DE19823513C1 - Engine catalyser heating method - Google Patents

Abstract

The catalyser heating method uses auxiliary injection of a fuel/air mixture in the engine combustion chambers (5) in the vicinity of the lower dead-point of each piston, for providing exothermic energy for heating the engine exhaust gas. The ignition timing point of the engine (6) may be adjusted during the catalyser heating mode, with the engine operated with a lambda value for the fuel/air mixture of approximately 1.

Description

The invention relates to a method for heating a Ka talysators at the start of a working with excess air Internal combustion engine according to the preamble of claim 1.

To know the fuel consumption of Otto internal combustion engines To reduce ter, internal combustion engines come with lean Combustion is increasingly used.

The size of the excess air in a lean operated Otto engine is limited in that the mixture must remain ignitable in the combustion chamber. A particularly poor Operation can be achieved with stratified loading operation, so that sufficient in the combustion chamber around the spark plug there is an ignitable fuel / air mixture with which Distance to the spark plug, however, the excess air increases. One method for achieving this stratified charge is in the publication by R. Houston, G. Cathcart, "Combustion and Emissions Characteristics of Orbital's Combustion Process Applied to Multi-Cylinder Automotive Direct Injected 4-Stroke Engines ", Society of Automotive Engineers' SAE Paper 980153, Volume SP 136 described. Known as the OCP system Process is fuel under pressure in a pre injected chamber and also independently controlled air blown into this antechamber, each combustion chamber one own antechamber is assigned. This fuel / air Mixture is then in under pressure (usually 6.5 bar) the combustion chambers of the internal combustion engine are injected. Here the internal combustion engine works partially with fully open Throttle valves. By premixing and injecting Air / fuel mixture can be ensured that in the There is an ignitable mixture in the area of the spark plug and the overall, a high excess of air is realized.  

Such internal combustion engines with lean combustion need a Ka to meet the required exhaust emission limit values Talysator in the exhaust system. The effectiveness of such a kata lysators usually sets only after a certain operation temperature. At the time to reach the operation temperature and thus the amount of emissions emitted To minimize pollutants, measures are necessary in order to Catalyst to its operating temperature as quickly as possible bring.

Usually for rapid heating of the catalyst a secondary air pump with an associated valve hen, the air into the exhaust gas during the warm-up phase Blows internal combustion engine. Due to the additional Chen excess air in the exhaust gas is said to still be the efficiency not warm catalyst to be improved.

It is an object of the present invention to provide a method for Heating up a catalytic converter when starting one after the OCP System working internal combustion engine with which in achieved rapid heating as simply as possible becomes.

The task is ge by the features of the main claim solves.

According to the invention at a time when the Piston near bottom dead center is in front of the Extension cycle an additional injection of power substance / air mixture carried into the combustion chamber. Thereby there is no need for a secondary air pump because the post-injected fuel / air exothermic energy Mixture for rapid heating of the catalyst leads.  

The exothermic reaction of the post-injected force Substance / air mixture takes place in the exhaust system, which causes the Exhaust gas temperature upstream and in the catalytic converter.

Advantageous embodiments of the invention are in the Un marked claims.

The invention is described below with reference to the a Zige figure of the drawing in one embodiment explained.

In Fig. 1, an internal combustion engine operating according to the OCP system is shown schematically. The internal combustion engine 6 has a catalytic converter 7 in its exhaust tract 8 . The operation of the internal combustion engine 6 with excess air is regulated by an operating control device 9 . In each combustion chamber 5 - the number depends on the type of internal combustion engine, single-cylinder internal combustion engines are also possible - a premixed fuel / air mixture is injected via an associated prechamber 1 by an injector 4 . The premixing takes place in the prechamber 1 , into which a separately regulated fuel injection takes place via a fuel injector nozzle 2 and a separately regulated air injection via an air injection nozzle 3 . Fuel injection and air injection into the pre-chamber 1 as well as the injection via the injector 4 are controlled by the operating control device 9 via lines (not shown). Further, the drive controller 9 detects Be diverse parameters of the internal combustion machine, in particular, as illustrated, the turaufnehmer from a temperature 10 detected temperature of the catalyst. 7 If no temperature sensor 10 is provided, the operating control unit 9 can also regulate the temperature of the catalyst 7 in another way, e.g. B. calculated by measuring the exhaust gas temperature or from a model.

To quickly heat up the catalytic converter 7 after the internal combustion engine 6 has started , the operating control device 9 simultaneously carries out the following three measures:

• a) At a point in time around the bottom dead center of each piston standing before the push-out cycle, a post-injection with premixed fuel / air mixture into the combustion chambers 5 takes place via the injector 4 .
• b) The total force supplied to the internal combustion engine The substance / air mixture is switched on with a lambda value λ ≈ 1 splashes or possibly greased. Here is the mixture homogeneous. The enrichment also causes the distillate to run engine with less uneven running.
• c) The ignition takes place later than in normal operation of the burner engine usual, so that there is an increase in filling gives.

These three measures result in a higher exhaust gas temperature, which means that the catalytic converter reaches its operating temperature more quickly. The post-injection of additional fuel / air mixture, which is atomized well due to the premixing, releases exothermic energy in the exhaust tract 8 , which heats the exhaust gas. The post-injection preferably follows shortly before the exhaust valve opens. This additional fuel / air mixture supplied in a post-injection is selected as a function of the air mass flow of the internal combustion engine 6 and the lambda value of the ignited mixture. The additional mixture is set so that the fuel / air mixture of the total mixture (normal combustion and post-injection) remains lean, ie the lambda value is above 1.

Of course, the three measures a) to c) will depend gig of operating parameters, such as speed and filling reali siert.

Claims (5)

1. A method for heating a catalytic converter when starting an internal combustion engine with excess air, in whose combustion chambers a pressurized fuel / air mixture is injected, which was mixed in the associated antechambers by a separately controlled fuel injection and a separately controlled air injection, thereby indicates that for heating the catalyst depending on the operation, a post-injection of the fuel / air mixture into the combustion chambers is carried out at a time around bottom dead center before the push-out cycle. 2. The method according to claim 1, characterized in that the The ignition point is later than in normal operation Internal combustion engine and the filling is increased. 3. The method according to claim 1 or 2, characterized in that the fuel / air supplied to the internal combustion engine Mixture has a lambda value close to or equal to one. 4. The method according to any one of the preceding claims, characterized characterized in that the composition of the injected fuel / air mixture depending on the the Air mass flow supplied to the internal combustion engine and the Lambda value of the fuel / air mixture of the normal ver burning is selected. 5. The method according to claim 4, characterized in that the Composition of the post-injected fuel / air Mixture is chosen so that the total mixture of normal Injection and post-injection to an exhaust gas upstream of the catalyst leads, ent ent a lambda value greater than 1 speaks.