KR20080083279A - Method for controlling an internal combustion engine - Google Patents

Abstract

The invention relates to a method for controlling an internal combustion engine (10) comprising at least one combustion chamber (12) into which fuel for combustion is injected by way of at least one first pilot injection (VE1) and a main injection (HE). According to said method, combustion features (VM_B) depending on an injected amount of fuel are detected, and an effect of the amount of fuel injected with the first pilot injection (VE1) is determined from the detected combustion features (VM_B). The method is characterized in that an effect of a second pilot injection (VE2) is determined from a comparison of combustion features (VM_VE1_ist, VM_VE12_ist) that were determined with activated and deactivated second pilot injection. The invention also relates to a control device which controls the method.

Description

METHOOD FOR CONTROLLING AN INTERNAL COMBUSTION ENGINE}

The present invention relates to a method for controlling an engine having at least one combustion chamber in which fuel for combustion is injected by at least one first pre-injection and main injection, wherein combustion characteristics in accordance with the injected fuel amount are measured and the first The effect of pre-injection is detected from the measured combustion characteristics. The invention also relates to a control device for executing the method, in accordance with the preamble of claim 10.

Such a method is known from DE 103 05 656 A1. According to the document, the signal of the body noise sensor component coupled to the engine is used as a combustion feature on the basis that there is a simple association between the noise emission and the fuel amount of the pre-injection. To detect the amount of fuel injected, the signal of the body noise sensor component is within at least one first crankshaft angle range (measurement window) assigned to pre-injection and at least one second crankshaft angle range assigned to the main injection. Are measured and filtered respectively.

Pre-injection is calibrated in a closed loop since specific samples of the combustion characteristics are presented according to the amount of fuel injected during pre-injection and main injection, from which injection time and injection volume can be deduced by comparison with reference samples. Can be. In German publication DE 103 05 656, the method is proposed as an example of one spray sample consisting of pre-injection and main injection. However, any integrated form of one first partial injection and at least one second partial injection may be used, and DE 103 05 656 refers to pre-injection, main injection and post injection in other parts.

Already several years ago the use of body noise sensors for regulation in gasoline engines, for example for knocking regulation, is known from DE 103 05 656. For diesel engines, so far only systems with body noise control have been available on the market that compensate for one pre-injection per combustion.

To improve combustion noise, vehicle manufacturers are increasingly demanding the possibility of implementing two pre-injections per combustion.

The pre-injection amount is adjusted by the control duration of the electrically controllable injector. Due to tolerances and aging (drifts) of the parts of the injection system, the actual relationship between the injection amount and the control duration differs from the relationship stored, for example, in the injector-characteristic field. As a result, emissions (exhaust gases and noise) can be worsened. This applies in particular to changes in the pre-injection amount.

In addition to the drift of the injector, the pressure waves initiated through the injection affect the subsequent injection. In operation with only one pre-injection per combustion, the pressure wave can be well calibrated by a fixed correction value detected by the test bench so that no disturbing action is given to the main injection.

However, for systems with two pre-injections per combustion, due to the pressure waves initiated by the first pre-injection, great inaccuracies in the fuel system are presented for the second pre-injection. Correction of this inaccuracy by preset fixed correction values is not accurate enough because the effect depends on many influence variables such as fuel temperature, fuel pressure and fuel quality that cannot be considered at acceptable costs. .

Therefore, there is a demand for improvement of the correction of the inaccuracy of the second pre-injection. In the case of the test by the method known from DE 103 05 656, it is suggested that the effects of a plurality of pre-injections consecutive to one another in the body noise signal cannot be clearly separated from each other. This is because the plural pre-injections are mainly combusted within one very narrow angular range so that the effects are not clearly separated from each other in the cylinder pressure, in particular in the body noise.

For this reason, it is an object of the present invention to present a method that allows a second pre-injection with improved accuracy in the operation of the engine also to be corrected.

This object is achieved in the case of a method of the type mentioned at the outset by the effect of the second pre-injection being detected from a comparison of the combustion characteristics which were detected by the activated and deactivated second pre-injection. In view of a control device of the type mentioned at the outset, this object is achieved by the features of claim 11.

The first and second pre-injection respectively refer to the injections separated in time while belonging to the same operating stroke. In the case of two or more pre-sprays of one spray sample, the first pre-spray may be a second or third pre-spray of the sample. Practically only the first pre-injection is located before the second pre-injection. The second preinjection may also be separated from the first preinjection by at least one other preinjection. Substantially only the second pre-injection is located after the first pre-injection.

The invention is based on the recognition that the noise of the plurality of pre-injections can be treated as an overlap of individual combustions, within a first approximation. The comparison thus provides a difference that can be assigned to the effect of the second pre-injection. This effect rises as the amount of injected fuel increases. In particular, the effect consists of the release of heat in the combustion chamber, the pressure rise and the emission of combustion noise. In the following, the concept of effect is also used as a synonym for the injected fuel amount.

The invention thus adjusts the amount of fuel metered to the individual cylinders or individual combustion chambers by the second pre-injection or by the sum of the first and second pre-injections of one injection sample comprising at least two pre-injections. Can be.

In blocking of individual pre-injections, the combustion characteristics of the plurality of pre-injections are compared with the measurement, so that the fuel amount of the individual pre-injections and the total fuel amount of the plurality of pre-injections can also be corrected. The correction relates to the correction for the effects of injector drift (hydraulic drift) and pressure waves.

The method also provides the advantage that a correction is already provided for the entire operating time of the vehicle from a new state. The method thus compensates for new part tolerances and aging variations. By correspondingly adjusted frequency of correction, the influence of fuel temperature can also be corrected.

Other advantages are presented from the description and the accompanying drawings.

It is understood that the above-mentioned and later described features can be used alone or in other combination forms as well as in each combination form presented, without departing from the scope of the invention.

Embodiments of the invention are shown in the drawings and described in more detail in the detailed description that follows. These are each shown in schematic form.

1 is a view showing the technical environment of the present invention.

2 is a diagram of a spray sample having two pre-injections and one main injection.

3 is a diagram of an injection sample of combustion characteristics for each range, processed within one curve.

4 is a diagram qualitatively illustrating a change in combustion characteristics upon a change in pre-injection.

5 is a diagram of an adjustment loop for correcting pre-injection.

1 shows an operating cycle of at least one combustion chamber 12, injector 14, fuel pressure reservoir 15, combustion characteristic sensors 16 and / or 18, fuel pressure sensor 19, and engine 10. An engine 10 with each sensor component 20, driver desired sensor 21, and control device 24 of the component 22 synchronously rotating with respect to is shown in detail. The combustion chamber 12 is movably sealed by a piston 26 connected to the component 22 by the crank driver 28. The part 22 is rotatably connected to the crankshaft of the engine. However, in other embodiments it may for example be connected to the cam shaft of the engine 10. The actual engine 10 includes additional parts such as, for example, a gas exchange valve and a corresponding actuator for controlling the charge exchange of the combustion chamber 12, which is not shown in FIG. 1 for ease of overview.

However, for practical understanding of the present invention, the control device 24 is in the form of pulse widths for the pre-injection VE1, VE2, main injection HE and optionally further partial injections of one injection sample. A control signal is output, whereby fuel for combustion in the combustion chamber 12 is measured. Combustion characteristic sensor 16 is a combustion chamber pressure sensor, while alternatively or supplementally provided combustion characteristic sensor 18 is a body noise sensor. The two sensors 16, 18 provide the control device 24 with a default value or raw value VM_B of the combustion characteristic, respectively.

In the embodiment of FIG. 1 each sensor component 20 provides crankshaft angle information ° KW as information about the position of the piston 26 in the operating cycle. The information can be inferred from the crankshaft-angle information as well as the camshaft-angle information. From each signal, information about the engine speed n can also be deduced. The driver's desire (FW) represents a value for the torque demand by the driver, for example measured as an accelerator pedal position.

2 shows a typical injection sample 30 as used in the environment of FIG. 1 when in a predetermined operating state of the engine 10. In Fig. 2 a control signal AS for the injector 14 of Fig. 1 is shown for the crankshaft angle ° KW. At the low value of the control signal, the injector 14 is closed while opening via pulses VE1, VE2 and HE for injection of fuel. Pulses VE1 and VE2 correspond to the pre-injection mentioned and pulse HE corresponds to the main injection mentioned. The value of 180 ° KW corresponds to the top dead center OT of the movement of the piston 26 between the compression stroke and the operating stroke. The start of the main injection is located 15 ° before the OT in the case of a passenger car. Likewise the pre-injection is located within the narrow angular range before the OT. The pre-injection carried out in the compression stroke raises the pressure and temperature levels in the combustion chamber 12 at the time of the main injection, which leads to a so-called ignition delay, ie between the start of the main injection and the start of combustion of the injected fuel. The time is shortened. This reduces in particular the combustion noise received by the body noise sensor 18.

3 shows the effect of the injection sample of the combustion characteristic VM_V processed within one curve on the crankshaft angle-range. The treated combustion characteristic (VM_V) is derived from the default through filtering (VM_B), which is known to the person skilled in the art as already described in the German publication DE 103 05 656 mentioned earlier.

Curves 32 and 34 of the processed combustion characteristics VM_V are presented for the injection sample 30 in which the total amount of fuel to be injected is distributed differently in three partial injections VE1, VE2 and HE. The fuel amount injected by the first pre-injection VE1 is kept constant, while the fuel amounts M_VE2 and M_HE injected by the second pre-injection VE2 and the main injection HE are variable to be supplemented with each other.

In the case of the curve 32, the fuel amount M_VE2 injected by the second pre-injection is small. Practically only the combustion characteristics of VE1 and the relatively large combustion characteristics of main injection (HE) can be seen. The magnitude of the combustion characteristics of the HE represents a relatively large combustion noise and / or a sudden pressure rise in the combustion chamber 12 as the effect of HE. The two appear as a result of the preconditioning of relatively poor combustion due to the low or insufficient amount M_VE2.

In contrast, for curve 34, M_VE2 is larger, so that the preconditioning is improved, resulting in a lower combustion noise of positive V_HE. Also larger pre-injection amount M_VE2 appears within the larger combustion characteristics of the pre-injection. Of course, it is likewise shown that the first and second pre-injections cannot be decomposed within the curve of the combustion feature 34, ie cannot be separated from each other.

4 shows the curve of the continuously processed combustion characteristic VM_VE12 for the control duration AD of the injection valve 14 for the second pre-injection VE2 in microseconds for a constant first pre-injection VE1. 36 is shown qualitatively.

For the embodiment operated by the main body noise sensor 18, the combustion feature VM_VE12 is qualitatively presented as the ratio of the two faces in FIG. 3, with the face below the peak of the pre-injection in the numerator and the main injection in the denominator. There is a surface below the peak.

In other words, VM_VE12 represents a normalized numerical value as a reference-combustion feature in terms of below the peak of the main injection, for the sum of two pre-injections VE1 and VE2. Similarly, combustion characteristic VM_VE1 is presented as a standardized size for the case of deactivated second pre-injection VE2. The increase curve of VM_VE12 in FIG. 4 reflects the peak increase of pre-injection when the peak of the main injection decreases.

For the embodiment operated by the combustion chamber pressure sensor 16, the combustion feature VM_VE12 corresponds to the amount of heat released by the sum of the two pre-injections. The calorific value can only be determined from the combustion chamber pressure signal for the two pre-injections. In contrast to the evaluation of the body noise signal, normalization in the reference-combustion feature is not necessary. 5 shows an adjustment loop for calibrating pre-injection VE1, VE2, which includes engine 10, at least one combustion characteristic sensor 16 and / or 18, and control device 24. Above all, the controller 24 is the default sensor that provides a default value (ADVE) (A nsteuer d auer V or e inspriztung) for the control duration for the pre-injection (VE1, VE2) as a function of operating parameters of the engine 10, (38). The default sensor 38 is a characteristic field which is addressed by the value of other operating parameters of the engine 10 such as, for example, number of revolutions n, driver desires FW and optionally fuel pressure p. The default value ADVE is logically operated with the correction value d_AD in the logical operation unit 40, and the logical operation may be multiplication or addition depending on occurrence of d_AD.

Since the injector 14 is controlled by AD_VE_korr = AS as a result of the logical operation, for example, the first pre-injection VE1 or the second pre-injection VE2 is executed. The combustion characteristic resulting from the combustion is measured as the default value VM_B by the combustion characteristic sensors 16 and / or 18 and is passed to block 42 of the control device 24 representing signal processing and filtering. The default value of the combustion characteristic VM_B is measured within a defined partial region of one operating cycle of the engine 10, which may be defined for example by a particular crankshaft angular range. Preferably the partial region is selected such that the first partial region contains the peak of the pre-injection and the other partial region contains the peak of the main injection.

Within block 42, the default values are the processed combustion characteristic (VM_V) and the continuously processed combustion characteristic (VM_VE1), through filtering, value formation, optionally averaged over several operating cycles and the aforementioned standardization. , VM_VE12). In conversion, the treated combustion characteristic (VM_V) is in particular standardized to a reference-combustion feature, alternatively the reference-combustion feature is derived from the pressure- or noise-curve of the main injection (HE), or the background-pressure-curve or It can be derived from the background-noise-curve.

Depending on whether the engine 10 is activated by an activated or deactivated second pre-injection VE2, block 42 provides the actual value VM_VE1_ist (VE2 deactivated) or VM_VE12_ist (VE2 activated). From the actual value, in block 44 the actual value VM_VE2_ist is calculated and detected as the difference between the actual values VM_VE1_ist and VM_VE12_ist:

VM_VE2_ist = VM_VE12_ist-VM_VE1_ist

Through this method, the effect of the second pre-injection VE2 is detected from the difference in combustion characteristics VM_VE12_ist and VM_VE1_ist that were detected by the activated and deactivated second preinjection.

Then in block 44 likewise, the setpoint for the second pre-injection VE2 is formed from the setpoint for the sum of the first and second pre-injections and the first pre-injection.

VM_VE2_soll = VM_VE12_soll-VM_VE1_soll

The combustion characteristic VM_VE2 corresponds to the difference between the peaks of the pre-injection of curves 32 and 34 of FIG. 3, except for the normalization factor.

Starting from the specific values VM_VE2_soll and VM_VE2_ist, the difference is formed as an adjustment deviation d_VM_VE2 used as an input variable for the controller 46. The adjuster 46 outputs the correction value d_AD already mentioned as an adjustment variable, whereby the default value provided from the default sensor 38 for the second pre-injection VE2 is corrected. Thus, the fuel amount metered by the second preinjection is adjusted to the set value in one closed loop.

This adjusting interference to the second pre-injection is based on a comparison of the combustion characteristics that were detected by the activated and deactivated second pre-injection.

In a preferred embodiment the method is executed only when the actual value VM_VE1_ist is adjusted to the set value VM_VE1_soll. This adjustment is likewise performed in the adjustment loop of FIG. In the case of the deactivated second pre-injection, the correction value for the first pre-injection is detected by comparing the actual value with the set value and forming an adjustment deviation from the comparison, from which the adjustment variable is formed as a correction value. This correction value is logically calculated with the default value for the first pre-injection. It is also preferred that the correction value is additionally used for correction of the default value for the second pre-injection. This is effectively used as a starting value for the described controlled interference for the second injection. Thus, the transient of regulation is accelerated.

Claims (11)

An engine 10 control method having at least one combustion chamber 12 in which fuel for combustion is injected by at least one first pre-injection VE1 and main injection HE, and a combustion characteristic according to the amount of injected fuel ( An engine control method in which VM_B) is measured and the effect of the first pre-injection VE1 is detected from the measured combustion characteristic VM_B, And the effect of the second pre-injection (VE2) is determined from a comparison of the combustion features (VM_VE1_ist, VM_VE12_ist) that were detected by the activated and deactivated second pre-injection. 2. The method of claim 1, wherein an adjustment interference d_AD for the second pre-injection VE2 is performed, wherein the adjustment interference d_AD is based on a comparison of the combustion characteristics VM_B. The method according to claim 2, wherein before the adjustment interference d_AD performed for the second pre-injection VE2, correction of the first pre-injection VE1 is performed, for which the correction value is deactivated second preinjection VE2. ) Is detected in the adjustment loop and logically computed with the default value ADVE for the first pre-injection VE1. 4. The engine control method according to claim 3, wherein the correction value (d_AD) is additionally used for correction of a default value for the second pre-injection (VE2). The engine control method according to any one of claims 1 to 4, wherein the amount of fuel metered by the second pre-injection (VE2) is adjusted to a set value in a closed loop. 6. The method of any one of claims 1 to 5, wherein the default value of the combustion characteristic (VM_B) is measured in a defined partial region of one operating cycle of the engine. 7. The method of claim 6, wherein the processed combustion characteristic (VM_V) is generated from the default value of the combustion characteristic (VM_B) through filtering, value shaping, and averaging performed during a plurality of operating cycles. 8. The method of claim 7, wherein the processed combustion feature (VM_V) is standardized to a reference-combustion feature. 8. Method according to claim 7, characterized in that the default value of the combustion characteristic (VM_B) is obtained from the signal of the main body noise sensor component (18) or the combustion chamber pressure sensor component (16). A control device 24 of the engine 10 having at least one combustion chamber 12 in which fuel for combustion is injected by at least one first pre-injection VE1 and main injection HE. In the control device for detecting the effect of the first pre-injection (VE1) from the following combustion characteristics (VM_B) and the measured combustion characteristics (VM_B), The control device (24) is characterized in that it determines the effect of the second pre-injection (VE2) from the comparison of the combustion characteristics (VM_VE1_ist, VM_VE12_ist) that were detected by the activated and deactivated second pre-injection. The control device according to claim 10, wherein at least one of the methods according to claims 2 to 9 is executed.

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