Internal-combustion engines – High tension ignition system – Responsive to engine or environmental condition
Reexamination Certificate
1999-07-22
2001-02-13
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
High tension ignition system
Responsive to engine or environmental condition
C123S637000, C123S644000
Reexamination Certificate
active
06186130
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a system for controlling ignition of an air/fuel mixture, and more particularly, to a system for use in generating a plurality of sparks during combustion in an internal combustion engine.
BACKGROUND OF THE INVENTION
There has been much investigation in the ignition art directed to systems for generating multiple spark events during combustion. Such systems are sometimes alternately referred to as “multicharge” systems. Such ignition systems, in particular, are known which provide a succession of spark breakdowns to ensure ignition of a combustible air/fuel mixture introduced into a cylinder of an internal combustion engine. Such systems, ostensibly, provide a series of sparks to increase the number of ignition events and hence the probability of combustion of the air/fuel mixture by extending the time and total energy available for combustion. Conventionally, an ignition coil undergoes an initial charge (i.e., initial dwell) wherein a primary current is established in a primary winding of the ignition coil. The initial dwell is immediately followed by an initial discharge of the ignition coil wherein a secondary current in a secondary winding thereof discharges through a spark plug to generate a first spark. Subsequent recharge intervals (i.e., subsequent dwell periods) follow, accompanied by respective discharge intervals (i.e. spark events). The number of sparks produced is generally determined by a predetermined operating strategy. However, such prior approaches have shortcomings.
One approach taken in the art requires a fixed spark duration (i.e., fixed time for allowing discharge of the secondary current) in combination with a recharge time selected as a predetermined fraction of the initial charge interval (e.g., recharge selected as ¼ of the charge time). Such an approach is stated to have as an advantage the relative efficiency in drawing energy from the main source such as the automotive vehicle battery. Another approach taken in the art also requires a fixed discharge time (i.e., spark duration), but further provides for a recharge interval that is interrupted by a control device when a primary current reaches a predetermined maximum value I
MAX
(therefore at I
p
=I
MAX
) so as to account for relatively high, medium, and small supply (e.g., battery) voltages. Applicants have determined, however, that due to variations in engine operating parameters and environmental factors appurtenant thereto that a fixed discharge time interval does not provide an optimum rate of energy delivery to the air/fuel mixture.
Accordingly, there is a need to provide an ignition control system suitable for use in generating repetitive sparks, that minimizes or eliminates one or more of the shortcomings as set forth above.
SUMMARY OF THE INVENTION
One object of the present invention is to provide an ignition system suitable for use in generating repetitive spark that maximizes energy delivered to an air/fuel mixture in a given time frame.
It is another object of the present invention to reduce power dissipation in one or more electrical components of an ignition system.
It is yet another object of the present invention to provide an ignition system having an increased electrical efficiency.
It is still yet another object of the present invention to provide an ignition system that improves the quality of the combustion event.
These and other objects, advantages, and features of the present invention are realized by a method of controlling ignition in an internal combustion engine in accordance with the present invention. The method involves secondary current sensing and includes five basic steps. The first step involves determining a secondary current threshold. Preferably, the secondary current threshold is determined as a function of an engine speed parameter and an ambient temperature parameter. The secondary current threshold defines the level at which to end secondary current discharge. The second step involves charging an ignition coil by establishing a primary current through a primary winding of the coil. Third, producing a first spark by interrupting the primary current to thereby induce a secondary current in a secondary winding of the coil. The fourth step involves determining the level of the secondary current through the secondary winding. Finally, the fifth step involves recharging the ignition coil by establishing the primary current through the primary winding. This recharging step, which in effect terminates the secondary current discharge, occurs when the secondary current level reaches the secondary current threshold. In a further embodiment, the primary current is thereafter again interrupted to produce a second spark.
An ignition system in accordance with the present invention maximizes the energy delivered to an air/fuel mixture in a given time frame. Maximizing the energy delivery rate improves the quality of the combustion event.
Other objects, features, and advantages of the present invention will become apparent to one skilled in the art from the following detailed description and accompanying drawings illustrating features of this invention by way of example, but not by way of limitation.
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Butler, Jr. Raymond O.
Skinner Albert Anthony
Argenbright Tony M.
Delphi Technologies Inc.
Dobrowitsky Margaret A.
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