Cylinder judgment apparatus and cylinder judgment method of engine

A cylinder judgment apparatus of an engine comprising:

• a plurality of cam sensors each of which outputs cylinder judgment signals at every uneven crank angle interval;
• signal output number counting means for counting up the number of cylinder judgment signals output from one cam sensor during a time period between a previous output and a present output of cylinder judgment signals from the other cam sensor;
• cylinder judgment means for judging a specific cylinder based on the number of outputs counted up by said signal output number counting means, and judging cylinders other than the specific cylinder based on the judgment result and the cylinder judgment signals;
• erroneous detection judgment means for calculating, each time the cylinder is judged by said cylinder judgment means, a period of from the previous cylinder judgment to the present cylinder judgment, to judge erroneous detection of cylinder judgment signal due to noise based on a ratio between a previous calculation value and a present calculation value of said period;
• and
• judgment result cancel means for, when said erroneous detection is judged by said erroneous detection judgment means, canceling the cylinder judgment result by said cylinder judgment means.

A cylinder judgment method of an engine for judging a cylinder corresponding to each stroke in engine combustion cycle, comprising the steps of:

• outputting cylinder judgment signals from a plurality of cam sensors at every uneven crank angle interval;
• counting up the number of cylinder judgment signals output from one cam sensor during a time period between a previous output and a present output of cylinder judgment signals from the other cam sensor;
• judging a specific cylinder based on the number of outputs counted up, and judging cylinders other than the specific cylinder based on the judgment result and the cylinder judgment signals;
• calculating, each time the cylinder is judged, a period of from the previous cylinder judgment to the present cylinder judgment, to judge erroneous detection of cylinder judgment signal due to noise based on a ratio between a previous calculation value and a present calculation value of said period;
• and
• when said erroneous detection is judged, canceling the cylinder judgment result based on said cylinder judgment signals.