Misfire monitor for engine analysis having automatic rescaling
First Claim
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1. In engine exhaust gas analysis apparatus having:
- means for sampling the exhaust gases including means for generating a first signal indicating the amount of a component present in the exhaust gases;
differentiating means connected to said sampling means and including means responsive to said first signal for generating a second signal indicating the rate of change of said first signal with respect to time;
means connected to said differentiating means for comparing said second signal to a limit; and
,means connected to said comparing means for indicating when said second signal exceeds said limit, the improvement comprising;
means for causing the values of said second signal and said limit to be normalized to a standard range before said comparing is done whereby the exceeding of said limit by said second signal will have substantially the same meaning regardless of the engine being analyzed.
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Abstract
An improvement to a misfire monitor sensing lean-roll in an internal combustion engine by comparing the rate of change in O2 in the exhaust gases with respect to time against a limit is disclosed. In the preferred embodiment, the sensed O2 level in the exhaust is used as an input to rescaling means which automatically normalizes the values used in the comparison to a standard range. Normalization is accomplished alternately by rescaling the rate of change value, rescaling the limit value used, or diluting the exhaust gases sampled to the level of a "standard" air blown engine to which the comparison limit is scaled.
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Citations
7 Claims
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1. In engine exhaust gas analysis apparatus having:
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means for sampling the exhaust gases including means for generating a first signal indicating the amount of a component present in the exhaust gases; differentiating means connected to said sampling means and including means responsive to said first signal for generating a second signal indicating the rate of change of said first signal with respect to time; means connected to said differentiating means for comparing said second signal to a limit; and
,means connected to said comparing means for indicating when said second signal exceeds said limit, the improvement comprising; means for causing the values of said second signal and said limit to be normalized to a standard range before said comparing is done whereby the exceeding of said limit by said second signal will have substantially the same meaning regardless of the engine being analyzed. - View Dependent Claims (2, 3, 4)
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5. The improved method of detecting a lean-roll condition in an internal combustion engine comprising the steps of:
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(a) sampling the exhaust gases from the engine to produce a first signal indicative of the percent of oxygen contained therein; (b) differentiating said first signal to produce a second signal indicative of the time rate of change of said first signal; (c) normalizing the second signal value and a limit value to a standardized range representing a lean-roll condition; (d) comparing said second signal to said limit value such that if said second signal exceeds said limit value the engine is in a lean-roll condition; and
,(e) activating means for indicating a lean-roll condition when said second signal exceeds said limit value. - View Dependent Claims (6, 7)
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Specification