Air-fuel ratio control apparatus for internal combustion engine
First Claim
1. An air-fuel ratio control apparatus for an internal combustion engine, comprising:
- an air-fuel ratio sensor to detect an air-fuel ratio of the internal combustion engine having a fuel injection unit;
an air-fuel ratio feedback control unit that has a calculation unit to calculate a fuel injection amount of the fuel injection unit to make a detection value of the air-fuel ratio sensor coincident with a previously given target air-fuel ratio and controls the fuel injection unit based on the fuel injection amount;
a start-up completion judgment unit to judge whether the internal combustion engine is in a state where start-up has been completed;
an engine condition judgment unit to judge whether the internal combustion engine enters a normal condition after the start-up has been completed; and
an upper/lower limit clipping unit that limits a maximum output of the calculation unit to an arbitrary first output range until the time when the engine condition judgment unit judges that the internal combustion engine enters the normal condition from the time when the start-up completion judgment unit judges that the start-up has been completed.
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Accused Products
Abstract
At the time of start-up, fuel supply is made excessive. When air-fuel ratio feedback control is started while the fuel is excessive, the control is put into a state of overshoot or hunting, and it takes a long time to converge to the target air-fuel ratio. In an air-fuel ratio control apparatus, a selection switch is provided at the output of an integration calculation circuit to perform air-fuel ratio feedback control, and immediately after start-up of the engine, an upper/lower limit clip value for use immediately after start-up, which is smaller than a normal one, is selected to perform the air-fuel ratio feedback control. Even if the air-fuel ratio feedback control is started immediately after the start-up in a state where the fuel is excessive, the actual air-fuel ratio does not overshoot with respect to the target air-fuel ratio and is quickly converged to the target air-fuel ratio.
16 Citations
16 Claims
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1. An air-fuel ratio control apparatus for an internal combustion engine, comprising:
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an air-fuel ratio sensor to detect an air-fuel ratio of the internal combustion engine having a fuel injection unit; an air-fuel ratio feedback control unit that has a calculation unit to calculate a fuel injection amount of the fuel injection unit to make a detection value of the air-fuel ratio sensor coincident with a previously given target air-fuel ratio and controls the fuel injection unit based on the fuel injection amount; a start-up completion judgment unit to judge whether the internal combustion engine is in a state where start-up has been completed; an engine condition judgment unit to judge whether the internal combustion engine enters a normal condition after the start-up has been completed; and an upper/lower limit clipping unit that limits a maximum output of the calculation unit to an arbitrary first output range until the time when the engine condition judgment unit judges that the internal combustion engine enters the normal condition from the time when the start-up completion judgment unit judges that the start-up has been completed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An air-fuel ratio control apparatus for an internal combustion engine, comprising:
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an air-fuel ratio sensor to detect an air-fuel ratio of the internal combustion engine having a fuel injection unit; an air-fuel ratio feedback control unit that has a calculation unit to calculate a fuel injection amount to make a detection value of the air-fuel ratio sensor coincident with a previously given target air-fuel ratio and controls the fuel injection unit based on the calculated fuel injection amount; a start-up completion judgment unit to judge whether the internal combustion engine is in a state where start-up has been completed; an engine condition judgment unit to judge whether the internal combustion engine enters a normal condition after the start-up has been completed; and an upper/lower limit clipping unit that limit a maximum output of the calculation unit to an arbitrary first output range until the time when the engine condition judgment unit judges that the internal combustion engine enters the normal condition from the time when the start-up completion judgment unit judges that the start-up has been completed, and limits the changing range within a second output range larger than the first output range after the engine condition judgment unit judges that the internal combustion engine enters the normal condition. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification