Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2003-03-19
2004-11-30
Yuen, Henry C. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406500, C123S406640
Reexamination Certificate
active
06823842
ABSTRACT:
BACKGROUND OF INVENTION
1. Technical Field
This invention relates generally to methods and systems for controlling the ignition timing of an internal combustion engine and more particularly to methods and systems for reducing engine knock during rapidly changing operating conditions (i.e., during rapid transients).
2. Background of the Invention
As is known in the art, it is desirable for an internal combustion engine to determine a spark advance parameter based on an estimate of cylinder air charge. The spark advance parameter generally represents the angle of the crankshaft at which the spark is fired in the combustion chamber. By accurately determining and using the spark advance parameter, fuel economy can be increased and engine knock can be avoided.
Under normal operating conditions, spark timing is based on Minimum spark advance for Best Torque (MBT) considerations. MBT is the spark timing providing peak power and fuel economy. During a rapid change in acceleration, however, often referred to as a tip-in event or a rapid transient, engine knock may be experienced if using MBT as the sole criteria for spark timing.
As is known in the art, borderline spark timing is also determined in response to a tip-in event. Borderline spark timing is spark timing which avoids knock. Borderline spark timing is retarded, with respect to MBT timing. It should be noted that both the MBT based spark timing and the borderline base timing are a function of cylinder air charge.
One technique used to reduce engine spark knock during a rapid transient, i.e., tip-in, is described in U. S. Pat. No. 5,445,127, “Method and System for Reducing Engine Spark Knock During a Rapid Transient”, inventors Cullen et al., issued Aug. 29, 1995, assigned to the same assignee as the present invention, the entire subject matter thereof being incorporated herein by reference.
In one known system, the borderline spark timing calculation is performed along with the MBT based timing calculation at regular time intervals, i.e., background computational events. The computations are performed using tables stored in a memory used in the engine control unit, sometimes referred to as the Engine Control Unit (ECU). An example of such tables used to determine borderline timing is shown in
FIG. 2. A
similar set of tables is used to determine MBT based timing. Thus, referring to
FIG. 2
, TABLE I, provides a base borderline spark timing for a cylinder approaching top dead center (TDC), here indicated as Base Borderline (BDL) for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis).
TABLES II through VIII are modifier tables which store data used to modify the base borderline spark timing of TABLE I. TABLE II shows swirl valve modifiers (Intake Manifold Runner Control (IMRC) modifiers) for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE II at such condition is multiplied by an a priori determined IMRC constant and the product is added to the Base BDL determined from TABLE I.
TABLE III shows cam position modifiers for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE III at such condition is multiplied by the cam angle of the cylinder to be fired and the product is also added to the Base BDL determined from TABLE I.
TABLE IV shows Engine Coolant Temperature (ECT) modifiers for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE IV at such condition is multiplied by a number which is a stored function of measure ECT and the product is also added to the Base BDL determined from TABLE I.
TABLE V shows Air Temperature (ACT) modifiers for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE V at such condition is multiplied by a number which is a stored function of measure ACT and the product is also added to the Base BDL determined from TABLE I.
TABLE VI shows Cylinder Head Temperature (Cht) modifiers for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE VI at such condition is multiplied by a number which is a stored function of measure Cht (Cylinder head Temperature) and the product is also added to the Base BDL determined from TABLE I. The Cht values are not used during normal operation. They are only used during failure mode management for a loss of engine coolant.
TABLE VII shows “Lugging time” modifiers for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE VI at such condition is multiplied by a number which is a stored function of measure “Lugging time” and the product is also added to the Base BDL determined from TABLE I. “Lugging time” refers to the elapsed time following a large increase in air charge, i.e. the elapsed time following a heavy tip-in event.
TABLE VIII shows “Octane adjustment” modifiers for a relationship between cylinder air charge, here also referred to as load, (i.e., the Y-axis) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and air charge, the value stored in the TABLE VI at such condition is multiplied by an “Octane Adjustment” constant and the product is also added to the Base BDL determined from TABLE I. The “Octane Adjustment” constant is normally set to ‘0,’ in the absence of octane information. However, it may set to a non-zero value to adjust for different fuel Octane levels, should such octane data be available. Alternatively, it may also be set to a non-zero value in the event of that a knock sensor becomes inoperable.
Other non-speed and air charge based modifiers are also added to the Base BDL determined from TABLE I. The summation is referred to as “Borderline Spark”.
TABLE IX shows Engine Coolant Temperature (ECT) modifiers for a relationship between Air Temperature (ACT) as a function of engine speed, N, (i.e., the X-axis). Thus, for a particular engine speed and ACT, the value stored in the TABLE IX at such condition is multiplied by a number which is a stored function of measured ECT and the product is the “Tip-in Slope”.
While ideally the table information described above should be calculated for each cylinder firing event, typically it is done once every 100 milliseconds to reduce the processing load on the ECU. Therefore, in accordance with the prior art, “Borderline Spark” and “Tip-in Slope” computations are made at a background computational rate, every 100 milliseconds, for example. Estimates are made for “Tip-in” timing at each cylinder firing event; i.e., at a foreground computational rate, one each cylinder firing event. Thus, these estimates are made at the foreground computational rate.
More particularly, for each cylinder firing event during a tip-in, the “Tip-in” spark timing is equal to the summation of: “Borderline Spark” determined as described above at the for example, once every 100 millisecond (i.e., at the “background computational rate”); and, the product of “Tip-in Slope”, also computed at the background computational rate, and “&Dgr; Air Charge”, where “&Dgr; Air Charge” is the change in air charge since the last background computational event and where “Tip-in Slope” i
Baskins Robert Sarow
Meek Bruce Allen
Sabuda Mark
Castro Arnold
Ford Global Technologies LLC
Yuen Henry C.
LandOfFree
Method and system for reducing engine spark knock during... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for reducing engine spark knock during..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for reducing engine spark knock during... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3283600