DE102004027474B4 - Four-stroke internal combustion engine with turbocharger and method for optimizing its operation - Google Patents

Abstract

internal combustion engine with turbocharger, in which each cylinder with at least one Exhaust valve is provided during each exhaust stroke of Cylinder exhaust gas from a combustion chamber to the exhaust gas turbocharger escape leaves, characterized in that the exhaust valve (34) during the exhaust stroke multiple actuated is to open it several times in the course of the exhaust stroke and to close again.

Description

The The invention relates to a four-stroke internal combustion engine with turbocharger and a method for optimizing the operation of a four-stroke internal combustion engine with exhaust gas turbocharger according to the preamble the claims 1 and 3 or 7 and 15.

At the Operation of internal combustion engines is an endeavor, already at lowest speeds a highest possible To provide torque. This is contrary to the fact that the combustion chambers the cylinder partly incomplete filled with fresh gas and that its implementation due to a strong knock limit by high residual gas contents in the combustion chambers with an unfavorable efficiency he follows. In internal combustion engines with turbocharger is added, that the turbocharger for the low mass flow rates can not be optimally designed in the lower speed range. Especially in four-cylinder turbocharged inline engines, where the exhaust gases all Cylinder in one and the same manifold is about to be ejected an interaction or overlay the outlet shocks of neighboring Cylinder watch because the exhaust valves over a crankshaft angle of more than 180 ° must remain open to At high speeds complete exhaustion ensure the residual gas from the cylinder. This interaction or overlay is particularly strong at low speeds, because there the overlay periods due to the crankshaft angle based opening times the exhaust valves longer are.

A Increase the performance of a turbocharger or its turbine is basically possible, by increasing the energy of the exhaust gas supplied to the turbocharger. A such increase the exhaust gas energy can either by increasing the exhaust gas mass flow or by increasing the exhaust gas enthalpy, i. Increase of Pressure and / or the temperature of the exhaust gas take place. There to enlarge the Exhaust gas mass flow, however, a stronger Charging the cylinder is required, separates such an approach as a primary measure to Raising the turbocharger turbine output. An improvement the exhaust enthalpy would be for example, possible by opening it early Exhaust valves are a part of the high pressure work of the cylinder to increase the Turbine power of the turbocharger is used. This, however, results especially in four-cylinder in-line engines again increased interaction or overlay the outlet shocks of neighboring Cylinder of the engine. Such an interaction or overlay Affects unfavorable on the so-called shock charging of the turbocharger, which in addition to the static pressure level before Exhaust gas turbocharger or the pressure drop in the exhaust gas turbocharger for the performance of its turbine decisive is. Under bump charging one understands the charge as a result of a brief burst of energy in the exhaust gas When opening an exhaust valve when the high pressure exhaust gas relaxed in the exhaust side, which is a strong acceleration of the Exhaust gas in the leading to the turbocharger Exhaust pipe and thus a steep increase in its kinetic Energy, which then in the turbine during the bumping charge is converted into turbine power.

The DE 40 21 204 C2 discloses a device for charging an internal combustion engine, in which the pressure and flow energy (enthalpy) of the exhaust gas flow is utilized for acceleration and compression of the intake air before the combustion chamber by an exhaust passage and a suction port of a cylinder are directly connected by an overflow channel and in the overflow a controllable shut-off is provided, when it opens a pressure surge generated in the exhaust pipe and thereby the air is accelerated in the intake manifold according to the injector principle. In order to increase the cylinder pressure effectively, there the exhaust valve of the cylinder can be opened several times, so that the pressure wave passes directly through this back into the cylinder.

From the DE 103 46 830 A1 It is also already known to repeatedly open a pulse flap arranged in a suction pipe of a cylinder of an internal combustion engine in front of its inlet valve during a suction stroke of the cylinder in order to generate a plurality of short intake mass flow pulses for increasing the cylinder charge.

In addition, the reveals DE 199 06 463 C1 a turbocharged internal combustion engine with exhaust gas recirculation, in which one or more cylinders, an additional exhaust gas recirculation valve is provided which is opened in the exhaust gas recirculation during the exhaust stroke of the respective cylinder to achieve operating point optimal exhaust gas recirculation rates.

From the DE 197 39 054 A1 For example, an internal combustion engine is known in which the exhaust tract of each cylinder comprises two exhaust pipes individually led to an exhaust gas turbocharger, one of which is always open and the other is closable to control gas exchange operations to optimally charge the engine and good turbocharger response and speed To achieve the onset of a catalyst.

Furthermore, the describes EP 0 730 706 B1 ( DE 694 05 247 T2 ) a method for improving the performance of a by an exhaust gas turbine the supercharged internal combustion engine, are exploited in the phases of a high instantaneous exhaust gas pressure to cause in a certain speed range, a reloading of the cylinder with the previously stored in the exhaust duct air.

outgoing This is the object of the invention, an internal combustion engine and to provide a method of the type mentioned, with in particular at low speeds, the charging of the Cylinder and thus the torque of the internal combustion engine significantly increase to let.

at Internal combustion engines with a single exhaust valve per cylinder This object is achieved by the invention solved, that the exhaust valve at least at low speeds in the course of Push-out or exhaust stroke opened several times and closed again while in internal combustion engines with two separately operable exhaust valves per Cylinder the two exhaust valves in the course of the exhaust stroke alternately pressed one after the other can be with which the same result can be achieved. Basically, that would be first This procedure also applies to internal combustion engines with two exhaust valves per cylinder applicable by both exhaust valves in the course of exhaust stroke open several times together and be closed again.

Of the Invention is based on the idea, in the course of an exhaust stroke a cylinder as in the prior art, a single shock charging in turbine turbocharger, if the exhaust valve or the exhaust valves of the respective cylinder at the beginning of the exhaust stroke to be opened but to exploit this effect several times in the course of the exhaust stroke, by after a first momentary opening of the exhaust valve or from one of the two exhaust valves at the beginning of the exhaust stroke the residual gas remaining in the cylinder in the course of the ejection TAK again is compressed while the exhaust valve or the two exhaust valves are closed, and by then the exhaust valve or the other of the two exhaust valves is opened again, around the thus compressed residual gas in the exhaust pipe to the turbocharger to escape and there is another bumping in the turbine cause. In the compression of the residual gas in the combustion chamber between the first and second opening the exhaust valve is the energy content of the residual gas through the supplied Piston or compression work increased, bringing a total of higher Torque and a higher one Achieve efficiency of the internal combustion engine, if this piston or compression work by increasing turbine performance of the turbocharger and a thereby caused stronger Charging the cylinder with compressed fresh gas and its thermodynamic Implementation in the form of a surplus of usable energy overcompensated during the combustion process becomes.

While the Number of opening and closing operations of Outlet valve or the exhaust valves of each cylinder during its exhaust stroke with a camshaft-mounted mechanical valve train system are expected to be limited to a total of two are with electromechanical or electrohydraulic valve train systems especially at low speeds also more than two opening operations during one exhaust stroke possible.

Around the exhaust strokes of the exhaust valves the individual cylinder of the internal combustion engine for optimum shock charging Cheap to coordinate with each other Both the times in which the exhaust valves of individual Cylinders or groups of cylinders are opened as well as the Duration of the respective opening operations of individual cylinders or groups of cylinders are chosen differently. The same applies to the opening time the several opening operations of a Exhaust valve or two exhaust valves of a cylinder in Course of its exhaust stroke.

While in particular in four-cylinder in-line engines, the exhaust valve or one of the two exhaust valves of each cylinder expediently at the bottom dead center of the Cylinder is opened for the first time, to an interaction or overlap of the preliminary blow this cylinder with the last ejection of the preceding cylinder can be avoided in other engines, in particular in six-cylinder V engines, where this problem occurs to a lesser extent, the energy content the exhaust gas at the first shock charging according to a further advantageous embodiment of the invention even more elevated be that exhaust valve or one of the two exhaust valves each cylinder just before reaching bottom dead center is opened, to a part of the high-pressure compression work of the piston to the other increase to use the turbine power.

In a four-cylinder in-line engine with two opening operations per exhaust stroke, another preferred embodiment of the invention provides for the exhaust valve or one of two exhaust valves to be opened for the first time at about bottom dead center to vent the pressurized exhaust gas in the cylinder to the exhaust side until the pressure difference before and behind the opened exhaust valve is about zero, that subsequently with the exhaust valve closed or the exhaust vents closed Tilen the residual gas in the cylinder is compressed by the piston, preferably until the pressure in the cylinder approximately equal to the pressure before the first opening of the exhaust valve or the one of the two exhaust valves, and then either at one exhaust valve per cylinder, this exhaust valve again at or at two exhaust valves to open the other exhaust valve to let another exhaust blow into the turbocharger leading exhaust pipe.

Around the remaining gas as completely as possible to rinse the cylinder, will follow the intake valve of the cylinder is opened and when open Fresh gas exhaust valve is fed into the cylinder, opening the Inlet valve preferably then takes place when the pressure on the Outlet side has fallen below the pressure on the inlet side, around a reverse flow to prevent towards the inlet side. At the latest before the first opening of the Exhaust valve of a cylinder adjacent to the exhaust pipe then the exhaust valve will be final closed, causing a delay avoided by residual gas in the cylinder and complete relaxation the pressure surge without overlap or interaction in the turbine can be ensured.

There the opening times the exhaust valves in dependence controlled by the crankshaft angle, provides a further advantageous Embodiment of the invention, that the valve control at higher speeds switchable to a conventional strategy, in other words the exhaust valve is opened only once in the course of the exhaust stroke.

The inventive method is for all four-stroke turbo engines independent of cylinder number and working method (petrol / diesel engine) applicable and allows the use of large, in the lower speed range not optimally operating turbocharger, their charging power in this area by means of the method according to the invention can be improved, so at low speeds for higher torques to care. Furthermore the response of the turbocharger is improved because of this through the increase the exhaust gas energy provided a faster startup behavior shows, with which the so-called "turbo lag" overcome faster can be. About that In addition, with the method according to the invention the potential for a so-called "down-sizing" of the internal combustion engine improves, because there is a shift of its operating points in the map into areas allowed with better efficiency.

in the The following is the invention with reference to an illustrated in the drawing embodiment explained in more detail. It demonstrate:

1 : a schematic representation of an internal combustion engine with exhaust gas turbocharger;

2a to 2d : Longitudinal views of a part of a cylinder of the internal combustion engine 1 at various stages during an exhaust stroke or at different crankshaft angles;

3 : the gas pressure in the cylinder as a function of the crankshaft angle;

4 : the pressure at the intake or exhaust side of the cylinder as a function of the crankshaft angle;

5 : the opening stroke of an exhaust valve of an intake valve of the cylinder depending on the crankshaft angle;

6 : the mass flow through the intake and exhaust valve of the cylinder as a function of the crankshaft angle.

The in 1 the drawing shown schematically, with an exhaust gas turbocharger 2 equipped and trained as direct injection four-stroke gasoline engine in four-cylinder in-line combustion engine 4 consists essentially of a cylinder block 6 with four cylinders 8th , each on the suction or inlet side 10 through a charge air line 12 compressed charge air from a compressor 14 the exhaust gas turbocharger 2 is fed and their exhaust gases respectively on the exhaust or exhaust side 16 through an exhaust pipe 18 to a turbine 20 the exhaust gas turbocharger 2 are passed, which in a known manner the compressor 14 drives. The from the turbine 20 Exiting exhaust gases are through an exhaust pipe 22 discharged to the environment while the out of the compressor 14 to the internal combustion engine 4 supplied compressed charge air before entering the cylinder 8th for cooling by one behind the compressor 14 in the charge air line 12 arranged intercooler 24 is directed.

How best in the 2a to 2d shown is that of the cylinder 8th as well as a cylinder head 26 and from a piston 28 limited combustion chamber 30 every cylinder 8th via an inlet valve 32 with the charge air line 12 and via an exhaust valve 34 with the exhaust pipe 18 connected. The connection between the combustion chambers 30 the cylinder 8th and the charge air line 12 or the exhaust pipe 14 takes place via one in the cylinder head 26 recessed inlet or outlet channel 36 respectively. 38 , The outlet channels 38 all cylinders 8th flow in an exhaust manifold 40 ( 1 ), which is part of the turbocharger 2 leading exhaust pipe 18 forms. Every cylinder 8th also has an injector (not shown) and one between the inlet valve 32 and the exhaust valve 34 arranged spark plug 42 on.

The 2a to 2d show longitudinal sectional views of the combustion chamber 30 with different piston positions and different opening and closing states of the intake and exhaust valves 32 . 34 during an exhaust stroke of the cylinder 8th , The illustrated states are each about a crankshaft angle of about 55 ° CA apart, wherein 2a the state at a crank angle φ of about 555 ° CA near the bottom dead center of the piston, 2 B the state at a crankshaft angle φ of about 610 ° CA, 2c the state at a crankshaft angle φ of about 665 ° KW and 2d shows the state at a crank angle φ of about 720 ° CA.

Analogously, the show 3 to 7 the gas pressure p _z in the cylinder 8th , the pressure p _e and p _a at the inlet and outlet sides, respectively 10 respectively. 18 of the cylinder 8th , the valve lift h of the intake and exhaust valves 32 . 34 of the cylinder 8th , as well as the mass flow dme through these valves 32 . 34 depending on the crankshaft angle φ.

How best in 3 shown, the pressure in the cylinder increases 8th after ignition it rises sharply to about 8 MPa and then drops steadily to about 1 MPa, while the piston 28 is driven by the combustion gases in the direction of its bottom dead center, which he reaches at a crankshaft angle φ of 540 ° CA. Immediately thereafter, the exhaust valve is opened at a crank angle φ of about 550 ° CA, as in 2a for a crankshaft angle φ of about 555 ° KW and in 5 represented by an increase in its valve lift from 0 to 8 mm. Almost half of that escapes in the cylinder 8th located combustion gases through the exhaust valve, which is why the pressure in the cylinder further decreases stepwise to about 0.4 MPa, as in 3 shown. At the same time, the escape of the combustion gases through the exhaust valve 34 on the outlet side, a steep rise in pressure to the same pressure of 0.4 MPa, as in 4 shown. This steep outlet-side pressure rise leads as a result of the relaxation of the exhaust gas in the exhaust pipe 18 to a strong increase in the speed and thus the kinetic energy of the exhaust gas. When reaching the turbine 20 This in turn leads to an impact charge, that is, a conversion of this additional kinetic energy of the exhaust gas in turbine power, which is the compressor 14 a higher compressor capacity and thus a stronger charge of the internal combustion engine 4 entails.

After balancing the pressure difference between the pressure in the combustion chamber 30 and the pressure of the outlet side 16 becomes the exhaust valve 34 closed at a crankshaft angle φ of about 560 ° KW, as in 5 represented by a drop in its valve lift from 8 to 0 mm. As in 4 shown decreases with the decay of the pressure surge then the pressure on the outlet side 16 down to a value of about 0.12 MPa, while conversely, the pressure in the cylinder 8th due to the upward movement of the piston 28 and the resulting compression of the residual gas in the combustion chamber 30 increases again to a value of about 1 MPa, as in 1 shown. This value is reached at a crank angle φ of about 630 ° CA, whereupon the exhaust valve 34 reopened as in 5 represented by an increase in its valve lift from 0 to 8 mm. This leads in the cylinder 8th to a further stepped pressure drop, as in 3 shown, while on the outlet side, the pressure abruptly again increases to about 0.3 MPa, as in 4 shown. The subsequent relaxation of this second pressure or exhaust stroke in turn leads to an increase in the velocity and kinetic energy of the leaked residual gas, as previously described for the first pressure or exhaust stroke. This has on the turbine 20 a second bump charge during the exhaust stroke of the cylinder 8th As a result, the previously from the piston 28 Performed compression work is implemented in turbine power.

How best 5 visible and as in 2c shown for a crank angle φ of 665 ° KW, the exhaust valve remains 34 at the second opening process considerably longer open, about a crankshaft angle φ of 100 ° KW compared to a crankshaft angle φ of about 10 ° KW at the first opening operation. How out 6 it can be seen has this open exhaust valve 34 As a result, even after the relaxation of the pressure surge from the piston 28 Residual gas from the cylinder 8th is pushed out what is in 6 by a gently sloping mass flow through the outlet valve 34 between the two crankshaft angles φ equal to 640 ° KW and φ equal to 680 ° KW can be seen.

How best in 2d and 5 is shown with the exhaust valve open 34 the inlet valve 32 starting at a crankshaft angle φ of about 680 ° KW slowly open to the combustion chamber 30 Remaining residual gas by flushing with fresh gas as far as possible to eliminate. This conditioner appears in 6 in the form of a substantially consistent mass flow through the inlet and outlet valves 32 . 34 until the latter is finally closed at a crank angle φ of about 730 ° CA, immediately before the exhaust valve of the adjacent cylinder 8th , whose ventilation duct 38 adjacent to the venting channel 38 of the cylinder 8th in the manifold 40 opens, is opened for the first time and therefore in 4 a new pressure surge on the outlet side 16 can be observed. By previously closing the exhaust valve 34 it is avoided that due to this pressure surge residual gas back into the cylinder 8th is pushed.

While the cylinders 8th in the embodiment shown in the drawing only one outlet valve in each case 34 that during the exhaust stroke of the cylinder 8th from a valvetrain system (not shown) of the internal combustion engine 4 can be opened twice in succession and closed again at a time interval, in cylinders with two exhaust valves and a valve train system can be provided which opens these two valves independently in alternation, the other one remains closed.

2

turbocharger

4

internal combustion engine

6

cylinder block

8th

cylinder

10

suction or inlet side

12

Turbo pipe

14

compressor

16

exhaust or exhaust side

18

exhaust pipe

20

turbine

22

exhaust pipe

24

Intercooler

26

cylinder head

28

piston

30

combustion chamber

32

intake valve

34

outlet valve

36

inlet channel

38

exhaust port

40

exhaust manifold

42

spark plug

Claims (24)

Combustion engine with turbocharger, in which each cylinder is provided with at least one exhaust valve, which allows exhaust gas to escape from a combustion chamber to the exhaust gas turbocharger during each exhaust stroke of the cylinder, characterized in that the exhaust valve ( 34 ) is repeatedly actuated during the exhaust stroke to repeatedly open and close it during the exhaust stroke. Internal combustion engine according to claim 1, characterized in that opening times of the exhaust valves ( 34 ) of individual cylinders ( 8th ) or groups of cylinders ( 8th ) of the internal combustion engine ( 4 ) are different in length. Internal combustion engine with turbocharger, in which each Cylinder is provided with several exhaust valves, which during each exhaust stroke of the cylinder exhaust gas escape from a combustion chamber to the exhaust gas turbocharger Let, characterized in that the exhaust valves during the exhaust stroke individually operable are to change them sequentially in the course of the ejection stroke to open and to close again. Method according to claim 3, characterized that the opening hours at least a portion of the exhaust valves during an exhaust stroke are different lengths. Internal combustion engine according to one of the preceding claims, characterized in that opening times of the exhaust valves ( 34 ) of individual cylinders ( 8th ) or groups of cylinders ( 8th ) of the internal combustion engine ( 4 ) are different in length. Internal combustion engine according to one of the preceding claims, characterized in that a valve train system of the internal combustion engine between a multiple opening of the or each exhaust valve ( 34 ) during an exhaust stroke and a single opening of the or each exhaust valve ( 34 ) is switchable. Method for optimizing the operation of a four-stroke internal combustion engine with an exhaust-gas turbocharger, in which exhaust gas is expelled from the combustion chamber of each cylinder of the internal combustion engine during each exhaust stroke of the cylinder through at least one exhaust valve into an exhaust-gas conduit leading to the exhaust-gas turbocharger, characterized in that the exhaust valve ( 34 ) is opened several times in the course of the exhaust stroke and closed again. Method according to claim 7, characterized in that the outlet valve ( 34 ) is opened at least twice as long during the exhaust stroke. Method according to claim 7 or 8, characterized in that the outlet valve ( 34 ) is opened twice in the course of the exhaust stroke and closed again. Method according to one of claims 7 to 9, characterized in that the outlet valve ( 34 ) approximately at the bottom dead center of a piston ( 28 ) of the cylinder ( 8th ) is opened for the first time and essentially after a reduction in the pressure difference in front of and behind the outlet valve ( 34 ) is closed again. Method according to claim 10, characterized in that the outlet valve ( 34 ) in the We sentlichen after a compression of the in the combustion chamber ( 30 ) residual gas is opened for the second time and at the latest before the first opening of the exhaust valve ( 34 ) one in relation to the exhaust pipe ( 18 ) adjacent cylinder ( 8th ) is closed again. Method according to one of claims 9 to 11, characterized in that at least one inlet valve ( 32 ) of the cylinder ( 8th ) during the second opening operation of the exhaust valve ( 34 ) is opened. Method according to claim 12, characterized in that the inlet valve ( 32 ) is opened when an outlet-side pressure level falls below an inlet-side pressure level. Method according to one of claims 7 to 13, characterized in that the outlet valve ( 34 ) is opened only once at higher speeds in the course of the exhaust stroke. Method for optimizing the operation of a four-stroke internal combustion engine with exhaust gas turbocharger, in which exhaust gas from the combustion chamber of each cylinder of the Internal combustion engine during every exhaust stroke of the cylinder through a plurality of exhaust valves in one to the exhaust gas turbocharger premier Exhaust pipe is pushed out, characterized in that at least a part of the exhaust valves in the course of the exhaust stroke one after the other and opened alternately closed again. Method according to claim 15, characterized in that that at least a portion of the exhaust valves in the course of the exhaust stroke opened for different periods becomes. Method according to claim 15 or 16, characterized that two exhaust valves are provided, which in the course of the exhaust stroke opened once each and closed again. Method according to one of claims 15 to 17, characterized that a first of the two exhaust valves at about bottom dead center opened and essentially after a reduction in the pressure difference before and behind the exhaust valve is closed again. Method according to 18, characterized in that the second of the two exhaust valves essentially after one Compression of remaining in the combustion chamber residual gas open and no later than before opening of the first exhaust valve of a neighboring with respect to the exhaust pipe Cylinder is closed again. Method according to one of claims 17 to 19, characterized that at least one inlet valve of the cylinder is opened, while that second exhaust valve opened is. Method according to claim 20, characterized in that that the inlet valve is opened when an outlet side pressure level is below an inlet side Pressure level drops. Method according to one of claims 15 to 21, characterized that the exhaust valves at higher Speeds are opened together become. Method according to one of claims 7 to 22, characterized that the exhaust valves of individual cylinders or groups of cylinders open differently become. Method according to one of claims 7 to 23, characterized in that a first-time opening of the or an exhaust valve ( 34 ) before reaching bottom dead center.