EP1526267A2 - Method and device for compensating the drift of an injector for an internal combustion engine with direct injection - Google Patents

Abstract

The method involves injecting a defined amount of fuel. A correction value is determined, where the correction value is applied to a value range of an operating parameter e.g. rail pressure, of an internal combustion engine. The complete range of values of the operating parameter is subdivided into discrete sections using a control unit (10), where an operating point is specified for each section. An independent claim is also included for a device for drift compensation of an injector.

Description

The invention relates to a method and a device for drift compensation of an injector for direct Fuel injection into a cylinder one Internal combustion engine according to the genus of siblings Claims 1 and 10. It is already known that one Control means determines a correction value, the Correction of the injection, in particular a minimum Fuel quantity is used. However, this correction value applies within a range of values of one injection duration dependent operating parameters of the internal combustion engine, For example, the speed, the start of injection or the Rail pressure in a direct injection system such as common rail, Pump nozzle system or the like. Another problem is seen also in that the learned correction value for a complete value range is used. He will always be used when one or more of the injection duration dependent operating parameters of the internal combustion engine within of the relevant value range. A targeted Adaptation for the case when the operating point at the upper or lower limit of the range of values, is not performed.

It is also critical that in determining a new Correction value for a certain range of values this new one Correction value replaces the previously valid correction value, without for example checking with a test if this new correction value is better suited than the old one Correction value. This can, for example, at a Multiple injection may be significant if a fore or a Post-injection was not properly discontinued. at an unwanted too low or too big Fuel injection can cause adverse operating conditions arise. In particular, unauthorized exhaust and Noise emissions arise, the smoothness of the internal combustion engine impaired, the fuel consumption can be increased or Damage to the internal combustion engine arise.

In the known methods for drift compensation of Injektors also appears unfavorable that occurring Changes in the fuel pressure in the rail not taken into account becomes. However, since the rail pressure in addition to the injection duration decisive factor in the determination of the injected substance Amount of fuel is, this results in a source of error, the can lead to unreliable injection results.

The invention is based on the object, a method or to provide a device that the Injector drift, especially when injecting minimal Fuel quantities more effectively compensated, so that a more accurate fuel injection at all possible Operating conditions can be performed more reliably. This task comes with the characteristics of the sibling Claims 1 and 14 solved.

In the method according to the invention for drift compensation an injector for direct fuel injection in a cylinder of an internal combustion engine or at the device according to the characteristics of the siblings Claims 1 and 14 there is the advantage that in one Range of values of considered at least one Operating point of the internal combustion engine can be set arbitrarily can. For example, in each case a correction value for an operating point at the top, middle and bottom Range of values of the operating parameter can be determined. When Particularly advantageous is considered that the determined correction values together with their operating points saved and learned with it. Is the Internal combustion engine just stored in such a Operating point, then easily can the associated Correction value read from the memory and for the Correction of the injection duration of the injector can be used. The inventive correction method can for each cylinder of the internal combustion engine individually the Injection quantities are corrected. This will be Series variations of the injectors and also the engines in advantageously automatically compensated. Come in addition, that through the passive interpretation of the system of Calibration effort is significantly reduced.

By the measures listed in the dependent claims are advantageous developments and improvements of in the independent claims 1 and 14 issued method or the device given. As special Advantageously, it is considered that the operating point in the Calculation is kept constant. This allows the Correction value, for example over several injection cycles be determined more accurately, so that the correction more reliable can be executed.

As very beneficial has also been shown that a achieved very efficient correction with great accuracy can be used when determining the correction value in the normal driving of the vehicle between two learned Value pairs is interpolated. Because the support points for the Interpolation can be chosen freely in this way Correction value can be optimally adapted to such areas, for example, a large range dependence of a Operating parameters have. Obtained by the interpolation a more accurate adaptive interpolation map than by the use of discrete values that only one are assigned to the whole area. Especially the smallest Fuel quantities can be more reliable in this way and adapt with greater accuracy.

A particularly favorable solution is that the Result for the interpolated correction value subsequently is checked. This ensures that the Corrective action was successful and the new one found Correction value better fits than the old correction value.

To have the injection of a certain amount of fuel several operating parameters have a decisive influence. In particular, occur at very small injection quantities relative large inaccuracies on, as the opening hours of the Injectors in this area extremely short and therefore difficult to control. Therefore, it is especially important that during injection, the speed of the internal combustion engine is kept constant.

Another advantage is the correction value in To determine dependence on the beginning of the injection. ever after the start of injection, the pressure conditions change especially in the rail, so that easily a may result in changed injection quantity.

The injected amount of fuel can be undesirable also be negatively influenced by the fact that the rail pressure not constant during the determination of the correction value is held. Depending on the volume of the buffer in the High pressure area and the opening time of the injector valve The rail pressure is subject to large fluctuations, the one corresponding negative influence on the determination of the Exercise corrective value.

Another advantage is the learning process during the normal driving operation of the vehicle. Thereby is ensured that an optimal correction of Fuel injection can be performed at any time can, even in such cases, if no suitable Correction value should be present.

In the device is advantageous in a momentary present operating point of the internal combustion engine to a suitable correction value either by interpolation or by reading from the memory to determine and the Correct the injection duration of the injector accordingly.

Figur 1

zeigt in schematischer Darstellung ein Blockschaltbild für ein erfindungsgemäßes Verfahren, mit dem eine Driftkompensation des Injektors durchführbar ist,

Figuren 2A bis 2C

zeigen drei Diagramme, mit denen Parameter abhängige Korrekturwerte ermittelbar sind und

Figur 3

zeigt ein schematisiertes vereinfachtes Blockschaltbild einer erfindungsgemäßen Vorrichtung zur Driftkompensation.

An embodiment of the invention is illustrated in the drawing and will be explained in more detail in the following description.

FIG. 1

shows a schematic representation of a block diagram for a method according to the invention, with which a drift compensation of the injector can be carried out,

FIGS. 2A to 2C

show three diagrams with which parameter dependent correction values can be determined and

FIG. 3

shows a schematic simplified block diagram of a device according to the invention for drift compensation.

In Figure 1 is a schematic of a Block diagram the basic operation of the inventive method for drift compensation of a Injector shown. The drift compensation is on the Injection system designed adaptable. Its functioning is the example of the rail pressure p_Rail in a Direct injection system, a common rail system explains as a dependent operating parameter of the internal combustion engine the injection duration of the injector and thus the injected Fuel quantity over the raildruckabhängige drift of Injectors can affect in an undesirable manner. Alternatively, it is provided, further operating parameters such as Start of the injection t_Start, the speed U min of the Internal combustion engine, etc. individually or in combination for the Drift compensation to use, as these parameters also the current operating state of the internal combustion engine can influence.

An essential element of the method according to the invention According to Figure 1 is a manager unit 1, which with a appropriate algorithm is formed. The Manager unit 1 essentially has one program-controlled control unit, which later is explained.

The manager unit 1 is connected to a memory in which learned correction values together with corresponding correction values Operating point values of considered Operating parameters preferably in the form of a table or a map 2 are stored. The values can for example, according to the order structure of the value range successive sections as correction value vector and Parameter vector be organized or stored. in addition come in each case an analogously organized mean vector and an adaptation number vector. These values or vectors become in particular for the correction of a minimum injection quantity (MFMA = minimum mass fuel adaptation) determines how they For example, in the partial load range or in a pre- or Post-injection are required.

In the method according to the invention are three different possibilities provided by a Mode selection 5 are selectable:

The first route leads from the mode selection 5 to the learning mode 3 and concerns the case when a suitable operating point is reached, the learning process can be activated. To are for the current operating state of Internal combustion engine, the corresponding values the map 2 taken and, together with the one at the entrance a and in unit 4 divided into sections Operating parameter value, to a learning mode 3 with Plausibility check given. An acceptable new one Correction value is then, if necessary, indirectly via a Interpolation unit 6, for operating-parameter-dependent Compensation of Injektordrift or for storage ready.

The second way, starting from mode selection 5, concerns the special case that the manager unit 1 targeted first activates a certain section of the value range to there, if necessary without plausibility check, one Determine correction value.

The third way leads from mode selection 5 to Interpolation unit 6 and relates to the case that in Operating mode for a current operating point of z. B. 300 bar rail pressure requires an additional correction value but, for example, only in the section 200 to 300 bar, at operating point B_Pkt (e.g., 250 bar), a current one Correction value of 0.4 and in the section 300 to 400 bar, on Operating point 360 bar, another current correction value of 0.6. The correction value for 300 bar can then advantageous from the two closest value pairs be interpolated.

The two units 3 and 6 is a unit 4 to Section indexing 4 upstream, with the Value range of a considered operating parameter in Any number of different sizes Sections, for example, ten sections, is divided. At an input a of the unit 4 becomes a current measured value the operating parameter, in our example the rail pressure p_Rail created by a corresponding pressure sensor in recycled form is available. At the same time the current measured value to the interpolation unit 6 and can here in the interpolation in a suitable way are processed. At an exit b the Interpolation unit 6 is then the determined current Correction values or a corresponding offset value can be tapped and can now be used to drift compensation of the injector become. Strictly speaking, this new correction value only applies for one, but representative for the given section Operating point of the internal combustion engine. He can through the Interpolation of adjacent values previously for a similar operating point were stored, almost arbitrary be adjusted exactly.

The following is the detailed operation of the in Figure 1 illustrated method explained. First becomes the entire value range of the dependency size, ie the considered dependent operating parameter, in unit 4 for section indexing into a predetermined number of divided into discrete sections. The number of Sections depending on the sensitivity of the drift be set with respect to the operating parameter. Should on the one hand increases the sensitivity of the operating parameter a higher number of sections is selected. Should On the other hand, the dependency is reduced, becomes a lower number of sections selected. In practice For example, the ranges from 0 to 300 bar and from 700 to 1000 bar rail pressure tighter with sections occupied be as the intermediate, possibly completely blank area.

For each section at least one operating point for which a corresponding correction value determined and learned. Alternatively, for some Sections determined a corresponding correction value and learned, if just a suitable, at least within the each section lying, operating state reached is. It has proven to be advantageous that in the Calculation of the correction value always the respective Operating point of the internal combustion engine is kept constant. The correction value is then combined with the respective Operating point stored in Table 2. For the typically less than one second calculation time the constancy can be brought about by the control unit. Should be in this short time the driver of the vehicle can intervene, for example, a desired performance from the control unit while maintaining the constancy of the Focusing operating parameter approximately by Change other parameters can be achieved, or the Calculation can be aborted. If z. B. when starting a certain operating condition is not reached, that can Control unit artificial the rail pressure p_Rail for a short time if this is consistent with the other conditions is.

In normal driving mode, the mode selection 5 has the Interpolation unit 6 is activated, so that between two stored adjacent value pairs an optimal new Correction value can be determined. It will takes into account in which part of the section is currently the instantaneous operating point of the internal combustion engine is located.

Are not yet learned for all sections learned correction values before, then automatically become the two for the interpolation closest values and a linear interpolation performed according to known computer rules. Subsequently, will Checks whether the result value for the new correction value within calibratable limits.

For example, if only one correction value is available, then alternatively provided for this case, this one value for to use all areas. If there is no value, then the correction value is set to the neutral value. These Boundary conditions are especially in the pre-calibration of Table 2 applicable.

There are already correction values for a specific one Section of the value range, then the newly learned value checked for plausibility with the respective mean, whereupon with the previous mean and the respective Number of previously learned values a new mean calculated and stored. This also adds a functional diagnosis of the correction value calculation reached.

For example, in the rail pressure section from 200 to 300 bar at least one of them in this section Operating point one after the other a correction value of 0.4; 0.5 to finally 0.6 are determined. As a criterion for the For example, a plausibility check should be a maximum Deviation of 0.3 may be specified. The second determined Correction value of 0.5 deviates only within the allowed Limit from the first determined correction value of 0.4, so that on the one hand 0.5 as a new correction value for this section and, on the other hand, the updated mean from now 0,45 together with the adaptation number (here: 2) is filed. In the next cycle, the third is determined Correction value of 0.6 with the current average of 0.45 compared. Its deviation (here: 0.15) is less than the given deviation (here: 0,3). The new Correction value of 0.6 is thus accepted. From the Mean value of 0.45 with associated adaptation number of 2 and The new correction value 0.6 can then be calculated according to the formula for the arithmetic mean of a new, updated Mean value of 0.5 (with associated adaptation number of 3) be calculated.

When saving invalid values by the new ones Values replaced after it was verified that the new values fit better than the old values.

The result of the determined old and new correction value is available at the output b of the interpolation unit 6 and can be used to control the injector.

The system is provided with a manager that monitors the number of correction values for a particular section. If no correction values have been calculated in a section over a longer period of time, this section becomes targeted
Adaptation triggered. If this is not possible or not desirable, for example, an internal display can be made that in this area a partially unreliable engine control is given.

The process is very simple and fast to perform, so that it is also for the control of an individual cylinder is applicable.

FIGS. 2A to 2C show three diagrams with which FIGS aforementioned embodiment of the invention Correction value for compensation of injector drift in Depending on the rail pressure can be determined. On the y-axis Fig. 2A is the amount of fuel to be injected m_Sprit applied. In contrast, on the y-axis of the figures 2B and 2C, the offset (correction value) of the minimum Injection duration of the injector t_Offset plotted. On the x-axis FIGS. 2A to 2C is the rail pressure p_Rail applied. In FIG. 2A is a linear ramp function shown. These include two saw teeth by way of example recognizable, the edge of which increases with increasing time. Of the left sawtooth is the underlying diagram of the figure 2B assigned. In the diagram of Figure 2B is the case considered when the mode selection 5 in the learning mode 3 has switched.

The second sawtooth of Figure 2A is the diagram of the figure 2C assigned. Here the case is considered when the mode selection 5 has switched to the interpolation unit 6.

With the ramp function of Figure 2A is in principle the Operating point of a range of values determined by the Internal combustion engine is currently located and for which the determining correction value for the drift correction of Injector is to be determined. The diagram of Figure 2B is the associated with the first sawtooth of Figure 2A. It shows in the Learning mode 3 as a learning curve a bowl-shaped offset curve, to correct the injection duration of an injection pulse determined and stored in advance using the algorithm has been. Depending on the operating point can now from the curve of FIG 2B the corresponding correction value (offset value) is read become. The diagram is especially for the adaptation a minimum amount of fuel used.

An alternative solution for determining the correction value is shown in Figure 2C. At this correction curve was during regular driving between two interpolated stored operating points. The in the curve recognizable individual stages arise through the calculation period for determining the offset value. In principle, this runs Curve similar to that in FIG. 2B.

In the block diagram of Figure 3 is a Control device 10 is provided, in which the aforementioned Implemented manager with the algorithm of the invention is. The control device 10 has a programmable Calculator with all required units. He is in particular with a program memory 11, a memory 12 for the algorithm and a memory 13 for correction values connected. The correction values are preferably in Form of a table or a map along with stored further associated parameter values.

The control device 10 is preferably via a Datenund Control bus 18 connected to at least one injector 14, the at a suitable location of the internal combustion engine 20 in the area a cylinder 17 is arranged. The injector 14 is preferably formed with a piezoelectric actuator, which can be controlled via the data and control bus 18.

The injector 14 is at a high pressure line (rail) 16th connected to those under high pressure Fuel, such as gasoline, diesel or gas filled is. The high pressure in the rail 16 is controlled by a Pump 21 is generated. A pressure sensor 19 on the pump 21 or on The rail records the current rail pressure.

On the internal combustion engine 20 is further a knock sensor 15 arranged, with the u.a. detects the combustion noise and from this, for example, the beginning of the injection or the actual amount of fuel injected will be determined can. Other sensors, such as a speed sensor for Speed detection of the internal combustion engine, etc. are predictable.

The system is cylinder-specific and thus enables for example, the compensation of injector scatters. The Realization of the system is generic, that is, it can for the compensation of different, even several Dependencies are used. The adaptation to the respective dependency is purely via calibration.

Claims (15)

Method for drift compensation of an injector (14) for the direct injection of fuel into a cylinder (17) of an internal combustion engine (20), wherein a correction value compensating for the drift of the injector (14) is determined and learned by a control device (10) to inject a defined quantity of fuel is valid for a range of values of at least one operating parameter (U_min, p_Rail, t_Start) of the internal combustion engine (20), characterized in that the entire range of values of the operating parameter (U_min, p_Rail, t_Start) is divided into at least two discrete sections that for at least a section is determined and learned at least one operating point dependent on the operating parameter (U_min, p_Rail, t_Start) correction value. A method according to claim 1, characterized in that the correction value is stored together with its corresponding operating point (B_Pkt) and / or other information in the form of a table or a map. Method according to at least one of the preceding claims, characterized in that the operating point of the internal combustion engine (20) is kept constant in the calculation of the correction value. Method according to one of the preceding claims, characterized in that is interpolated in normal driving operation for determining the correction value between two learned value pairs. A method according to claim 4, characterized in that between two closest pairs of values is interpolated when no usable value pairs are stored. Method according to at least one of Claims 4 or 5, characterized in that the result is checked as to whether the interpolated correction values lie between calibratable limits. Method according to one of the preceding claims, characterized in that the correction values in dependence on the speed (U_min) of the internal combustion engine (20) and / or from the beginning of the injection (t_Start) and / or in a direct injection system from the rail pressure (p_Rail) is determined. Method according to one of the preceding claims, characterized in that the learning process is activated during the driving operation of the vehicle when a suitable operating point is reached. Method according to one of the preceding claims, characterized in that for the injection of a minimum amount of fuel drift-compensating correction values for a minimum injection duration of the injector (14) are determined and learned. Method according to one of the preceding claims, characterized in that a new correction value is determined for the ongoing adaptation of a section, and that the new correction value is checked for plausibility by comparison with the current mean value of all correction values previously learned in the respective section and learned only in the case of predefinable criteria becomes. A method according to claim 10, characterized in that the new correction values are respectively checked to see whether the deviation from the current average value is below a calibratable limit. Method according to at least one of claims 10 or 11, characterized in that the plausibility check is activated only after a predefinable minimum number of correction values already learned in the respective section. Method according to at least one of Claims 10 to 12, characterized in that a specific section of the range of values is specifically activated for adaptation if no or no new correction value has been learned there over a specifiable period of time. Device for drift compensation of an injector (14) according to one of the preceding claims, with a control device (10) for determining at least one correction value dependent on an operating parameter and with a memory (13) for the correction value, characterized in that the control device (10) has a Algorithm with which the correction value in at least a portion of a subdivided into at least two discrete sections value range for at least one operating point can be determined. Device according to claim 14, characterized in that the algorithm of the control device (10) is designed to determine a suitable correction value for a current operating point of the internal combustion engine (20) either by interpolation or read-out from the memory (13) and the injection duration of the injector ( 14) to correct accordingly.

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