreement with a target temperature value; and (b) a target temperature value determining circuit determining the target temperature value as a function of an environmental condition in which the gas concentration sensor is used and a use of the gas concentration sensor.
In the preferred mode of the invention, the target temperature value determining circuit changes the target temperature value based on whether it is required to use the gas concentration output from the gas concentration sensor or not.
The target temperature value determining circuit decreases the target temperature value when it is not required to use the gas concentration output from the gas concentration sensor and increases the target temperature value when it is required to use the gas concentration output.
The gas concentration sensor is designed to measure the concentration of a given gaseous component contained in either of exhaust gasses and induction gasses of an internal combustion engine of a vehicle and provide the gas concentration output indicative thereof for use in feedback control of an air-fuel ratio of mixture supplied to the internal combustion engine. A decision circuit is provided for deciding whether a given control execution condition is met or not which is used in determining whether the feedback control of the air-fuel ratio is to be executed or not. The target temperature value determining circuit changes the target temperature value depending upon a decision of the decision circuit.
The gas concentration sensor measures the concentration of oxygen contained in exhaust gasses or induction gasses of the engine to determine an air-fuel ratio for use in feedback control of an air-fuel ratio of mixture supplied to the engine. The target temperature value determining circuit changes the target temperature value as a function of the air-fuel ratio determined by the gas concentration sensor.
When the air-fuel ratio determined by the gas concentration sensor is leaner than a stoichiometric air-fuel ratio, the target temperature value determining circuit elevates the target temperature value above that determined when the air-fuel ratio determined by the gas concentration sensor shows the stoichiometric air-fuel ratio.
When the air-fuel ratio determined by the gas concentration sensor is richer than a stoichiometric air-fuel ratio, the target temperature value determining circuit elevates the target temperature value above that determined when the air-fuel ratio determined by the gas concentration sensor shows the stoichiometric air-fuel ratio.
When a mixture supplied to the internal combustion engine is controlled to be leaner than the stoichiometric air-fuel ratio, the target temperature value determining circuit may elevate the target temperature value above that when the mixture supplied to the internal combustion engine is controlled to have the stoichiometric air-fuel ratio.
When the mixture supplied to the internal combustion engine is controlled to be richer than a stoichiometric air-fuel ratio, the target temperature value determining circuit may elevate the target temperature value above that when the mixture supplied to the internal combustion engine is controlled to have the stoichiometric air-fuel ratio.
The gas concentration sensor is controlled by the air-fuel ratio feedback control system to selectively output an electromotive force signal according the concentration of oxygen when the air-fuel ratio of mixture lies within a narrower range across a stoichiometric air-fuel ratio and a limiting current signal changing linearly with a change in the air-fuel ratio of mixture when the air-fuel ratio changes within a wider range from a rich air-fuel ratio to a lean air-fuel ratio. The target temperature value determining circuit changes the target temperature value depending upon whether the gas concentration sensor is outputting the electromotive force signal or the limiting current signal.
The target temperature value determining circuit may alternatively change the target temperature value depending upon whether the gas concentration sensor is controlled by the air-fuel ratio feedback control system to output the electromotive force signal or the limiting current signal.
The gas concentration sensor may be designed to output a plurality of signals indicating given parameters different from each other, temperatures of the heater required to indicate the given parameters correctly being different. In this c
Hada Satoshi
Haseda Satoshi
Okazaki Kazuhiro
Yamashita Yukihiro
Denso Corporation
Kwon John
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