System and method for estimating the temperature of oxygen sensor installed in exhaust system of internal combustion engine

In a motor vehicle having an internal combustion engine mounted thereon, said engine being controlled by an air/fuel ratio feed-back control system wherein an oxygen sensor is used for sensing an oxygen concentration in an exhaust system of the engine, said oxygen sensor having an electric heater mounted thereon,

• a system for estimating the temperature of the oxygen sensor installed in the exhaust system of the engine, comprising:
• first means for sensing a load of the engine;
• second means for sensing a rotation speed of the engine;
• third means which, based on both the sensed engine load and the sensed engine rotation speed, calculates a basic estimated temperature of the oxygen sensor appearing under a normal condition;
• fourth means for sensing a speed of the vehicle;
• fifth means which, based on the sensed vehicle speed, determines a first correction factor for correcting said basic estimated temperature;
• sixth means for sensing the temperature of outside air;
• seventh means which, based on the sensed outside air temperature, determines a second correction factor for correcting said basic estimated temperature;
• eighth means which, based on said basic estimated temperature and said first and second correction factors, calculates a target estimated temperature of the oxygen sensor and issues an output signal representative of said target estimated temperature;
• and
• ninth means for suppressing said eighth means from calculating said target estimated temperature until a predetermined time passes from a time on which energization of the electric heater starts.

In a motor vehicle having an internal combustion engine mounted thereon, said engine being controlled by an air/fuel ratio feed-back control system wherein an oxygen sensor is used for sensing an oxygen concentration in an exhaust system of the engine, said oxygen sensor having an electric heater mounted thereon,

• a method for estimating the temperature of the oxygen sensor installed in the exhaust system of the engine, comprising the steps of:
• sensing a load of the engine;
• sensing a rotation speed of the engine;
• calculating, based on both the sensed engine load and the sensed engine rotation speed, a basic estimated temperature of the oxygen sensor which would appear under a normal condition;
• sensing a speed of the vehicle;
• determining, based on the sensed vehicle speed, a first correction factor for correcting said basic estimated temperature;
• sensing the temperature of outside air;
• determining, based on the sensed outside air temperature, a second correction factor for correcting said basic estimated temperature;
• calculating, based on said basic estimated temperature and said first and second correction factors, a target estimated temperature of the oxygen sensor and issuing an output signal representative of said target estimated temperature;
• and
• suppressing issuance of said output signal until a predetermined time passes from a time on which energization of the electric heater starts.

In a motor vehicle having an internal combustion engine mounted thereon, said engine being controlled by an air/fuel ratio feed-back control system wherein an oxygen sensor is used for sensing an oxygen concentration in an exhaust system of the engine, said oxygen sensor having an electric heater mounted thereon,

• a method for estimating the temperature of the oxygen sensor installed in the exhaust system of the engine, comprising the steps of:
• sensing a load of the engine;
• sensing a rotation speed of the engine;
• calculating, based on both the sensed engine load and the sensed engine rotation speed, a basic estimated temperature of the oxygen sensor which would appear under a normal condition;
• sensing a speed of the vehicle;
• determining, based on the sensed vehicle speed, a first correction factor for correcting said basic estimated temperature;
• sensing the temperature of outside air;
• determining, based on the sensed outside air temperature, a second correction factor for correcting said basic estimated temperature;
• calculating, based on said basic estimated temperature and said first and second correction factors, a target estimated temperature of the oxygen sensor and issuing an output signal representative of said target estimated temperature;
• and
• suppressing calculation of said target estimated temperature until a predetermined time passes from a time on which energization of the electric heater starts.