Determining in-cylinder pressure by analyzing current of a spark plug

An ignition device for an internal combustion engine in which a discharge voltage is generated between electrodes of a spark plug connected to a secondary coil by energizing a primary current to a primary coil of an ignition coil and interrupting the primary current, comprising:

• a controller configured to:
• monitor a secondary current flowing across the electrodes of the spark plug;
• estimate an in-cylinder pressure at ignition timing based on both i) an engine revolution speed and ii) a discharge duration during which the secondary current flows, wherein the discharge duration shortens as the in-cylinder pressure increases, and wherein the discharge duration shortens as the engine revolution speed increases;
• detect an amount of time-dependent change in mechanical compression ratio based on the estimated in-cylinder pressure;
• and
• determine whether the amount of time-dependent change in mechanical compression ratio exceeds a threshold value,
• wherein, when the amount of time-dependent change in mechanical compression ratio exceeds the threshold value, a fuel injection amount of an associated cylinder is incrementally corrected.

An ignition device for an internal combustion engine in which a discharge voltage is generated between electrodes of a spark plug connected to a secondary coil by energizing a primary current to a primary coil of an ignition coil and interrupting the primary current, comprising:

• a controller configured to:
• monitor a secondary current flowing across the electrodes of the spark plug;
• estimate an in-cylinder pressure at ignition timing based on both i) an engine revolution speed and ii) a discharge duration during which the secondary current flows, wherein the discharge duration shortens as the in-cylinder pressure increases, and wherein the discharge duration shortens as the engine revolution speed increases;
• detect an amount of time-dependent change in mechanical compression ratio based on the estimated in-cylinder pressure;
• and
• determine whether the amount of time-dependent change in mechanical compression ratio exceeds a threshold value,
• wherein, when the amount of time-dependent change in mechanical compression ratio exceeds the threshold value, deposit combustion operation is executed to positively raise combustion temperature for burning and removing deposits accumulated in cylinders.

An ignition device for an internal combustion engine in which a discharge voltage is generated between electrodes of a spark plug by energizing a primary current to a primary coil of an ignition coil and interrupting the primary current, wherein the spark plug is connected to a secondary coil of the ignition coil, the ignition device comprising:

• a controller configured to:
• monitor a secondary current flowing across the electrodes of the spark plug;
• determine a time instant at which an event of capacitive discharge of the spark plug is completed;
• determine a parameter of the secondary current derived from behavior of the secondary current acquired at the determined time instant;
• estimate an in-cylinder pressure at ignition timing based on the parameter of the secondary current;
• and operate the internal combustion engine based on the estimated in-cylinder pressure, wherein the parameter of the secondary current is a current value of the secondary current acquired at the determined time instant.

An ignition device for an internal combustion engine in which a discharge voltage is generated between electrodes of a spark plug by energizing a primary current to a primary coil of an ignition coil and interrupting the primary current, wherein the spark plug is connected to a secondary coil of the ignition coil, the ignition device comprising:

• a controller configured to:
• monitor a secondary current flowing across the electrodes of the spark plug;
• determine a time instant at which an event of capacitive discharge of the spark plug is completed;
• determine a parameter of the secondary current derived from behavior of the secondary current acquired at or after the determined time instant;
• estimate an in-cylinder pressure at ignition timing based on the parameter of the secondary current;
• and operate the internal combustion engine based on the estimated in-cylinder pressure, wherein the parameter of the secondary current is a discharge duration of the spark plug during which the secondary current flows;
• and wherein the controller is further configured to implement the estimation of the in-cylinder pressure by estimating the in-cylinder pressure based on the parameter of the secondary current and based on an engine revolution speed of the internal combustion engine.

An ignition method for an internal combustion engine in which a discharge voltage is generated between electrodes of a spark plug by energizing a primary current to a primary coil of an ignition coil and interrupting the primary current, wherein the spark plug is connected to a secondary coil of the ignition coil, the ignition method comprising:

• monitoring a secondary current flowing across the electrodes of the spark plug;
• determining a time instant at which an event of capacitive discharge of the spark plug is completed;
• determining a parameter of the secondary current derived from behavior of the secondary current acquired at the determined time instant;
• estimating an in-cylinder pressure at ignition timing based on the parameter of the secondary current;
• and operating the internal combustion engine based on the estimated in-cylinder pressure, wherein the parameter of the secondary current is a current value of the secondary current acquired at the determined time instant.

An ignition method for an internal combustion engine in which a discharge voltage is generated between electrodes of a spark plug by energizing a primary current to a primary coil of an ignition coil and interrupting the primary current, wherein the spark plug is connected to a secondary coil of the ignition coil, the ignition method comprising:

• monitoring a secondary current flowing across the electrodes of the spark plug;
• determining a time instant at which an event of capacitive discharge of the spark plug is completed;
• determining a parameter of the secondary current derived from behavior of the secondary current acquired at or after the determined time instant;
• estimating an in-cylinder pressure at ignition timing based on the parameter of the secondary current;
• and operating the internal combustion engine based on the estimated in-cylinder pressure, wherein the parameter of the secondary current is a discharge duration of the spark plug during which the secondary current flows;
• and wherein the estimation of the in-cylinder pressure is implemented by estimating the in-cylinder pressure based on the parameter of the secondary current and based on an engine revolution speed of the internal combustion engine.