Apparatus and method for detecting misfiring in an internal combustion engine
First Claim
1. A misfiring detecting apparatus for an internal combustion engine, comprising:
- a pressure sensor for sensing the pressure in a cylinder of the engine and for generating a corresponding output signal;
a differentiator for differentiating the output signal of said pressure sensor and for generating a corresponding output signal;
a signal processor for processing the output signal of said differentiator to generate a power stroke pressure information signal;
a threshold calculator for calculating a threshold for a misfiring determination based on operating conditions of the engine, wherein said threshold calculator includes means for generating a first threshold having a first prescribed value which is predetermined based on the engine operating conditions and stored in a memory when said engine has a first running condition, and for generating a second threshold having a second prescribed value which is predetermined based on the engine operating conditions and stored in said memory when said engine has a second running condition;
a comparator for comparing the power stroke pressure information signal from said signal processor with the threshold from said threshold calculator; and
a misfiring determiner for determining, based on a result of the comparison made by said comparator, whether misfiring took place in the cylinder of the engine.
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Abstract
Misfiring in an engine cylinder can be detected based on the pressure therein as sensed by a pressure sensor with a high degree of reliability at any time even if the output signal of the pressure sensor contains an offset component superposed on a pressure component representative of the actual cylinder pressure. In one form, the pressure sensor output is differentiated to eliminate the influence of the offset component and then processed to generate a power stroke pressure information signal in the form of the time of a pressure-change peak in the differentiated pressure sensor output or an integrated value of the differentiated output, which is then compared with a threshold so as to determine whether misfiring took place in the cylinder. In another form, the offset component is calculated based on the pressure in the cylinder at two different crank angles during a compression stroke, and it is then removed from the pressure sensor output and compared with a threshold or it may be integrated for a prescribed crank angle range around TDC before comparison with the threshold. In a further form, an expected pressure in the cylinder at a third crank angle during a power stroke is calculated based on the cylinder pressures at first and second crank angles during a compression stroke preceding the power stroke, and then compared with the cylinder pressure as sensed by the pressure sensor at the third crank angle for misfiring determination.
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Citations
7 Claims
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1. A misfiring detecting apparatus for an internal combustion engine, comprising:
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a pressure sensor for sensing the pressure in a cylinder of the engine and for generating a corresponding output signal; a differentiator for differentiating the output signal of said pressure sensor and for generating a corresponding output signal; a signal processor for processing the output signal of said differentiator to generate a power stroke pressure information signal; a threshold calculator for calculating a threshold for a misfiring determination based on operating conditions of the engine, wherein said threshold calculator includes means for generating a first threshold having a first prescribed value which is predetermined based on the engine operating conditions and stored in a memory when said engine has a first running condition, and for generating a second threshold having a second prescribed value which is predetermined based on the engine operating conditions and stored in said memory when said engine has a second running condition; a comparator for comparing the power stroke pressure information signal from said signal processor with the threshold from said threshold calculator; and a misfiring determiner for determining, based on a result of the comparison made by said comparator, whether misfiring took place in the cylinder of the engine. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification