Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
2001-01-31
2002-04-23
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C123S406640, C701S102000
Reexamination Certificate
active
06374801
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ignition control device and a corresponding ignition control method.
Although it can be applied to any ignition control system, the present invention and its underlying principle are explained in relation to an engine control unit on board a motor vehicle.
BACKGROUND INFORMATION
Ignition control devices for controlling ignition events for ignition-coil ignition systems and devices, generally have two control functions: to control a desired ignition power via the ignition coil turn-on time, i.e., charging time, and to control the angle of an ignition pulse via the ignition coil turn-off time, i.e., end of charge.
The ignition power supplied over the ignition coil charging time in coil ignition systems varies in length depending on the vehicle electrical supply voltage applied to the electric circuit of the coil as well as the time constant of the electric circuit.
The respective setpoints are usually stored as a function of engine rpm and other possible engine parameters in the form of a characteristic map in the control unit.
To output angle signals, customary control units have an angle sensor wheel that supplies equidistant-angle pulses to the ignition control device. Most ignition control device architectures, however, allow the ignition events to be calculated only in segments, due to the computation time, with one segment equaling a 720° angle interval of the crankshaft, divided by the number of cylinders, i.e., 180° in a four-cylinder engine, for example. While the angular positions of the ignition events determined in the calculation can therefore be gauged with a sufficient degree of accuracy via the angle sensor wheel and the usual timer and counter circuits in ignition control devices, the calculation itself is based on a detected rpm.
The cylinder-specific control quantities for ignition output are therefore usually calculated once per ignition interval, i.e., segment, and synchronized with ignition output using a cylinder counter. This means that a cylinder counter informs the ignition control device to which cylinder it should send the next ignition signal to be triggered, which includes the start and end of the charge (i.e., ignition).
To calculate the ignition events, the angle/time characteristic for the rotational movement of the internal combustion engine is focused, since the energy in the ignition system is defined over a specific charging time, and the charging time ends at a defined ignition angle position. Thus, we need to know the angle interval to which the charging time corresponds after charging begins. To describe this angular movement, we need to have information about engine rpm.
In most ignition control devices commonly used today for spark ignition engines, this information is determined once per ignition interval at a defined speed measuring point with a fixed angular position in relation to the upper dead center of the next cylinder to be fired. With a longer charging time and/or higher speed, the start of the charging time moves closer to the angular position of the speed measuring point until the speed measuring point finally coincides with the charge interval, and the speed information from the previous segment is used for calculating the ignition event. This is known as overlapping ignition output.
Upon reaching overlap mode, the cylinder counter is corrected by an offset. This means that the ignition events for an ignition interval following the current ignition interval are triggered as early as the current ignition interval. If the ignition output determines, during the current ignition interval, that charging of the current event actually began in the past, the start of charging for the current cylinder is triggered immediately during the current ignition interval, and the start of charging for the subsequent cylinder is triggered with a delay. It is precisely during this transition from non-overlap mode to overlap mode that many ignition output methods lack information about the ignition angle and charging time of the subsequent cylinder, so that the values for the current cylinder are used for the ignition angle and charging time of the subsequent cylinder.
More precise procedures calculate the setpoints of the subsequent cylinders along with the data of the current ignition interval, and buffer this data for the transition to overlap mode. Up to now, however, there has been no clear, transparent system for showing the system user, for example the mechanic, which setpoints are used for ignition output. Furthermore, there is no standard, universally applicable method that could also be used by other output devices.
To explain the underlying principle,
FIG. 2
shows a schematic representation of the ignition sequence in a four-cylinder internal combustion engine.
In
FIG. 2
, crank angle KW is plotted in degrees on the x-axis, ignition ZZ, which has the sequence . . . -2-1-3-4-2- . . . , is plotted on the y-axis. A complete cycle equals 720° KW, with a cycle time t
ZYK
. One segment equals 720°KW/4=180°, with a segment time t
SEG
.
FIG. 3
shows a schematic representation of the ignition control function sequences in the segment for the first cylinder of the four-cylinder internal combustion engine, when applying ignition coil current I
Z
.
Rotation speed N is detected at 0°, and, immediately afterwards, charging time t
L
and ignition angle W
Z
(which are more or less equal to the end-of-dwell angle and end-of-charge angle, respectively) are taken from a characteristic map or calculated at calculation time B.
Start-of-dwell or start-of-charge angle W
LB
is then calculated from the following equation:
W
LB
=W
Z
−t
L
×&ohgr;,
assuming a uniform movement, where &ohgr; is the angular velocity corresponding to rotation speed N. Due to the computing time, this time and angular position of the ignition events is calculated only once per ignition interval.
To determine the start-of-charge angle, a counter C
1
detects angle W
LB
starting at 0°, via crankshaft sensor signal KWS, and activates the ignition coil output stage upon reaching angle W
LB
. A further counter C
2
detects angle W
Z
starting at 0° via crankshaft sensor signal KWS, and discontinues activation upon reaching angle W
Z
.
In the overlap mode mentioned above, it is determined that the event to be triggered by counter C
1
lay in the past, and therefore the charge should begin immediately at 0°.
SUMMARY OF THE INVENTION
The ignition control device according to the present invention, and the corresponding ignition control method, have an advantage over known approaches in that they provide a uniform, transparent procedure, which can be used universally on an engine control platform to control the transmission of cylinder-specific control quantities to the ignition output. If desired, the procedure can also be used concomitantly by other output devices, such as the injection output. The transmission of values to the output device can be easily followed.
According to the idea underlying the present invention, the ignition events are managed in two memory blocks.
In a first memory block, which is designed as a simple array, the ignition control device stores the ignition event setpoints for the cylinder that is moving toward its upper ignition dead center during the current segment as well as for all subsequent cylinders.
Based on its internal states, the ignition output process determines the currently active degree of overlap and sets an overlap counter.
A second memory block is organized as a FIFO (first-in first-out) memory (shift register). With each ignition interval, the FIFO elements shift down one element. The overlap counter defines the element in the first memory block to be copied to the top element in the FIFO memory.
Instead of the usual arrangement according to the related art, the ignition output receives the ignition angle not directly from the first memory block of the ignition control device, but from the ignition angle FIFO memory, which can be implemented as separate har
Friedmann Harry
Haussmann Martin
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