DE102014006032A1 - Method for operating an internal combustion engine - Google Patents

Abstract

Method for operating an internal combustion engine, wherein: - the internal combustion engine has at least one working cylinder, in which a reciprocating piston is received in a displaceable manner between an upper and a lower dead center; - The working cylinder is associated with an outlet valve arrangement with at least one outlet valve; - The working cylinder is associated with an inlet valve assembly having at least three inlet valves; - The internal combustion engine is operated according to the Miller method with during a charge change before reaching the bottom dead center closing intake valves.

Description

The present invention relates to a method for operating an internal combustion engine, in particular a reciprocating engine.

In the prior art, internal combustion engines with three intake valves per cylinder have been proposed to increase efficiency, z. B. according to the document DE 196 14 490 C2 or the publication DE 690 16 289 T2 , From such solutions, however, was again moved away, as these regularly associated with a complex design, especially the complicated valve train and the difficult arrangement of the valves go along, are therefore costly.

In the prior art, it is also known to operate an internal combustion engine advantageous low emissions with early Miller tax times. Characterized in that the time point "intake valve closes" is postponed, ie close the intake valves during a charge change before reaching the bottom dead center or before the start of the compression stroke, cooling of the charge is effected, ie by polytropic expansion, wherein the Filling loss can be compensated to a certain degree by a charge. From this, a reduction in the NOx emission and a reduction in the tendency to knock can advantageously result, see, for example, the document DE 199 05 636 A1 or the publication DE 10 2007 039 210 A1 ,

However, a problem associated with early intake closing is that the valve lift and thus the released opening cross-section decreases with increasing shortening of the opening duration. In this case, the maximum permissible valve acceleration or the permissible forces in the valve drive have a limiting effect, as well as the unintended over flushing of fresh gas into the outlet channels (flushing losses), which causes the valve overlap to be minimized. In addition, the valve lift is also limited by the minimum distance from piston to intake valve (combustion chamber geometry, compression ratio). These limitations result in significant charge cycle work which reduces efficiency.

Based on the known prior art, the present invention, the object of the invention to propose a method for operating an internal combustion engine, with which a low-emission operation with advantageously minimized charge exchange work is possible.

This object is achieved by a method having the features of claim 1.

Advantageous developments and embodiments of the invention are specified in the further claims.

According to the invention, a method is proposed for operating an internal combustion engine, in particular a supercharged internal combustion engine. The internal combustion engine can in this case a gasoline engine, for. As a gasoline or a gas engine, or a diesel engine, z. B. a large diesel engine. The internal combustion engine may be suitable for a mobile application, e.g. B. in the vehicle, or for a stationary application, for. B. be provided in an industrial environment or in a combined heat and power plant. Preferably, the internal combustion engine is a high-speed engine.

The internal combustion engine used with the method comprises at least one working cylinder, in particular a plurality of working cylinders - for example 4, 6, 8, 12, 20 or more cylinders - in each of which a piston or reciprocating piston between a top dead center ( OT) and a bottom dead center (UT) is recorded displaced stroke.

The or a respective working cylinder is further associated with an outlet valve arrangement having at least one outlet valve, preferably with two outlet valves. The exhaust valve assembly may be mounted to a cylinder head of the engine or cylinder, with a respective exhaust valve configured to selectively block an associated exhaust passage on the power cylinder, in particular a main combustion chamber defined therein, for example via a cam (shaft) control.

With the method according to the invention, the (or a respective) working cylinder is further assigned an inlet valve arrangement with at least three inlet valves, preferably with exactly three inlet valves. The intake valves are - like the exhaust valves - preferably also added to the cylinder head of the engine or the working cylinder, and arranged to selectively each set an associated intake passage on the working cylinder, in particular a defined therein main combustion chamber or obstruct, for example, via a cam (waves )control. Via a respective, via the associated inlet valve selectively lockable, inlet channel fresh gas, z. B. ignitable mixture, for. B. after the intake manifold principle, or air, for example, according to the direct injection principle, are conveyed to the combustion chamber of the working cylinder, for example by means of a charge air flow.

In the inventively proposed method for operating the internal combustion engine, the internal combustion engine according to the Miller method (Miller cycle) with during a charge cycle operated before reaching the bottom dead center closing intake valves, that is with an early Miller tax time. The inlet valves may in this case preferably be variably or fully variable controlled, for example via a camshaft adjustment or an eccentric shaft in conjunction with inlet tilting or rocking levers, z. B. also a bucket tappet drive, so that an inlet-closing time of a charge change according to the Miller method with early control time is also advantageously variable.

By the inventive method, which proposes so far the combination of an engine operation with early Millersteuerzeit and an engine operation with at least three intake valves per cylinder, especially in the context of a 5-valve technology with three intake and two exhaust valves per cylinder, the charge exchange work with four-valve solutions two inlet and two outlet valves advantageously reduced. This insofar as by means of the at least three inlet valves, a larger inlet cross-section (typically up to 20%) compared to the millergemäß hitherto only small possible valve lift according to the prior art is releasable. By providing at least three intake valves, the moving mass of a respective valve can furthermore be reduced or advantageously kept low (in particular due to reduced diameter of the valves) (assuming the same material), so that higher valve opening and closing speeds are made possible. The steeper opening and closing ramps - due to reduced flow resistance - again reduces the charge exchange work, thus increasing efficiency. To design an internal combustion engine according to the invention, the intake valve lift curves can be scaled to the maximum permissible acceleration / forces in the valve train.

In the context of the invention, it has been recognized that in the proposed method, the advantages in terms of the achievable reduction of NOx emission and the tendency to knock sufficiently outweigh the disadvantages in terms of any additional design effort when using at least three intake valves per cylinder, the advantages even outweigh.

It is also proposed with the method according to the invention in a further development thereof to operate the internal combustion engine with charging, for example with two-stage or generally multi-stage charging. In this way, the filling loss, which sets in operation with an earlier Millersteuerzeit against a maximize cylinder filling can be compensated by increasing the boost pressure of a supercharger assembly for charging. The charging can be provided, for example, via a charging arrangement with (exhaust) turbocharger, in particular by means of at least one supercharger with variable turbine geometry (VTG supercharger).

Furthermore, for the method preferably, the internal combustion engine is operated with at least one intercooler. The intercooler may preferably be arranged downstream of a supercharger stage or the supercharging arrangement (compressor side), i. H. for cooling the charge air or fresh gas flow (supplied to the working cylinder via the respective inlet channel). In that regard, the intercooler is preferably connected between the supercharger and the cylinder or its inlet valves. With such an arrangement, which provides charging and intercooler, provided with the Miller process temperature reduction can be optimized in the working cylinder.

In addition, an exhaust gas recirculation (EGR) is proposed in the context of the invention, in particular in combination with charging and / or charge air cooling.

According to the invention, an internal combustion engine is also proposed, which is set up to carry out the method explained above. Reference is made in particular to the above explanations for the method.

Further features and advantages of the invention will become apparent from the following description of embodiments of the invention, with reference to the figures of the drawings, which show details essential to the invention, and from the claims. The individual features can be realized individually for themselves or for several in any combination in a variant of the invention.

Preferred embodiments of the invention are explained below with reference to the accompanying drawings. Show it:

1 by way of example and schematically a sectional view focusing a working cylinder of an internal combustion engine usable with the invention.

2 By way of example and schematically a diagram illustrating an early Miller control time in the context of a charge exchange according to the prior art.

3 exemplary and schematically a possible valve arrangement on a cylinder of an internal combustion engine for carrying out the method according to the invention.

1 exemplifies and schematically illustrates a greatly simplified (detail) view of an internal combustion engine 1 , which with the inventive method for operating an internal combustion engine 1 is usable.

The internal combustion engine 1 has at least one cylinder or working cylinder 3 on, in particular a plurality of working cylinders 3 , in which or which ever a (stroke) piston 5 Hubverlagerbar is received, ie between a top dead center (TDC) and a bottom dead center (UT) movable or hubverlagerbar.

The internal combustion engine is preferred 1 a four-stroke engine in which charge cycle and working strokes alternate in a known per se. A respective charge change stroke in this case comprises in particular an exhaust stroke (in the context of which exhaust valves 7 at the working cylinder 3 open and close) and an intake stroke (in the context of intake valves 9 at the working cylinder 3 open and close), a respective working stroke a compression or compression stroke and a power stroke. Furthermore, preference is given by means of the respective piston 5 a crankshaft of the internal combustion engine driven (not shown), the control of the intake 9 and exhaust valves 7 takes place preferably as a function of the angle of rotation of the crankshaft, z. B. via at least one camshaft.

The valves 7 . 9 are preferred on a cylinder head 11 of the internal combustion engine 1 or on the working cylinder 3 arranged, with the intake valves 9 are set up, depending on their control position per an inlet channel 13 to the main burning room 15 to steer, and where the exhaust valves 7 are set up, each an outlet channel 17 from the main burning room 15 to control (depending on their tax position, to the exhaust side). The internal combustion engine 1 can work externally ignited (Ottoprinzip), z. B. via an ignition device 19 , and / or auto-igniting (diesel principle), z. B. with an injector 21 for z. B. equipped a direct injection.

2 shows by way of example and schematically a diagram which illustrates the shift of the inlet closing timing early according to the Miller method according to the prior art, ie in the context of a charge cycle or before a compression stroke. The valve lift in millimeters [mm] is shown here above the crank angle or above the crankshaft angle (KW) in degrees [°].

Obvious, s. the exemplary lift curve A of an intake valve 9 with early Miller tax time in 2 , the intake closing t is made _to a respective intake valve 9 (Valve lift zero) at early Miller control time before reaching the bottom dead center (UT), ie from the early Miller control so far all closing times before UT are included as part of a charge cycle.

For comparison is shown in 2 further exemplarily a lift curve B of an intake valve 9 with conventional control time at which the inlet dead center at bottom dead center (ideally 540 ° CA) causes a maximum delivery or filling level (in relation to the cylinder charge).

As 2 it can be seen, is the valve lift h _{a of} an inlet valve 9 Which is also controlled according to the invention according to the Miller-process with early timing (time intake closing _t over the conventional timing toward top dead center (TDC) is moved, arrow C) with respect to the valve stroke h _b of an open controlled with conventional control time the intake valve 9 reduced. In the prior art, the valve lift h _{a has a} limiting effect on the factors explained in the introduction.

3 now schematically illustrates a possible arrangement of intake valves 9 and exhaust valves 7 on the at least one working cylinder 3 of the combustion engine proposed by the method according to the invention 1 or at a main combustion chamber 15 thereof.

Obvious is the working cylinder 3 associated with an exhaust valve assembly, which two exhaust valves 7 includes. Deviating from this, for example, only an exhaust valve 7 or more than two exhaust valves 7 be provided.

According to the invention, the internal combustion engine provided for the method according to the invention comprises 1 at least three intake valves 9 , which the at least one working cylinder 3 are assigned, in particular exactly three intake valves 9 , By means of the three intake valves 9 In this case, a feasible inlet cross-section or opening cross-section with respect to only two inlet valves 9 ' (shown in dashed lines) advantageously increased (typically by about 20%). Furthermore, the weight of a respective intake valve 9 this compared to conventional intake valves 9 ' reduced (assuming the same material), so that advantageously higher valve lift speeds can be allowed, ie without running the risk of causing damage to the valve components.

According to the method of the invention thus formed internal combustion engine 1 here after - based on 2 - Miller cycle or Miller cycle operated with early intake-to-close timing, ie with intake valves closing during a charge cycle before bottom dead center 9 , The intake closing time t can thus _be generally in the range between OT and UT are located (corresponding eg 360 ° KW to 540 ° CA), preferably z. B. in the range of 0 ° to 120 ° after TDC.

By the inventive combination of an operation of the internal combustion engine 1 with early Miller timing and an intake valve assembly having at least three intake valves 9 , in particular exactly three inlet valves 9 , the advantages of the charge cooling can be realized by the Miller method, wherein also advantageously the charge exchange work is reduced, insofar as larger opening cross-sections can be provided in addition to steeper opening and closing ramps.

The internal combustion engine is preferred 1 as a five-valve engine in particular according to 3 provided.

In particular, in an advantageous combination with a fully variable valve train, the inlet closing time t _{can be} optimally adjusted depending on the operating state of the internal combustion engine. For example, in low load points where a high compression ratio for a good cold start behavior of the internal combustion engine 1 is required, a relatively late closing time for the respective intake valve 9 to get voted. At high load points, where the knocking of the engine 1 problematic may be a low compression ratio by early closing of the respective intake valve 9 to get voted.

LIST OF REFERENCE NUMBERS

1

internal combustion engine

3

working cylinder

5

reciprocating

7

outlet valve

9

intake valve

9 '

intake valve

11

cylinder head

13

inlet channel

15

Main combustion chamber

17

exhaust port

19

ignition device

21

Injector

UT

bottom dead center

OT

Top Dead Center

t _too

Intake closing

h _a , h _b

stroke

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 19614490 C2 [0002]
• DE 69016289 T2 [0002]
• DE 19905636 A1 [0003]
• DE 102007039210 A1 [0003]

Claims (7)

Method for operating an internal combustion engine ( 1 ), where: - the internal combustion engine ( 1 ) at least one working cylinder ( 3 ), in which a reciprocating piston ( 5 ) is received displaceable stroke between an upper (TDC) and a bottom dead center (UT); - the working cylinder ( 3 ) an exhaust valve assembly having at least one exhaust valve ( 7 ) assigned; - the working cylinder ( 3 ) an intake valve arrangement having at least three intake valves ( 9 ) assigned; - the internal combustion engine ( 1 ) according to the Miller method with closing during a charge change before reaching bottom dead center (UT) inlet valves ( 9 ) is operated. Method according to claim 1, characterized in that - the internal combustion engine ( 1 ) is operated with charge; and / or the internal combustion engine ( 1 ) is operated with a two-stage charge; and / or the internal combustion engine ( 1 ) is operated with a multi-stage charge. Method according to one of the preceding claims, characterized in that - the internal combustion engine ( 1 ) is operated with a variable or fully variable valve control, by means of which an inlet-closing time (t _to ) of a change of charge according to the Miller method is variable. Method according to one of the preceding claims, characterized in that - the internal combustion engine ( 1 ) is operated with an exhaust gas recirculation. Method according to one of the preceding claims, characterized in that - the internal combustion engine ( 1 ) is operated with at least one intercooler. Internal combustion engine ( 1 ), characterized in that - the internal combustion engine ( 1 ) is arranged to carry out the method according to one of the preceding claims. Internal combustion engine ( 1 ) according to claim 6, characterized in that - the internal combustion engine ( 1 ) is operated on the Otto principle or as a diesel engine.

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