Cylinder detection in a four-stroke internal combustion engine

A four-stroke internal combustion engine comprising:

• a crankshaft;
• at least two cylinders each associated with a respective piston;
• a camshaft connected to the crankshaft, wherein the crankshaft performs a 720-degree rotation while the camshaft performs a 360-degree rotation, wherein each piston is connected to the crankshaft and reciprocates in its cylinder, each piston being arranged to assume an ignition top dead center position corresponding to a top rotational position (TRP1-TRP6) of the crankshaft over the 720-degree rotation of the crankshaft, wherein an interspace angle (α) of the crankshaft extends between each of the top rotational positions (TRP1-TRP6);
• and
• an arrangement for cylinder detection comprising:
• a first disc connected to the crankshaft, the first disc comprising a first mark (M11-M13) within each interspace angle (α);
• a second disc connected to the camshaft and comprising one second mark (M21-M26) per number of cylinders;
• a fixed first sensor for detecting the first mark (M11-M13), or a plurality of first marks (M11-M13);
• a fixed second sensor for detecting the second marks (M21-M26),
• wherein the first mark (M11-M13) is arranged on the first disc, or the plurality of first marks (M11-M13) are arranged in relation to each other on the first disc, and the second marks (M21-M26) are arranged in relation to each other on the second disc such that for each interspace angle (α), the relevant first mark (M11-M13) on the first disc is detectable by the first sensor and the relevant second mark (M21-M26) on the second disc is detectable by the second sensor at a respective different relative rotational position between the first disc and the second disc, wherein such different relative rotational position defines a phase difference between the respective relative first mark and the second mark, wherein such phase difference identifies a particular cylinder of the at least two cylinders;
• and
• a combustion engine control unit configured to:
• receive signals from the first fixed sensor and the second fixed sensor;
• identify first signals (S11-S16) related to the relevant first mark (M11-M13), or the plurality of relevant first marks (M11-M13), based on signals received from the first sensor and identify second signals (S21-S26) related to the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26), based on signals received from the second sensor;
• and
• identify the phase difference between the first signals (S11-S16) and the second signals (S21-S26) indicating when the relevant first mark (M11-M13), or the plurality of relevant first marks (M11-M13) was detected relative to when the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26) was detected, and wherein the combustion engine control unit is configured to evaluate the phase difference to determine a momentary rotational position of the crankshaft, where the phase difference is associated with a particular cylinder for which its associated piston is approaching the piston's ignition top dead center position.

A method for cylinder detection in a four-stroke internal combustion engine, the four-stroke internal combustion engine comprising a crankshaft, at least two cylinders each associated with a respective piston, and a camshaft connected to the crankshaft, wherein the crankshaft performs a 720-degree rotation while the camshaft performs a 360-degree rotation, wherein each piston is connected to the crankshaft and reciprocates in its cylinder, each piston being arranged to assume an ignition top dead center position corresponding to a top rotational position (TRP1-TRP6) of the crankshaft over the 720-degree rotation of the crankshaft, wherein an interspace angle (α) of the crankshaft extends between each of the top rotational positions (TRP1-TRP6), wherein the arrangement comprises a first disc connected to the crankshaft, the first disc comprising a first mark (M11-M13) within each interspace angle (α);

• a second disc connected to the camshaft and comprising one second mark (M21-M26) per number of cylinders;
• a fixed first sensor for detecting the first mark (M11-M13), or plurality of first marks (M11-M13);
• a fixed second sensor for detecting the second marks (M21-M26);
• and a combustion engine control unit configured to receive signals from the first sensor and the second sensor, wherein the first mark (M11-M13) is arranged on the first disc, or the plurality of first marks (M11-M13) are arranged in relation to each other on the first disc, and the second marks (M21-M26) are arranged in relation to each other on the second disc such that for each interspace angle (α), the relevant first mark (M11-M13) on the first disc is detectable by the first sensor and the relevant second mark (M21-M26) on the second disc is detectable by the second sensor at a respective different relative rotational position between the first disc and the second disc, wherein such different relative rotational position defines a phase difference between the respective relative first mark and the second mark, wherein such phase difference identifies a particular cylinder of the at least two cylinders, and wherein the method comprises steps of:
• detecting the relevant first mark (M11-M13), or one of the plurality of relevant first marks (M11-M13), with the first sensor;
• detecting the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26) with the second sensor;
• identifying first signals related to the relevant first mark (M11-M13), or the plurality of relevant first marks (M11-M13), based on a signal received from the first sensor;
• identifying second signals related to the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26), based on signals received from the second sensor, indicating when the relevant first mark (M11-M13), or the plurality of relevant first marks (M11-M13) was detected relative to when the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26) was detected;
• and
• determining a relative rotational position between the first disc and the second disc based on the step of detecting the relevant first mark (M11-M13), or one of the plurality of relevant first marks (M11-M13), and the step of detecting one of the relevant second marks (M21-M26) or one of the plurality of relevant second marks (M21-M26), wherein said determining comprises:
• identifying a phase difference between the first signals and the second signals;
• and
• evaluating the phase difference to determine the relative rotational position between the first and second discs, where the phase difference is associated with a particular cylinder for which its associated piston is approaching the piston's ignition top dead center position.

A computer program product stored on a non-transitory computer-readable medium, said computer program product for performing a cylinder detection in a four-stroke internal combustion engine, the four-stroke internal combustion engine comprising a crankshaft, at least two cylinders with one piston each, and a camshaft connected to the crankshaft, wherein the crankshaft performs a 720-degree rotation while the camshaft performs a 360-degree rotation, wherein each piston is connected to the crankshaft and reciprocates in its cylinder, each piston being arranged to assume an ignition top dead center position corresponding to a top rotational position (TRP1-TRP6) of the crankshaft over the 720-degree rotation of the crankshaft, wherein an interspace angle (α) of the crankshaft extends between each of the top rotational positions (TRP1-TRP6), wherein the arrangement comprises a first disc connected to the crankshaft, the first disc comprising a first mark (M11-M13) within each interspace angle (α);

• a second disc connected to the camshaft and comprising one second mark (M21-M26) per number of cylinders;
• a fixed first sensor for detecting the first mark (M11-M13), or plurality of first marks (M11-M13);
• a fixed second sensor for detecting the second marks (M21-M26);
• and a combustion engine control unit configured to receive signals from the first sensor and the second sensor, wherein the first mark (M11-M13) is arranged on the first disc, or the plurality of first marks (M11-M13) are arranged in relation to each other on the first disc and the second marks (M21-M26) are arranged in relation to each other on the second disc such that for each interspace angle (α) the relevant first mark (M11-M13) on the first disc is detectable by the first sensor and the relevant second mark (M21-M26) on the second disc is detectable by the second sensor at a respective different relative rotational position between the first disc and the second disc, wherein such different relative rotational position defines a phase difference between the respective relative first mark and the second mark, wherein such phase difference identifies a particular cylinder of the at least two cylinders, wherein the computer program product comprises computer instructions to cause one or more calculation units of a combustion engine control unit of the four-stroke internal combustion engine to perform the following operations:
• detecting the relevant first mark (M11-M13), or one of the plurality of relevant first marks (M11-M13), with the first sensor;
• detecting the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26) with the second sensor;
• identifying first signals related to the relevant first mark (M11-M13), or the plurality of relevant first marks (M11-M13), based on a signal received from the first sensor;
• identifying second signals related to the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26), based on signals received from the second sensor, indicating when the relevant first mark (M11-M13), or the plurality of relevant first marks (M11-M13) was detected relative to when the relevant second mark (M21-M26), or the plurality of relevant second marks (M21-M26) was detected;
• and
• determining a relative rotational position between the first disc and the second disc based on the step of detecting the relevant first mark (M11-M13), or one of the plurality relevant first marks (M11-M13), and the step of detecting one of the relevant second marks (M21-M26), or one of the plurality of relevant second marks (M21-M26), wherein said determining comprises:
• identifying a phase difference between the first signals and the second signals;
• and
• evaluating the phase difference to determine the relative rotational position between the first and second discs, where the phase difference is associated with a particular cylinder for which its associated piston is approaching the piston's ignition top dead center position.