Misfiring detecting method and apparatus

A method of detecting the occurrence of misfiring in an internal combustion engine including at least one cylinder and a crankshaft operatively coupled to said cylinder, said method comprising the steps of:

• successively determining a time ratio representing a ratio between a first time taken for said crankshaft to rotate a first predetermined angular distance, extending in precedence to a predetermined angular reference position of said crankshaft, as indicated by a first level of a pulse signal representing angular positions of said crankshaft, and a second time taken for said crankshaft to rotate a second predetermined angular distance, extending in succession to said predetermined angular reference position, as indicated by a second level of said pulse signal;
• determining an angular acceleration of said crankshaft on the basis of a difference between the time ratios determined in current and preceding engine cycles, respectively;
• determining a change in said angular acceleration at a predetermined crank position of said cylinder;
• comparing said change in the angular acceleration with a predetermined value;
• and
• deciding the occurrence of misfiring in said cylinder when said change in the angular acceleration exceeds said predetermined value.

A method of detecting the occurrence of misfiring in an internal combustion engine including a plurality of cylinders operating in a predetermined sequence and a crankshaft operatively coupled to said cylinders, said method comprising the steps of:

• determining a time ratio representing a ratio between a first time taken for said crankshaft to rotate a first predetermined angular distance, extending in precedence to a predetermined angular reference position of said crankshaft, as indicated by a first level of a pulse signal representing angular positions of said crankshaft, and a second time taken for said crankshaft to rotate a second predetermined angular distance, extending in succession to said angular reference position, as indicated by a second level of said pulse signal;
• determining an angular acceleration of said crankshaft on the basis of a difference between the time ratios determined in successive engine cycles;
• successively determining a change in the angular acceleration at a predetermined crank position for each of said cylinders;
• comparing said change in the angular acceleration with a predetermined value;
• and
• deciding the occurrence of misfiring in one of said cylinders which was last ignited if said change in the angular acceleration exceeds said predetermined value.

A method of detecting the occurrence of misfiring in an internal combustion engine including a plurality of cylinders operating in a predetermined sequence and a crankshaft operatively coupled to said cylinders, said method comprising the steps of:

• determining a time ratio representing a ratio between a time taken for said crankshaft to rotate a first predetermined angular distance extending in precedence to a predetermined angular reference position of said crankshaft and a time taken for said crankshaft to rotate a second predetermined angular distance extending in succession to said angular reference position;
• determining an angular acceleration of said crankshaft on the basis of a difference between the time ratios determined in current and preceding engine cycles, respectively;
• determining a first quantity representing a change in said angular acceleration at a first predetermined crank position for a given one of said cylinders;
• comparing said first quantity with a first predetermined value;
• determining a second quantity representing a change in said angular acceleration at a second predetermined crank position for a succeeding cylinder operating in succession to said given cylinder;
• comparing said second quantity with a second predetermined value;
• and
• deciding the occurrence of misfiring in one of said cylinders which was last ignited if said first quantity exceeds said first predetermined value and if said second quantity exceeds said second predetermined value.

An apparatus for detecting the occurrence of misfiring in an internal combustion engine including at least one cylinder and a crankshaft operatively coupled to said cylinder, said apparatus comprising:

• a crank angle sensor for generating a pulse signal representative of angular positions of said crankshaft, said pulse signal having a first duration of a first level before a predetermined angular reference position of said crankshaft and a second duration of a second level after said predetermined angular reference position;
• and
• an arithmetic unit operable to process said pulse signal for making decision as to the occurrence of misfiring in said cylinder;
• said arithmetic unit comprising;
• means for successively determining a time ratio representing a ratio between said first and second durations of said pulse signal;
• means for determining an angular acceleration of said crankshaft on the basis of a difference between the time ratios determined in current and preceding engine cycles, respectively;
• means for determining a change in said angular acceleration at a predetermined crank position for said cylinder;
• means for comparing said change in said angular acceleration with a predetermined value;
• and
• means for deciding the occurrence of misfiring in said cylinder if said change in said angular acceleration exceeds said predetermined value.

An apparatus for detecting the occurrence of misfiring in an internal combustion engine including at least one cylinder and a crankshaft operatively coupled to said cylinder, said apparatus comprising;

• a crank angle sensor for generating a pulse signal representative of angular positions of said crankshaft, said pulse signal having a first duration of a first level before a predetermined angular reference position of said crankshaft and a second duration of a second level after said predetermined angular reference position;
• and
• an arithmetic unit operable to process said pulse signal for making decision as to the occurrence of misfiring in said cylinder;
• said arithmetic unit comprising;
• means for successively determining a time ratio representing a ratio between said first and second durations of said pulse signal;
• means for determining an angular acceleration of said crankshaft on the basis of a difference between the time ratios determined in successive engine cycles;
• means for successively determining a change in said angular acceleration at a predetermined crank position for each of said cylinders;
• means for comparing said change in said angular acceleration with a predetermined value;
• and
• means for deciding the occurrence of misfiring in one of said cylinders which was last ignited if said change in said angular acceleration exceeds said predetermined value.

An apparatus for detecting the occurrence of misfiring in an internal combustion engine including at least one cylinder and a crankshaft operatively coupled to said cylinder, said apparatus comprising:

• a crank angle sensor for generating a pulse signal representative of angular positions of said crankshafts, said pulse signal having a first duration of a first level before a predetermined angular reference position of said crankshaft and a second duration of a second level after said predetermined angular reference position;
• and
• an arithmetic unit operable to process for making decision as to the occurrence of misfiring in said cylinder;
• said arithmetic unit comprising;
• means for successively determining a time ratio representing a ratio between said first and second durations of said pulse signal;
• means for determining an angular acceleration of said crankshaft on the basis of a difference between the time ratios determined in current and preceding engine cycles, respectively;
• means for determining a first quantity representing a change in said angular acceleration at a first predetermined crank position for a given one of said cylinders;
• means for comparing said first quantity with a first predetermined value;
• means for determining a second quantity representing a change in said angular acceleration at a second predetermined crank position of a succeeding cylinder operating in succession to said given one cylinder;
• means for comparing said second quantity with a second predetermined value;
• and
• means for deciding the occurrence of misfiring in one of said cylinders which was last ignited if said first quantity exceeds said first predetermined value and if said second quantity exceeds said second predetermined value.