DE10324176B4 - Method for operating an Otto internal combustion engine - Google Patents

Abstract

Method for operating an Otto internal combustion engine in the 4-stroke cycle,
in which fuel is injected for mixture formation by direct injection into a combustion chamber of at least one cylinder and optimized engine operating control signals adapted to the operating condition corresponding to the values of mixture formation parameters such as injection quantity, injection timing, multiple injection division factor, injection timing to ignition timing .
wherein the Otto internal combustion engine is operated in a homogeneous operation or in a shift operation or in a multiple injection operation and is switched by means of the engine control between these operating modes in dependence on predetermined and / or detected operating parameters in each case at a switching time,
wherein, in the homogeneous operation, the amount of fuel for one working cycle is injected in a single injection operation with an operation injection time predetermined by the engine control corresponding to a predetermined amount of fuel in the intake phase,
wherein in the stratified operation, the amount of fuel for a duty cycle is injected in a single injection operation with a predetermined by the engine control operating injection time according to a predetermined fuel quantity in the compression phase, and
where in multi-injection operation ...

Description

The The invention relates to a method for operating an Otto internal combustion engine in the 4-stroke duty cycle according to the preamble of claim 1.

at a well-known, generic method of operation an Otto internal combustion engine in the 4-stroke duty cycle is used for mixture formation Fuel by direct injection into a combustion chamber at least of a cylinder of the gasoline engine injected and of a motor control are adapted to the operating condition optimized Mixture-forming operation control signals corresponding to the values of Provided mixture preparation parameters. As a mixture formation parameter are, for example, the injection quantity, the injection time, the division factor for multiple injection or the distance between injection time and ignition point. The Otto internal combustion engine is in a homogeneous operation or in a Shift mode or operated in a multi-injection operation and by means of the motor control is between these modes in dependence predetermined and / or detected operating parameters each at one Switching time switched.

in the Homogenous operation is the amount of fuel for one work cycle in one single injection with a predetermined by the engine control Operating injection time corresponding to a predetermined amount of fuel injected in the intake phase. In shift operation, the fuel quantity for a duty cycle in a single injection with one of the engine control predetermined operating injection time corresponding to a predetermined Fuel quantity injected in the compression phase. In multiple injection operation is the total fuel amount for a duty cycle in a plurality of temporally successive Teileinspritzvorgängen with Partial injection times predetermined by the engine control according to predetermined amounts of fuel in the intake phase and / or in the compression phase and / or in the extension phase injected. The quantity ratio the part injection operations associated fuel subset corresponds to an operation sharing factor.

One Difference of these three modes is in the quality of the See combustion chamber formed fuel / air mixture. Homogeneous operation is sufficient due to the fuel injection in the intake phase greater Period until ignition given, so that a homogeneous fuel / air mixture with about λ = 1 is formed. With Lambda λ becomes thereby The relationship the amount of fuel referred to the amount of air in the combustion chamber. Consequently is in homogeneous operation of the entire combustion chamber with an ignitable Mixture completed, so that an optimal combustion is expected at the ignition. As in the Shift operation the fuel injection only in the compression phase is done, the time to ignition is too short to a homogeneous fuel / air mixture to obtain. Thus arises in the combustion chamber in inhomogeneous, stratified Fuel / air mixture, due to a targeted injection a fuel-rich mixture cloud in the area of the spark plug is present. Around the mixture cloud are areas in the combustion chamber with a high excess of air before, so that λ> 1 is present. In the Multiple injection is an inhomogeneous fuel / air mixture before, so depending on the Injection times in the intake phase and / or in the compression phase and / or in the Ausschubphase λ values less than, equal to or greater than 1 received can be.

Due to the corresponding λ values, the homogeneous operation is preferably used at full load and associated high rotational speeds, the shift operation preferably being used in the partial load range at low rotational speeds. From the DE 198 24 915 C1 a method for operating an Otto internal combustion engine is known in which there is no change in the running behavior of the gasoline engine in a mode change between homogeneous operation and stratified operation. In this case, a regulation of the engine torque and thus a comparison of the power output of the Otto internal combustion engine is made possible by adjusting the ignition timing.

A Switchover from homogeneous operation or shift operation into the Multiple injection operation regularly recurs to catalyst heating a cold start of the gasoline engine used since the exhaust gas temperatures in a multiple injection compared to the exhaust gas temperatures Homogeneous or shift operation are relatively high, allowing a fast Catalyst heating takes place. Furthermore, a switch in the multiple injection mode, a reduction in knock tendency enable at full load. It may be in the switching within the operating modes to short-term, dynamically induced changes in mixture formation come in the combustion chamber, the incomplete incomplete burns or even cause intermittent burns. This leads to a restless engine running, which felt the vehicle occupant bothersome can be.

Furthermore, the shows EP 0 943 793 A2 a method for operating a gasoline engine in the 4-stroke duty cycle with mode change. In order to reduce the hydrocarbon emissions in conjunction with a catalyst arrangement is after a mode change to a multiple injection mode, the split factor changes for the entire duration of the multiple injection mode. As a result, the HC emissions during the activation process of the catalyst arrangement can be reduced.

It is the object of the present invention, in the switching between Operating modes an incomplete To avoid combustion or intermittent burns.

These The object is achieved with the features of claim 1.

According to claim 1 are immediately before or during a mode changeover for one or a few duty cycles from the engine control deviating from the mixture forming operation control signals Mixture educational short-term switching control to disposal so that in a short-term window at the switching time the mixture formation according to the mixture formation short-time switching control signals he follows.

By the mixture formation short-time switching control signals generated by the Mixing operation control signals differ, the possible mixture mismatch becomes the mode switching is corrected so that incomplete combustion or even intermittent combustion is avoided. The short-term window on Switching time available concern mixture formation short-time switching control signals For example, the injection quantity, the injection timing, or the distance between the injection time and the ignition point. Is at the operating mode changeover Involved in multiple injection, so too is a switching division factor as a mixture formation short-time switching control signal. The Corresponding selection of the short-term during a mode changeover to be changed in the short-term window Blend operation control signals are specific to the different ones options the operating mode changeover. Here is the switching between the homogeneous operation and the stratified operation, the homogeneous operation and the Multiple injection operation and the stratified operation and the multi-injection operation to be distinguished for each mode switch suitably in a series of experiments the one or the others to be changed Mixture formation operation control signals are detected. That's the way it is the temporal arrangement of the short-term window before and / or after the switching time depends on the corresponding operating mode changeover.

For a catalyst heating after the cold start or as part of a knock control has been found that the multiple injection operation the homogeneous or stratified operation is preferable. According to claim 2 can after the cold start for a Katalysatoraufheizung or as part of a knock control on Switched a two-injection mode as a multi-injection operation At this time, the operation division factor becomes a mixture formation operation control signal in the short-term window, changing to a shift sharing factor such that a relatively larger fuel subset when first partial injection process is injected.

In the engine management system determines the operational distribution factor by value, where an operational split factor of 0.7 has been found to be favorable Has. According to claim 3, an operational split factor of about 0.7 may be provided that of a partial fuel quantity of 30% in the first partial injection process and 70% at the second part injection. In the short-term window the operation sharing factor becomes the switching division factor changed from about 0.4 with a focus shift the injected fuel fraction to about 60% at first Part injection and about 40% on the second part injection process.

According to claim 4 can also be used for a reverse switching from dual injection mode to homogeneous or shift mode in a short-term window with a relatively larger fuel subset be injected the first part injection process. In test series it turned out that for a reverse switching according to claim 5 at a Katalysatoraufheizung depending on the heating condition the reverse switching time is determined and switching to a switching division factor in a short-term window immediately before the return switching time.

The respective values of the switching division factor and the temporal Arrangement of the short-term window when switching from the homogenous or Shift operation in the two-injection mode or at the corresponding Reverse switching from Dual-injection operation in the homogeneous or shift operation are depend on the type of gasoline engine and can by means of test series be determined accordingly. By this adaptation the mixture influencing parameters the dynamic changes the mixture formation in the combustion chamber are largely prevented, so that incomplete Burns or intermittent burns avoided advantageous are.

In addition to the change of the operating distribution factor in the switching division factor, the possibility according to claim 6 after the cold start for a catalyst heating or in the context of a knock control to a two times Switch injection operation as a multi-injection operation and thereby change the operating injection time as a mixture formation operation control signal in the short-term window so at a switching injection time that a leaning of the fuel / air mixture takes place.

at a reverse switching from the two-injection operation in the homogeneous or stratified operation can according to claim 7 shows the operation injection time in the short-term window so at a return switching injection time changed be that an enrichment of the fuel / air mixture takes place. The change the operation injection time in the short time window at a switching injection time or to a return switching injection time can as a sole measure for one homogeneous transition concerning the Engine running when switching between the homogeneous or shift operation and the two-injection operation, wherein basically the possibility exists, the change of the operation allocation factor to a switching division factor combined with the change the operation injection time to a switching injection time or to a return switching injection time apply.

According to claim 8 may be the short-term window of time for one or up to five 4-stroke duty cycles correspond to all cylinders of a multi-cylinder Otto internal combustion engine. In experiments, it has been found that the duration of the short-term window for one 4-stroke duty cycle of all cylinders of the gasoline engine may be sufficient this value depends on the type of internal combustion engine.

For an exact one Detecting the 4-stroke duty cycles of each cylinder can claim 9 the 4-talk working cycles are detected with an ignition counter, Thus is guaranteed functionally reliable, that the switching from the mixture forming short-time switching control signals back to the Mixture operation control signals after that in the engine control predetermined number of 4-stroke duty cycles.

According to claim 10, the lead at least one of the mixture forming operation control signals to the associated one Mixture educational short-term switching control at the beginning of the short-term window, jump or in the starting area of the short-term window in a continuous transition respectively. Accordingly, the return of at least one of Mixture formation short-time switching control signals to the associated Blending operation control signals according to claim 11 at the end of the short-term window abruptly or in the end of the short-term window in a continuous transition respectively. The interpretation of the transition between the mixture-forming operation control signals and the mixture-forming short-time switching control signals be determined by series of experiments, with a dependency of the type of gasoline engine with respect to the optimal transition between the mixture formation operation control signals and the mixture formation short-time switching control signals is present.

Based a drawing, the invention is explained in detail.

It demonstrate:

1 a schematic, graphical plot over the time of an operating division factor when switching from a homogeneous operation in a two-injection operation,

2 a schematic, graphical plot over the time of the operational distribution factor at a return switching from the two-injection operation in the homogeneous operation.

3 a schematic, graphical plot over the time of an operating injection time when switching from the homogeneous operation in the two-injection operation, and

four a schematic, graphical plot over the time of the operating injection time at a return switching from the two-injection operation to the homogeneous operation.

In 1 and 3 is the switchover from a homogeneous operation 3 in a dual injection mode four and in the 2 and four is the reverse switching from the dual injection mode four in the homogeneous operation 3 exemplified schematically and graphically over time. With a vertical, broken line is always the switching time 1 or the reverse switching time 1' for the corresponding mode change in the 1 to four located. Below the respective coordinate system with a solid line is a corresponding signal 2 the motor control for the homogeneous operation 3 or the two-injection mode four shown. With an ignition counter 5 be the 4-stroke cycles of the gasoline engine, in the 1 to four exemplified as a four-cylinder gasoline engine is detected Thus, the time duration of a short-term window 6 . 6 ' . 12 . 12 ' in mode switching between the homogeneous operation 3 and the dual injection mode four based on the numerically recorded 4-stroke duty cycles using the ignition counter 5 be determined. In 1 is an example of a numbering of the four-cylinder of the gasoline engine by a Circled numbers drawn.

In the 1 and 2 the adjustment takes place at the switchover time 1 or reverse switching time 1 an operational distribution factor 7 as a mixture forming operation control signal. The operating distribution factor 7 , which is plotted on the ordinate, is also in the engine control during the homogeneous operation, with no operational distribution factor 7 necessary because the injection of the amount of fuel is a single injection process, set. At the switching time 1 becomes the operation sharing factor 7 into a shift sharing factor 8th changed, so that in the first partial injection operation of the present double injection operation four a relatively larger fraction of fuel is injected as compared to the fractional amount of fuel of the first fractional injection operation at the operation-sharing factor 7 , The short-term window 6 in which the switching division factor 8th is turned on, is maintained for the time for a 4-stroke duty cycle of all four cylinders of the gasoline engine, the duration of the short-term window 6 with the ignition counter 5 is determined. Subsequently, the shift sharing factor becomes 8th back to the operating distribution factor 7 changed, so that in the first partial injection operation, a relatively smaller partial fuel quantity compared to the partial fuel quantity of the first partial injection operation with activated Umschaltteilteilungsfaktor 8th is injected.

In 2 is schematically and graphically over time the reverse switching from the dual injection mode four in the homogeneous operation 3 shown. The two-injection mode four is activated, for example, after a cold start for a catalyst heating, since this higher exhaust gas temperatures for a faster heating of the catalyst are present, so that the return switching from the two-injection mode four in the homogeneous operation 3 can be done depending on the heating state of the catalyst. Upon reaching a predetermined temperature of the catalyst, the reverse switching time point becomes a switching time 1' determined, wherein the switching to Umschaltaufteilungsfaktor 8th in the short-term window 6 immediately before the reverse switching time 1 he follows. A signal 9 , which is present depending on the heating state of the catalyst is in 2 Plotted below the coordinate system with a dashed line, wherein in the presence of the corresponding Aufheizzustandes the beginning of the short-term window 6 ' with a vertical dash-dotted line in 2 is drawn. Thus, in the presence of the corresponding heating condition of the catalyst, the operational distribution factor becomes 7 in the shift sharing factor 8th changed, with the short-term window 6 ' is maintained for the time for a 4-stroke duty cycle of all four cylinders of the Otto internal combustion engine. At the reverse switching time 1' On the one hand, the operating mode of the two-injection mode four in homogeneous operation 3 and on the other hand, the switching sharing factor 8th in the operating distribution factor 7 switched.

Both at the switchover, the in 1 shown as well as in the reverse switching, in 2 is shown, the change of the operational distribution factor takes place 7 in the shift sharing factor 8th or vice versa each leaps and bounds, which has been found by experiments for the 4-cylinder gasoline engine to be optimal.

In addition or as an alternative to the change of the operational distribution factor 7 in the shift sharing factor 8th in the short-term window 6 and 6 ' can be an operation injection time 10 to a switching injection time 11 to be changed. This is exemplary and schematic in the 3 , in which a switchover from homogeneous operation 3 in the two-injection mode four is shown and in four in which a switch from the two-injection mode four in the homogeneous operation 3 shown is shown. Again, below the coordinate system is the signal 2 recorded the engine control for the switching between the modes, each with a vertical dashed line of the switching time 1 or the reverse switching time 1' is drawn. In 3 , the switching from homogeneous operation 3 in the two-injection mode four is shown is at the switching time 1 the operation injection time 10 , which is plotted on the ordinate, in the switching injection time 11 for the duration of the short-term window 12 so changed that a leaning of the fuel / air mixture takes place, since the switching injection time 11 relatively shorter than the operating injection time 10 with respect to the length of time. Thus, in the short-term window 12 injected less fuel, so that the fuel / air mixture is leaner.

In the reverse switching from the two-injection mode four in the homogeneous operation 3 , which takes place, for example, as a function of the heating state of the catalyst, becomes the operation injection time 10 in the short-term window 12 ' so at a return switching injection time 13 changes that an enrichment of the fuel / air mixture takes place. In test series, it has been shown that at each switching time 1 or at the return switching time 1' a sudden change between the operating injection time 10 and the switching injection time 11 or the return switching injection time 13 is advantageous. For a 4-stroke duty cycle of all four cylinders, which means the ignition counter 5 is determined, the switching injection time 11 or the return switching injection time 13 maintained constant, followed by a time Lich continuous transition of the switching injection time 11 or the Rü ckumschalt injection time 13 to the operation injection time 10 he follows. Basically, even at the end of the short-term window 12 respectively. 12 ' a sudden change between the injection times occur, which is exemplary and schematically with a dotted line in four is drawn. The operating injection time 10 in two-injection mode four is split to the two partial injection operations that corresponding fuel sub-quantities can be injected in the individual injection operations in accordance with the engine control. The corresponding sum of the partial injection times gives the operating injection time 10 ,

Overall, therefore, a method for operating the gasoline engine in the 4-stroke duty cycle is created, in which due to the adaptation of the mixture formation operation control signals, here exemplified as an operational distribution factor 7 or operating injection time 10 chosen and based on the 1 to four are explained in more detail, the dynamically induced changes in the mixture formation in the combustion chamber can be largely avoided, so that no incomplete burns or intermittent burns are caused. As a result, an optionally restless engine operation is advantageously prevented when changing the operating mode. Due to the adaptation of the mixture formation operating control signals, an avoidance of incomplete burns is possible even with a mode switchover between the homogeneous operation and the stratified operation or between the stratified operation and the multiple injection operation, so that here too there is an advantageously smooth engine run when the operating mode is changed. The type of adaptation, ie which mixture formation operation control signals are changed, is dependent on the design of the Otto internal combustion engine, so that in each case the optimum adaptation of the mixture formation operation control signals and the corresponding design of the short-term window in test series 6 . 6 ' . 12 . 12 ' he follows.

Claims (11)

Method for operating an Otto internal combustion engine in the 4-stroke duty cycle, is injected for mixture formation fuel by direct injection into a combustion chamber of at least one cylinder and optimized by an engine control the operating condition mixture formation operation control signals corresponding to the values of mixture formation parameters, such as injection quantity, injection timing , Division factor in multiple injection, distance injection time to ignition, are provided, the Otto internal combustion engine is operated in a homogeneous operation or in a shift operation or in a multi-injection operation and by means of the engine control between these modes in accordance with predetermined and / or detected operating parameters respectively is switched to a switching time, wherein in the homogeneous operation, the amount of fuel for a duty cycle in a single injection with one of the engine control vorgebe NEN operating injection time is injected according to a predetermined amount of fuel in the intake phase, wherein in the stratified fuel quantity for a working cycle in a single injection process with a predetermined by the engine control operating injection time according to a given fuel quantity is injected in the compression phase, and wherein in the multiple injection operation, the total fuel amount for a Operating cycle is injected in a plurality of temporally successive Teileinspritzvorgängen with the engine control each predetermined Teileinspritzzeiten corresponding predetermined fuel subset in the intake and / or in the compression phase and / or in the Ausschubphase, wherein the ratio of the partial injections associated fuel subset corresponds to an operating division factor, characterized in that immediately before or during a mode changeover at the switchover time nkt ( 1 . 1' ) briefly for one or a few work cycles, in relation to the total number of work cycles in one mode, by the engine controller of the mixture formation operation control signals ( 7 . 10 ) different mixture formation short-time switching control signals ( 8th . 11 . 13 ), so that in a short-term window ( 6 . 6 ' . 12 . 12 ' ) at the switching time ( 1 . 1' ) the mixture formation according to the mixture formation short-time switching control signals ( 8th . 11 . 13 ) he follows. A method according to claim 1, characterized in that after the cold start for a catalyst heating or as part of a knock control on a two-injection mode ( four ) is switched as a multi-injection operation and thereby the operational distribution factor ( 7 ) as a mixture-forming operation control signal in the short-term window ( 6 ) so to a switching division factor ( 8th ) is changed so that a relatively larger proportion of fuel is injected in the first part injection process. Method according to claim 2, characterized in that an operational distribution factor ( 7 ) of about 0.7 is provided corresponding to a fuel fraction of 30% in the first partial injection process and of 70% in the second partial injection process occurring in the short-term window (FIG. 6 ) is changed to about 0.4 with an emphasis shift of the injected fuel fraction to about 60% on the first part injection and about 40% on the second partial injection process. A method according to claim 2 or 3, characterized in that even in a reverse switching from the two-injection mode ( four ) in the homogeneous ( 3 ) or shift operation in a short-term window ( 6 ' ) a relatively larger proportion of fuel is injected with the first part injection process. A method according to claim 4, characterized in that for a reverse switching in a catalyst heating in dependence of the heating state ( 9 ) the reverse switching time ( 1' ) and switching to a switching division factor ( 8th ) in a short-term window ( 6 ' ) immediately before the reverse switching time ( 1' ) he follows. Method according to one of claims 1 to 5, characterized in that after the cold start for a catalyst heating or as part of a knock control to a two-injection mode ( four ) is switched as a multiple injection operation while the operating injection time ( 10 ) as a mixture-forming operation control signal in the short-term window ( 12 ) so at a switching injection time ( 11 ) is changed so that a leaning of the fuel / air mixture takes place. Method according to claim 6, characterized in that in the case of a return changeover from the two-injection mode ( four ) in the homogeneous ( 3 ) or shift operation the operating injection time ( 10 ) in the short-term window ( 12 ' ) so at a return switching injection time ( 13 ) is changed, that an enrichment of the fuel / air mixture takes place. Method according to one of claims 1 to 7, characterized in that the short-term window ( 6 . 6 ' . 12 . 12 ' ) corresponds to the time for one or up to five 4-stroke duty cycles of all cylinders of a multi-cylinder Otto internal combustion engine. A method according to claim 8, characterized in that the 4-stroke duty cycles with an ignition counter ( 5 ), Method according to one of claims 1 to 9, characterized in that the introduction of at least one of the mixture formation operation control signals ( 7 . 10 ) to the associated mixture formation short-time switching control signals ( 8th . 11 . 13 ) at the beginning of the short-term window ( 6 . 6 ' . 12 . 12 ' ) occurs abruptly or in the beginning region of the short-term window in a temporally continuous transition. Method according to one of claims 1 to 10, characterized in that the return of at least one of the mixture formation short-time switching control signals ( 8th . 11 . 13 ) to the associated mixture formation operation control signals ( 1 . 10 ) at the end of the short-term window ( 6 . 6 ' ) abruptly or in the end area of the short-term window ( 12 . 12 ' ) takes place in a temporally continuous transition.