Method for operating the vehicle engine for regenerating the solid particle filter

Abstract

The subject matter of the invention is a method for operating a vehicle engine for regenerating the solid particle filter in the idling mode, in which the pre-ignition is delayed in such a way that the actual ignition takes place at the time at which the piston is in the position after the top dead centre, in the direction of rotation of the crankshaft. At the same time, the ignition timing of the fuel into the intake air in the combustion chamber of at least one cylinder is shortened in such a way that the mixing ratio λ of 1 is increased by at least 5%.

Description

[0001] Method for operating the vehicle engine to regenerate the

[0002] Solid particle filter

[0003] Technical subject area

[0004] The invention relates to the field of the operation of passenger car engines, in particular focusing on the operation of a vehicle engine with multi-point injection for the regeneration of a solid particulate filter, which runs in idle mode.

[0005] State of the art: Methods for regenerating underfloor particulate filters in passenger cars are known today. For example, document US20180334977 A1 discloses a method and system for regenerating a soot filter for vehicles with internal combustion engines, where the system includes a catalytic converter and an underfloor soot filter. In this method, the filter load is monitored with a sensor, and the engine operation is adjusted accordingly.

[0006] Furthermore, document US20190032585 A1, for example, discloses a method and system for regenerating a soot filter. Here, the engine cylinders operate alternately with a lean and a rich fuel mixture, with the unburned fuel from the rich-fuel cylinders interacting with the residual oxygen from the lean-fuel cylinders near the soot filter. The reaction is exothermic, heating the soot filter. The system therefore requires pumps to bring secondary air into the system.

[0007] The underfloor soot filter can be advantageously used in vehicles that lack sufficient space in the engine compartment to safely install the soot filter next to the engine. These underfloor filters are located significantly farther from the engine, which poses a problem with the sufficient filter heating required for effective filter regeneration at low load or while the engine is idling. Therefore, various support systems are used to ensure adequate filter heating, such as a pre-catalyst and a secondary air supply. These underfloor systems are very complicated, which significantly increases production costs.

[0008] From the point of view of reducing production costs, it would therefore be desirable to develop a method for operating the vehicle engine for the regeneration of the solid particulate filter that does not require a complicated design of the exhaust system or major interventions in the engine design and ensures sufficient regeneration of the solid particulate filter in the required quality at idle and low engine load.

[0009] Summary of the invention

[0010] The present solution for a new method for operating a vehicle engine to regenerate a particulate filter was proposed to reduce manufacturing costs by eliminating a complex support system.

[0011] The shortcomings of the prior art solutions are eliminated by the proposed method for operating the vehicle engine at idle for regeneration of the particulate filter. This method involves delaying the ignition advance so that ignition occurs at the time the piston is in the position after top dead center. At the same time, the fuel injection time into the intake air in the combustion chamber of at least one cylinder is shortened so that the mixture ratio λ is increased from 1 by at least 5 percent. These changes increase the exhaust gas temperature sufficiently to enable regeneration of the particulate filter when using a simplified exhaust line that includes only the catalyst and the particulate filter.Advantageously, this method for operating the vehicle engine to regenerate the solid particulate filter in engines with multi-point injection is implemented in idle mode and at low engine load.

[0012] Preferably, the multi-point injection engine comprises at least one cylinder with a piston moving in the cylinder and a combustion chamber between the piston moving in the cylinder and the spark plug. Furthermore, each cylinder preferably comprises an intake valve, an exhaust valve, and a spark plug on top, with the spark plug being arranged in the cylinder head, most often midway between the intake valve and the exhaust valve, with these valves preferably each being arranged on an opposite side of the combustion chamber. The engine is preferably controlled via the engine control program in the engine control unit. An exhaust line comprising a catalytic converter and a solid particulate filter in series is preferably arranged behind the engine. The exhaust line is preferably arranged in the underfloor space of the vehicle.This simplification of the exhaust piping system, in which the exhaust piping does not include the pre-catalyst on the particulate filter and the secondary air supply support system, significantly reduces manufacturing costs and eliminates the complex hardware of the underfloor system.

[0013] Pre-ignition is the point in time at which the electric spark jumps at the spark plug, followed by the ignition of the gasoline-air mixture, usually before the piston reaches top dead center and thus before the piston, in a spark-ignition internal combustion engine, reaches the position closest to the cylinder head. With pre-ignition retardation, the fuel mixture is preferably ignited when the piston is located past top dead center in the direction of rotation of the crankshaft. An advantage of the method for operating the vehicle engine to regenerate the particulate filter is that pre-ignition is retarded. This is achieved by changing data in the engine control program, in the engine control unit.

[0014] By delaying the ignition advance, the exhaust gases flow into the exhaust at a significantly higher temperature after the exhaust valve opens. The exhaust gases heated in this way can be used to heat the particulate filter to a temperature sufficient to burn off the soot in the filter.

[0015] The ignition advance retardation rate is preferably at least twice the usual ignition advance retardation rate used to warm up the catalyst after a cold engine start, when the catalyst has reached the temperature required to catalyze the chemical reactions in the exhaust gas. These are exothermic catalytic reactions that generate only a small amount of heat compared to the extreme ignition advance retardation. Advantageously, the ignition advance retardation is dependent on engine speed, with higher idle speeds requiring a shorter ignition advance retardation. The ignition advance retardation leads to a reduction in the effective efficiency of the engine and thus to a decrease in engine power.In order to keep engine power constant during regeneration of the particulate filter at idle speed, even at low engine load and thus with reduced engine efficiency, the engine throttle valve is preferably opened more widely than during operation without pre-ignition delay, thereby increasing the flow of working fluid through the engine. The opening of the engine throttle valve is preferably controlled by a program in the engine control unit. By shortening the injection time of the fuel into the intake air, the fuel mixture is advantageously enriched. The mixture enrichment is advantageously achieved by a data change in the engine control program with multi-point injection in the control unit of this engine. The injection time of the fuel into the intake air is shortened in at least one combustion chamber such that the mixture ratio λ is increased from 1 by more than 5%.The mixture ratio A expresses the ratio of the weight of air in the mixture to the weight of fuel and the theoretical air quantity. The value 1 represents the so-called stoichiometric ratio, where, depending on the chemical composition of the fuel, approximately 14.8 kg of air is required to burn 1 kg of fuel. By shortening the injection time, a higher oxygen content is preferentially achieved in the combustion gases produced after the combustion of a slightly lean fuel mixture in the engine's combustion chamber. Thanks to the presence of oxygen, the soot in the particulate filter burns at a sufficient temperature, thus regenerating the filter.

[0016] The time between the combustion of the fuel mixture in the cylinder and the opening of the exhaust valve of the engine cylinder is advantageously shortened in proportion to the degree of ignition advance retardation. By shortening this time, the energy of the hot exhaust gases in the cylinder cannot be transferred to the piston to perform mechanical work on the engine or dissipated for engine cooling, and the exhaust gas temperature at the engine outlet is advantageously significantly increased. The increase in exhaust gas temperature is preferably at least twice the standard ignition advance retardation. In addition, a further increase in exhaust gas temperature, to a lesser extent, is advantageously achieved by an exothermic reaction in the catalytic converter. This is then advantageously used to increase the temperature of the individual components in the exhaust line. The individual components of the exhaust line preferably include a catalytic converter and a solid particulate filter.Thanks to the high temperature of the particulate filter and the oxygen content from the engine exhaust gases, the soot in the particulate filter is burned, thereby regenerating the particulate filter.

[0017] The ignition advance is preferably retarded to a maximum value at which ignition in the combustion chamber has not yet failed. With extreme ignition advance retardation at a given engine speed, ignition must preferably not fail, and thus combustion of the fuel mixture in the engine's combustion chamber must not fail. The failure of ignition advance is preferably verified by displaying cylinder pressure and analyzing the unburned hydrocarbon emissions. Explanation of drawings

[0018] The essence of the invention is further explained by means of embodiments which are described with the aid of the accompanying drawings, which show:

[0019] Fig. 1 Schematic representation of individual steps leading to the regeneration of the solid particle filter in an embodiment of the simplified control algorithm without feedback

[0020] Fig. 2 Schematic representation of individual steps leading to the regeneration of the solid particle filter in an embodiment of the extended control algorithm by means of feedback on the temperature in the solid particle filter

[0021] Embodiments of the invention

[0022] The invention is explained in more detail using exemplary embodiments with reference to the corresponding drawings.

[0023] The subject of the invention is a method for operating a vehicle engine for regenerating the particulate filter in idle mode, in which the pre-ignition is delayed so that ignition occurs at the time when the piston is in the position after top dead center. At the same time, the injection time of the fuel into the intake air in the combustion chamber of at least one cylinder is shortened such that the mixture ratio λ is increased from 1 by at least 5 percent.

[0024] In a first exemplary embodiment, the multi-point injection engine comprises four cylinders, where each cylinder contains a piston and a combustion chamber. In another embodiment, the engine can comprise a smaller number of cylinders, down to one. In another embodiment, the engine can also comprise more than four cylinders. Furthermore, each cylinder has an intake valve, an exhaust valve, and a spark plug arranged in the cylinder head. The engine is controlled via the control program in the engine control unit. Arranged behind the engine is an exhaust line which comprises, in a row, a catalytic converter directly on the vehicle engine and a particulate filter in the vehicle underfloor area. In this exemplary embodiment, the exhaust line is preferably arranged in the underfloor space of the vehicle.In another embodiment, the exhaust pipe can be located in the immediate vicinity behind the engine under the hood.

[0025] In the multi-point injection engine control program of this engine, a data change is made in the control unit to enable extreme retardation of the ignition advance, which triggers the step of the instruction from the control unit in Fig. 1 and Fig. 2. This change causes the electrical spark to jump to the spark plug in the combustion chamber at the time when the piston is in the position past top dead center due to the crankshaft rotation. The ignition advance in this embodiment is retarded by twice the usual retardation rate of the ignition advance, which is used during the period after a cold engine start, while the catalyst warms up to operating temperature for the catalytic reaction. These are exothermic catalytic reactions that generate only a small amount of heat compared to the extreme retardation of the ignition advance.

[0026] In addition, in the engine control program with multipoint injection, a data change is made in the control unit of this engine to shorten the injection time of the fuel into the intake air in the cylinder's combustion chamber by increasing the mixture ratio λ from 1 by at least 5 percent. By shortening the injection time of the fuel into the intake air, the fuel mixture is depleted, resulting in a slightly higher oxygen content in the engine exhaust gases flowing into the exhaust pipe. Thanks to the presence of oxygen, the soot burns in the sufficiently heated particulate filter, thus regenerating the filter. The depletion of the fuel mixture step is shown in Fig. 1 and occurs simultaneously with the ignition advance retardation step, followed by the exhaust valve opening step and the exit of the hot exhaust gases from the engine into the exhaust pipe.In contrast, in the version of the extended control algorithm shown in Fig. 2, which uses feedback to the temperature in the particulate filter, the step of depleting the fuel mixture only takes place when the condition of reaching the minimum temperature in the particulate filter is met. Combustion of the stoichiometric mixture releases more heat energy, and therefore the advantage of this version is faster heating of the particulate filter. The temperature of the particulate filter can be measured using special temperature sensors upstream or downstream of the filter, as well as by correcting this temperature using a computational model.

[0027] In this exemplary embodiment, after retarding the ignition advance, the time between the combustion of the fuel mixture in the cylinder and the opening of the exhaust valve of the engine cylinder is reduced so that the exhaust valve opens only shortly after the combustion of the fuel mixture in the engine cylinder. By shortening this time, the temperature of the exhaust gases at the engine outlet increases, so that the energy of the hot combustion gases does not have time to be transferred to the piston to induce mechanical energy or to be dissipated for engine cooling. The hot combustion gases flow into the exhaust and increase the temperature of the individual components in the exhaust line, thereby increasing the temperature of the catalytic converter and the particulate filter.The exhaust temperature can be up to twice as high with the ignition advance retardation compared to the standard ignition advance retardation, so that the exhaust temperature at the engine outlet can exceed 700°C even at idle. Furthermore, a further increase in the exhaust temperature, albeit to a lesser extent, is achieved by an exothermic reaction in the catalyst. Thanks to the sufficiently high temperature of the particulate filter (at least 600°C) and the oxygen content of the engine exhaust gases, the soot in the particulate filter is burned, thereby regenerating the particulate filter.

[0028] Retarding the ignition advance reduces the effective efficiency of the engine. In order to maintain the same engine power at low load or constant idle speed during an extreme retardation of the ignition advance, the engine throttle valve is opened more widely, thereby increasing the flow of the working fluid through the engine. The throttle valve opening is controlled by a program change in the engine control unit. The ignition advance is retarded to a maximum value at which ignition still does not fail. With an extreme retardation of the ignition advance at a certain speed, ignition must not fail, and thus there cannot be a failure of the fuel mixture in the engine's combustion chamber. The failure of ignition can be verified by displaying the cylinder pressure and by analyzing the emissions of unburned hydrocarbons.

[0029] In an alternative embodiment, the injection time of the fuel into the intake air is shortened such that the value of the mixture ratio λ is increased from 1 by more than 10%, the further procedure in this embodiment being analogous to the first exemplary embodiment.

[0030] In another exemplary embodiment, the pre-ignition is retarded by up to three times the usual pre-ignition retardation rate used to warm the catalyst after a cold start of the engine, whereby the non-missing ignition condition is met. Furthermore, this exemplary embodiment is designed analogously to the first exemplary embodiment. In a further exemplary embodiment, the method for regenerating the particulate filter is applied to an engine with direct injection.

Claims

Patent claims 1. A method for operating a vehicle engine for regenerating a particulate filter in idle mode, characterized in that the pre-ignition is delayed so that the ignition occurs at the time when the piston is in the position behind the top dead center, and at the same time the injection time of the fuel into the intake air in the combustion chamber of at least one cylinder is shortened so that the value of the mixture ratio λ increases from 1 by at least 5% 2. A method of operating a vehicle engine for regenerating a particulate filter according to claim 1, characterized in that the pre-ignition retardation rate is at least twice as high as the pre-ignition retardation rate used to warm up the catalyst in the period following a cold start of the engine.

3. A method for operating a vehicle engine for regenerating a solid particle filter according to one of the preceding claims, characterized in that the injection time of the fuel into the intake air in at least one combustion chamber is shortened such that the value of the mixing ratio λ increases from 1 by more than 10%.

4. A method for operating a vehicle engine for regenerating a solid particulate filter according to one of the preceding claims, characterized in that the time between the combustion of the fuel mixture in the cylinder and the opening of the exhaust valve of the engine cylinder is further shortened.

5. A method for operating a vehicle engine for regenerating a solid particle filter according to one of the preceding claims, characterized in that the pre-ignition is delayed to a maximum value at which the ignition does not fail.

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