Internal-combustion engines – High tension ignition system – Having dwell control
Reexamination Certificate
2003-02-25
2004-10-19
Kwon, John T. (Department: 3747)
Internal-combustion engines
High tension ignition system
Having dwell control
C123S610000, C123S406180, C123S406580
Reexamination Certificate
active
06805110
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an engine, and more particularly, to a method and apparatus for engine ignition control.
BACKGROUND OF THE INVENTION
The ignition timing of an engine substantially influences the performance of the engine and therefore has to be controlled precisely, cylinder by cylinder. Ignition timing is indicated by the rotation angle of the crankshaft with reference to TDC (Top Dead Center) during a piston stroke. The rotation angle of the crankshaft is detected by a crank-position sensor (CPS). A crank-position sensor includes a toothed gear and a magnetic sensor that generates pulse signals in response to the rotation of the teeth. This toothed gear is also sometimes a toothed ring that is placed about a rotating member of the crankshaft. The teeth are uniformly displaced except where a tooth is intentionally left out. A tooth or teeth are intentionally deleted from the toothed gear so the missing tooth region can be used to find a specific angular position on the crankshaft.
The resolution of the crank-position sensor depends on the number of teeth formed on the toothed gear. For example, if a toothed gear has 30 teeth (counting the missing teeth also), the angle between adjacent pulses of the toothed gear is 12°, and therefore the toothed gear has a resolution of 12°.
But the ignition timing must be controlled much more precisely than the resolution of this type of a crank-position sensor. Therefore, a timer is used to monitor the elapsed time between adjacent pulses and estimate when a desired between-pulse crank angle will arrive. For example, in the case of a toothed gear of 12° resolution, to find 18° BTDC (18° Before Top Dead Center), the pulse from 24° BTDC is detected and the remainder angle of 6° is estimated by the timer. In practical use, however, the 36° BTDC pulse is found (that is, the second pulse before the theoretically calculated one) and the remainder angle 18° is estimated by the timer. This takes into account the fact that a small time period is needed to execute the timer instructions in a control unit.
Another point to be considered regarding ignition is that the ignition coil must supply a sufficiently large current to a spark plug. To do this, an ignition coil conducts current for a predetermined time period (referred to as “dwell period”). The current begins at a point at which the dwell period starts (referred to as “dwell-on point”). After the dwell period from the dwell-on point, the current is stopped, causing ignition in a cylinder. This is the starting time point of the ignition and is referred to as the “ignition timing”. The dwell angle is the crank angle change corresponding to the dwell period. To keep the dwell period to a specific value, dwell angle must be constantly re-calculated because the dwell angle varies in response to engine speed.
Therefore, the Dwell-On timing as well as the ignition timing must be precisely controlled based on the crank angle obtained by the crank-position sensor, and a lot of research regarding ignition control of an engine is related to increasing precision and accuracy thereof.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.
SUMMARY OF THE INVENTION
A preferred embodiment of an engine ignition control apparatus includes: a crank-position sensor for generating a pulse signal at each rotation angle of a crankshaft of the engine except for one or more missing pulses; an engine speed detector for detecting engine speed; an ignition coil driven by an electric current for Dwell-On and Ignition-On activation, said ignition coil generating a voltage for ignition of the spark plug under said Ignition-On activation; and an electric control unit for controlling said Dwell-On and Ignition On activation of the ignition coil based on the pulse signal and the engine speed. The electric control unit executes a set of instructions including instructions for each step of an ignition control method of an engine according to the present invention.
An exemplary ignition control method according to an embodiment of the present invention includes: calculating a dwell angle and an ignition angle of a reference cylinder based on an engine speed; calculating a first number of pulses and a first timer-monitored angle corresponding to a pre-Dwell-On period with regard to the reference cylinder, the pre-Dwell-On period being a period from occurrence of a first reference pulse to a Dwell-On timing with regard to the reference cylinder; comparing the first number of pulses with a predetermined number corresponding to 180° of crank angle; determining an ignition cylinder based on the comparison of the first number with the predetermined number; and actuating ignition of a spark plug of the ignition cylinder based on the first number of pulses, the first timer-monitored angle, and the ignition angle of the reference cylinder.
The first reference pulse is preferably one of a secondly occurring pulse after a missing pulse of a crank-position sensor and a pulse having a 180° angular difference thereto.
In a further preferred embodiment, said calculating a first number of pulses and a first timer-monitored angle includes: comparing a remainder of a first operation with a reference angle, the first operation being an operation of dividing an angular difference acquired by subtracting the dwell angle and the ignition angle from a BTDC angle of the first reference pulse by an angular difference between adjacent pulses; determining, when the remainder of the first operation is greater than the reference angle, the first number of pulses as a quotient of the first operation and the first timer-monitored angle as the remainder of the first operation; and determining, when the remainder of the first operation is not greater than the reference angle, the first number of pulses as a quotient of the first operation subtracted by 1 and the first timer-monitored angle as the remainder of the first operation plus the angular difference between adjacent pulses.
The reference angle is preferably less than the angular difference between adjacent pulses and greater than an angle corresponding to a required time for a timer to be is activated. In practical use, the reference angle may preferably be set to about 5°.
In another further embodiment, said determining an ignition cylinder based on the comparison determines the ignition cylinder as the reference cylinder when the first number is not greater than the predetermined number, and as another cylinder otherwise.
In a further preferred embodiment, said actuating ignition of a spark plug of the ignition cylinder includes: reducing the first number of pulses by the predetermined number when the ignition cylinder is different from the reference cylinder; counting the first number of pulses from occurrence of the first reference pulse; monitoring by timer for the first timer-monitored angle after said counting the first number of pulses; and actuating Dwell-On of an ignition coil of the ignition cylinder when the first timer-monitored angle elapsed.
In a further preferred embodiment, said actuating ignition of a spark plug of the ignition cylinder further includes: determining if a determination state of said determining ignition cylinder has been changed from a state such that the ignition cylinder is different from the reference cylinder to a state such that the ignition cylinder is the reference cylinder; and forcibly actuating Dwell-On of an ignition coil of said another cylinder when the determination state is determined to have been changed.
The exemplary method that is useful with the present invention preferably further includes: determining if a target pulse occurring after the first number of pulses after the first reference pulse lies in a missing pulse range, said missing pulse range covering a
Hyundai Motor Company
Kwon John T.
Morgan & Lewis & Bockius, LLP
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