DE102015221546B4 - Internal combustion engine with internal flow connection - Google Patents

Abstract

Method for controlling a gas flow in an internal combustion engine with at least one first (1a) and at least one second cylinder (1b), an intake tract (2) and an exhaust tract (3), in which each cylinder (1a, 1b) has at least one intake passage and the exhaust gas passage of the first cylinder (1a) into a first exhaust manifold (3a) and the exhaust passage of the second cylinder (1b) into a second exhaust manifold (3b ), - the first exhaust manifold (3a) and the second exhaust manifold (3b) open into a third exhaust manifold (3c), - the intake manifold (2) has a first intake manifold (2a) which is inserted into a second intake manifold (2b) for the the second exhaust manifold (3b) upstream of the third exhaust manifold (3c) into an internal flow connection (4) to the third Ansaugkrümme r (2c) and a flow connection to the third exhaust manifold (3c) branches, - at the location of the branching a switching valve (5) is arranged, through which a gas flow from the second exhaust manifold (3b) to the exhaust tract (2) and / or to the intake ( 3), wherein during a regeneration at least one cylinder of the internal combustion engine (1) is deactivated and at least one cylinder (1a) of the internal combustion engine remains activated, and a gas flow from the deactivated cylinder through the internal flow connection (4) to the intake tract (2 S1) initiating a substoichiometric operation of the internal combustion engine (2), S2) deactivating at least one cylinder (1b) of the internal combustion engine (2), S3) adjusting the switching valve (5) in such a way that it moves in the direction of Intake tract (2) is fully opened and fully closed in the direction of the exhaust tract (3), so that a gas flow from the deactivated cylinder (1b) by the internal S flow connection (4) to the intake tract (2) is passed and exhaust gas from the active cylinder (1 a) through the exhaust gas duct (3) is passed.

Description

The invention relates to a method for controlling a gas flow in an internal combustion engine with an internal flow connection of an exhaust passage of a deactivatable cylinder to the intake of the cylinder.

In internal combustion engines, a catalytic aftertreatment of the exhaust gases has become established in order to comply with the legally prescribed emission values. Modern internal combustion engines often work to increase the efficiency with lean fuel-air mixtures with an excess of oxygen. Leaking nitrogen oxides can not be reduced in lean operation, since their catalytic reduction is possible only in a rich operation. The nitrogen oxides in the exhaust gas are therefore temporarily stored in lean-burn operation in a nitrogen oxide storage catalyst, also referred to as a lean NOx trap (LNT). If the absorption capacity of the LNT is exhausted, a cycle with a rich exhaust gas mixture or in a substoichiometric mode (λ <1) is carried out for the regeneration of the LNT. Such regeneration is also called rich purge. In this cycle, the cached nitrogen oxides are reduced to nitrogen in a nitrogen oxide reduction catalyst and the catalyst for the storage of nitrogen oxides free again.

Nitrogen oxide storage catalysts are subject to legal regulations for regular monitoring of their aging state. One way to monitor the function of a nitrogen oxide storage catalyst is by e.g. in an indirect method in which signals from oxygen sensors, e.g. Lambda sensors or UEGOs (Universal exhaust gas oxygen sensors), upstream and downstream of a nitrogen oxide storage catalyst can be recorded, which are related to known aging conditions of catalysts, whereby the functionality of the catalyst can be determined. All methods are subject to so-called performance requirements (IUPR), in which a minimum of control events must be performed during operation under real conditions. However, this minimum may be difficult to achieve. Since the kinetics of a nitrogen oxide storage catalyst depends primarily on the temperature, the control events depend on a temperature window in which a good separation of the measured values of the sensors can be observed. Furthermore, the function of a nitrogen oxide storage catalyst also depends on a volume flow of exhaust gas. It is therefore the object to provide suitable temperatures and volume flow of the exhaust gas during a control event of a nitrogen oxide storage catalyst.

This object is achieved by a method having the features of claim 1. Further advantageous embodiments and embodiments of the invention will become apparent from the dependent claims and claims, the figures and the embodiments.

• - jeder Zylinder mindestens einen Ansaugkanal und mindestens einen Abgaskanal aufweist,
• - der zweite Zylinder ausgebildet ist, deaktiviert zu werden,
• - der Abgaskanal des ersten Zylinders in einen ersten Abgaskrümmer und der Abgaskanal des zweiten Zylinders in einen zweiten Abgaskrümmer übergeht,
• - der erste Abgaskrümmer und der zweite Abgaskrümmer in einen dritten Abgaskrümmer münden,
• - der Ansaugtrakt einen ersten Ansaugkrümmer aufweist, der in einen zweiten Ansaugkrümmer für den ersten Zylinder und einen dritten Ansaugkrümmer für den zweiten Zylinder verzweigt,
• - der zweite Abgaskrümmer stromaufwärts des dritten Abgaskrümmers in eine interne Strömungsverbindung zum dritten Ansaugkrümmer und eine Strömungsverbindung zum dritten Abgaskrümmer verzweigt,
• - an der Stelle der Verzweigung ein Schaltventil angeordnet ist, durch das die Öffnung der interne Strömungsverbindung zum Abgastrakt oder zum Ansaugtrakt variiert werden kann.

An arrangement for carrying out the method is known in the prior art. The DE 10 2015 207 595 B3 discloses an internal combustion engine having at least a first and at least one second cylinder, an intake tract and an exhaust tract, in which an exhaust aftertreatment system is arranged, in which

• each cylinder has at least one intake passage and at least one exhaust passage,
• the second cylinder is designed to be deactivated,
• the exhaust passage of the first cylinder merges into a first exhaust manifold and the exhaust passage of the second cylinder into a second exhaust manifold,
• the first exhaust manifold and the second exhaust manifold open into a third exhaust manifold,
• the intake manifold has a first intake manifold that branches into a second intake manifold for the first cylinder and a third intake manifold for the second cylinder,
• the second exhaust manifold branched upstream of the third exhaust manifold into an internal flow connection to the third intake manifold and a flow connection to the third exhaust manifold,
• - At the point of branching, a switching valve is arranged, through which the opening of the internal flow connection to the exhaust tract or the intake tract can be varied.

The internal combustion engine thus has a type of feedback, in which no exhaust gas, but an air mixture that is sucked into the deactivated cylinder, through open inlet and exhaust valves and through the internal flow connection again flow to the intake valves and thus can circulate, as long as the switching valve from the second exhaust manifold to the third intake manifold is switched to passage. The non-deactivated cylinders are under a higher load during the deactivation of the other cylinders, thus generating a higher torque and thus higher exhaust gas temperatures. Furthermore, the amount of exhaust gas depends on the number of active cylinders, so that advantageously both the temperature and the exhaust gas volume flow can be controlled by the catalyst to be controlled. As the deactivation or Shutdown of cylinders is known in the art.

In the case of a number of n cylinders, a maximum number of n-1 cylinders is preferably designed to be deactivated in the internal combustion engine. In this way, one cylinder is always active, i. At least one cylinder produces exhaust gas as long as the internal combustion engine is in operation.

Furthermore, it is preferred if in the internal combustion engine, the switching valve per flow direction can be opened continuously in the range of zero to 100%. Thereby, the switching valve can be fully opened in the direction of the intake and thereby be completely closed in the direction of the exhaust tract, or completely closed in the direction of the intake and thereby be completely opened completely in the direction of the exhaust tract. Furthermore, a partial opening in one direction are also possible, so that a gas flow from the deactivated cylinders can, if necessary, also be mixed into the exhaust gas stream from the active cylinders.

In a preferred embodiment of the internal combustion engine, at least one cooling device is arranged in the internal flow connection. The cooling device is advantageously used for cooling the circulated gas flow in order to avoid damage due to the effect of temperature on the material of the intake manifold.

Preferably, additional valves for controlling a flow in the exhaust ducts are arranged in the internal combustion engine. Several valves in the system are advantageous because in this way the gas flow of different cylinders can be flexibly controlled. Other valves can advantageously be used to create different configurations of active and deactivated cylinders.

Furthermore, the exhaust aftertreatment system is preferably arranged in the exhaust gas tract of the internal combustion engine, a nitrogen oxide storage catalyst. The internal combustion engine advantageously makes it possible to control the function of a nitrogen oxide storage catalytic converter.

• S1) Einleiten eines unterstöchiometrischen Betriebes der Brennkraftmaschine,
• S2) Deaktivieren mindestens eines Zylinders der Brennkraftmaschine,
• S3) Einstellen des Schaltventils derart, dass es in Richtung des Ansaugtrakts vollständig geöffnet und in Richtung des Abgastrakts vollständig geschlossen wird,

so dass ein Gasstrom aus dem deaktivierten Zylinder durch die interne Strömungsverbindung zum Ansaugtrakt geleitet wird und Abgas aus dem aktiven Zylinder durch den Abgastrakt geleitet wird.The invention relates to a method for controlling a gas flow in an internal combustion engine as described above, wherein during a regeneration at least one cylinder of the internal combustion engine is deactivated and at least one cylinder of the internal combustion engine remains activated, with the steps:

• S1) initiating a substoichiometric operation of the internal combustion engine,
• S2) deactivating at least one cylinder of the internal combustion engine,
• S3) adjusting the switching valve such that it is fully opened in the direction of the intake tract and completely closed in the direction of the exhaust gas tract,

such that a gas flow from the deactivated cylinder is conducted through the internal flow connection to the intake tract and exhaust gas from the active cylinder is passed through the exhaust gas tract.

• S0) Vorbereiten der Regeneration durch deaktivieren mindestens eines Zylinders (1b) während eines Normalbetriebs der Brennkraftmaschine,

so dass bereits vor dem Beginn der Regeneration die Temperatur des Abgases optimiert werden kann.In an advantageous embodiment, the inventive method additionally contains the step

• S0) preparing the regeneration by deactivating at least one cylinder (1b) during a normal operation of the internal combustion engine,

so that the temperature of the exhaust gas can be optimized before the start of the regeneration.

• 1 eine schematische Darstellung einer Ausführungsform einer im Stand der Technik bekannten Anordnung einer Brennkraftmaschine.
• 2 eine schematische Darstellung einer Ausführungsform einer im Stand der Technik bekannten Anordnung einer Brennkraftmaschine.
• 3 ein Fließdiagramm einer Ausführungsform des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to FIGS. Show it

• 1 a schematic representation of an embodiment of an arrangement known in the art of an internal combustion engine.
• 2 a schematic representation of an embodiment of an arrangement known in the art of an internal combustion engine.
• 3 a flow diagram of an embodiment of the method according to the invention.

An embodiment of an internal combustion engine 1 indicates according to the illustration of 1 four cylinders 1a . 1b . 1c and 1d on. The configuration of the in-line engine, as in 1 is shown, is only an example. The number of cylinders of the internal combustion engine 1 may alternatively be, for example, 2, 3, 5, 6 or 8. Furthermore, the internal combustion engine 1 also have a V-motor or boxer engine configuration, without being limited thereto.

The internal combustion engine 1 is connected to an intake tract 2 for providing intake air. Furthermore, the internal combustion engine 1 connected to an exhaust tract 3 for discharging exhaust gas. The intake tract 2 has a first intake manifold 2a downstream, into a second 2b and third intake manifold 2c branched. The second 2b and third intake manifold 2c each pass into an intake passage, the intake air for the cylinders 1a and 1c respectively. 1b and 1d provides.

The exhaust tract 3 is subdivided directly into the exhaust gas ducts on the cylinders. The exhaust ducts of cylinder 1a and 1c go a first exhaust manifold 3a and the exhaust ports of the cylinders 1b and 1d in a second exhaust manifold 3b via. The first and the second exhaust manifold 3a respectively. 3b go into a common exhaust manifold 3c above.

In the area of the transition from the second 3b to the third exhaust manifold 3c branches an internal flow connection 4 from the exhaust tract 3, which connects the exhaust tract 3 with the intake tract 2, by entering the third intake manifold 2c opens. In the branch of the internal flow connection 4 From the exhaust tract 3 is a switching valve 5 arranged. The switching valve 5 is formed, the degree of connection from the second exhaust manifold 3b to the internal flow connection 4 or to the third exhaust manifold 3c to vary. The switching valve 5 can be opened per flow direction continuously in the range of zero to 100%, ie for example in the direction of the internal flow connection 4 completely open, in different degrees partially open or completely open.

In the configuration according to 1 are the cylinders 1b and 1d designed to be deactivated depending on the operating situation. In a four-cylinder configuration, the exhaust ports of three cylinders may alternatively be used 1b . 1c . 1d , which are formed deaktivbar, open into the second exhaust manifold and an exhaust passage of cylinder 1a in the first. This configuration can be made directly. Preferably, however, the exhaust passages of the cylinders have additional shift valves (not shown) through which connect either the first or second exhaust manifolds 3a respectively. 3b can be produced. Thus, a flow connection to the third exhaust manifold 3c or to the intake tract 2 can optionally be established by the cylinders. Analogous to this configuration, other configurations with a different number of cylinders are conceivable, for example, with three cylinders, in which the exhaust passage of a cylinder in a first exhaust manifold and the exhaust passages of two further cylinders in a second exhaust manifold, via which a flow connection to the intake tract 2 produced is. In a configuration with several cylinder blocks, eg a V-engine, all cylinders of one cylinder block can also be deactivated if the other cylinder block of the V-engine is operated with at least one active cylinder.

In exhaust tract 3 is downstream of the third exhaust manifold 3c an exhaust aftertreatment system 6 with a nitrogen oxide storage catalyst 6a arranged. In the exhaust aftertreatment system 6 It is also possible to arrange further catalysts, for example an oxidation catalyst, a three-way catalyst, a catalyst for selective catalytic reduction or else a particle filter. Upstream of the exhaust aftertreatment system 6 is a first sensor 7a and downstream of the exhaust after-treatment plant 6, a second sensor 7b arranged. The sensors are especially oxygen sensors, eg lambda probes or UEGOs. Instead of the oxygen sensors or in combination with them, nitrogen oxide sensors can also be arranged. Oxygen, nitrogen oxide and other sensors, such as temperature sensors, may also be arranged at other locations of the exhaust tract 3. Furthermore, a turbine 8th a turbocharger arranged in the exhaust tract 3.

In 2 is another embodiment of the internal combustion engine 1 with one in the internal flow connection 4 arranged cooling device 9 shown. The cooling device is provided for cooling the circulating gas flow to the material of the intake manifold, especially of the third intake manifold 3c , to protect.

With the internal combustion engine 1 For example, the temperature and amount of exhaust stream may be controlled to control the nitrogen oxide storage catalyst during a control event 6a flows through, ie if its function is to be checked. In a method according to the representation of 3 for controlling a gas flow in the internal combustion engine 1 In a first step S1, a substoichiometric operation of the internal combustion engine 1 is initiated. The exhaust gas is thereby richer, causing a regeneration of the nitrogen oxide storage catalyst 6a is possible. The function of the nitrogen oxide storage catalyst 6a is determined by measurements of the air conditions by means of the sensors 7a and 7b upstream or downstream of the catalyst 6a determined. In order to produce exhaust gas with a corresponding temperature, are in the internal combustion engine 1 as they are in 1 and 2 is shown, in a second step S2, the cylinder 1b and 1d disabled. The cylinders 1a and 1c will continue to operate. The intake and exhaust valves (not shown) of deactivated cylinders 1b and 1d stay open. In a third step S3, the switching valve 5 set so that it is toward the internal flow connection 4 completely open, creating a gas flow from the deactivated cylinders 1b . 1d through the internal flow connection 4 to the third intake manifold 2c is passed, and thus by the deactivated cylinder 1b . 1d circulated. At the same time, exhaust gas flows out of the cylinders 1a and 1c into the exhaust tract 3 and through the catalyst 6a , In step S3, the switching valve 5 even with deactivated cylinders 1b . 1d be set so that they are partly for both internal flow connection 4 as well as to the exhaust manifold 3c are open to regulate the exhaust flow.

Will the regeneration and thus the control event of the catalyst 6a finished, the cylinders are 1b and 1d re-activated and the switching valve 5 is set so that it is in the direction of the third exhaust manifold 3c is completely opened.

LIST OF REFERENCE NUMBERS

1

= Internal combustion engine

1a

= first cylinder

1b

= second cylinder

1c

= third cylinder

1d

= fourth cylinder

2a

= first intake manifold

2 B

= second intake manifold

2c

= third intake manifold

3a

= first exhaust manifold

3b

= second exhaust manifold

3c

= third exhaust manifold

4

= internal flow connection

5

= Switching valve

6

= Exhaust aftertreatment system

6a

= Nitrogen oxide storage catalyst

7a

= first sensor

7b

= second sensor

8th

= Turbine

9

= Cooling device

Claims (7)

Method for controlling a gas flow in an internal combustion engine having at least one first (1a) and at least one second cylinder (1b), an intake tract (2) and an exhaust tract (3), in which each cylinder (1a, 1b) has at least one intake passage and at least one exhaust passage, the second cylinder (1b) is designed to be deactivated, the exhaust passage of the first cylinder (1a) merges into a first exhaust manifold (3a) and the exhaust passage of the second cylinder (1b) into a second exhaust manifold (3b), the first exhaust manifold (3a) and the second exhaust manifold (3b) open into a third exhaust manifold (3c), the intake tract (2) has a first intake manifold (2a) which branches into a second intake manifold (2b) for the first cylinder (1a) and a third intake manifold (2c) for the second cylinder (1c), the second exhaust manifold (3b) branches upstream of the third exhaust manifold (3c) into an internal flow connection (4) to the third intake manifold (2c) and a flow connection to the third exhaust manifold (3c), - At the point of branching a switching valve (5) is arranged, by which a gas flow from the second exhaust manifold (3b) to the exhaust tract (2) and / or the intake tract (3) can be directed, wherein during a regeneration at least one cylinder of the internal combustion engine (1) is deactivated and at least one cylinder (1a) of the internal combustion engine remains activated, and a gas flow from the deactivated cylinder through the internal flow connection (4) to the intake tract (2) is passed, comprising the steps: S1) initiating a substoichiometric operation of the internal combustion engine (2), S2) deactivating at least one cylinder (1b) of the internal combustion engine (2), S3) setting the switching valve (5) such that it is fully opened in the direction of the intake tract (2) and completely closed in the direction of the exhaust tract (3), so that a gas flow from the deactivated cylinder (1b) through the internal flow connection (4) to the intake tract (2) is passed and exhaust gas from the active cylinder (1a) through the exhaust gas duct (3) is passed. Method according to Claim 1 comprising the step S0) preparing the regeneration by deactivating at least one cylinder (1b) during a normal operation of the internal combustion engine, so that the temperature of the exhaust gas can be optimized even before the beginning of the regeneration. Method according to one of the preceding claims, wherein in the internal combustion engine (1) at a number of n cylinders, a maximum number of n-1 cylinder is formed to be deactivated. Method according to one of the preceding claims, wherein in the internal combustion engine (1), the switching valve (5) per flow direction can be opened continuously in the range of zero to 100%. Method according to one of the preceding claims, wherein in the internal combustion engine (1) at least one cooling device (9) in the internal flow connection (4) is arranged. Method according to one of the preceding claims, wherein in the internal combustion engine (1) additional valves for controlling a flow in the exhaust ducts are arranged. Method according to one of the preceding claims, wherein in the internal combustion engine (1) a Nitrous oxide storage catalyst (6a) in the exhaust system (3) is arranged.

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