Internal-combustion engines – High tension ignition system – Having dwell control
Reexamination Certificate
2000-02-11
2001-06-19
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
High tension ignition system
Having dwell control
C123S625000, C123S645000
Reexamination Certificate
active
06247465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system and method for preventing spark-on-make in an internal combustion engine, using manifold pressure information.
2. Discussion of the Related Art
A typical automotive ignition system includes a spark plug for each combustion chamber of an engine, at least one ignition coil and at least one device adapted to selectively charge the coil(s) and cause the energy stored in the coil(s) to be discharged through the spark plugs in a timed manner. As a result, a spark is generated and ignition of a fuel-air mixture in each combustion chamber occurs at a specified timing.
When charging of the coil is initiated, however, a transient voltage is created. In some situations, this transient voltage may be high enough to create a spark at the spark plug. This kind of sparking event is commonly referred to as a spark-on-make event or condition because historically it would occur when the breaker points of the ignition system made contact to commence charging of the ignition coil. The term “spark-on-make”, as used in this disclosure however, is not limited to situations where conventional breaker points are used. To the contrary, it refers to any situation where initiation of coil or ignition system charging causes a spark at one or more of the spark plugs. This kind of sparking event, however, is undesirable because it is not timed for proper engine operation. It can cause severe damage to engine components.
Recent advances in technology have made it more practical and desirable in some situations to provide a coil-per-cylinder ignition arrangement (i.e., wherein a coil is provided for each cylinder of the engine). While the coil-per-cylinder arrangements provide some benefits and advantages, the spark-on-make condition is more likely to occur in such an arrangement. The spark-on-make conditions or events, as a result, tend to detract from the benefits achieved by providing a coil from each cylinder.
Efforts therefore have been directed at eliminating or reducing the likelihood that a spark-on-make event will occur. While conventional techniques of avoiding the spark-on-make condition can be generally effective, there is significant room for improvement. Many such techniques involve complicated and/or time-consuming manufacturing and/or installation processes, and/or involve customized or otherwise relatively expensive parts. The conventional techniques therefore can be relatively expensive, complicated, and time-consuming.
Examples of the conventional techniques of avoiding a spark-on-make condition include 1) providing a high voltage diode that is used to permit the flow of current in one direction to the spark plug but not in the reverse direction, thereby allowing the coil to be discharged after sufficient charging and at the proper time while preventing application of the transient voltage created during initiation of the charging process, and 2) by reducing the number of turns in the coil.
The first technique is relatively expensive. A high voltage diode can cost several cents per diode, even when purchased as part of a high volume transaction. In automotive manufacturing, where the number of parts and the cumulative cost thereof can escalate, a per-part cost of several cents should be avoided whenever possible. In addition, the use of a high voltage diode is not always compatible with ignition systems that have ion sense capabilities. Typically, the way to provide compatibility of the high voltage diode technique with ignition systems that have ion sense capabilities is to use a positive polarity spark. It is more desirable, however, to not be limited to use of such positive polarity sparks because they have a higher demand voltage (e.g., 10% higher).
The second technique, namely, reducing the number of turns in the secondary winding of the coil disadvantageously tends the increase the overall cost of the coil driving electronics. In some cases, the reduction in number of turns also prevents the coil from satisfying other requirements imposed by the consumer (e.g., an engine or ignition system manufacturer).
There is consequently a need in the art for a less complicated, less expensive, more reliable, and/or more practical system and method for preventing spark-on-make in an internal combustion engine. This need extends to a system and method that is not limited to use on positive spark polarity ignition systems.
SUMMARY OF THE INVENTION
It is a primary object of the present invention to overcome at least one of the foregoing problems and/or to satisfy at least one of the aforementioned needs by providing a more practical, less expensive, more reliable, and/or less complicated system and method for preventing spark-on-make in an internal combustion engine.
To achieve this and other objects and advantages, the present invention provides a system and method for preventing spark-on-make in an internal combustion engine, using manifold pressure information. The system comprises a pressure sensor and a controller. The pressure sensor is adapted to detect pressure in an intake manifold and provide an output signal indicative of that pressure. The controller is at least indirectly connected to the pressure sensor and is adapted to delay initiation of ignition dwell in a coil by a period of time sufficient to avoid spark-on-make, in response to the output signal from the sensor. Preferably, the pressure sensor is a manifold absolute pressure (MAP) sensor. In addition, the controller preferably is adapted to calculate, based on a present value of a supply voltage, a make voltage level that would be developed across a secondary winding of the ignition coil upon connection of the supply voltage to a primary winding of the ignition coil. Preferably, the controller is associated with a memory, the memory containing a plurality of tables, each table being associated with a respective value or range of values of the pressure and containing a plurality of safety voltage maximum levels, each safety voltage maximum level being correlated in each table to an earliest safe crank angle value at which dwell can be commenced without causing the make voltage to exceed the correlated safety voltage maximum level. Each safety voltage maximum level in each table preferably is less than the spark demand voltage by a predetermined safety margin at a respective pressure and at the earliest safe crank angle correlated to that safety voltage maximum level. The controller also can be adapted to access, based on the output signal, one of the tables that corresponds to the present value of the pressure, and to access, within that table and based on the make voltage level calculated by the controller, the earliest safe crank angle value at which dwell can be commenced without causing the make voltage to exceed the correlated safety voltage maximum level. The controller also can be adapted to prevent initiation of dwell until the crank angle indicated by the earliest safe crank angle value selected by accessing the tables using the make voltage level, is reached.
Also provided by the present invention is a method for preventing spark-on-make in an internal combustion engine. The method comprises the steps of detecting pressure in an intake manifold, providing an output signal indicative of that pressure, and delaying initiation of ignition dwell in an ignition coil by a period of time sufficient to avoid spark-on-make, in response to the output signal. The pressure preferably is a manifold absolute pressure (MAP).
Preferably, the step of delaying includes calculating, based on a present value of a supply voltage, a make voltage level that would be developed across a secondary winding of the ignition coil upon connection of the supply voltage to a primary winding of the ignition coil; providing a plurality of tables, each table being associated with a respective value or range of values of the manifold pressure and containing a plurality of safety voltage maximum levels, each safety voltage maximum level being correlated in each t
Argenbright Tony M.
Delphi Technologies Inc.
Dobrowitsky Margaret A.
LandOfFree
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