Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
1999-04-15
2001-04-10
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C073S035080
Reexamination Certificate
active
06213092
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for determining the running smoothness of an Otto spark ignition engine by measuring the ionic current in at least one combustion chamber of the Otto spark ignition engine.
RELATED TECHNOLOGY
German Patent Nos. 40 15 191 C2, 195 24 539 C1, 195 24 540 C1 and 195 24 541 C1 disclose devices used for measuring the ionic current in the combustion chamber of an Otto spark ignition engine. In the process, the spark plug is used generally as a measuring sensor, a measuring voltage being applied to the electrodes of the spark plug following each firing. This accelerates the ions and electrons present in the electric field of the spark plug's electrodes due to the combustion in the combustion chamber, thereby inducing the ionic current. Reference is also made to the fact that the ionic current can be used to control running smoothness on a cylinder-selective basis. However, no specific embodiments are disclosed for implementing the running smoothness control.
SUMMARY OF THE INVENTION
An object of the present invention is to develop a method for determining the running smoothness of an Otto spark ignition engine which will ensure a reliable determination of running smoothness.
The present invention provides a method for determining the running smoothness of an Otto spark ignition engine by measuring the ionic current (I) in at least one combustion chamber of the Otto spark ignition engine once the spark plug allocated to the combustion chamber has fired, a measuring voltage being applied to the spark plug for measuring ionic current. Following each ionic current measurement, initially an active, average ionic-current value is defined, a running-smoothness value being subsequently determined from a reference value and the ionic-current average value.
By generating the average ionic-current value from a plurality of ionic-current measurements, a high level of accuracy can be achieved for the running-smoothness value. By including the reference value in the running-smoothness value, one attains a weighting of the ionic-current average value, which enters into the running-smoothness value.
Advantageous further embodiments of the method according to the present invention may include that: (a) the reference value is formed from an average deviation value (A
M
), the deviation being derived from the amount of the difference between the most recently measured ionic current (I) and the active ionic-current average value (I
M
); (b) the running-smoothness value (L) is determined from the integrated reference value and an integrated ionic-current weighting quantity (IB), which is a function of the average ionic-current value (I
M
) and/or the measured ionic current (I); (c) the quotient obtained by dividing the integrated reference value by the integrated ionic weighting quantity (IB) indicates the running-smoothness value (L); (d) the ionic-current weighting quantity (IB) is formed from the integrated, average ionic-current value (I
M
); (e) the ionic-current weighting quantity (IB) is formed from the differential value attained by subtracting the last measured ionic current (I
n
) from the average ionic-current value (I
M
); (f) the average ionic-current value (I
M
) and/or the average deviation value (A
n
) is formed with the aid of a shift register device (
16
); (g) a plurality of measured ionic currents (I) are stored in a first shift register (
17
) of the shift-register device (
16
), and a plurality of deviation values (A) are stored in a second shift register (
18
) of the shift-register device (
16
); (h) the active, average ionic-current value (I
M
) and/or the active, average deviation value (A
M
) are determined directly from the average value that precedes it in each instance and from the last measured ionic current (I
n
), i.e., the active deviation (A
n
); (i) the running-smoothness value (L) is used for controlling in open/or closed loop at least one valve-timing device, such as the exhaust-gas recirculation valve, injection system, or ignition system; (j) the running-smoothness value (L) is defined in a computational unit (
12
); and/or (k) ionic current (I) measured at the spark plug is an analog current signal, which is initially converted into a digital current signal, and subsequently routed to computational unit (
12
).
The reference value is expediently formed from an average deviation value, the deviation being derived from the amount of the difference between the most recently, i.e. last, measured ionic current and the active ionic-current average value. In this case, the difference between the ionic current and the average ionic-current value enters into the running-smoothness value, with the result that the last ionic current measurement is weighted with respect to the previously determined, average ionic-current value.
The running-smoothness value is advantageously determined from the integrated reference value and an integrated ionic-current weighting quantity, which is a function of the average ionic-current value and/or the measured ionic current. By generating the integral of the reference value, i.e., the ionic-current weighting quantity, one obtains in each case a scalar value, from which the running-smoothness value can then be determined.
In this case, the quotient obtained by dividing the integrated reference value by the integrated ionic weighting quantity can indicate the running-smoothness value, so that the integrated reference value is scaled to the integrated ionic weighting quantity.
An especially simple method for generating the average ionic-current value and/or the average deviation value is to determine these values with the aid of a shift register device, a plurality of measured ionic current values being storable in particular in a first shift register, and a plurality of deviation values being storable in a second shift register. In the process, the average values are calculated from the sum of the individual shift register entries, divided by the number of shift-register memory locations.
Alternatively, it is also possible to determine the active, average ionic-current value and/or the active average deviation value directly from the average value that precedes it in each instance and from the last measured ionic current, i.e., the active deviation. It suffices in this case to store merely the active, average ionic-current value or the average deviation value, so that only little memory capacity is needed.
In another expedient embodiment, the running-smoothness value is used for controlling in open/or closed loop at least one valve-timing device, such as the exhaust-gas recirculation valve, injection system, or ignition system, making it possible to optimize the emissions from the Otto spark ignition engine or its running smoothness.
In one beneficial circuit arrangement for implementing the method, the running-smoothness value is defined in a computational unit.
REFERENCES:
patent: 4535406 (1985-08-01), Johnson
patent: 5785020 (1998-07-01), Takahashi et al.
patent: 5895839 (1999-04-01), Takahashi et al.
patent: 6073611 (2000-06-01), Ohuchi et al.
patent: 43 24 312 (1994-02-01), None
patent: 40 15 191 (1995-02-01), None
patent: 44 02 938 (1995-08-01), None
patent: 195 245 40 (1996-06-01), None
patent: 195 24 539 (1996-11-01), None
patent: 195 24 541 (1996-12-01), None
Hohner Peter
Schenk Jurgen
Wilstermann Hartung
Argenbright Tony M.
Castro Arnold
Daimler-Chrysler AG
Kenyon & Kenyon
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