Knock control process for an internal combustion engine

Details Knock control process for an internal combustion engine Knock control process for an internal combustion engine

1997-05-02

1998-06-30

Nelli, Raymond A.

Internal-combustion engines

Combustion chamber means combined with air-fuel mixture...

F02P 514

Patent

active

057718628

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND INFORMATION

A knock control process is described in German Patent No. 40 08 170, where the firing angle is adjusted by using an engine characteristics map based on the operating parameters detected, and when knocking occurs, the firing angle is retarded to prevent knocking. Then the retarded firing angle is adjusted back to the mapped firing angle by advancing it incrementally. With this known knock control method, the operating range of an internal combustion engine is subdivided into various ranges. On leaving an operating range during operation of the internal combustion engine, the instantaneous firing angle is saved, and when the internal combustion engine is operated in this range again, the saved firing angle is output as the starting value.


SUMMARY OF THE INVENTION

The process according to the present invention has the advantage, in comparison with the known process, that it prevents sudden changes in firing angle. Therefore, there are no sudden changes in engine torque either, so driving comfort is improved.
It is advantageous to retain the firing angle from the preceding operating range that was the prevailing firing angle when leaving this operating range for operation in the new operating range if the load and/or speed dynamics when changing ranges do not exceed a predefined value; the value that can be predefined is determined for the various operating conditions in the application and is saved in a memory. In addition, it is advantageous to calculate a representative value for the firing angles that have occurred in the previous operation of the internal combustion engine in this range and to use this value as the starting value for the firing angle for operation of the internal combustion engine after changing ranges. Ultimately, the engine characteristics map in the microprocessor can be continuously updated on the basis of operating parameters for output of the firing angle so the knock limit is constantly being learned by the microprocessor. This can be accomplished, for example, by having the last firing angle before occurrence of knocking entered in the engine characteristics map as the new firing angle for this operating point. Another possibility is for the first firing angle after knocking occurs to be entered in the engine characteristics map. It is also conceivable to apply a small correction such as a definable firing angle displacement .DELTA.ZW to the firing angle before knocking occurs and then enter this value in the engine characteristics map. Moreover, it is also possible for this correction of the mapped firing angle to be implemented only if the firing angle saved in the engine characteristics map differs from the new firing angle to be entered in the engine characteristics map by a predetermined difference DZW. This has the advantage that it ensures operation of the internal combustion engine as close to the knock limit as possible.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 show a schematic diagram for an adaptive knock control process.
FIG. 2 an adaptive engine characteristics map.
FIG. 3 illustrates the change in the firing angle on the basis of the process according to the present invention, and
FIG. 4 show a diagram of the individual process steps.


DETAILED DESCRIPTION

FIG. 1 shows a block schematic for carrying out the process of adaptive knock control. The internal combustion engine (not shown) is operated with a controller 1 that has a knock sensor analysis circuit 2, a microprocessor 3, an analog-digital converter 4 and a firing output stage 5. One or more knock sensors 6 are provided on the engine block of the internal combustion engine and are connected to the knock sensor analysis circuit 2. Knock sensor analysis circuit 2 is connected to microprocessor 3 via analog-digital converter 4. The measured parameters of the internal combustion engine are also sent to microprocessor 3. Thus, for example, the load L, which is determined from the throttle valve angle setting and/or the intake manifold pressure, the speed n and temperature T are sent to

REFERENCES:
patent: 5531201 (1996-07-01), Boverie et al.
patent: 5560337 (1996-10-01), Bolander et al.
patent: 5598822 (1997-02-01), Fujishita et al.
patent: 5608633 (1997-03-01), Okada et al.

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