EP1797308A1

EP1797308A1 - Method for the operation of an internal combustion engine

Info

Publication number: EP1797308A1
Application number: EP05777895A
Authority: EP
Inventors: Andreas Pfaeffle; Marco Gangi; Gerit Von Schwertfuehrer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2004-10-01
Filing date: 2005-08-18
Publication date: 2007-06-20
Also published as: DE102004048008A1; US20080103673A1; US7500465B2; JP2008514857A; WO2006037690A1

Abstract

The invention relates to a method for operating an internal combustion engine (1), according to which fuel is injected into a combustion chamber (4) of a cylinder (3) of the internal combustion engine (1) in at least two partial injection quantities, an actual torque supplied by the internal combustion engine (1) is determined from operational parameters of the internal combustion engine (1), said actual torque is compared to an admissible torque, and an error reaction is induced if the actual torque is at a predefined ratio to the admissible torque. According to the inventive method, a moment efficiency (eta_M) of the respective partial injection is taken into account when determining the actual torque, thus allowing the actual torque to be monitored more accurately.

Description

Method for operating an internal combustion engine

State of the art

The present invention relates to a method for

Operating an internal combustion engine, in which fuel is injected into at least two partial injections in a combustion chamber of a cylinder of the internal combustion engine, and in which a given by the internal combustion engine torque is determined from operating variables of the internal combustion engine, said actual torque is compared with an allowable torque and initiated an error response is when the actual torque is in a predetermined ratio to the allowable torque.

The present invention further relates to an internal combustion engine and a control device for an internal combustion engine. Moreover, the present invention also relates to a computer program for a control unit of an internal combustion engine.

Conventional operating methods of the type mentioned have the disadvantage that a determination of the actual torque of the internal combustion engine in particular at Operating modes of the internal combustion engine, in which partial injections are made, only with low accuracy is possible.

Purpose and advantages of the invention

Accordingly, it is an object of the present invention to develop a generic operating method and an internal combustion engine and a control device for an internal combustion engine and moreover also a computer program for such a control device so that a more accurate determination of the actual torque is possible.

This object is achieved in the above-mentioned operating method according to the invention that a torque efficiency of the respective partial injection is taken into account in the determination of the actual torque.

This takes into account the fact that not every partial injection makes the same contribution to an actual torque output by the internal combustion engine. Rather, the respective torque contribution of a partial injection depends on a plurality of parameters.

According to an advantageous embodiment of the method according to the invention, the torque efficiency is determined as a function of a rotational speed of the internal combustion engine.

Another very advantageous embodiment of the method according to the invention provides that the torque efficiency is determined as a function of a crank angle and / or a control starting angle of the internal combustion engine. By considering the Crank angle and the driving start angle, the influence of a temporal relationship between the relevant partial injection and the duty cycle of the internal combustion engine is modeled on the torque efficiency. In this case, the Ansteuerbeginnwinkel indicates at which crank angle, ie at which time, based on the duty cycle of the internal combustion engine, a control of an actuator begins, which causes the partial injection.

In addition, in another very advantageous embodiment of the method according to the invention, it is proposed to determine the torque efficiency as a function of a partial injection quantity corresponding to the respective partial injection.

It is particularly advantageous according to another

Embodiment of the present invention also a determination of the torque efficiency as a function of a time difference between different partial injections, whereby u.a. a preheating of the combustion chamber by previous burns and a concomitant improved ignitability can be considered.

In a particularly advantageous embodiment of the present invention, the torque efficiency is determined as a function of a time difference between a main injection and another partial injection.

Here, a main injection is understood as meaning that of a plurality of partial injections, which generally supplies the largest torque contribution to the actual torque output by the internal combustion engine with the same injection quantity. In addition to the main injection is in the the following description still distinguish between so-called pilot injections and so-called post-injections, with pre-injection those partial injections are called, which take place before the main injection, and with

After injections those part injections are called, which take place after the main injection.

Another very advantageous embodiment of the method according to the invention provides that the

Torque efficiency is determined as a function of a time course of combustion. If further data about a course of the combustion are available or can be determined, these can advantageously be used according to the invention for more accurate determination of the torque efficiency. Such data may be, for example, a temporal pressure or temperature profile in the combustion chamber.

According to a further embodiment of the method according to the invention, it is also possible to determine the torque efficiency as a function of an intake air temperature and / or an air pressure and / or signals of a knock sensor and / or of further sensor signals and / or operating variables of the internal combustion engine.

In a further advantageous embodiment of the present invention, the torque efficiency or a variable derived therefrom is linked in an additive and / or multiplicative manner and / or via a characteristic map with a partial injection quantity corresponding to the respective partial injection.

Furthermore, in another embodiment of the It is proposed according to the present invention that stored values of the torque efficiency are stored and / or reused, wherein it is also conceivable to use a characteristic map containing different values of the torque efficiency with the determined values of the torque efficiency

Torque efficiency build or supplement and / or adjust.

According to a further very advantageous embodiment of the method according to the invention, a virtual total fuel quantity, preferably as a function of the torque efficiency, is determined to determine the actual torque. This total virtual fuel amount represents the amount of fuel that would have to be injected into the combustion chamber of the internal combustion engine instead of the multiple partial injections in a single main injection to effect the same torque as the partial injections underlying the total virtual fuel quantity calculation.

The total virtual fuel quantity thus allows a computationally simple summary of various factors that can influence the actual torque of the internal combustion engine and thus also efficient processing, for example. In a control unit.

According to a very advantageous embodiment of the method according to the invention is an operating point of

Plausibilisiert internal combustion engine, wherein the operating point is preferably defined at least by a virtual total fuel quantity and / or a rotational speed of the internal combustion engine.

Such a plausibility check according to the invention is advantageous if in the case of determining the actual torque provided control unit no maps or the like are present, which directly contain the relationship described above between eg a speed of the internal combustion engine, a Ansteuerbeginnwinkels etc. and the torque efficiency. For example, different maps are rather present, which depend, inter alia, on an operating point of the internal combustion engine. In this case, the torque efficiency can not be directly calculated as in the above-described embodiments.

Although it is possible to use for the determination of the actual torque to values of the operating variables that are used in a control of the internal combustion engine, but these values may not in particular for the inventive determination of the actual torque, which can serve to monitor the internal combustion engine without validation from the Control can be taken over.

Therefore, for example based on determined operating variables of the internal combustion engine and with the aid of the values from the control with simultaneous application of the inventive plausibility check of an operating point of the internal combustion engine, the use of existing characteristic maps is possible. As soon as a corresponding operating point has been made plausible by means of the plausibility check according to the invention, it is possible with the existing maps, e.g. the torque efficiency can be calculated or a fuel correction amount that corresponds to the torque efficiency.

Another very advantageous embodiment of the method according to the invention is characterized in that the plausibility of the operating point as a function of an operating mode of the internal combustion engine is carried out.

Such an operating mode is, for example, the so-called regeneration mode, in which u.a. is set by at least one post injection, the highest possible exhaust gas temperature to a in the exhaust line of the

Internal combustion engine particulate filter to regenerate by burning it accumulated soot particles.

Another very advantageous embodiment of the method according to the invention provides that criteria for the plausibility be selected depending on the operating mode.

In a further variant of the present invention, it is provided that in an operating mode of the internal combustion engine without post-injections, an injection duration determined from operating variables of the internal combustion engine of a post-injection is monitored for the exceeding of a predefinable threshold value. This can ensure that an undesired post-injection based on an error, for example in the control of the internal combustion engine, is detected.

Another very advantageous embodiment of the operating method according to the invention is characterized in that the internal combustion engine is operated in an operating mode with at least one post-injection, in particular in a regeneration mode for the regeneration of a particulate filter in an exhaust tract of the internal combustion engine.

According to another very advantageous embodiment of the invention, the internal combustion engine is in a Operating mode operated with at least one pilot injection.

Another very advantageous variant of the operating method according to the invention provides that the internal combustion engine is operated in an operating mode in which a torque output by the internal combustion engine is adjustable by changing a quantity of air. The change in the amount of air can be effected for example by a throttle in an intake tract of the internal combustion engine.

A further variant of the method according to the invention is characterized in that injection parameters determined from operating variables of the internal combustion engine, in particular an injection start time and an injection duration, are monitored for compliance with desired injection parameters determined in a control of the internal combustion engine.

Yet another variant of the present invention provides that an influence of a lambda control, preferably to the exceeding of a predefinable limit value, is monitored. The lambda control is at the

Internal combustion engine provided to set a certain air / fuel ratio in order to ensure a particularly low emissions and reliable operation of the internal combustion engine. The lambda control usually has an effect within the scope of the activation of the internal combustion engine in that a desired value for a fuel quantity to be injected is changed by a corresponding value dependent on the lambda control. If the value for the fuel quantity to be corrected on the basis of the lambda control exceeds a predefinable limit value, an error reaction is initiated, for example. According to a further very advantageous embodiment of the method according to the invention, an error reaction is initiated, preferably after a filter time has elapsed, if the plausibility check fails.

Another variant of the method according to the invention provides that, preferably during the filter time, a maximum possible torque efficiency is assumed. In fact, during the filter time, an error can not yet be conclusively assumed; On the other hand, it is possible that an error actually exists, so that in this case determined in the controller torque efficiencies could possibly be wrong.

Another very advantageous embodiment of the method according to the invention is characterized in that the maximum possible torque efficiency is obtained from a control of the internal combustion engine, so that in determining this maximum possible torque efficiency, the sizes already present in the control can be used.

As a further solution to the problem of the present

Invention, a control device according to claim 26 and an internal combustion engine according to claim 28 is provided.

Of particular importance is the realization of the method according to the invention in the form of a computer program according to claim 24, wherein the

Computer program has program code which is adapted to perform the inventive method when it is executed on a computer. Furthermore, the program code can be stored on a computer-readable data carrier, for example on a so-called flash memory. In these cases, so the invention realized by the computer program, so that this computer program represents the invention in the same way as the method, for the execution of which the computer program is suitable.

drawing

Other features, applications and advantages of the invention will become apparent from the following description of embodiments of the invention, which are illustrated in the figures of the drawing.

FIG. 1 shows a schematic block diagram of an internal combustion engine according to the invention,

Figure 2 shows a functional diagram of an embodiment of the method according to the invention, and

FIG. 3 shows a functional diagram of a further embodiment of the method according to the invention.

Description of the embodiments

1 shows an internal combustion engine 1 of a motor vehicle is shown, in which a piston 2 in a cylinder 3 back and forth. The cylinder 3 is provided with a combustion chamber 4 which is delimited inter alia by the piston 2, an inlet valve 5 and an outlet valve 6. With the intake valve 5, an intake pipe 7 and with the exhaust valve 6, an exhaust pipe 8 is coupled.

In the region of the intake valve 5 and the exhaust valve 6, an injection valve 9 projects into the combustion chamber 4, via the

Fuel can be injected into the combustion chamber 4. In the exhaust pipe 8, a catalyst 12 is housed, the the purification of the resulting by the combustion of the fuel exhaust gases is used.

The injection valve 9 is connected via a pressure line with a fuel storage 13. In a corresponding manner, the injection valves of the other cylinders of the internal combustion engine 1 are connected to the fuel storage 13. The fuel storage 13 is supplied via a supply line with fuel. For this purpose, a preferably mechanical fuel pump is provided which is adapted to build up the desired pressure in the fuel accumulator 13.

Furthermore, a pressure sensor 14 is arranged on the fuel storage 13, with which the pressure in the fuel storage 13 is measurable. This pressure is that pressure which is exerted on the fuel and with which therefore the fuel is injected via the injection valve 9 into the combustion chamber 4 of the internal combustion engine 1.

During operation of the internal combustion engine 1, fuel is conveyed into the fuel reservoir 13. This fuel is injected via the injection valves 9 of the individual cylinders 3 into the associated combustion chambers 4. By combustion of the prevailing in the combustion chambers 4 air / fuel mixture, the piston 2 will be placed in a reciprocating motion. These movements are transmitted to a non-illustrated crankshaft and exert on this torque.

A control unit 15 is acted upon by input signals 16, which represent measured operating variables of the internal combustion engine 1 by means of sensors. For example, the control unit 15 with the pressure sensor 14, a Air mass sensor, a speed sensor and the like connected. Furthermore, the control unit 15 is connected to an accelerator pedal sensor which generates a signal indicative of the position of a driver-actuated accelerator pedal and thus the requested torque. The control unit 15 generates output signals 17 with which the behavior of the internal combustion engine 1 can be influenced via actuators or actuators. For example, the control unit 15 is connected to the injection valve 9 and the like and generates the signals required for their control.

Among other things, the control unit 15 is provided to control the operating variables of the internal combustion engine 1 and / or to regulate. For example, the fuel mass injected by the injection valve 9 into the combustion chamber 4 is controlled and / or regulated by the control unit 15, in particular with regard to low fuel consumption and / or low pollutant development. For this purpose, the control unit 15 is provided with a microprocessor which has stored in a storage medium, in particular in a flash memory, a computer program which is adapted to perform said control and / or regulation.

Also implemented in the control unit 15 is a function monitoring of the internal combustion engine 1, which is based on a determination of the output from the internal combustion engine 1 torque, which is hereinafter referred to as actual torque.

The actual torque is detected by the control unit 15 operating variables of the internal combustion engine 1, see. the input signals 16, calculated in the control unit 15. Such operating variables are, for example, an injection duration, ie the length of a time interval the fuel is injected into the combustion chamber 4 and an injection pressure, ie the determined using the pressure sensor 14 pressure in the fuel reservoir 13, with which the fuel is injected into the combustion chamber 4.

An embodiment of the operating method according to the invention is described below with reference to FIG. 2, in which fuel is injected into the combustion chamber 4 of the internal combustion engine 1 from FIG. 1 by means of five partial injections. Correspondingly, the partial injection quantities QtI assigned to the five partial injections are

Qt2, Qt3, Qt4, Qt5 are listed in Figure 2, top left, as inputs to the functional diagram depicted.

In this case, the partial injection quantities QtI, Qt2, Qt3 each designate an amount of fuel injected into the combustion chamber 4 as part of a so-called pilot injection, while the partial injection quantity Qt4 represents a partial injection quantity injected during a so-called main injection. The partial injection quantity Qt5 is associated with a so-called post-injection, which is usually carried out to increase the exhaust gas temperature and can be used, for example, to regenerate a particulate filter (not shown) located in the exhaust tract of the internal combustion engine 1.

As can be seen from FIG. 2, the partial injection quantities QtI and Qt2 are added to the partial injection quantity Qt3 by means of the adder 101 and the sum 101 'resulting therefrom by means of the adder 102. The resulting sum signal 102 'at the output of the adder 102 is finally fed to the adder 103, in which the main injection corresponds

Partial injection quantity Qt4 is added, resulting in the sum signal 103 'at the output of the adder 103. The sum signal 103 'indicates the fuel quantity that is injected into the combustion chamber 4 of the internal combustion engine 1 as a whole as part of the three pilot injections with the respective partial injection quantities QtI, Qt2, Qt3 and the main injection with the partial injection quantity Qt4.

In contrast to the pilot injections and the main injection, which have approximately the same torque efficiency with respect to a given by the internal combustion engine 1 actual torque causes a injected as part of the post-injection into the combustion chamber 4 of the internal combustion engine 1 partial injection quantity Qt5 a comparatively lower actual torque. This difference is taken into account by the moment efficiency eta M, which at the

Output of the multiplier 106 is obtained and whose determination is described below.

The partial injection quantity Qt5 of the post-injection multiplied by the torque efficiency eta M in the multiplier 107 at the output of the multiplier 107 results in the effective partial injection quantity 107 'of the post-injection which is finally added to the sum signal 103' in the adder 104, from which at the output of the adder 104 a so-called virtual Total fuel amount Q_v is obtained.

The total virtual fuel quantity Q_v represents that amount of fuel which, in the main injection or in another partial injection with the same torque efficiency as the main injection, that is, for example also during a pre-injection, into the

Combustion chamber 4 of the internal combustion engine 1 would have to be injected in order to achieve the same actual torque as in a Injection of the actually used

Partial injection quantities QtI to Qt5. In the present example, only the post-injection has a torque efficiency eta M reduced from the main injection, so that the effective post-injection amount 107 'is smaller than the actual post-injection partial injection amount Qt5, whereby the total virtual fuel amount Q v is also smaller than an unweighted sum Partial injection quantities QtI to Qt5.

As can be seen from Figure 2, is the

Torque efficiency eta M the post-injection of several input variables together.

A first factor f_l is obtained from a rotational speed n_BKM of the internal combustion engine 1 (FIG. 1) and from a so-called actuation starting angle phi by means of a characteristic map 108. Instead of the Ansteuerbeginnwinkels phi and another size can be used, which indicates the injection timing or its temporal position in relation to a crank angle of the crankshaft of the internal combustion engine 1.

Based on the partial injection quantity Qt5 of the post-injection and the characteristic curve 109, a second factor f 2 is formed, which is multiplied in the multiplier 105 by the first factor f_l. The signal 105 'present at the output of the multiplier 105 outputs

Influence of the time position of the post-injection with respect to the crank angle and the partial injection quantity Qt5 injected in the post-injection to the torque efficiency eta M of the post-injection.

Since at the post-injection from a certain temporal

Distance delta_t to the main injection no or at least If there is no longer complete combustion of the post-injected fuel quantity, this time interval delta_t is taken into account by the map 110. The injected during the main injection partial injection quantity Qt4 also enters into the relationship described above and is therefore used according to Figure 2 as an input signal for the map 110.

The factor f 3 obtained by means of the map 110 is multiplied by the output signal 105 'of the multiplier 106

Multiplier 105, i. multiplied by the product of the factors f_l and f_2, from which finally the moment efficiency eta M of the post-injection is obtained.

According to the invention, the torque efficiency eta_M is thus dependent on a partial injection quantity Qt4 of the main injection, a partial injection quantity Qt5 of the post-injection, as well as the rotational speed n BKM of the internal combustion engine 1, the actuation starting angle phi and a time difference delta t between the main injection and the post-injection.

Depending on these parameters, the

Torque efficiency eta M a value between 0 and 1 at. Correspondingly, the influence of the partial injection quantity Qt5 of the post-injection weighted with the torque efficiency eta M on the actual torque that can be determined in the control unit 15 (FIG. 1) from the total virtual fuel quantity Q_v is large or small.

When determining the actual torque from the virtual total fuel quantity Q v, the torque contributions of the respective partial injections and their possibly 100% Deviating torque efficiencies, as is the case for example in the post-injection, all already combined in the virtual total amount of fuel Q_v, so that a particularly simple determination of the actual torque using known methods is possible.

As an alternative to the evaluation of the actuation starting angle phi, the time position of the post-injection, for example based on the top dead center of the working cycle of the cylinder 3, can also be represented by any other variables. For example, instead of the

Ansteuerbeginnwinkels phi also be used injection timing of the main injection or the post-injection, if a corresponding map is available.

In a further very advantageous embodiment of the present invention, analogous to the factors f 1, f_2, f_3, other factors (not shown) which are suitable for influencing the torque efficiency eta_M can also be taken into account.

The moment efficiency eta_M can e.g. also in

Dependence of an intake air temperature and / or an air pressure and / or signals of a knock sensor and / or other sensor signals and / or operating variables of the internal combustion engine 1 are determined.

It is also conceivable for the torque efficiency eta_M in

Determine dependence of a chronological course of combustion. In this case, for example, a pressure and / or temperature profile in the combustion chamber 4 could be used for even more precise determination of the torque efficiency eta_M. In a further variant of the invention, it is also possible to store values of the torque efficiency eta_M, for example as a function of some or all input variables QtI, Qt2, Qt3, Qt4, Qt5, n_BKM, phi, delta_t, determined in the manner described above, for example

Diagnostic purposes or to create corresponding maps.

Very particularly advantageous here is also a creation or an adjustment of a multi-dimensional map for the torque efficiency eta_M, which summarizes the input variables shown in Figure 2 Qt4, Qt5, n BKM, phi, delta_t.

The inventive method for taking into account a torque efficiency is not limited to the determination of the torque efficiency of a post-injection. For example, it is also possible to determine a torque efficiency of a pilot injection with the method according to the invention.

The total virtual fuel quantity Q v is used - as already described - for a calculation of the of

Internal combustion engine 1 delivered actual torque, which provides a more accurate result than conventional methods due to the consideration of the torque efficiency eta M of the post-injection according to the invention.

Due to the more accurate calculation of the actual torque and an improvement in the monitoring of the same, for example in the context of a comparison with an allowable torque allows, because the monitoring lower tolerance thresholds must be recognized and deviations of the actual torque can therefore be detected faster. This will ensure a safer operation of the Internal combustion engine 1 allows.

The method described above with reference to FIG. 2 is applicable independently of the specific design of the injection system of the internal combustion engine 1. For example, it is so-called common rail

Injection systems with magnetically or piezoelectrically actuated injection valves 9 as applicable as in the case of pump-nozzle injection systems. A superimposed lambda control for optimizing the emission behavior of the internal combustion engine 1 does not exclude the application of the method according to the invention.

Another embodiment of the present invention is described below with reference to FIG.

The functional diagram shown in FIG. 3, like the functional diagram according to FIG. 2, shows a variant of the method according to the invention, as implemented in the control unit 15 (FIG. 1) of the internal combustion engine 1.

In contrast to the method explained with reference to FIG. 2, in the method according to FIG. 3 no characteristic curves or characteristic diagrams are available for the function monitoring according to the invention based on read-in operating variables of the internal combustion engine 1, which have a direct relationship between a control starting angle, an injection duration Specify the speed of the internal combustion engine and possibly other parameters and the torque efficiency.

The method according to FIG. 3 is used to determine a so-called correction quantity Q korr, which, comparable to the signal 107 'from FIG. 2, has a computationally determined value Fuel quantity, which is determined for partial injections, which have a non-100% torque efficiency eta_M (Fig. 2). In this case, the correction amount Q corr indicates the fuel quantity which, for example, would have to be injected during a main injection in order to provide the same torque contribution to the actual torque as the partial injection quantity actually injected in the partial injection with a torque efficiency deviating from 100%.

Analogous to the signal 107 'of FIG. 2, the

Correction quantity Q corr added to the amount of fuel corresponding to the amount of fuel 103 'of FIG. 2 in order to obtain the total virtual fuel quantity Q v (FIG. 2) on the basis of which a simple determination of the actual torque, for example by means of a Kennfeldes, is possible.

The correction quantity Q korr with respect to the actually injected partial quantity (compare Qt5 from FIG. 2) corresponds to the torque efficiency eta M (FIG.

FIG. 3 shows a variant of the method according to the invention, as used in an operating mode of the internal combustion engine 1 (FIG. 1) with a post-injection, that is to say for example for realizing a regeneration operation. That is, the

Correction quantity Q_korr can only be determined for a partial injection quantity corresponding to the post-injection (compare Qt5 from FIG.

In principle, it is also possible to use the method described below for determining further

Correction quantities, eg corresponding to pre-injections To use partial injection quantities.

According to the invention, in the method according to FIG. 3, a plausibility check of an operating point of the internal combustion engine 1 takes place, and depending on this plausibility check, the correction quantity Q korr is either a function of the operating point of the engine

Internal combustion engine 1 determined correction amount Q korr or, in the case of failed plausibility, a corresponding substitute value Q korr 'output. The plausibility check is based on several criteria, which are evaluated centrally as shown in Fig. 3 of the OR gate 210 and described below.

First, the signal 209 is evaluated, which is symbolized in FIG. 3 by a logic variable which can assume the value one or zero. The signal 209 indicates, at a value of one, that the internal combustion engine 1 is not in a regeneration mode. According to the present embodiment, this means that no post-injections are provided for the operation of the internal combustion engine 1.

The presence of a possibly erroneous yet performed post-injection is checked by the comparator 211, which compares a measured actual post-injection duration 212 with a predefinable threshold value 212a. If the post-injection duration 212 is greater than the threshold value 212a, the comparator 211 provides at its output a signal 211 'having the value one.

This signal 211 ', as well as the signal 209 described above, the AND gate 213 supplied so that when not activated regeneration mode and a simultaneously exceeding the threshold value 212a by the post-injection duration 212, an output signal 213 'of the AND gate 213 having the value one is output to the OR gate 210.

Regardless of the other input variables of the OR element 210, an output signal 210 'of the OR element 210 also assumes the value one, so that the correction value at the output of the multiplexer 210a is the substitute value Q_korr ^f instead of the correction quantity Q korr.

When the output 210 'of the OR gate 210 is one for a time greater than the filter time 210b, an error response is initiated which is controlled by the signal 214.

However, if the output 210 'of OR gate 210 is unity for only a time less than the filter time 210b, the substitution value Q korr' is temporarily output as the correction amount at the output of the multiplexer 210a, but no error response as described above occurs.

The AND gate 213 thus serves to monitor that in the absence of a regeneration operation of the internal combustion engine, i. In general, in a mode without post-injection, actually no post-injection takes place, by the Nacheinspritzdauer 212 with the predetermined, e.g. Applicable threshold 212a compares.

Hereinafter, the further criteria Kl, K2, K3, K4 will be described, each of which is dependent on an operating point of the internal combustion engine 1. The operating point of the internal combustion engine 1 is in this case by the input signals n_BKM, Q_v defined, where n_BKM analogous to FIG. 2, the speed of the internal combustion engine 1, and Q v indicates the total virtual fuel amount.

The speed n_BKM is already in the described embodiment as a secured, i. validated quantity in a functional monitoring implemented in the control unit 15 (FIG. 1) to which the method according to FIG. 3 belongs. This means that for the monitoring of the internal combustion engine 1 and thus u.a. It is not necessary to check the input quantity n_BKM to determine the actual torque.

In contrast to this, the total virtual fuel quantity Q_v from FIG. 3 is a quantity that directly depends on the function monitoring mentioned above from a function also implemented in the control unit 15

Control of the internal combustion engine 1 is read. The quantity Q_v obtained in this way may not be used without plausibility to determine the correction quantity Q korr, since it has only been calculated within the activation, but has not already been validated.

Such a plausibility check is carried out according to the invention in FIG. 3 using the four criteria K1, K2, K3, K4. If all four criteria K1, K2, K3, K4 are fulfilled, the virtual fuel quantity Qv read from the control is sufficiently plausible and can be used to determine the correction quantity Q_korr, on the basis of which the actual torque is finally calculated.

In addition, at the same time a regeneration operation must be present, ie an operating mode of the internal combustion engine 1 with a post-injection, since the presently described Plausibilisierung depends on a mode of operation of the internal combustion engine 1 and is provided specifically for the regeneration operation. in the

Regeneration mode, the signal 209 has the value zero, so that also at the output of the AND gate 213 is zero.

Concerning the criterion Kl, from the input signals n_BKM, Q_v in connection with the characteristic map 217, a setpoint value 218 for a delivery start angle is determined, from which in the subtracter 219 one from the operating quantities of the

Internal combustion engine 1 as part of a function monitoring determined delivery start angle 220 is subtracted, and wherein the resulting difference 219 'is supplied to an absolute value generator 220', so that in the comparator 221, an amount of the difference signal 219 'with a threshold value 222 is compared. When the threshold value 222 is exceeded, that is to say when the delivery start angle 220 determined from operating variables of the internal combustion engine 1 deviates too much from the delivery start angle 218 determined from the input signals n_BKM, Q_v, this increases as supplied to the OR element 210 Output 221 'of the comparator 221 a value of one, so that in turn the substitute value Q korr' is output instead of the value Q_korr for the correction amount. If the limit value is exceeded for a prolonged period

222, an error response is also initiated by the signal 214.

Instead of the delivery start angle, it is also possible to use a drive start angle or another variable which indicates the injection time or its temporal position in relation to a crank angle of the crankshaft of the internal combustion engine 1. Within the criterion K2, it is checked whether a lambda correction quantity 225 is greater in magnitude than a predefined threshold value 226, which is made possible by the magnitude generator 227 and the comparator 228. The lambda correction quantity 225 represents an amount of fuel which is added to an overall fuel quantity to be injected on the basis of a lambda control of the internal combustion engine 1 superimposed on the actual torque determination, in order to maintain a predetermined lambda value of the exhaust gas of the internal combustion engine 1.

If the lambda correction quantity 225 or its magnitude 227 'exceeds the threshold value 226, the criterion K2 initiates an output of the substitute value Q korr' or an error response by means of the signal 214, in which the output signal 228 'of the comparator 228 assumes the value one ,

Within the framework of the criterion K3, it is checked whether a partial injection quantity 232 of the post-injection (see Qt5 from FIG. 2) determined for the function monitoring from operating variables of the internal combustion engine 1 corresponds to the setpoint value 229 for the partial injection quantity of the post-injection plus the lambda correction quantity 225. For this purpose, the lambda correction quantity 225 and the desired value 229 are summed in the adder 230, and the partial injection quantity 232 already described is subtracted in the subtracter 231.

The resulting difference 233 is applied to the absolute value generator 234, whose output 234 'is supplied to the comparator 235, as well as the threshold value 236. As soon as the magnitude 234' of the difference 233 exceeds the threshold value 236, the output signal 235 'of FIG

Comparator 235, which is supplied to the OR gate 210, initiated an error response in the manner already described several times above, or at least the temporarily issuing the replacement amount Q_korr ^f causes.

In the criterion K4, which is optional for the described operating method, a quantity balance of different partial injection quantities is evaluated. In this case, a total injection quantity 240 determined during the activation of the internal combustion engine 1 2, i. the sum of all partial injection quantities for possibly occurring pre- and post-injections and the main injection is then checked as to whether it corresponds to a main injection quantity 241 determined from operating variables of the internal combustion engine 1 plus a pre-injection quantity 242 likewise determined from operating variables of the internal combustion engine 1 and a post-injection quantity 243. In this case, the post-injection quantity 243 is determined from the virtual total injection quantity Q v and the rotational speed n BKM of the internal combustion engine according to FIG. 3.

If none of the above-described criteria K1 to K4 or the output signal 213 'of the AND gate 213 results in a non-zero output signal of the comparator of the OR gate 210, is referred to as

Output signal of Figure 3 as correction amount Q_korr the post-injection amount 243 output.

Otherwise, that is to say, if at least one of the criteria K1 to K4 is not met, or if the output signal 213 'of the AND gate 213 differs from zero, the substitute value Q_korr ^{f is} output.

The substitute value Q_korr ^f is calculated from a partial injection quantity 232 of the post-injection (see Qt5 from FIG. 2) determined from operating variables of the internal combustion engine 1, which multiplies in the multiplier 232a with a maximum possible efficiency 232b of a main injection becomes. In this way, it is ensured that in the event of an error, ie in the event of a failed plausibility check, the determination of the actual torque as part of the function monitoring is based on a maximum possible fuel quantity as a substitute value Q_korr '. Therefore, the determined actual torque is not erroneously calculated as too low in case of error.

The efficiency 232b can be calculated automatically or stored as a constant in the control unit 15.

The method according to the invention can also be used in other operating modes of the internal combustion engine 1, wherein in each case other criteria for plausibility checking are to be selected. For example, analogous to the method described correction amounts or

Torque efficiencies are also determined for pre-injections.

In operating modes in which the actual torque can be controlled by changing the air supply, for example by means of a throttle valve, the inventive method can also be used.

Moreover, the method according to the invention can be implemented with a relatively low expenditure of resources such as e.g. RAM, ROM and run time are implemented in the controller 15.

Claims

claims

1. A method for operating an internal combustion engine (1), in which fuel in at least two partial injections in a combustion chamber (4) of a cylinder (3) of the internal combustion engine (1) is injected, and in which one of the internal combustion engine (1) output actual torque Operating variables of the internal combustion engine (1) is determined, this actual torque is compared with an allowable torque and an error response is initiated when the actual torque is in a predetermined ratio to the allowable torque, characterized in that in determining the actual torque, a torque efficiency (eta M) of the respective partial injection is taken into account.

2. The method according to claim 1, characterized in that the torque efficiency (eta_M) in dependence on a rotational speed (n BKM) of the internal combustion engine (1) is determined.

3. The method according to any one of the preceding claims, characterized in that the torque efficiency (eta_M) in dependence of a crank angle and / or a Ansteuerbeginnwinkels (phi) of the internal combustion engine (1) is determined.

4. The method according to any one of the preceding claims, characterized in that the torque efficiency (eta_M) in dependence of the respective partial injection corresponding partial injection quantity (QtI, Qt2, Qt3, Qt4, Qt5) is determined.

5. The method according to any one of the preceding claims, characterized in that the torque efficiency (eta M) is determined as a function of a time difference (delta T) between different partial injections.

6. The method according to claim 5, characterized in that the torque efficiency (eta_M) is determined as a function of a time difference (delta T) between a main injection and another partial injection.

7. The method according to any one of the preceding claims, characterized in that the torque efficiency

(eta M) is determined as a function of a chronological course of a combustion.

8. The method according to any one of the preceding claims, characterized in that the torque efficiency (eta M) in dependence on an intake air temperature and / or an air pressure and / or signals of a knock sensor and / or other sensor signals and / or operating variables of the internal combustion engine (1) is determined.

9. The method according to any one of the preceding claims, characterized in that the torque efficiency

(eta M) additive and / or multiplicative and / or via a map with a respective partial injection corresponding partial injection quantity (QtI, Qt2, Qt3, Qt4, Qt5) is linked.

10. The method according to any one of the preceding claims, characterized in that determined values of the Torque efficiency (eta_M) stored and / or reused.

11. The method according to any one of the preceding claims, characterized in that for determining the actual torque, a virtual total amount of fuel (Q_v), preferably as a function of the torque efficiency (eta_M), is determined.

12. The method according to any one of the preceding claims, characterized in that an operating point of the internal combustion engine (1) is plausibility, wherein the

Operating point is preferably at least defined by a virtual total amount of fuel (Q v) and / or a speed (n BKM) of the internal combustion engine (1).

13. The method according to claim 12, characterized in that the plausibility of the operating point in

Dependence of an operating mode of the internal combustion engine (1) is performed.

14. The method according to claim 13, characterized in that criteria for the plausibility be selected depending on the operating mode.

15. The method according to any one of the preceding claims, characterized in that in an operating mode of the internal combustion engine (1) without post-injections determined from operating variables of the internal combustion engine (1) injection duration (212) of a post-injection to the exceeding of a predetermined threshold value (212a) is monitored.

16. The method according to any one of the preceding claims, characterized in that the internal combustion engine (1) is operated in an operating mode with at least one post-injection, in particular in one Regeneration mode for regeneration of a particulate filter in an exhaust tract of the internal combustion engine (D •

17. The method according to any one of the preceding claims, characterized in that the internal combustion engine (1) is operated in an operating mode with at least one pre-injection.

18. The method according to any one of the preceding claims, characterized in that the internal combustion engine (1) is operated in an operating mode in which one of the

Internal combustion engine (1) output torque is adjustable by changing a quantity of air.

19. The method according to any one of the preceding claims, characterized in that from operating variables of the internal combustion engine (1) determined injection parameters, in particular an injection start time and an injection duration, are monitored for compliance with in a control of the internal combustion engine (1) determined target injection parameters.

20. The method according to any one of the preceding claims, characterized in that an influence of a lambda control is preferably monitored for exceeding a predetermined limit value.

21. The method according to any one of claims 12 - 20, characterized in that, preferably after expiry of a

Filter time (210b), an error response is initiated if the plausibility check fails.

22. The method according to claim 21, characterized in that, preferably during the filter time (t_Filter), a maximum possible torque efficiency (232b) is assumed.

23. The method according to claim 22, characterized in that the maximum possible torque efficiency (232b) is obtained from a control of the internal combustion engine (1).

Computer program for a control unit (15) of an internal combustion engine (1) with program code, which is suitable for carrying out the method according to one of claims 1 to 23 when it is executed on a computer.

25. Computer program according to claim 24, wherein the program code is stored on a computer-readable medium.

26. Control unit (15) for an internal combustion engine (1), in which fuel in at least two partial injections in a combustion chamber (4) of a cylinder (3) of the internal combustion engine (1) can be injected, and in which one of the internal combustion engine (1) Actual torque from operating variables of the internal combustion engine (1) can be determined, this Istdrehmoment is comparable with an allowable torque and an error response can be initiated when the actual torque is in a predetermined ratio to the allowable torque, characterized in that when determining the actual torque Torque efficiency (eta M) of the respective partial injection can be considered.

27. Control device (15) according to claim 26, characterized in that the control device (15) for carrying out the method according to one of claims 2 - 23 is suitable.

28. Internal combustion engine (1), wherein the fuel in at least two partial injections in a combustion chamber (4) of a cylinder (3) can be injected, and in the one of the internal combustion engine (1) output actual torque Operating variables of the internal combustion engine (1) can be determined, this Istdrehmoment is comparable to an allowable torque, and an error reaction can be initiated if the actual torque is in a predetermined ratio to the allowable torque, characterized in that when determining the actual torque, a torque efficiency (eta_M) of the respective partial injection can be considered.

29. Internal combustion engine (1) according to claim 28, characterized in that the internal combustion engine (1) for

Execution of the method according to one of claims 2 - 23 is suitable.