Control system for a combustion engine

Details Control system for a combustion engine Control system for a combustion engine

1996-09-25

1998-11-03

Argenbright, Tony M.

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

123478, 123676, F02D 4114, F02D 3702

Patent

active

058292470

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND INFORMATION

This invention relates to a control system for a combustion engine.
In controlling a combustion engine it may sometimes be necessary to shift the ignition angle from the normal position in the direction of retarding it. Such a shift in ignition angle may be considered, for example, in conjunction with methods for reducing or preventing knocking during combustion or methods of reducing drive slip. As a rule, however, the exhaust gas temperature increases when the ignition angle is retarded. If the exhaust gas temperature is too high, it may damage the exhaust valves or the exhaust system, especially the exhaust gas catalyst. To prevent an unacceptably high exhaust gas temperature with the known control systems, the air-fuel mixture supplied to the combustion engine is enriched whenever the ignition angle exceeds a certain threshold value. The degree of enrichment is usually set as a function of the extent to which the threshold value is exceeded.
German Patent Application No. DE 41 03 419 A1 describes a control system for a combustion engine in which the air-fuel mixture is enriched when a signal indicating the efficiency of the engine drops below a threshold value. The efficiency is determined on the basis of the cylinder pressure. The exhaust gas temperature has no effect on the calculated efficiency.
An object of the invention is to prevent the exhaust gas temperature from rising to an unacceptable level.


SUMMARY OF THE INVENTION

The advantage of this invention is that components in thermal contact with the exhaust gas can be protected from damage caused by overheating.
The air-fuel mixture is enriched when a signal indicating the efficiency of the combustion engine either directly or indirectly is below a threshold value, the air-fuel mixture is enriched. It is especially advantageous here that the degree of enrichment is based very accurately on the actual requirements, thus preventing an over-rich mixture. This has an especially advantageous effect on the consumption and exhaust balance of the combustion engine.
An especially great reliability of this invention can also be achieved specifically by enriching the air-fuel mixture only when one or more secondary conditions are met. Secondary conditions include, for example, the elapse of an interval since the signal indicating efficiency drops below the threshold value or after the threshold value for the exhaust gas temperature or the catalyst temperature is exceeded.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a control system for a combustion engine.
FIG. 2 shows a circuit for controlling the enrichment of the air-fuel mixture in the combustion engine.
FIGS. 3a and 3b show the plots of two characteristics used in this invention.


DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a control system for a combustion engine in accordance with the present invention. A combustion engine 100 is supplied with an air-fuel mixture through an intake duct 102 and the exhaust gases are delivered to an exhaust channel 104. Intake duct 102 contains, as seen in the direction of flow of the air intake, an air flow sensor or air mass meter 106, such as a hot-film air mass meter, a temperature sensor 108 for sensing the intake air temperature, a throttle valve 110 and at least one injection nozzle 112. Exhaust channel 104 has, as seen in the direction of flow of the exhaust gas, an exhaust gas sensor 114 and a catalyst 116. A temperature sensor 118 for detecting the temperature of the combustion engine and an engine speed sensor 120 are mounted on combustion engine 100. Combustion engine 100 also has four spark plugs 122, for example, for igniting the air-fuel mixture in the cylinders.
The output signals mL of the air mass meter or air flow sensor 106, TAns of temperature sensor 108, .lambda. of exhaust gas sensor 114, TBKM of temperature sensor 118 and n of engine speed sensor 120 are sent to a central control unit 124 over appropriate connecting lines. Control unit 124 analyzes the sensor signals and controls injection nozzle(s) 112

REFERENCES:
patent: 4716873 (1988-01-01), Takaba et al.
patent: 4825836 (1989-05-01), Hirose
patent: 5027773 (1991-07-01), Shimomura et al.
patent: 5107815 (1992-04-01), Van Duyne
patent: 5156126 (1992-10-01), Ohkubo et al.
"Patent Abstracts of Japan", vol. 15, No. 457 (M-1181), abstract of JP-3-194153, Nov. 1991.

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