Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
1999-05-17
2001-06-19
Solis, Erick (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406640, C123S406210, C123S406220
Reexamination Certificate
active
06247448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to engine control systems in general and more particularly to a closed loop spark control system and algorithm operating around borderline knock spark timing and using the characteristics of a sensor related to combustion quality to determine the borderline knock spark timing.
2. Description of the Related Art
Spark timing in current production engines may be under open loop or closed loop control. If open loop, the spark timing is determined by calibrated look-up tables and calculated algorithms based on overall engine operating parameters and control inputs. If this method is used, the spark timing must be conservative (retarded) enough in order that the engine will not knock under worst-case conditions of compression ratio, fuel octane, combustion chamber deposits, and humidity. Since worst-case conditions are rare, retarded spark timing most or possibly all of the time will artificially reduce engine torque/efficiency.
To regain this torque/efficiency and maintain protection under worst-case conditions, many programs put the spark timing under closed loop control with a knock detection system. In some cases the same open loop spark tables are used to determine spark advance, and if knock is detected spark is retarded from that spark advance. Spark is then advanced if no further knocking events are detected until the original reference is reached. If more knocking events are detected, then spark is retarded further.
In other cases, the spark timing look-up tables contain upper and lower limits for different overall engine operating parameters, and feedback from the knock detector is used to find the optimal spark advance within those limits. The desired setpoint is the limit of knock audibility or the threshold of knock-induced piston damage or maximum engine torque, whichever comes first.
In both closed-loop cases the control strategy is arranged so that the knock detection system classifies each combustion event as knocking or non-knocking. If a combustion event is classified as non-knocking, the spark timing is advanced or maintained for the next engine cycle. However, if a combustion event is classified as knocking, the spark timing is retarded for the next engine cycle. There are many implementations of such strategies which differ in the details of how far and how fast the spark is advanced or retarded as well as how the knocking
on-knocking classification is made. Some systems maintain running averages and statistical measures of the individual cycle results for self-calibration purposes, and it is common to treat the knocking and non-knocking cycles differently in these statistical calculations.
U.S. Pat. No. 4,527,524 issued to Guipaud on Jul. 9, 1985, teaches the amount of spark retard used is based on the number of knock events detected and the rate used to advance spark after a knock event. Less spark retard is used with each successive knock event. Spark is advanced at an increasing rate if knock is not detected as the original spark advance is reached. This system relates strictly to spark advance/retard strategy with no mention of how an event is declared knocking or non-knocking. There is no attempt to correlate spark advance to actual borderline knock spark timing value.
U.S. Pat. No. 4,971,007 issued on Nov. 20, 1990 to Gopp et al. and assigned to a common assignee, is concerned both with finding the knock threshold and finding “Minimum spark for Best Torque”, MBT. The knock threshold is detected by counting the number of engine cycles between successive knocking events. The system is not designed to optimize knock threshold accuracy.
These and other prior art systems do not attempt to correlate knock to actual borderline spark advance values. In addition the prior art systems are not designed to optimize knock threshold accuracy.
SUMMARY OF THE INVENTION
A common feature of the existing prior art systems is that the knocking
on-knocking classification does not make use of a valuable piece of information, namely the value of spark timing in effect when each cycle was measured.
It is therefore a principal advantage of the system to control spark timing directly by the powertrain control module, wherein the value of spark timing in effect when each cycle is measured is readily available on a cycle resolved basis.
It is another advantage of the system described and defined herein to use a knock sensor or some similar sensor, to determine borderline knock spark timing relative to the location of borderline knock.
It is still another advantage of the system to define on either a cylinder by cylinder basis or on a global basis, the optimum spark timing to accomplish ignition without engine knock by optimizing knock threshold accuracy.
It is yet another advantage of this system to determine and use borderline knock spark timing to maximize ignition timing without engine knock.
The invention is a method and system for determining borderline knock in an internal combustion engine such as may be found in motor vehicles. The method sets the spark timing at a value equal to a predetermined borderline spark timing angle minus a fixed number of crankshaft angle degrees. Spark timing is advanced in a staircase manner by an incremental number of crankshaft angle degrees in each step. The signal amplitude of a combustion-related event at each staircase step is measured. The slope is calculated between the measured signal amplitude at each staircase step with the prior staircase step signal amplitude. Finally the staircase step angular value is identified as the borderline knock spark timing wherein the calculated slope becomes greater than a predetermined value of slope.
REFERENCES:
patent: 4527524 (1985-07-01), Guipaud
patent: 4541382 (1985-09-01), Hosoe et al.
patent: 4699106 (1987-10-01), Haraguchi et al.
patent: 4700677 (1987-10-01), Bonitz et al.
patent: 4809660 (1989-03-01), Marsh et al.
patent: 4825832 (1989-05-01), Satoh et al.
patent: 4829962 (1989-05-01), Hafner et al.
patent: 4896639 (1990-01-01), Holmes
patent: 4936276 (1990-06-01), Gopp
patent: 4971007 (1990-11-01), Gopp et al.
patent: 5033417 (1991-07-01), Van Basshuysen et al.
patent: 5035219 (1991-07-01), Ohkumo et al.
patent: 5233962 (1993-08-01), Fodale et al.
patent: 5243942 (1993-09-01), Entenmann et al.
patent: 5421304 (1995-06-01), Gibtner et al.
patent: 5535722 (1996-07-01), Graessley et al.
patent: 5645034 (1997-07-01), Entenmann et al.
patent: 5771862 (1998-06-01), Unland et al.
Carlstrom Kevin Ronald
Scholl David James
Drouillard Jerome R.
Ford Global Technologies Inc.
Solis Erick
LandOfFree
Closed loop spark control method and system utilizing a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Closed loop spark control method and system utilizing a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Closed loop spark control method and system utilizing a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2522340