EP2952712A1 - Method for controlling a combustion engine with deactivatable cylinders - Google Patents

Abstract

Method for controlling an internal combustion engine (1) with more than one cylinder (2), wherein depending on the required power output individual cylinders (2) can be switched off according to a predeterminable pattern, the pattern of a chronological sequence of commands for ignition and commands for suspending the Ignition exists, wherein the pattern is derived with a calculation rule such that, for example, each third or fifth or seventh cylinder or (2n + 1) te cylinder is exposed, (2n + 1) is preferably a prime parent to the number of cylinders.

Description

The invention relates to a method for controlling an internal combustion engine having the features of the preamble of claim 1.

Method for cylinder shutdown, "Skip firing", are known from the prior art. Cylinder deactivation is primarily used on larger engines with more than 6 cylinders to reduce fuel consumption and emissions with reduced power demand.

In the DE 43 10 261 It is described that, for protection against overloading of an engine, patterns for selective cylinder deactivation (referred to as fading patterns in the text) can be specified.
The patterns are advantageously matched to the number of cylinders that result in circumferential Ausblendsequenzen, ie within a very short time each cylinder is relieved.

From the DE 2928075 It is known that the sequence of commands for ignition and cylinder deactivation is selected so that the internal combustion engine runs as smoothly as possible, that in particular harmonics of the resonance frequencies of the engine mount and the drive train are avoided and that the operation of individual piston-cylinder units not more than two - expose three times so that these piston-cylinder units do not cool down too much.

Methods for skip-firing are also known from the scriptures US2013289853 . US2013298870 . US8099224 . US2013092128 . US2012109495 . US8336521 . US8131447 . US2013092127 ,

It has been found in tests by the Applicant that the specification of fixed Zündabschaltungsmuster is unfavorable because there is a timing uncertainty in the regulation of whether a single cylinder receives the signal for firing at the next power stroke or not. Inadvertent discharge of a cylinder intended for ignition leads to a decrease in the rotational speed of the engine while inadvertent ignition of a cylinder intended for discharge leads to an undesired speed increase.

This blurring can be countered by a crank angle synchronous control. A crank angle synchronous control with discrete timing for the ignition timing of each cylinder is expensive.

Even if a plurality of patterns for cylinder deactivation are predetermined and these patterns are alternated, this has the disadvantage that when switching the patterns, several cylinders change from a fired to an unfired state and vice versa. For thermal reasons, however, it is unfavorable if, for example, a cylinder is ignited only once and then switched off again. In addition, it is unfavorable if several cylinders change their status per cycle (2 crank angle revolutions corresponding to 720 ° for 4-stroke engines). Thus, in the transition from one pattern to cylinder deactivation to another pattern, it may happen that several cylinders, one behind the other in their firing order, are turned off, i.e., in the same way. a longer sequence without ignition events arises.

The object of the invention is therefore to provide an improved method for the omission of cylinder firing, in which the thermal load is distributed more uniformly on the cylinder.

This object is achieved by a method for controlling with the features of claim 1. Preferred embodiments are specified in the subclaims.

Characterized in that the pattern is derived with a calculation rule such that the distance between cylinders to be deployed in relation to the firing order is an odd number, and preferably least common to the number of cylinders, a uniform heat input to all cylinders is achieved.

In the context of the present disclosure, "suspending" cylinders means that these cylinders do not ignite, which in turn can be accomplished by eliminating ignition and / or elimination of fuel delivery. The latter is particularly relevant for internal combustion engines, which are equipped with a cylinder-specific fuel supply, such as port injection valves. The terms "fired" and "unfocused" are used synonymously for "ignited" or "unlit".

• die Zündreihenfolge ist eine durch die Kröpfungen der Kurbelwelle, also mechanisch und für einen vorliegenden Motor unveränderlich vorgegebene zeitliche Abfolge der Zündzeitpunkte der einzelnen Zylinder. Die Zündreihenfolge ist häufig so gewählt, dass eine örtlich und zeitlich günstig verteilte Einleitung der Drehmomente auf die Kurbelwelle erfolgt, die Kurbelwelle möglichst nicht zu Torsionsschwingungen angeregt wird, und, bei Vorliegen zweier Zylinderbänke, die gegenüberliegenden Zylinder nacheinander zünden.

In the proposed method, the pattern for cylinder deactivation ( skip firing order) is first derived from the firing order of the relevant engine. The procedure is as follows:

• The firing order is a chronological sequence of the firing times of the individual cylinders which is fixed by the crankshaft cranks, ie mechanically and for a given engine. The firing order is often chosen so that a locally and temporally distributed favorable introduction of the torques on the crankshaft, the crankshaft is possible not excited to torsional vibrations, and, in the presence of two cylinder banks, the opposite cylinders ignite successively.

In conventional notation, the cylinders are numbered so as to start counting against the output side and, if there are several cylinder banks in the left cylinder bank. Table 1 shows the numbering of the cylinders of a V-20 engine as a two-column table. The left column with the entries one to ten corresponds to the left cylinder bank, the right column with the entries eleven to twenty of the right cylinder bank. Table 1: Numbering of the cylinders of a V-20 engine as a two-column table 10 20 9 19 8th 18 7 17 6 16 5 15 4 14 3 13 2 12 1 11

• Für Sechszylinder Reihenmotoren: 1-5-3-6-2-4 oder 1-2-4-6-5-3 oder 1-4-2-6-3-5 oder 1-4-5-6-3-2
• Für Achtzylinder Reihenmotoren: 1-6-2-5-8-3-7-4 oder 1-3-6-8-4-2-7-5 oder 1-4-7-3-8-5-2-6 oder 1-3-2-5-8-6-7-4.
• Für V-Motoren sind beispielsweise folgende Zündfolgen gängig:
  • Sechszylinder: 1-4-3-6-2-5 oder 1-2-5-6-4-3 oder 1-4-5-6-2-3
  • Zwölfzylinder: 1-7-5-11-3-9-6-12-2-8-4-10 oder 1-12-4-9-2-11-6-7-3-10-5-8 Besonders in Kraftfahrzeugen bestehen noch etliche weitere Varianten.

Typical ignition sequences for in-line engines are:

• For six-cylinder inline engines: 1-5-3-6-2-4 or 1-2-4-6-5-3 or 1-4-2-6-3-5 or 1-4-5-6-3- 2
• For eight-cylinder in-line engines: 1-6-2-5-8-3-7-4 or 1-3-6-8-4-2-7-5 or 1-4-7-3-8-5-2- 6 or 1-3-2-5-8-6-7-4.
• For example, the following ignition sequences are common for V-engines:
  • Six-Cylinder: 1-4-3-6-2-5 or 1-2-5-6-4-3 or 1-4-5-6-2-3
  • Twelve Cylinders: 1-7-5-11-3-9-6-12-2-8-4-10 or 1-12-4-9-2-11-6-7-3-10-5-8 Especially in motor vehicles there are still several other variants.

Table 2 shows a typical firing order of a V-20 cylinder engine. In the first line, the chronological order of the ignition and in the line below the number - according to the above-explained notation - of the respective cylinder is shown. The firing order shown corresponds to two crank revolutions in the case of 4-stroke engines and of one crank revolution in the case of 2-stroke engines and starts again from the beginning after the last cylinder. Table 2: Ignition order of a V-20 cylinder engine 1 2 3 4 5 6 7 8th 9 10 11 12 13 14 15 16 17 18 19 20 17 7 13 3 19 9 15 5 20 10 14 4 18 8th 12 2 16 6 11 1

It is preferably provided that the pattern can be described by an algorithm as a function of the number of cylinders.

Based on the firing order, a pattern of skip firing order is derived such that the cylinders expose in odd order.

It can also be provided that the pattern is derived via an algorithm from the firing order in such a way that the commands for firing are distributed uniformly over the cylinder banks.

It may be, for example, every third or fifth or seventh cylinder, generally described as two n + 1 (2n + 1) with n of a natural number. This ensures that the omissions are distributed over both cylinder banks. Particularly favorable is the choice of a number that is not divisor of the number of cylinders, about three for a 20-cylinder engine, or five for a 12-cylinder engine.

If the series hits again on a cylinder already considered in the skip firing order, that is skipped, the rule is deviated from and goes back and forth from that cylinder to the next cylinder, which has not yet been considered in the skip firing order. The next cylinder to be subjected to suspension is again fixed with the rule defined above. The skip firing order can of course be started on any cylinder.

Thus, the rule with (2n + 1) = 3 results from the firing order of a V12 cylinder engine, which reads: 1-7-5-11-3-9-6-12-2-8-4-10 the skip firing order 1-11-6-8-7-3-12-4-5-9-2-10.

In another example, the distance 5 is selected as the rule for selecting the cylinder to be replaced, ie the fifth cylinder after the last one.

This results in the following skip firing order from the firing order 1-7-5-11-3-9-6-12-2-8-4-10: 1-9-4-11-2-7-6-10- 3-8-5-12.

• Bevorzugt kann vorgesehen sein, dass nach einem vorgebbaren Zeitintervall auf eine vorgebbare Listenposition mit einem Befehl zur Zündung eine Anzahl von mindestens einer weiteren Listenposition mit Signal zur Zündung hinzukommt, und der Listenabschnitt mit Befehlen zur Nicht-Zündung um die gleiche Anzahl an Listenpositionen mit Signalen zur Nicht-Zündung ergänzt wird. Mit Liste bzw. Listenposition ist folgendes gemeint: das Muster der Zündabschaltung lässt sich als Liste von Befehlen zum Zünden, dargestellt durch eine Eins, und Befehlen zum Aussetzen (Nicht-Zünden), dargestellt durch eine Null, abbilden. Dies sei anhand nachfolgender Tabelle illustriert. So zeigt die Tabelle 3 in der ersten Zeile das Muster der Zündabschaltung bezüglich des betroffenen Zylinders, und in der Zeile darunter die Befehle zum Aussetzen, dargestellt durch eine Null, bzw. die Befehle zum Zünden, dargestellt durch eine Eins. Im konkreten Beispiel erhalten die Zylinder 11, 2 und 18 den Befehl zum Aussetzen, gefolgt von den Zylindern 10, 15, 3, 17, 6, 12, 4, 20, 9 mit Befehl zum Zünden, gefolgt von den Zylindern 13, 16, 8, 14, 5, 19 und 7 mit Befehl zum Aussetzen. Das Aussetzen wird also in der Liste durch eine Null wiedergegeben, während das Zünden durch eine Eins signalisiert wird.

For an even distribution of the load on the cylinders, the pattern is changed over time:

• Preferably, it can be provided that, after a predeterminable time interval, a number of at least one further list position with signal for ignition is added to a predefinable list position with an ignition command, and the list section with commands for non-ignition by the same number of list positions with signals for Non-ignition is supplemented. By list or list position is meant the following: the pattern of the ignition cutoff can be represented as a list of commands to fire, represented by a one, and commands to suspend (not fire) represented by a zero. This is illustrated by the following table. Thus, Table 3 in the first line shows the pattern the ignition off with respect to the affected cylinder, and in the line below the commands to suspend, represented by a zero, and the commands to ignite, represented by a one. In the concrete example, the cylinders 11, 2 and 18 receive the command to deploy, followed by the cylinders 10, 15, 3, 17, 6, 12, 4, 20, 9 with command to ignite, followed by the cylinders 13, 16, 8, 14, 5, 19 and 7 with command to suspend. The suspension is therefore represented in the list by a zero, while the ignition is signaled by a one.

The temporal change of the pattern takes place in such a way that at least one further list position with signal for ignition is added to a predefinable list position with a command for ignition, and the subsequent block of commands for non-ignition by at least one further list position with signal for non-ignition is supplemented. In the concrete example, this is shown in line 3 of Table 4: Cylinder 13 changes from non-firing to firing while Cylinder 10 transitions from the fired to the un-fired state. Table 3: Skip firing order deposited with commands to suspend (zero) or ignite (ones). 11 2 18 10 15 3 17 6 12 4 20 9 13 16 8th 14 5 19 7 0 0 0 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0

The uniform distribution of the load over the cylinders is thus effected by extending the list entry with the commands for firing by one increment, while at the same time the list entry with commands for ignition exposure is also increased by the same increment.

This results in a shift of the ignition commands by the selectable increment. This may include, for example, one or more cylinders.

By shifting the ignition commands by a selectable increment, it is achieved that the sequence, or in other words the list section, "moves" with commands for ignition during operation of the internal combustion engine, that is, moves over all cylinders.

This is a very simple way created a way to evenly distribute the load and heat input to the engine.

In a preferred embodiment, it is provided that the pattern is changed after a predefinable time interval, wherein the time interval is 1 to 20 seconds, particularly preferably 5-10 seconds. In other words, the firing pattern remains unchanged for 1-20 seconds, more preferably 5-10 seconds unchanged.

It is preferably provided that the temporal change of the pattern occurs in such a way that as few cylinders as possible, more preferably only one cylinder, change from an unfired to a fired state and transfer as few cylinders as possible from a fired to an unfired state. As mentioned above, it is favorable for thermal reasons, if in a period of observation most possible few cylinders, particularly preferably only one cylinder, change their firing status.

It can preferably be provided that at least one cylinder remains excluded from the cylinder deactivation. For example, for diagnostic purposes, such as instrumentation of a cylinder, it may be interesting to exclude this cylinder from cylinder deactivation.

When deriving the skip firing order, the cylinders to be removed are removed from the firing order and then the procedure described above for determining the skip firing order with the reduced firing order is carried out. This is illustrated in Table 4. Table 4 shows the reduced firing order of a V-20 cylinder engine with the last position, that is cylinder number one, hidden. The chronological order of the ignition is shown in the first line and the number of the respective cylinder in the line below. Of course, Cylinder One is not really exempt from the ignition, but only from the list for determining which cylinders to expire. Since only nineteen cylinders remain in the reduced firing order, the stride length of five is suitable, which would be a divisor of the number of cylinders for the 20-cylinder engine. Table 4: Reduced firing order of a V-20 cylinder engine, cylinder one is excluded 1 2 3 4 5 6 7 8th 9 10 11 12 13 14 15 16 17 18 19 17 7 13 3 19 9 15 5 20 10 14 4 18 8th 12 2 16 6 11

Now, if the misfire rule is applied to the reduced firing order, cylinder one remains excluded from the misfire. In other words, cylinder one is ignited quite regularly.

The result will be explained using the example of the reduced firing order according to Table 4. The rule of suspending after every third cylinder is applied to the firing order of Table 4. To illustrate that the direction of the determination (ie in the list from left to right or from right to left) and the starting position for the determination are irrelevant, starts with cylinder eleven and proceed from right to left. That is, after eleven comes two, then 18, then ten and so on. The result, that is the skip firing order of the reduced firing order, is shown in Table 5. The resulting skip firing order has only 19 entries for the 20-cylinder engine, since one cylinder is exempted from the ignition exposure. Table 5: skip firing order of the reduced firing order of a V-20 cylinder engine 11 2 18 10 15 3 17 6 12 4 20 9 13 16 8th 14 5 19 7

However, this skip firing order is not yet adapted to a specific load request, but only describes the sequence which is to follow in the suspension of cylinders.

In the proposed procedure, the skip firing order received is then stamped with another pattern which determines which of the cylinders defined in the skip firing order are actually intended to be ignited.

This pattern may be construed as a list or sequence of non-firing commands expressed by a zero followed by one-entry list entries for the firing command.

If this pattern is then overlaid with the previously defined skip firing order, the number of actually deploying cylinders can be determined and thus adapted to a load request. The process shall be illustrated by Table 6 below. Table 6 again follows the example of the reduced firing order, with cylinder one being excluded from exposure. This may be provided, for example, for diagnostic purposes or the like. The load requirement in the example is such that ten of the twenty cylinders should ignite. Thus, Table 6 in the first line shows the pattern of the ignition shutdown with respect to the cylinder concerned, and in the line below the commands to suspend, represented by a zero, and the commands to ignite, represented by a one. In the concrete example, the cylinders 11, 2 and 18 receive the command to deploy, followed by the cylinders 10, 15, 3, 17, 6, 12, 4, 20, 9 with command to ignite, followed by the cylinders 13, 16, 8, 14, 5, 19 and 7 with command to suspend. The suspension is therefore represented in the list by a zero, while the ignition is signaled by a one. Table 6: Skip firing order deposited with commands to suspend (zero) or ignite (ones) 11 2 18 10 15 3 17 6 12 4 20 9 13 16 8th 14 5 19 7 0 0 0 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0

Represented as list entries, therefore, results in a sequence of entries with signal for ignition, represented by ones, followed by a list section with the information for misfiring, shown by zeros. It can already be seen from the example of Table 6, that it is very easy to determine the proportion of those cylinders that should continue to ignite, in other words, to what proportion of load the engine should be operated. Using the example of Table 6, ten out of twenty cylinders ignite, that is, the load reduction is around 50%.

Particularly preferably, it can be provided that with increased power requirement, the list block with commands for ignition is extended by at least one further command for ignition.

Thus, if the load requirement increases, this can be achieved simply by extending the list section with ignition signals by a further increment. By increment is meant at least one list entry.

Table 7 shows, for example, that the list section with commands for ignition, ie list entries with one, is extended by another list position. In the concrete example, the cylinder 13 is now also provided for ignition. Table 7: 11 2 18 10 15 3 17 6 12 4 20 9 13 16 8th 14 5 19 7 0 0 0 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0

Thus, the number of fired cylinders increases to eleven, while nine cylinders remain unsurfaced.

It is preferably provided that the pattern can be changed over time such that, with reduced power requirement, the list block is extended by at least one further command for ignition exposure with commands for misfiring.

Table 8 shows this case. Here, the sequence of non-ignitions is extended by another list entry, so now eleven cylinders do not ignite and ignite nine cylinders. Thus, a further power reduction can be achieved. In this specific case, in comparison with the initial state according to Table 6, cylinders with the number ten are additionally deployed. Table 8: 11 2 18 10 15 3 17 6 12 4 20 9 13 16 8th 14 5 19 7 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0

The examples given show the time unchanged case, that is ignite always the same cylinder, while the remaining cylinders remain unfired. For a uniform time distribution of the load on the cylinder, as described above, the pattern changed over time.

If one imagines the firing order as a closed circle in which the last ignited cylinder joins the first-ignited cylinder, then the block of ignited cylinders rotates in a circle.

Fig. 1

eine gattungsmäßige Verbrennungskraftmaschine (schematisch)

Fig. 2

eine Darstellung der Zündreihenfolge als geschlossenen Kreis

The invention will be explained in more detail below with reference to FIGS. Showing:

Fig. 1

a generic internal combustion engine (schematic)

Fig. 2

a representation of the firing order as a closed circle

FIG. 1 schematically shows an internal combustion engine 1 in a plan view. The figure shows the notation of naming the cylinders: the arrow symbolizes the line of sight, so you look at the output, called G, opposite side, where counting is started. The cylinder with number one lies on the cylinder bank in the direction of view. Shown is a V-16-cylinder engine.

FIG. 2 serves to illustrate the concept of the rotating skip firing order and shows the firing order as a closed circle. the example of a 20-cylinder engine in which the cylinder number one is excluded from the Zündaussetzung, so ignites regularly. The numbers in the fields correspond to the number of the respective cylinder. The black-colored fields show ignited cylinders, the white fields represent unburned cylinders. The order of the cylinders corresponds to the pattern of the ignition switch-off. The arrows between the fields symbolize the chronological firing order.
Due to the temporal change of the skip-firing pattern, the block moves with commands for ignition in a circle. This is indicated by the details D1 and D2. For example, cylinder number ten receives the command for non-ignition (detail D1), thus changing its status from ignition to suspension. In the following, cylinder 13 changes from the ignition-unfired condition to the fired condition (detail D2). Thus, the number of fired or unfired cylinders remains constant, but the pattern "wanders" over the cylinders, resulting in a uniform heat input to the cylinders.

Claims (9)

Method for controlling an internal combustion engine (1) with more than one cylinder (2), wherein depending on the required power output individual cylinders (2) can be switched off according to a predeterminable pattern, the pattern of a chronological sequence of commands for ignition and commands for suspending the Ignition is characterized in that the pattern is derived with a calculation rule such that the distance between cylinders (2) to be deployed relative to the firing order is an odd number, and preferably least common to the number of cylinders. Method according to one of the preceding claims, characterized in that the pattern is described by an algorithm as a function of the number of cylinders. Method according to one of the preceding claims, characterized in that the pattern is derived via an algorithm from the firing order so that the commands to the ignition evenly distributed to the cylinder banks. The method of claim 1, wherein the pattern can be described as a list of commands for ignition followed by commands for non-ignition, characterized in that the pattern is temporally variable so that after a predetermined time interval to a predetermined list position with an ignition command a number of at least one further list position with signal for ignition is added, and the list section is supplemented with commands for non-ignition by the same number of list positions with signals for non-ignition. Method according to one of the preceding claims, characterized in that the pattern is changed after a predeterminable time interval, wherein the time interval is 1 to 20 seconds, more preferably 5-10 seconds. Method according to one of the preceding claims, characterized in that the temporal change of the pattern occurs so that as few cylinders (2), more preferably only one cylinder (2), from an unfired to a fired state and exceed as few cylinders (2 ) from a fired to an unfired state. Method according to one of the preceding claims, characterized in that at least one cylinder (2) remains excluded from the cylinder deactivation. Method according to one of the preceding claims, characterized in that the pattern is temporally changed so that, for increased power demand the list block of commands for ignition to a further command to ignition is extended at least. Method according to one of the preceding claims, characterized in that the pattern is temporally variable so that at reduced power demand of the list block is extended with commands for misfiring by at least one further command for misfiring.

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