DE102013021528A1 - Method for cylinder suppression in an internal combustion engine - Google Patents

Abstract

The invention relates to a method for cylinder suppression in a combustion engine of a motor vehicle comprising a plurality of cylinders, in which at least one of the cylinders is switched off and at least a second of the cylinders is operated in a switching operation of a transmission of the motor vehicle, the second cylinder having a stratified one Burning process is operated.

Description

The invention relates to a method for cylinder suppression in an internal combustion engine according to the preamble of patent claim 1.

Such a method is for example the DE 42 39 711 B4 to be known as known. The internal combustion engine is designed here as a reciprocating internal combustion engine and comprises a plurality of combustion chambers in the form of cylinders. In the method, at least one first of the cylinders is switched off and at least one second of the cylinders operated in a switching operation of a transmission of the motor vehicle. In the context of the shutdown of the cylinder, an introduction of fuel into the deactivated cylinder as well as an ignition in the deactivated cylinder, so that the at least one deactivated cylinder is operated in an unfired operation, that is, non-fired. Thus, the at least one deactivated cylinder is hidden. By switching off or hiding at least one of the cylinders and the fired operation of at least one other cylinder, a torque reduction is effected during the switching process.

While the first cylinder is switched off, the second cylinder is operated fueled, so that introduced into the second cylinder fuel, in particular directly injected. This results in the second cylinder, a fuel-air mixture which is ignited in the second cylinder and thereby burns.

As a rule, in the at least one second cylinder, which is operated as a fuel, the ignition of the fuel-air mixture is adjusted in the direction of late. In other words, an ignition timing at which the fuel-air mixture is ignited in the second cylinder is retarded.

This adjustment of the ignition timing takes place in comparison to a cylinder blanking beforehand operating state in which there is no shift of the transmission. In other words, is changed in a switching operation of an operating condition of the internal combustion engine for cylinder blanking, in the context of which the cylinder is turned off and usually the ignition timing of the second cylinder is adjusted in the late direction.

This cylinder suppression can be a gentle and comfortable switching operation. However, a disadvantage of the known method is the fact that it can lead to misfiring or incomplete combustion in the late-adjustment of the ignition. As a result, unburned air-fuel mixture can remain in the fired cylinder or be ejected first from the second cylinder and then sucked in again in the following work cycle. In fired cylinders, which are to fire several times in the cylinder blanking, so go through several cycles, it may come to undefined air-fuel mixtures in the combustion chamber of the fired cylinder, so that it can lead to uncontrolled combustion conditions such as a pre-ignition or a delayed combustion, which can eventually lead to damage to the internal combustion engine.

Object of the present invention to provide a method of the type mentioned, in which uncontrolled combustion conditions such as pre-ignition can be avoided.

This object is achieved by a method having the features of patent claim 1. Advantageous embodiments with expedient and non-trivial developments of the invention are specified in the remaining claims.

In order to provide a method of the type specified in the preamble of claim 1, in which uncontrolled combustion conditions such as pre-ignition can be avoided in fired operated second cylinder, it is inventively provided that the second cylinder is operated with a layered combustion process. In other words, according to the invention, a stratified operation of the fired, second cylinder with stratified combustion or with a stratification of the fuel-air mixture is provided. By this stratification of the mixture or by the stratified combustion during the cylinder suppression during the switching operation of the transmission, for example, the full, provided by an exhaust gas turbocharger boost can be obtained while reducing the provided by the internal combustion engine torque (engine torque) according to a predetermined torque from the transmission.

The cylinder blanking is thus a so-called engine torque intervention, in which, in order to realize a smooth and comfortable circuit, the torque provided by the internal combustion engine is reduced in relation to an operating state that anticipates the gearshift operation. In order to avoid now uncontrolled combustion conditions such as Vorentflammungen, the stratified operation is provided. As a result, a particularly stable ignition of the mixture is generated. In addition, it comes to a clean burning of the mixture. A stay of Reactive residual gas and any pre-ignition in a subsequent cycle can be prevented. In addition, the method according to the invention enables the representation of a particularly fast switching operation as well as reproducible switching operations.

It has proven to be particularly advantageous if the ignition time for the stratified combustion process is adjusted to early or toward early. In other words, it is provided in comparison to the shift operation anticipated operating state that the ignition timing at which the fuel-air mixture is ignited in the second cylinder, is moved toward early. As a result, a particularly stable ignition of the mixture can be generated and a clean burn can be ensured.

A further embodiment is characterized in that the second cylinder changes alternately to another cylinder after its duty cycle. It can be particularly advantageously provided that the fired second cylinder cyclically alternately alternates to another cylinder. Furthermore, it can be provided that the fired second cylinder alternately alternates in a rolling manner with another cylinder.

Even if at later ignition the fuel-air mixture in the second cylinder is initially not completely burned and the still at least partially combustible fuel-air mixture in the following cycle returns to the second cylinder, the re-sucked mixture in the duty cycle, the is followed by a fired duty cycle of the second cylinder, not burned, since the second cylinder is no longer operated in the subsequent cycle, so that ignition of the re-sucked mixture is omitted. The partially unburned mixture entering the second cylinder is expelled in the next cycle. A new fuel-air mixture is formed again in the second cylinder only when the second cylinder is to be operated again fired and then also supplied with fuel again. After completion of a single fired duty cycle of the second cylinder, another cylinder of the internal combustion engine is operated alternately.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the figure description and / or alone in the single figure can be used not only in the respectively indicated combination but also in other combinations or alone, without the frame to leave the invention.

The drawing shows in the single FIGURE is a flow diagram illustrating a method for cylinder suppression in a plurality of cylinders comprising an internal combustion engine of a motor vehicle, wherein at a switching operation of a transmission of the motor vehicle at least a first of the cylinders off and at least a second of the cylinder operated operated with the second cylinder operated by a stratified combustion process.

FIG. 1 is a flow chart illustrating a method of operating an internal combustion engine of a motor vehicle. In particular, the flowchart shown in the figure serves to illustrate a method for cylinder suppression in the internal combustion engine.

The internal combustion engine is designed as a reciprocating internal combustion engine and comprises a plurality of combustion chambers in the form of cylinders. The internal combustion engine serves to drive the motor vehicle. The motor vehicle also includes a transmission with a plurality of switchable gears. A change from one of the gears to another of the gears is referred to as a "shift". In the course of such a shift, one gear is designed and the other gear engaged. The gears have different translations from each other, so that a torque provided by the internal combustion engine is converted in one of the gears with a different ratio than in another of the gears.

The internal combustion engine comprises an output shaft in the form of a crankshaft, via which the internal combustion engine provides the torques for driving the motor vehicle.

Prior to a switching operation of the transmission, the internal combustion engine is operated in a first step S1 in a normal operation. In this normal operation, that is, in the first step S1, there is no switching operation of the transmission. In other words, a switching operation is omitted in the first step S1. In the first step S1, there is no cylinder blanking.

If it now comes to a switching operation of the transmission, so in a second step S2 of the method, a so-called cylinder blanking is performed in the internal combustion engine. Through this cylinder suppression is during the switching process of the Internal combustion engine generated and provided via its crankshaft torque compared to the first step S1, that is, compared to the normal operation at least briefly lowered. As part of the cylinder blanking at least a first of the cylinder is hidden, that is switched off, so that the first cylinder is not supplied with fuel, at least during a first cycle of the first cylinder. In addition, there is no ignition in the first cylinder during the first cycle.

However, in order to maintain a minimum torque, at least a second of the cylinders is fired in at least a first duty cycle of the second cylinder during the second step S2, that is, during the gearshifting of the transmission. This means that the second cylinder is supplied with fuel during its first cycle. For example, the fuel is injected directly into the second cylinder in the first cycle of operation of the second cylinder. This results in the second cylinder, a fuel-air mixture, which is ignited in the second step S2 and in the first cycle of the second cylinder to a predetermined ignition timing. As a result, combustion of the fuel-air mixture in the second cylinder is effected in its first cycle.

Such a duty cycle is commonly referred to as a "work cycle". Such a work cycle includes in the internal combustion engine, which operates on the four-stroke principle, an intake stroke, a compression stroke, a power stroke and an exhaust stroke, which is also referred to as Ausschiebetakt. Furthermore, such a work cycle comprises two complete revolutions of the crankshaft.

In order to avoid now uncontrolled combustion conditions and in particular unwanted Vorentflammungen and to realize particularly fast switching operations and reproducible switching operations, it is provided that the second cylinder is operated in a layered manner in the second step S2 and in the first cycle of the second cylinder. In other words, the second cylinder is operated in its first cycle with a stratified combustion process. As a result of this stratified operation, a stoichiometric or rich mixture is present in a first subregion of the second cylinder, while in a different, second subregion there is a very lean mixture. Globally, there is a lean mixture in the second cylinder in its first cycle.

Moreover, in the second step S2, the ignition timing is advanced toward the first step S1 (normal operation). Due to the stratified combustion in the second cylinder and the early position of the ignition, which is also referred to as the ignition angle, a particularly stable ignition of the mixture is generated and ensures a clean burn. Remaining reactive residual gas and a possible pre-ignition in a subsequent to the first cycle second cycle of the second cylinder can be prevented.

If the switching operation and the cylinder blanking (torque reduction) are completed, the first step S1, that is to say the normal operation, can be connected to the second step S2 again.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4239711 B4 [0002]

Claims (3)

Method for cylinder blanking in a combustion engine of a motor vehicle comprising a plurality of cylinders, in which at least one of the cylinders is switched off and at least one second of the cylinders is operated in a switching operation of a transmission of the motor vehicle, characterized in that the second cylinder has a stratified combustion method is operated. A method according to claim 1, characterized in that the ignition timing for the stratified combustion method is advanced. Method according to one of claims 1 or 2, characterized in that the second cylinder alternates after its working cycle alternately to another of the cylinder.

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