DE102017208788A1 - Method and device for operating a spark-ignited internal combustion engine - Google Patents

Abstract

The invention relates to a method for operating an internal combustion engine (2) with a plurality of cylinders (3), wherein the cylinders (3) of the internal combustion engine (2) are operated in normal operation according to an intake stroke, a compression stroke, an expansion stroke and a discharge stroke of a duty cycle During operation of the internal combustion engine (2) at least one cylinder (3) is deactivated, wherein a deactivated cylinder of the internal combustion engine (2) by the operation of the internal combustion engine (2) is towed and operated according to the following steps: - Opening an inlet valve (31) of the deactivated cylinder (3) at the beginning of the intake stroke, - closing the intake valve (31) during the compression stroke, - opening the intake valve (31) of the deactivated cylinder (3) during the expansion stroke, - closing the intake valve (31) at the end of the exhaust stroke or after the exhaust stroke.

Description

Technical area

The invention relates to spark ignition internal combustion engines, in particular gasoline engines. In particular, the present invention relates to the operation of gasoline engines in partial cylinder operation in which one or more of the cylinders are inactive and are being towed by the remaining active cylinders.

Technical background

Partial cylinder operation is a common mode of operation of spark-ignited internal combustion engines to achieve increased efficiency through cylinder deactivation at low speed / load. In the cylinder deactivation takes place in one or more cylinders no combustion, so that no moment contribution is provided by these cylinders.

So far, cylinder deactivation has been implemented in internal combustion engines having at least four cylinders, wherein fresh air is included in one or more of the cylinders by deactivating the function of the intake and exhaust valves. The switching of the valve operation is usually done via a switchable backdrop in particular by switching to a zero cam. Furthermore, the injection of fuel and the generation of a spark in the respective cylinders are deactivated.

The efficiency increase in the partial cylinder operation is achieved in that the remaining, operated in normal operation cylinders must provide an increased indexed moment to keep the power or the torque provided constant. The operation of these cylinders requires a higher air mass, which is achieved by opening the throttle valve and thus by increasing the intake manifold pressure. As a result, the charge cycle losses decrease, which leads to an increase in the overall efficiency and thus to a reduction in fuel consumption.

From the publication DE 10 2008 005 205 A1 For example, a method is known for operating one or more cylinders having an internal combustion engine. In a partial engine operation in which at least one cylinder is switched off, a cylinder change between the deactivated cylinders is made while maintaining the number of deactivated cylinders.

Disclosure of the invention

According to the invention, a method for operating a spark-ignited internal combustion engine according to claim 1 and a device and an engine system according to the independent claims are provided.

Further embodiments are specified in the dependent claims.

• - Öffnen eines Einlassventils des deaktivierten Zylinders während oder zu Beginn des Ansaugtakts;
• - Schließen des Einlassventils während des Kompressionstakts;
• - Öffnen des Einlassventils des deaktivierten Zylinders während des Expansionstakts;
• - Schließen des Einlassventils während oder am Ende des Ausstoßtakts.

According to a first aspect, a method for operating an internal combustion engine having a plurality of cylinders is provided, wherein the cylinders of the internal combustion engine are operated in normal operation according to an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke of a duty cycle, wherein at least one cylinder is deactivatable during operation of the internal combustion engine in which a deactivated cylinder of the internal combustion engine is towed by the operation of the internal combustion engine and is operated according to the following steps:

• Opening an intake valve of the deactivated cylinder during or at the beginning of the intake stroke;
• Closing the inlet valve during the compression stroke;
• - opening the inlet valve of the deactivated cylinder during the expansion stroke;
• - Close the inlet valve during or at the end of the exhaust stroke.

In conventional cylinder deactivation methods, there is the problem that during cylinder deactivation with the intake and exhaust valves closed in the deactivated cylinder, there is a strong vacuum due to the expansion of the cylinder charge due to the downward movement or expansion of the piston in the cylinder. This can lead to oil or oil mist being sucked out of the crankcase via the piston rings into the combustion chamber and thus resulting in increased pollutant emissions.

An idea of the above method is to prevent the generation of negative pressure in the combustion chambers of deactivated cylinders in the partial cylinder operation by closing the inlet valve of a deactivated cylinder during the compression stroke at an appropriate time and opening it during the expansion stroke at an appropriate time. Thereby, a part of the air or the air-fuel mixture can be ejected during the compression stroke from the cylinder into the Saugrohrabschnitt before it is further compressed, and avoided by a corresponding further opening of the intake valve during the subsequent expansion stroke, the formation of a negative pressure , For this, the intake valve becomes at least during the intake stroke and during the exhaust stroke partially open, so that the inlet valve opens twice during the deactivation of the injection and ignition within a power stroke.

By closing the inlet valve during the compression stroke, the amount of gas remaining in the combustion chamber can be adjusted so that the formation of a negative pressure during the subsequent expansion of the combustion chamber is avoided. In order to avoid charge exchange losses, the inlet valve can already be opened during the expansion stroke as soon as the pressure in the combustion chamber corresponds to the pressure in the suction pipe section.

Furthermore, it can be provided that the exhaust valve of the deactivated cylinder remains closed at least during the exhaust stroke, in particular during the cylinder deactivation.

Furthermore, the intake valve of the deactivated cylinder may be closed during the compression stroke at a crank angle of between 20 ° and 60 ° after the piston bottom dead center.

Alternatively or additionally, the inlet valve of the deactivated cylinder during the expansion stroke between 20 ° and 180 ° before the bottom dead center of the piston movement can be opened.

It may be provided that the intake valve of the deactivated cylinder is closed at a crankshaft angle after the bottom dead center, which corresponds to the crankshaft angle before the bottom dead center to which the intake valve is opened during the expansion phase.

Furthermore, the opening duration of the intake valve can be controlled by a cam structure of an intake valve camshaft, wherein by selecting the cam structure, the valve opening duration of the intake valve for an activated and deactivated cylinder is switchable, wherein the cam structure for the control of the deactivated cylinder provides a longer opening phase of the intake valve than the cam structure for controlling the activated cylinder.

According to one embodiment, the cylinders may be deactivated in a rolling manner so that a cylinder is deactivated only during a work cycle starting with the intake stroke, wherein an opening phase of the exhaust valve of a cylinder to be deactivated overlaps with an opening phase of the intake valve when deactivated.

As a result, there is also a valve overlap of the opening sides of the inlet and outlet valves, even if the cylinder is deactivated, so that throttling can continue on an operating-point-dependent basis via an increase in the internal residual gas rate. Overall, this can reduce the charge cycle losses for the deactivated cylinder (s). Particularly in the case of a rolling cylinder deactivation, as used, for example, in three-cylinder internal combustion engines, the fuel consumption advantage of the partial cylinder operating mode is significantly dependent on the reduction of the charge exchange losses. In particular, in the case of rolling cylinder deactivation, it must be ensured that no or as little as possible charge exchange losses occur with each cycle. The requirements for the charge cycle are thus higher in the case of rolling cylinder deactivation than in the case of conventional cylinder deactivation, as used, for example, in four cylinder engines or internal combustion engines with more than four cylinders.

• - ein Einlassventil des deaktivierten Zylinders während oder zu Beginn des Ansaugtakts zu öffnen;
• - das Einlassventil während des Kompressionstakts zu schließen;
• - das Einlassventil des deaktivierten Zylinders während des Expansionstakts zu öffnen;
• - das Einlassventil am Ende des Ausstoßtakts oder nach dem Ausstoßtakt zu schließen.

According to a further aspect, an apparatus for operating an internal combustion engine having a plurality of cylinders is provided, wherein the cylinders of the internal combustion engine are operable in normal operation according to an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke of a duty cycle, wherein at least one cylinder is deactivatable during operation of the internal combustion engine wherein a deactivated cylinder of the internal combustion engine is towed by operation of the internal combustion engine, the apparatus being configured to:

• to open an intake valve of the deactivated cylinder during or at the beginning of the intake stroke;
• to close the inlet valve during the compression stroke;
• - to open the inlet valve of the deactivated cylinder during the expansion stroke;
• - Close the inlet valve at the end of the exhaust stroke or after the exhaust stroke.

In another aspect, an engine system including an internal combustion engine and the above apparatus is provided.

list of figures

• 1 eine schematische Darstellung eines Motorsystems mit einem Verbrennungsmotor;
• 2 eine schematische Darstellung eines Verfahrens zum Betreiben eines Verbrennungsmotors mit einer Zylinderabschaltung;
• 3 ein Zylinderdruckverlauf und Verläufe der Öffnungsphasen der Einlass- und Auslassventile bei drei Arbeitszyklen eines Zylinders des Verbrennungsmotors mit einer Abschaltung des Zylinders im zweiten Arbeitszyklus; und
• 4 ein Verlauf der Öffnungsphasen eines Einlassventils bei einer Zylinderabschaltung mit verlängerten Nocken.

Embodiments are explained below with reference to the accompanying drawings. Show it:

• 1 a schematic representation of an engine system with an internal combustion engine;
• 2 a schematic representation of a method for operating an internal combustion engine with a cylinder deactivation;
• 3 a cylinder pressure profile and curves of the opening phases of the inlet and Exhaust valves at three working cycles of a cylinder of the internal combustion engine with a shutdown of the cylinder in the second cycle; and
• 4 a course of the opening phases of an intake valve in a cylinder deactivation with extended cam.

Description of embodiments

1 shows a schematic representation of the engine system 1 with an internal combustion engine 2 in the present embodiment, three cylinders 3 having. The internal combustion engine 2 Air is supplied via an air supply section 4 fed in which a throttle 5 is arranged to adjust the amount of air supplied.

Downstream of the throttle 5 there is a Saugrohrabschnitt 41 , in using an injector 6 Fuel can be injected to the cylinders 3 the internal combustion engine to provide an air-fuel mixture. The suction pipe section 41 opens at intake valves 31 in the associated cylinders 3 , The in the Saugrohrabschnitt 41 generated air-fuel mixture is through the intake valves 31 in the cylinders 3 of the internal combustion engine 2 according to a known four-stroke operation of the internal combustion engine 3 admitted. In alternative engine systems, the fuel may also flow directly into the cylinders through respective injectors 3 be injected to form an air-fuel mixture there.

Furthermore, an exhaust gas removal tract 7 provided to combustion exhaust gas, which has an opening clearance of exhaust valves 32 is ejected from the cylinders during an exhaust stroke, to collect and dissipate into the environment. The opening times of the intake and exhaust valves 31 . 32 is usually due to a crankshaft position of a crankshaft 8th by the internal combustion engine 2 is driven, certainly. This is the crankshaft 8th via a suitable mechanical coupling, such. B. a toothed belt, with an intake valve camshaft 9 and an exhaust valve camshaft 10 for controlling the exhaust valves 32 coupled.

The camshafts 9 . 10 each have cams, through the respective plunger of the inlet and outlet valves 31 . 32 be operated. By a suitable mechanical adjusting device can act on the valve tappets cam of the camshaft 9 . 10 so as to adjust the opening and closing timing of the intake and exhaust valves 31 . 32 to change.

It is in every cylinder 3 an ignition device 11 provided a spark to ignite an actively operated cylinder 3 to create.

The operation of the internal combustion engine is controlled by a control unit 15 controlled, depending on state variables that may be measured or modeled, for example, positioner in the engine system 1 adjusted to provide a desired torque. The torque is predetermined, for example, by an operation of an accelerator pedal (not shown) as a driver's desired torque or depending thereon. About the throttle actuator 5 , the injection valve 6 , the specification of ignition timing of the ignition devices 11 and if necessary. Other positioner can the operation of the internal combustion engine 2 be controlled in a conventional manner.

To the efficiency in the operation of the internal combustion engine 2 To increase, a partial cylinder operation may be provided. The operation of the cylinders 3 takes place in a working cycle consisting of an intake stroke for sucking an air-fuel mixture (or fresh air with direct injection) from the Saugrohrabschnitt 41 , a compression stroke for compressing the air-fuel mixture in the combustion chamber of the cylinder 3 an expansion stroke for burning the air-fuel mixture and an exhaust stroke for discharging combustion exhaust gas from the cylinder 3 , In partial cylinder operation, no ignition of the air-fuel mixture takes place in one operating cycle, so that no torque contribution by this cylinder 3 takes place during this expansion stroke.

For internal combustion engines 2 which, as described in the above embodiment, only three cylinders 3 a rolling cylinder deactivation can take place in order to ensure quieter operation of the internal combustion engine 2 to ensure partial cylinder operation.

In 2 is explained in more detail with reference to a flowchart, the method for operating the internal combustion engine in a partial cylinder operation.

In step S1, it is checked if a cylinder 3 not in an active, ie fired operation, operated. If this is the case (alternative: yes), then the method is continued with step S2, otherwise it jumps back to step S1.

In step S2, the intake valve is opened at the beginning of the working cycle, ie with the intake stroke, and in step S3, after reaching the bottom dead center (largest combustion chamber volume) of the piston movement in the cylinder 3 closed during the subsequent compression stroke, in particular at a crankshaft angle of 0 ° to 100 ° after the bottom dead center. There is neither fuel injection nor ignition in the cylinder 3 so that in a subsequent expansion stroke, in which cylinder is deactivated 3 no combustion takes place, a decompression of the previously compressed cylinder charge takes place.

During the subsequent expansion stroke, ie during a crankshaft angle of about 80 ° to 180 ° after top dead center (smallest combustion chamber volume) of the piston movement in the cylinder 3 In step S4, the inlet valve will now be 31 opened again, so that the cylinder charge during a subsequent exhaust stroke in the intake passage, ie in the Saugrohrabschnitt 41 , is ejected. This allows for a portion of the expansion of the combustion chamber of the cylinder 3 in the area of bottom dead center, an open inlet valve 31 is present, so that the emergence of a negative pressure in the combustion chamber of the cylinder in question 3 is avoided.

In step S5, the intake valve is closed again in the region of top dead center.

In 3 is a cylinder pressure diagram shown in which the curves (KE, KA) of the opening strokes H of the intake and exhaust valves 31 . 32 and the cylinder pressure curve P over the crankshaft angle KW for an exemplary cylinder 3 is shown. You can see the corresponding courses during three working cycles Z1 . Z2 . Z3 , where the cylinder concerned 3 is deactivated or switched off for the middle of the illustrated work cycles. One recognizes in 3 in that the inlet valve 31 370 to 400 ° CA (ie 10 ° to 40 ° after oT) is opened shortly after top dead center oT during the intake stroke and at about 560 ° to 600 °, ie between 20 ° and 60 ° after bottom dead center uT, closed again. The compression then takes place only starting from the piston position of about 20 ° to 60 ° after the bottom dead center uT, so that a lower air mass is available for compression.

In order to minimize the gas exchange losses, the opening time becomes the opening of the intake valve 31 chosen accordingly, ie during the expansion stroke corresponding to 20 ° to 60 ° before the bottom dead center uT, so that the pressure in Saugrohrabschnitt 41 same or similar pressure in the cylinders 3 equivalent. As a result, charge exchange losses can be minimized. At the same time is achieved by the reduced compression volume that in the expansion stroke or in the intake stroke no negative pressure in the combustion chamber of the deactivated cylinder 3 arises, can pass through the oil or oil mist from the crankcase via the piston rings in the combustion chamber.

Furthermore, it can be provided that a valve overlap the opening phases of inlet and outlet valve 31 . 32 exists, so that can be further throttled operating point dependent on an increase in the internal residual gas rate.

As through the opening strokes of the intake valve 31 in 4 shown, the opening duration of the intake valves 31 be extended for the deactivated cylinder by a suitable provided for the cylinder deactivation cam shape of the intake valve camshaft. In particular, the cam shape for driving the intake valve should be extended so that the closing time during the compression stroke and the opening time during the expansion stroke as close as possible, ie between 0 ° and 90 ° or at (0 °) top dead center oT. In this way, the charge cycle losses can be further reduced, since the compression end pressure and thus the wall heat transfer in the deactivated cylinders are the lowest.

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 102008005205 A1 [0005]

Claims (12)

Method for operating an internal combustion engine (2) with a plurality of cylinders (3), wherein the cylinders (3) of the internal combustion engine (2) are operated in normal operation according to an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke of a duty cycle, wherein during operation of the internal combustion engine (2) at least one cylinder (3) is deactivated, wherein a deactivated cylinder of the internal combustion engine (2) by the operation of the internal combustion engine (2) is towed and operated according to the following steps: - Opening an inlet valve (31) of the deactivated cylinder (3) at the beginning of the intake stroke; Closing the inlet valve (31) during the compression stroke; - Opening the inlet valve (31) of the deactivated cylinder (3) during the expansion stroke; Closing the inlet valve (31) at the end of the exhaust stroke or after the exhaust stroke. Method according to Claim 1 wherein the exhaust valve (32) of the deactivated cylinder (3) remains closed at least during the exhaust stroke, in particular during the cylinder deactivation. Method according to Claim 1 or 2 wherein the intake valve (31) of the deactivated cylinder (3) is closed during the compression stroke between crankshaft angles of 20 ° and 60 ° after the piston bottom dead center. Method according to one of Claims 1 to 3 wherein the deactivated cylinder intake valve (31) is opened during the expansion stroke between crankshaft angles of 20 ° and 180 ° before the piston bottom dead center. Method according to one of Claims 1 to 4 wherein the intake valve (31) of the deactivated cylinder (3) is closed at a crank angle after the bottom dead center, which corresponds to the crankshaft angle before the bottom dead center to which the inlet valve (31) is opened during the expansion phase. Method according to one of Claims 1 to 5 wherein the opening duration of the intake valve (31) is controlled by a cam structure of an intake valve camshaft (9), wherein by selecting the cam structure, the opening duration of the intake valve (31) for an activated and deactivated cylinder (3) is switchable, wherein the cam structure for the control of the deactivated cylinder (3) provides a longer opening phase of the intake valve (31) than the cam structure for the activation of the activated cylinder (3). Method according to one of Claims 1 to 6 in that the cylinders (3) are deactivated in a rolling manner, so that a cylinder (3) is deactivated in each case only during a work cycle which in particular begins with the intake stroke, wherein an opening phase of the exhaust valve of a cylinder (3) to be deactivated when deactivated with an opening phase of the inlet valve (31) overlaps. Device for operating an internal combustion engine (2) with a plurality of cylinders (3), wherein the cylinders (3) of the internal combustion engine (2) are operable in normal operation according to an intake stroke, a compression stroke, an expansion stroke and an exhaust stroke of a working cycle, wherein during operation of the internal combustion engine (2) at least one cylinder (3) is deactivatable, wherein a deactivated cylinder of the internal combustion engine (2) is towed by the operation of the internal combustion engine (2), the device being designed to: to open an intake valve (31) of the deactivated cylinder (3) during or at the beginning of the intake stroke; to close the inlet valve (31) during the compression stroke; to open the inlet valve (31) of the deactivated cylinder (3) during the expansion stroke; to close the inlet valve (31) at the end of the exhaust stroke or after the exhaust stroke. Engine system with an internal combustion engine (2) and a device according to Claim 8 , Computer program adapted to perform all steps of a method according to one of Claims 1 to 7 perform. Machine-readable storage medium on which a computer program is based Claim 10 is stored. Electronic control unit, which is an electronic storage medium after Claim 11 having.

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