AT501185A1 - METHOD FOR OPERATING AN INTERNAL COMBUSTION ENGINE - Google Patents

Description

55180

The invention relates to a method for operating an internal combustion engine, in particular a spark-ignited internal combustion engine, wherein at least in an engine operating range both an external and internal exhaust gas recirculation is performed, and an internal combustion engine for carrying out this method. Furthermore, the invention relates to a motor controller for the application of the method.

JP 04-175449 A describes an internal combustion engine, which has an internal and an external exhaust gas recirculation system to reduce the pumping losses in the partial load range and to prevent the occurrence of knock events. Here, an internal exhaust gas recirculation is performed in the low part load range and an external exhaust gas recirculation in the high load range. As the load increases, the proportion of the internally recirculated exhaust gas quantity is thus reduced and the proportion of the externally recirculated exhaust gas quantity is increased. The internal exhaust gas recirculation is controlled by adjusting the control times by means of a phase shifter. The recirculation of external exhaust gas in the high load range causes an increase of the cylinder pressure and a lowering of the cylinder temperature. Increasing the cylinder pressure has an accelerating effect on the combustion, but lowering the combustion temperature counteracts this and slows down combustion. As a result, the knocking behavior and the residual gas compatibility at full load can not be significantly improved.

The object of the invention is to avoid these disadvantages and to improve the knock behavior and the Restgasverträglichkeit, especially at medium to high partial load and at full load.

According to the invention, this is achieved in that to reduce the tendency to knock, in particular during or before a knocking event, the turbulent kinetic energy in the cylinder is increased at least for a short time compared with a reference operating point, preferably at the same load. For example, the same operating point at maximum internal residual gas recirculation rate without external residual gas recirculation can be considered as the reference operating point.

To reduce the tendency to knock and ensure the Restgasverträglichkeit the combustion process, the turbulent kinetic energy in the cylinder is increased with simultaneous increase in the recirculated exhaust gas amounts, while adjusting the timing of the recirculated external residual gas. The method according to the invention makes use of the fact that, with increasing turbulent kinetic energy, the flame propagation speed increases, thereby increasing the residual gas compatibility of the combustion process and decreasing the tendency to auto-ignition (knocking).

In order to increase the turbulent kinetic energy, individual or a combination of different charge movement measures can be taken. According to the invention, to increase the turbulent kinetic energy in the cylinder space, the valve lift of at least one exhaust valve and / or at least one intake valve is reduced and / or the intake closing time is retarded. In addition, it may be provided that the turbulent kinetic energy is increased by at least one combustion chamber side, injection-side or channel charge movement measure, combustion chamber side preferably the turbulent kinetic energy is increased by a Ventilmaskierung or by expressing a squish flow in the cylinder chamber. By targeted charge movement and increase in kinetic energy, the residual gas compatibility can be lifted and thus a high exhaust gas recirculation rate can be realized.

Furthermore, it can be provided that the residual gas content in the cylinder chamber is adjusted at least during the increase of the turbulent kinetic energy by varying the opening time of the inlet valve, the closing time of the inlet valve and / or the closing time of the outlet valve.

A further measure according to the invention provides that the profile of the closing edge and / or the closing ramp of at least one inlet valve is changed with respect to the reference operating point with internal residual gas, wherein the closing edge and or the closing ramp during operation with internal and external Restgasbeimengung flatter than in the reference operating point with pure internal residual gas admixture is set.

Cooling of the externally recirculated exhaust gas also has an advantageous effect on reducing the tendency to knock.

For carrying out the method, an internal combustion engine with external and internal exhaust gas recirculation system, which has at least one means for increasing the turbulent kinetic energy in the cylinder chamber, is suitable. The means for raising the kinetic energy can be formed by a variable, preferably a fully variable valve train. In simple variable valve train systems with phase adjustment of one or both valve lift functions of the intake and exhaust camshafts, the increase in kinetic energy is achieved by retarding the intake closing timing from the reference operating point. In doing so, the completion of the energy input is postponed, resulting in a higher kinetic turbulent energy!

veau is generated during the combustion process. In this case, the internal residual gas quantity, in the case of simple variable valve train systems, is ensured by simultaneous late adjustment of the outlet closing time. In fully variable valve train systems, in addition to simply variable valve timing systems with phasing, it is possible to limit the lift of the intake and / or exhaust valves and thus further increase the inflow velocity into the cylinder space, causing an additional increase in turbulent energy in the cylinder space. Further, as with simple variable valve train systems, the intake closing timing may be retarded, thereby maintaining an increased kinetic energy level in the cylinder until the combustion event. Additional enhancement of the turbulent kinetic energy may be achieved by a combustion chamber side fuel injection side or channel side charge motion device, such as channel shutoff or tumble flap. Here, the fuel injection-assisted charge movement by direct injection into the combustion chamber is of particular importance. The injection pulse occurring in the case of direct injection into the combustion chamber, in addition to the charge movement measures mentioned above, increases the turbulent kinetic energy in the combustion chamber while simultaneously cooling the charge quantity in the cylinder to reduce the charge temperature. By using targeted direct multiple injection into the combustion chamber, the turbulent kinetic energy level in the combustion chamber can thus be additionally controlled.

It is preferably provided that the internal combustion engine has a supercharger system for increasing the inlet pressure. Alternatively, the internal combustion engine but also be a naturally aspirated engine.

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

1 shows the tendency to knock as a function of the pressure-temperature coefficient, FIG. 2 shows the tendency to knock as a function of the kinetic turbulent energy, FIG. 3 shows the tendency to knock as a function of parameters in the cylinder space, FIG. 4 shows a valve lift crank angle and FIG a turbulent kinetic energy-crank angle diagram.

As shown in FIGS. 1, 2 and 3, the knocking tendency K depends on the cylinder pressure p, the cylinder temperature T and the turbulent kinetic energy Ekin in the cylinder. The tendency to knock K increases approximately proportionally with the product p * T of the cylinder pressure p and the cylinder temperature T and decreases with increasing turbulent kinetic energy Ekm- Kl with the knock limit is indicated. BDC and TDC in FIGS. 4 and 5 denote the lower and upper dead center of the piston, respectively.

The aim is to achieve a reduction in knock tendency K with a high p * T coefficient in the cylinder. High exhaust gas recirculation rates at high load are to be guaranteed.

The high residual gas compatibility is achieved by raising the turbulent kinetic energy Ekm, see Fig. 5. This can be increased at medium / high part load and full load, the external exhaust gas recirculation amount and the internal exhaust gas recirculation amount are kept approximately the same. The increase of the turbulent kinetic energy Ekin takes place by means of at least one charge movement measure, for example the reduction of the intake valve lift by means of a fully variable valve drive device or the retardation of the intake closing time. This effect can be intensified by the direct injection of fuel into the combustion chamber. Where this effect can be increased again by multiple injection, see FIG. 4 and FIG. 5. In order to ensure the same cylinder filling, the inlet closing Ic is retarded and adjusted or via a throttle valve.

In FIG. 4, 0 indicates the exhaust and, with I, the intake valve lift curve in a reference operating point assigned, for example, to the high partial load. The exhaust valve lift O and O 'examples, in combination with the intake valve lift functions Γ and Γ, show possible operating settings with increased turbulent kinetic energy as shown in FIG. The delayed inlet closure I'c and I "c causes a high level of turbulence to be delayed late into the combustion area, which has an advantageous effect on the rate of combustion (Figure 5: Ekin '). In example Γ with a smaller valve lift, the charge flows into the cylinder space at increased speed and thus increases the kinetic energy Ekln in the cylinder space (FIG. 5: Ekln "). By means of the fully variable valve train further the edge velocity, and the ramp speed of the survey curves can be changed so that a high turbulent kinetic energy is generated in the cylinder chamber. Furthermore, it is possible to change the exhaust port, the intake port, and the intake port start to optimize knock tendency, residual gas compatibility, and combustion. In addition, the turbulent kinetic energy can be increased by further charge movement measures, such as valve masking for inlet and / or outlet openings, by crimp flow-generating design measures, by channel-side measures or injection-based measures. In Fig. 4, for example, the fuel injection portions Inj. 1, Inj. 2 are shown for multiple injection. The resulting increase in turbulent kinetic energy is exemplified in Fig. 5 by the 1 1 ···· ·· - · 5 ·

Line Ekln " Inj., Where here an overlap of the turbulent kinetic energy with Ekin " is shown. Channel-side measures in this context are, for example, tumble and swirl channels, as well as swirl and / or tumble control devices in the inlet or outlet channel.

It is particularly favorable if the internal combustion engine has a supercharger system, for example a turbocharger, compressor, or the like. In this case, it may be advantageous, in particular in unthrottled engines, when the external exhaust gas recirculation line opens into the inlet line via a Venturi unit. In this way, high exhaust gas recirculation rates can be achieved even under unfavorable pressure conditions between the exhaust and inlet systems.

Low temperatures of the externally recirculated exhaust gas have an advantageous effect on the tendency to knock. Therefore, a recirculated exhaust gas cooling device is advantageous.

The inventive method is particularly suitable for Otto internal combustion engine, regardless of clocking and / or Zylinderabschaltstrategien.

What is essential is that the knock limit can be shifted in the direction of early ignition times, so that the internal combustion engine can be operated in the region of optimum efficiency or close to this range in the full load and in the high partial load, resulting in significant advantages for consumption and emissions.

The inventive method is independent of the injection system, the ignition system, the supercharging system, the air / fuel strategy and can be used in combination with various exhaust aftertreatment systems. While the method is best suited to fully variable valve train systems, it is also advantageous to employ the method with partially variable valve train systems.

Claims (19)

1 PATENT CLAIMS 1. A method for operating an internal combustion engine, in particular a spark-ignited internal combustion engine, wherein both an external and internal exhaust gas recirculation is performed at least in an engine operating range, characterized in that to reduce the tendency to knock, especially during or before a knock event, the kinetic turbulent Energy in the cylinder - compared to a reference operating point, preferably at high load - is increased at least briefly. 2. The method according to claim 1, characterized in that when increasing the turbulent kinetic energy, the internal exhaust gas recirculation amount is kept constant or increased. 3. The method according to claim 1 or 2, characterized in that when increasing the turbulent kinetic energy, the external exhaust gas recirculation amount is increased. 4. The method according to any one of claims 1 to 3, characterized in that to increase the turbulent kinetic energy in the cylinder chamber, the inlet closing timing of the intake valve lift function is retarded. 5. The method according to any one of claims 1 to 3, characterized in that to increase the turbulent kinetic energy in the cylinder chamber, the valve lift of at least one exhaust valve and / or at least one intake valve is reduced. 6. The method according to any one of claims 1 to 4, characterized in that the residual gas content in the cylinder chamber at least during the increase of the turbulent kinetic energy by means of varying the opening time of the intake valve, the closing time of the intake valve and / or the closing time of the exhaust valve is adjusted. 7. The method according to any one of claims 1 to 5, characterized in that the course of the closing edge and / or the closing ramp of at least one inlet valve in operation with high residual gas rate, preferably with internal and external Restgasbeimengung compared to the reference operation with lower or equal residual gas rate without external Restgasbeimengung , is changed, wherein preferably the closing edge is set flatter in operation with internal and external residual gas additive than in the reference mode. * ···· ····· • · · ········· 8. The method according to any one of claims 1 to 6, characterized in that the turbulent kinetic energy is increased by at least one combustion chamber side, fuel injection side or channel-side charge movement measure. 9. The method according to claim 8, characterized in that the turbulent kinetic energy is increased by at least one injecting into the combustion chamber fuel introduction, wherein preferably fuel is injected multiple times during a power stroke. 10. The method according to claim 8, characterized in that the kinetic turbulent energy is increased by a Ventilmaskierung or by expressing a squish flow in the cylinder chamber. 11. The method according to any one of claims 1 to 10, characterized in that the inlet pressure is raised with a supercharger system. 12. The method according to any one of claims 1 to 11, characterized in that the externally recirculated exhaust gas is cooled. 13. Internal combustion engine for carrying out the method according to one of claims 1 to 12, wherein the internal combustion engine has an external and an internal exhaust gas recirculation system, characterized in that the internal combustion engine has a means for increasing the turbulent kinetic energy in the cylinder chamber. 14. Internal combustion engine according to claim 13, characterized in that the means for raising the turbulent kinetic energy is formed by a fully variable valve drive means. 15. Internal combustion engine according to claim 13 or 14, characterized in that the means for raising the turbulent kinetic energy has a combustion chamber side, fuel injection side or channel-side charge movement device. 16. Internal combustion engine according to one of claims 13 to 15, characterized in that the internal combustion engine has a supercharger system for raising the inlet pressure, wherein the supercharger system preferably consists of an exhaust gas turbocharger or a mechanically driven compressor. 17. Internal combustion engine according to any one of claims 13 to 16, characterized in that the external exhaust gas recirculation system comprises an exhaust gas recirculation cooler. 18. Internal combustion engine according to any one of claims 13 to 17, characterized in that in the region of the confluence of the exhaust gas recirculation line of the external exhaust gas recirculation system in the inlet line, a Venturi unit is arranged. 19. Engine control device using the method according to one of claims 1 to 12, which controls the internal combustion engine so that to reduce the tendency to knock, especially during or before a knock event, the kinetic turbulent energy in the cylinder - compared to a reference operating point, preferably at high Load - at least temporarily increased, with internal and external exhaust gas recirculation is performed. Patent Attorney Dipl.-Ing. Mag. Michael Babelul «A-11S0 Vienna. Mariahilfer Gürtel 39/17 Tel .: (+43 1) 892 89 33-0 fax: (+43 1) S92 89 333 e-mail: o »tent © babe! Uk.at 2004 12 16 Fu / Sc