Crank angle detecting system for engines

Abstract

A crank angle detecting system for a multicylinder engine includes a disc formed with a large number of slits to detect one-degree crank angular positions and a small number of slits to detect a predetermined piston stroke for each cylinder. Since the widths of a small number of slits are different from each other, it is possible to separately discriminate each cylinder in crank angular position on the basis of the crank angle signals obtained by a large number of slits. In the case where the detecting system is incorporated with a group-ignition system, it is possible to detect a predetermined piston stroke for each cylinder immediately after the engine is started, thus preventing the engine from erroneous ignition.

What is claimed is: .[.1. A crank angle detecting system for a multicylinder engine having at least three cylinders classified as groups, which comprises: 
     
        on said counted crank angle signals..]. .[.2.  A crank angle detecting system for a multicylinder engine having at least three cylinders classified as groups, which comprises: (a) a disc rotatable with a crankshaft and formed with a first group of slits containing a large number of slits for indicating crankshaft angular positions and a second group of slits containing a small number of slits for indicating each predetermined piston stroke of each engine cylinder, the slits of said second group having at least three widths which are different from each other;   (b) sensing means for indicating crankshaft angular positions by detecting said slits of said first group of slits and producing crank angle signals corresponding to said detected slits of said first group and for indicating each predetermined piston stroke of each engine cylinder by detecting said slits of said second group of slits and producing cylinder signals corresponding to said detected slits of said second group, each of said cylinder signals having a duration which corresponds to one of said different widths; and   (c) means (17, 18) for identifying the detected cylinder signals by counting crank angle signals occurring during the duration of each said crank angle signal and classifying the cylinder signals based on the counted number of crank angle signals..]. .[.3. The crank angle detecting system as set forth in claim 1, wherein there are four cylinders and the cylinders are classified into two groups and further wherein said disc is formed with a first slit having a narrowest width, two second slits having an intermediate width, and a third slit having a widest width..]. .[.4. The crank angle detecting system as set forth in claim 2, wherein there are four cylinders and the cylinders are classified into two groups and further said disc is formed with a first slit having a narrowest width, a second slit having a first intermediate width, a third slit having a second intermediate width wider than that of the first intermediate width,   
     
     
        and a fourth slit having a widest width..]. .Iadd.5.  A crank angle detecting system for a multicylinder engine, comprising: a) a plurality of engine cylinders in which spark plugs are installed respectively, said cylinders being classified into a plurality of groups and each group being constituted by a pair of cylinders such that while the one of the cylinders is in an explosion stroke, the other is in an exhaust stroke;   b) indicating means disposed so as to synchronize with a rotation of an engine crankshaft and formed with a large number of slits for detecting crankshaft angular positions and a small number of slits, the large number of slits being provided for indicating crankshaft angular positions and the small number of slits being provided for indicating predetermined stroke angular positions of respective cylinder pistons and wherein respective widths of said small number of slits with respect to the crankshaft angular position are at least different between those belonging to said groups;   c) sensing means for detecting crankshaft angular positions in cooperation with the large number of slits of the indicating means and outputting a crank angle signal representing each of the crank angular positions and for detecting the predetermined stroke angular positions in cooperation with the small number of slits of the indicating means and outputting the predetermined stroke angular signals having different widths corresponding to those of the small number of slits; and   d) discriminating means for identifying each cylinder group and outputting cylinder group identification signals on the basis of the crank angle signal and the predetermined stroke angular signals derived form said sensing means. .Iaddend. .Iadd.6. A crank angle detecting system as set forth in claim 5, wherein said indicating means comprises a disc which rotates with a camshaft linked to the engine crankshaft, the disc having the large number of slits along a peripheral surface of the disc and the number of the slits corresponding to the crank angle through which the crankshaft has rotated two rotations and wherein the sensing means outputs the crank angle signal whenever the engine crankshaft has rotated one degree. .Iaddend. .Iadd.7. A crank angle detecting system as set forth in claim 6, wherein the number of the engine cylinders are four, a first cylinder and fourth cylinder are grouped into a first group of the cylinders, and a third cylinder and second cylinder are grouped into a second group of cylinders. .Iaddend. .Iadd.8. A crank angle detecting system as set forth in claim 7, wherein the small number of slits are disposed along a surface of the disc adjacent to the peripheral surface so that the two of the small number of slits are disposed symmetrically with the other two and at positions corresponding to 110 degrees before piston top dead centers in compression strokes of the respective cylinders. .Iaddend. .Iadd.9. A crank angle detecting system as set forth in claim 8, wherein the widths of the small number of slits belong to the first group of cylinders are wider than those belonging to the second group of cylinders. .Iaddend. .Iadd.10. A crank angle detecting system as set forth in claim 8, wherein the width of a first slit of the small number of slits belonging to the first cylinder is substantially 24 degrees in the crank angle, the width of a second slit thereof belonging to the third cylinder being substantially 16 degrees in the crank angle, the width of a third slit thereof belonging to the fourth cylinder being substantially 8 degrees in the crank angle, the width of a fourth slit thereof belonging to the second cylinder being substantially 16 degrees in the crank angle. .Iaddend. .Iadd.11. A crank angle detecting system as set forth in claim 9, wherein the width of a first slit of the small number of slits belonging to the first cylinder is substantially 24 degrees in the crank angle, the width of a second slit thereof belonging to the third cylinder being substantially 16 degrees in the crank angle, the width of a third slit thereof belonging to the fourth cylinder being substantially 8 degrees in the crank angle, the width of a fourth slit thereof belonging to the second cylinder being substantially 4 degrees in the crank angle. .Iaddend. .Iadd.12. A crank angle detecting system as set forth in claim 10, wherein the discriminating means counts the number of the crank angle signals during receipt of the pulse widths of the predetermined stroke angular signals and identifies the first and second cylinder groups and outputs first and second cylinder group identification signals whenever the counted number of the crank angle pulses reaches predetermined angular vanes defining the identifications of the first and second cylinder group. .Iaddend. .Iadd.13. A crank angle detecting system as set forth in claim 11, wherein the discriminating means counts the number of the crank angle signals during receipt of the pulse widths of the predetermined stroke angular signals and identifies the first and second cylinder groups and outputs first and second cylinder group identification signals whenever the counted number of the crank angle pulses reaches each of predetermined angular values defining the identifications of the first, third, fourth, and second cylinders. .Iaddend. .Iadd.14. A crank angle detecting system as set forth in claim 8, wherein said sensing means comprises a pair of photo sensors integrally installed in an electro-optic pick up, each photo sensor having a light emitting diode and photo receiving diode disposed at an opposite position to the light emitting diode, the photo sensors detecting passages of the small and large number of slits provided in the disc therethrough. .Iaddend. .Iadd.15. A crank angle detecting system for a multicylinder engine, comprising:   a) a plurality of engine cylinders in which spark plugs are installed respectively, said cylinders being classified into a plurality of groups and each group being constituted by a pair of cylinders such that while the one of the cylinders is in an explosion stroke, the other is in an exhaust stroke;   b) indicating means disposed so as to synchronize with a rotation of an engine crankshaft and formed with a large number of slits for detecting crankshaft angular positions and a small number of slits, the large number of slits being provided for indicating crankshaft angular positions and the small number of slits being provided for indicating predetermined stroke angular positions of respective cylinder pistons and wherein respective widths of said small number of slits with respect to the crankshaft angular position are different from each other to distinguish between piston strokes of at least the groups of cylinders;   c) sensing means for detecting crankshaft angular positions in cooperation with the large number of slits of the indicating means and outputting a crank angle signal representing each of the crank angular positions and for detecting the predetermined stroke angular positions in cooperation with the small number of slits of the indicating means and outputting the predetermined stroke angular signals having different widths corresponding to those of the small number of slits; and   d) discriminating means for identifying each cylinder group and outputting cylinder group identification signals on the basis of the crank angle signal and the predetermined stroke angular signals derived from said   
     
     
        sensing means. .Iaddend. .Iadd.16.  A crank angle detecting system as set forth in claim 15, which further comprises spark plug igniting means for igniting spark plugs separately according to the respective cylinder groups on the basis of the group identification signals and crank angle signal derived from said discriminating means and from said sensing means. .Iaddend.