CZ2023187A3 - A method to set a vehicle engine mode for the particulate filter regeneration - Google Patents

Abstract

A method of adjusting the engine mode of a diesel particulate filter regeneration vehicle running in the idle mode includes the step of adjusting the ignition advance, in which step the ignition advance is delayed so that the ignition occurs when the piston is in the position beyond the top dead center, and the step of adjusting the injection time of fuel, while in this step, simultaneously with the ignition advance setting step, the time of fuel injection into the intake air in the combustion space of at least one cylinder is shortened so that the value of the mixing ratio λ is increased from the value of 1 by at least 5%. The mixing ratio λ expresses the ratio of the mass of the intake air to the mass of the air, which corresponds to the stoichiometric ratio of the mass of the air to the mass of the fuel.

Description

Method for setting a vehicle engine mode for particulate filter regeneration

Field of technology

The invention relates to the field of passenger car engine operation, and specifically focuses on setting up a multi-point injection vehicle engine for idling particulate filter regeneration.

Current state of the art

In the current state of the art, methods are known for regenerating under-floor particulate filters in passenger cars. For example, document US 20180334977 A1 discloses a method and system for regenerating a soot filter for vehicles with internal combustion engines, wherein the system includes a catalytic converter and an underfloor soot filter. In this method, the load on the filter is checked using a sensor, according to which the engine operation is adjusted.

Furthermore, for example, document US 20190032585 A1 discloses a method and system for regeneration of a carbon black filter. Here, the engine cylinders work alternately on a lean and rich fuel mixture, with the fact that near the soot filter unburned fuel from the cylinders working on a rich fuel mixture meets with residual oxygen from the cylinders working on a lean fuel mixture, while their reaction is exothermic in nature, resulting in heats the soot filter. In the system, it is therefore necessary to use pumps for the entry of secondary air into the system.

The underfloor soot filter can be advantageously used in vehicles that have a lack of space in the engine compartment for the safe placement of the soot filter right next to the engine. These underfloor filters are located significantly further from the engine, which creates a problem with sufficient heating of the filter necessary for functional regeneration of the filter at low load, i.e. when the engine is idling. Therefore, various support systems including, for example, an upstream catalyst and a secondary air supply are used to ensure sufficient heating of the filter. These under-floor systems are quite complicated, which greatly increases production costs.

From the point of view of reducing production costs, it would therefore be advisable to come up with a method of operating the vehicle engine for the regeneration of the particulate filter, which would not require a complex design of the exhaust system or a fundamental intervention in the engine structure, and which would ensure sufficient regeneration of the particulate filter in the required quality, both at idle and at low engine load.

The document EP 3655633 A1 describes in general the possibility of using the ignition advance delay and adjusting the mixing ratio to regenerate the particulate filter. However, this document does not describe the specific parameters of when to use this delay or how much delay is appropriate. It would therefore be advisable to come up with a solution that would provide more specific parameter values usable for particulate filter regeneration.

The essence of the invention

The presented solution of a new method for setting the vehicle engine mode for particulate filter regeneration was designed to reduce manufacturing costs by eliminating a complex support system.

The shortcomings of the solutions known from the state of the art are eliminated by the proposed method for setting the vehicle engine mode for the regeneration of the particulate filter taking place in idling mode. This method includes:

- 1 CZ 2023 - 187 A3 • The ignition advance adjustment step, in which the ignition advance is delayed so that the ignition takes place at the moment when the piston is in the position beyond the top dead center.

• The step of setting the fuel injection time, and in this step, simultaneously with the step of setting the ignition advance, the time of fuel injection into the intake air in the combustion chamber of at least one cylinder is shortened by increasing the value of the mixing ratio λ from the value of 1 by at least 5%.

Where the mixing ratio λ expresses the ratio of the mass of the intake air to the mass of the air, which corresponds to the stoichiometric ratio of the mass of the air to the mass of the fuel.

These modifications increase the temperature of the exhaust gases enough to allow regeneration of the particulate filter using a simplified exhaust manifold system comprising only the catalytic converter and particulate filter. Preferably, this method for setting the engine mode for regeneration of the particulate filter is implemented for engines with multi-point injection in idle mode and at low engine load.

A multi-point injection engine preferably includes at least one cylinder with a piston moving within the cylinder and a combustion space between the moving piston and the spark plug. Furthermore, each cylinder advantageously includes an intake valve, an exhaust valve and a spark plug from the top, with the spark plug being located in the cylinder head, most often in the middle between the intake valve and the exhaust valve, with these valves being located most often each on the opposite side of the combustion chamber. The engine is preferably controlled by the engine control program in the engine control unit. An exhaust pipe is preferably located behind the engine, including a sequentially arranged catalyst and a solid particle filter. The exhaust pipe is preferably located in the under-floor area of the motor vehicle. Due to this simplification of the exhaust manifold system, where the pre-catalyst of the particulate filter and the support system for the secondary air intake are not included in the exhaust manifold, the manufacturing costs are significantly reduced and the complex hardware of the under-floor system is eliminated.

Ignition advance is the moment when the electric spark jumps on the spark plug, resulting in the ignition of the gasoline-air mixture, usually before reaching the top dead center of the piston, and thus before reaching the position where the piston is closest to the cylinder head, in a gasoline internal combustion engine. When the ignition advance is delayed, the ignition of the fuel mixture takes place preferably when the piston is located behind the top dead center, in the direction of rotation of the crankshaft. Advantageously, in the method for setting the vehicle engine mode for regenerating the particulate filter, the ignition advance is delayed. This is achieved through a data change in the engine control program, in the engine control unit.

As a result of the ignition advance delay, exhaust gases with a significantly increased temperature advantageously flow into the exhaust after opening the exhaust valve. Exhaust gases heated in this way can advantageously be used to heat the particulate filter to a temperature sufficient to burn the soot in the filter.

The amount of advance ignition delay is preferably at least twice the usual amount of advance ignition delay used during the time after a cold start of the engine to heat the catalyst, when the necessary temperature for catalyzing chemical reactions in the exhaust gases is reached in the catalyst. These are exothermic catalytic reactions producing a certain smaller amount of heat compared to the extreme delay of the ignition advance. Advantageously, the ignition advance delay depends on the engine speed, where at higher idling speeds, a smaller ignition advance delay is needed. Delaying the ignition advance will cause a reduction in the effective efficiency of the engine, resulting in a drop in engine power. In order to maintain constant engine performance during regeneration of the particulate filter at idling speed and at low engine load, and therefore with reduced engine efficiency, the engine throttle is advantageously opened more than during operation without delaying the ignition advance, thereby increasing the flow of the working substance through the engine. The opening of the engine throttle is advantageously regulated by a program in the engine control unit.

- 2 CZ 2023 - 187 A3

By shortening the time of fuel injection into the intake air, the fuel mixture is advantageously lean. Depletion of the mixture is advantageously achieved by a data change in the control program of a multi-point injection engine in the control unit of this engine. The time of fuel injection into the intake air is advantageously shortened in at least one combustion space by increasing the value of the mixing ratio λ from the value of 1 by more than 5%. The mixing ratio λ expresses the mixing ratio of the mass of air in the mixture to the mass of fuel and the theoretical amount of air, where a value of 1 expresses the so-called stoichiometric ratio, where approximately 14.8 kg of air is needed to burn 1 kg of fuel, according to the chemical composition of the fuel. By shortening the injection time, a higher oxygen content is advantageously achieved in the exhaust gases from the engine, which are created after burning a slightly lean fuel mixture in the combustion chamber of the engine. Thanks to the presence of oxygen, at sufficient temperature in the particulate filter, soot burns and thus the filter regenerates.

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 delay of the ignition advance. By shortening this time, the energy of the hot exhaust gases in the cylinder does not have time to be transferred to the piston to perform the mechanical work of the engine or to be diverted to the cooling of the engine, and advantageously the temperature of the exhaust gases at the exit from the engine is significantly increased. The increase in exhaust gas temperature is preferably at least double the standard ignition advance delay. In addition, a further increase in the temperature of the exhaust gas, to a lesser extent, is advantageously achieved due to the exothermic reaction in the catalyst. This is then advantageously used to increase the temperature of individual parts in the exhaust pipe. The individual parts of the exhaust pipe preferably include a catalyst and a particulate filter. Due to the high temperature of the particulate filter and the oxygen content of the engine exhaust, soot burns in the particulate filter, which regenerates the particulate filter.

The ignition advance is advantageously delayed to a maximum value at which there is still no misfire in the combustion chamber. In the case of an extreme delay in the advance of the ignition at the given revolutions, there should preferably be no misfire, and thus no combustion of the fuel mixture in the combustion chamber of the engine. Misfire is preferably verified by cylinder pressure indication and unburned hydrocarbon emissions analysis.

Clarification of drawings

The essence of the invention is further clarified by examples of its implementation, which are described using the attached drawings, where on:

Fig. 1 shows schematically the individual steps leading to the regeneration of the particulate filter, in the implementation of a simplified adjustment algorithm without feedback;

Fig. 2 shows schematically the individual steps leading to the regeneration of the solid particle filter, in the embodiment of the extended adjustment algorithm using feedback on the temperature in the solid particle filter.

Examples of implementation of the invention

The invention will be further explained by examples of implementation with reference to the respective drawings.

The subject of the invention is a method for setting the vehicle engine mode for regeneration of the solid particle filter taking place in the idling mode, where the ignition advance is delayed so that the ignition takes place at the moment when the piston is in the position beyond the top dead center. At the same time, the time of fuel injection into the intake air in the combustion chamber of at least one cylinder is shortened by increasing the value of the mixing ratio λ from the value of 1 by at least 5%.

- 3 CZ 2023 - 187 A3

In the first exemplary embodiment, the multi-point injection engine includes four cylinders, each cylinder having a piston and a combustion chamber. In another embodiment, the engine may include as few as one cylinder. Also, in another embodiment, the engine may include more than 4 cylinders. Furthermore, each cylinder includes an intake valve, an exhaust valve and a spark plug located in the cylinder head. The engine is then controlled by the control program in the engine control unit. Behind the engine is an exhaust manifold including a sequential catalytic converter next to the vehicle's engine and a particulate filter under the vehicle's floor. In this exemplary embodiment, the exhaust pipe is conveniently located in the under-floor space of the motor vehicle. In another embodiment, the exhaust pipe can be located in the immediate vicinity behind the engine under the hood.

In the control program of a multi-point injection engine, a data change is made in that engine's control unit to allow extreme ignition advance delay, which initiates the instruction step from the control unit shown in Fig. 1 and Fig. 2. This change causes the electrical spark to jump to spark plugs in the combustion chamber at the moment when the piston is in the position beyond the top dead center due to the rotation of the crankshaft. In this embodiment, the ignition advance is delayed by twice as much as the usual amount of ignition advance delay used during the time after the cold start of the engine, during the heating of the catalyst to the operating temperature for the catalytic reaction. These are exothermic catalytic reactions producing a certain lesser amount of heat compared to the extreme delay of the ignition advance.

Furthermore, in the control program of the engine with multi-point injection, in the control unit of this engine, a data change is made that enables the time of fuel injection into the intake air in the combustion chamber of the cylinder to be shortened by increasing the value of the mixing ratio λ from the value of 1 by at least 5%. By shortening the time of fuel injection into the intake air, the fuel mixture is leaner, and this results in a slightly higher oxygen content in the exhaust gases from the engine, which flows into the exhaust manifold. Thanks to the presence of oxygen, soot burns in a sufficiently heated solid particle filter, and thus the regeneration of this filter. The step of depleting the fuel mixture is shown in Fig. 1 and takes place simultaneously with the step of delaying the advance of ignition, which are followed by the step of opening the exhaust valve and discharging the hot exhaust gases from the engine into the exhaust manifold.

In contrast, in the embodiment of the extended adjustment algorithm using feedback on the temperature in the particulate filter, shown in Fig. 2, the fuel mixture depletion step takes place only after the condition of reaching the minimum temperature in the particulate filter is met. By burning the stoichiometric mixture, more thermal energy is released, and thus the advantage of this design is faster heating of the particulate filter. The temperature of the particulate filter can be measured using special temperature sensors in front of the filter or behind the filter, as well as by correcting this temperature with a computer model.

In this exemplary embodiment, 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 after the ignition advance delay, and thus 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 exit from the engine will increase, and therefore the energy of the hot exhaust gases will not have time to transfer the piston to the action of mechanical energy or be diverted to the engine cooling. The hot exhaust gases flow into the exhaust and increase the temperature of individual parts in the exhaust pipe, thereby increasing the temperature of the catalytic converter as well as the particulate filter. The temperature of the exhaust gases can be up to twice as high as with the standard ignition delay, and therefore the temperature of the exhaust gases at the engine outlet can be higher than 700 °C even in the engine idling mode. In addition, a further increase in the temperature of the exhaust gas, albeit to a lesser extent, is achieved due to the exothermic reaction in the catalyst. Due to the sufficiently high temperature of the particulate filter, i.e. at least 600 °C, and the oxygen content of the engine exhaust, soot burns in the particulate filter, which regenerates the particulate filter.

By delaying the ignition advance, the effective efficiency of the engine is reduced. In order to maintain the same engine performance under low load, i.e. constant idling speed, with an extreme ignition advance delay, the engine throttle opens more, thereby increasing the working flow

- 4 CZ 2023 - 187 A3 substances by motor. Throttle opening is regulated using a program change in the engine control unit.

The ignition advance is delayed to a maximum value at which there is still no misfire. With an extreme delay in the advance of the ignition at the given revolutions, there must be no misfire, and therefore no combustion of the fuel mixture in the combustion chamber of the engine. Misfires can be verified by cylinder pressure indication or unburned hydrocarbon emissions analysis.

In an alternative embodiment, the time of fuel injection into the intake air is shortened by increasing the value of the mixing ratio λ from the value of 1 by more than 10%, while the further procedure in this embodiment is analogous to the first exemplary embodiment.

In another exemplary embodiment, the ignition advance is delayed up to three times the usual amount of ignition advance delay used during the time after the engine cold start to warm up the catalyst while maintaining the no misfire condition. Furthermore, this exemplary embodiment is solved analogously to the first exemplary embodiment.

In another exemplary embodiment, the method for regenerating a particulate filter is used for a direct fuel injection engine.

Claims (4)

1. A method for adjusting the engine mode of a diesel particulate filter regeneration vehicle running in the idling mode, characterized in that it includes: the step of adjusting the ignition advance, wherein • in this step, the ignition advance is delayed such that ignition occurs when the piston is in the position beyond the top dead center, and • the step of setting the fuel injection time, while in this step, simultaneously with the step of setting the ignition advance, the time of fuel injection into the intake air in the combustion chamber of at least one cylinder is shortened by increasing the value of the mixing ratio λ from the value of 1 by at least 5%, where the mixing ratio λ expresses the ratio of the mass of the intake air to the mass of air, which corresponds to the stoichiometric ratio of the mass of air to the mass of fuel. 2. A method for setting the vehicle engine mode for particulate filter regeneration according to claim 1, characterized in that in the step of setting the fuel injection time, the time of fuel injection into the intake air is shortened in at least one combustion chamber by increasing the value of the mixing ratio λ from a value of 1 by more than 10%. 3. A method for adjusting the engine mode of a particulate filter regeneration vehicle according to any one of the preceding claims, characterized in that it further comprises the step of adjusting the opening of the exhaust valve, in which step the time between the combustion of the fuel mixture in the cylinder and the opening of the exhaust valve of the cylinder is shortened engine. 4. A method for setting the vehicle engine mode for particulate filter regeneration according to any one of the preceding claims, characterized in that in the step of setting the ignition advance, the ignition advance is delayed to a maximum value at which misfire does not yet occur.