Method of and apparatus for detecting misfire
First Claim
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1. An apparatus for detecting misfire in an internal combustion engine having a plurality of pistons and cylinders, said apparatus comprising:
- measuring means for making measurements representing engine speeds between a same first point and a same second point of each cycle of each of the plurality of pistons and cylinders.determining means responsive to said measuring means for determining variations by comparing each xth, (x+1)th, (x+a)th, and (x+a+1)th of the measurements, where a is a product of an integer greater than zero and a number of combustion events per revolution of an output shaft of the engine, the xth and (x+a)th measurements have opposite signs in comparison, and the (x+1)th and (x+a+1)th measurements have opposite signs in the comparison; and
a comparator responsive to said determining means for comparing the variations with a threshold level and for signalling a misfire when the threshold level is exceeded.
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Abstract
In order to detect misfire in an internal combustion engine, engine speed is determined by measuring the time of passage of a crankshaft disc from a first position to a second position during every revolution. A detection circuit takes the reciprocal of the measured times of passage to form a series of engine speeds and forms the difference between consecutive engine speeds. These differences are compared with a threshold to signal a misfire when the threshold is exceeded.
56 Citations
6 Claims
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1. An apparatus for detecting misfire in an internal combustion engine having a plurality of pistons and cylinders, said apparatus comprising:
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measuring means for making measurements representing engine speeds between a same first point and a same second point of each cycle of each of the plurality of pistons and cylinders. determining means responsive to said measuring means for determining variations by comparing each xth, (x+1)th, (x+a)th, and (x+a+1)th of the measurements, where a is a product of an integer greater than zero and a number of combustion events per revolution of an output shaft of the engine, the xth and (x+a)th measurements have opposite signs in comparison, and the (x+1)th and (x+a+1)th measurements have opposite signs in the comparison; and a comparator responsive to said determining means for comparing the variations with a threshold level and for signalling a misfire when the threshold level is exceeded. - View Dependent Claims (2)
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3. An apparatus for detecting misfire in an n cylinder internal combustion engine, where n is an integer greater than 1, said apparatus comprising:
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measuring mean for making measurements representing engine speeds between a same first point and a same second point of each cycle of each of the cylinders; determining means responsive to said measuring means for determining variations as a difference between sums (T(x)+T(x+n-1)) and (T(y)+T(z)), where T(x) is an xth measurement, T(x+n-1) is a (x+n-1)th measurement, and T(y) and T(z) are measurements between the xth and (x+n-1)th measurements; and the comparator responsive to said determining means for comparing the variations with a threshold level and for signalling a misfire when the threshold level is exceeded. - View Dependent Claims (4, 5, 6)
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Specification