DE102011078710A1 - Method for correcting e.g. target injection mass of injector of diesel engine of motor car, involves correcting parameter at operating point using transfer function that transfers value at another operating point into value at former point - Google Patents

Abstract

The method involves correcting an injection quantity characteristic parameter of an injector (109) of a combustion engine (116) at an operating point using a correction value that is determined in a closed loop by a controller. The characteristic parameter is corrected at another operating point using the correction value and a transfer function that transfers the correction value at the former operating point into the correction value at the latter operating point and comprises an operating point-dependant correction map for an injection quantity adjustment process. An independent claim is also included for a computing unit for correcting an injection quantity characteristic parameter of an injector of a combustion engine.

Description

The present invention relates to a method for correcting a quantity indicative of an injection quantity for an internal combustion engine injector according to the preamble of claim 1.

State of the art

Fuel injection pads allow the metering of the fuel required for combustion in an internal combustion engine by means of one or more injectors. In gasoline direct injection and common rail injection, the fuel is injected directly into the combustion chamber. For the quality of combustion and thus the consumption and the exhaust gas behavior of the internal combustion engine, the metered amount of fuel is of crucial importance.

However, the metered amount of fuel is affected by properties of the injector itself. Due to copy discrepancies that occur in the injectors used within an internal combustion engine, the amount of fuel metered by different injectors is usually different for identical actuations, resulting in reduced combustion quality.

Also not all cylinders of the internal combustion engine produce the same torque with the same control. The consequence of these torque differences is a poor engine run and increased emissions. For example, in the DE 195 27 218 A1 or the DE 2004 010 412 A1 Cylinder Equilibrium (also known as "creep control"), also known as "Fuel Balance Control" (FBC). In this case, the current rotational speed of the internal combustion engine is detected with the aid of sensor devices and the detected course of the rotational speed is analyzed. In this way, the torque fluctuations can be determined, which can be deduced from fluctuations in the fuel injected into the individual cylinders of the engine fuel masses. Differences in the injected fuel masses can then be corrected by correcting the desired injection mass with a mass correction value. This is done as closed-loop control.

However, at some operating points, disturbances of the speed signal occur, which prevent the FBC from being executed (corresponds to a fault in the actual value of the control). Causes may be, for example, torsional vibrations of the crankshaft, which occur especially at higher speeds or at higher loads. Another disturbing cause may lie in non-equidistant ignition intervals in the internal combustion engine. Such faulty operating points are usually determined in advance and stored in the control unit as locked for FBC. A cylinder equalization does not occur in these operating points.

It is therefore desirable to extend the scope of cylinder equalization.

Disclosure of the invention

According to the invention, a method for correcting a variable indicative of an injection quantity for an injector of an internal combustion engine having the features of claim 1 is proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

Advantages of the invention

With the measure according to the invention, the scope of the cylinder equalization can be extended substantially to all operating points.

This is done by performing the correction in at least one second operating point using an injector-specific correction value for at least one first operating point, wherein a transfer function is provided which converts the correction value for the at least one first operating point into the correction value for the at least one second operating point , The correction value is used to equalize cylinder different torques. The extension of the scope of application makes it easier to comply with modern emission regulations (eg in the USA, CARB).

An operating point per se is characterized by the torque, engine speed, pressure, temperature and / or volume of the injected fuel generated by the internal combustion engine. The variable characterizing an injection quantity is preferably a desired injection mass or a nominal injection volume. A desired injection volume can be determined from a desired injection mass, preferably temperature-dependent. A correction value may be a mass correction value that corrects an injection mass or a volume correction value that corrects an injection volume.

A first operating point is characterized in particular by the fact that it is suitable for a cylinder equalization. Here are now correction values for one or more first operating points (within the closed control, ie during the operation) and, for example, stored in a control unit. If the vehicle is now operated at a second operating point at which (for example due to disturbances of the rotational speed evaluation) no controlled cylinder equalization is possible, a correction value to be used here is determined from one or more stored correction values using the transfer function.

Conveniently, the at least one first operating point is characterized in that it is suitable for a speed-based cylinder equalization (eg FBC of the Applicant). The invention may use established methods such as the FBC to determine correction values for one or more operating points.

The transfer function may include extra and / or interpolation. The transfer function may alternatively or additionally include an operating point-dependent correction map, in which operating point-dependent, for example, weighting factors for the weighting of a correction value are included. By specifying a correction map, the transfer can be carried out very easily and without much computational effort.

A particularly advantageous solution results from the use of already known and proven transfer functions. For example, the use of the known from Injektormengenabgleichsänderung correlation maps offers here. During operation of the internal combustion engine, the (possibly torque-corrected) desired injection mass, usually temperature-dependent, is converted into a desired injection volume, from which the activation times for the injector are then determined. In order to counteract the above-mentioned specimen spreads, procedures (so-called injector balance IMA) have been developed to specify this conversion. Such a method is, for example, from the DE 102 15 610 A1 known. In order to achieve the lowest possible fuel consumption in compliance with strict emission standards and a very good running smoothness, the injectors may only have very small tolerances with respect to the injection volume during operation. These required low tolerances can not be met due to the mechanical manufacturing tolerances. Therefore, the injectors are measured after production at (a few) characteristic operating points on their injection quantity and classified into classes of different volume deviations (essentially by comparison of target injection volume actual injection volume). The respective class is known to the engine control unit during operation, so that the control can be adapted to the specific features of the class by injecting specific volume correction values and correction maps (IMA correlation maps). During operation, the desired injection volume is then corrected (in open loop) by converting from the volume correction values for the characteristic operating points (first operating points) via the correction map to volume correction values for the current operating point (second operating points). A volume correction value thus serves to adapt a desired injection volume to the existing injector. The correction maps (so-called IMA correlation maps), which are known from the injector balance, are also used with particular advantage as part of the transfer function for the cylinder equalization. The first operating points then preferably those above-mentioned (few) characteristic operating points are used, to which the correlation map is tuned. If during operation a first operating point is assumed which corresponds to one of the characteristic operating points, the correction value resulting here from the cylinder equalization is stored. If during operation a second operating point is taken which does not correspond to any of the characteristic operating points, the correction value for this second operating point is calculated from the stored correction value for the first operating point and the IMA correlation map. Surprisingly, it has also been found that IMA correlation maps, which are also used for a purely controlled process (ie in the open loop), are well suited as cylinder equalization transfer functions, which is a closed loop process.

Another particularly advantageous solution is obtained by combining the invention with a Injektormengenabgleichsverfahren, as for example. Based 3 is explained.

An arithmetic unit according to the invention, e.g. a control device of a motor vehicle is, in particular programmatically, configured to perform a method according to the invention.

The implementation of the method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore exists anyway. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.).

The invention usually uses existing elements in modern internal combustion engines and can therefore also be advantageously implemented in existing systems, for example in the form of an update of a control unit software.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

1 schematically shows a common rail fuel injection system, as the invention may underlie.

2 schematically shows a control scheme according to a first preferred embodiment of the invention.

3 schematically shows a control scheme according to a second preferred embodiment of the invention.

Embodiment (s) of the invention

In 1 is an engine designed here as a common rail engine comprising a common rail fuel injection system 100 and an internal combustion engine 116 , For example, a diesel engine, shown schematically, as can be based on the present invention.

In a partially cutaway shown, with cooling water 114 cooled cylinder 124 of the internal combustion engine 116 is a piston 126 movably arranged. An injector 109 for injecting fuel into the cylinder is on the cylinder 124 assembled. Although here only one cylinder 124 is shown, a suitable internal combustion engine usually has at least two cylinders when using a speed-based cylinder equalization.

The fuel injection system includes a fuel tank 101 , which is shown in almost filled condition. Inside the fuel tank 101 is a prefeed pump 103 arranged by a pre-filter 102 Fuel from the tank 101 sucked in and at a low pressure of 1 bar to a maximum of 10 bar through a fuel line 105 up to a fuel filter 104 promoted. From the fuel filter 104 leads another low pressure line 105 ' to a high pressure pump 106 , which compresses the supplied fuel to a high pressure, which is typically between 100 bar and 2000 bar depending on the system. The high pressure pump 106 has a metering unit (ZME) 113 for adjusting a fuel amount. The high pressure pump 106 feeds the compressed fuel into a high-pressure line 107 and a rail connected to it 108 (High-pressure accumulator), the so-called common rail. From the rail 108 leads another high-pressure line 107 ' to the injector 109 ,

A system of return lines 110 allows the return of excess fuel from the fuel filter 104 , the high pressure pump 106 or metering unit 113 , the injector 109 and the rail 108 in the fuel tank 101 , It is between the rail 108 and the return line 110 a pressure control valve (DRV) 112 switched by changing the from the rail 108 in the return line 110 outgoing fuel quantity in the rail 108 prevailing high pressure, the so-called rail pressure, can regulate.

On a crankshaft (not shown) is a speed sensor 135 provided for detecting a speed signal. The speed signal serves as the basis for a speed-based cylinder equalization.

The entire common rail injection system 100 is through a control unit 111 controlled, via electrical lines 128 including with the pre-feed pump 103 , the high pressure pump 106 , the metering unit 113 , the injector 109 , the speed sensor 135 , a pressure sensor 134 on the rail 108 , the pressure control valve 112 as well as temperature sensors 130 . 132 . 122 on the combustion engine 116 or at the fuel supply line 105 connected is.

In 2 a first preferred embodiment of a method according to the invention in the form of a control scheme for a cylinder or injector is shown. It is a closed loop.

The rule scheme includes a rule member 201 for a speed-based cylinder equalization. As a controller output variable, an injection mass _correction q _cor is a quantity indicative of an injection quantity to a controlled system 202 which, inter alia, comprises conversion elements for the conversion into an injection volume and / or a drive duration for the injector, the behavior of the internal combustion engine and the drive train and the speed detection. As output variable of the controlled system 202 becomes a speed-based signal n to the control element 201 or an upstream reference junction 203 recycled. This known per se speed-based cylinder equalization serves to equalize the torque and thus the injection mass of the cylinder.

As mentioned, operating points exist in which the cylinder equalization does not work due to disturbances of the speed-based signal. To provide the operability especially in these areas is now a correction block 210 intended. The correction block includes a memory member 211 in which the mass correction _value q _{cor is} stored. The element outputs a second mass correction _value q _{cor '} , which is _transmitted via a multiplication element 212 to an addition member 213 to be led.

The multiplier 212 becomes an output value of one here as a correction map 214 realized transfer function supplied. The product of the second mass correction value and the output value of the map becomes the third correction value q _{cor ''} the adder 213 fed, linked to the first mass correction _value q _cor and to the controlled system 202 guided.

The correction map 214 become the current operating point characterizing parameters 215 , such as speed, torque, load, and the current rail pressure 216 fed. The correction map 214 serves to convert the stored mass correction value for a first operating point into a mass correction value for a second operating point, wherein in the second operating point the control element 201 is disabled in particular. In this way, a cylinder equalization (ie, the alignment of the injection mass for several cylinders) can also be achieved for operating points in which a conventional cylinder equalization is not possible.

In 3 a second preferred embodiment of the invention is illustrated by a further control scheme. The embodiment according to 3 differs from the embodiment according to 2 by an advantageous combination with a Injektormengenabgleichsverfahren (ie, the adjustment of the target injection volume to the existing injector). Identical or equivalent elements are provided with the same reference numerals.

The speed-based cylinder equalization in 3 corresponds in principle to the cylinder equalization according to 2 , However, it is a conversion element 304 provided, which performs a, in particular temperature-dependent, conversion of the injection mass _{correction value} q _cor in an injection _{volume correction} value v _cor . The injection volume correction value for the cylinder equalization v _cor is via the adder 213 linked to injector balance. This contains a value field 305 , in which volume deviations are stored at specific operating points (cf the above-mentioned characteristic operating points). These volume deviations are usually measured after the production of the injector and stored at the injector, for example in the form of bar codes. These bar codes can then be read into the engine control unit. Furthermore, the injector balance includes a correction map 214 (the so-called IMA correlation map), the volume deviations from the field 305 transferred to the current operating point. The correction map 214 For this purpose, weighting factors are output, which at the multiplication element 212 multiplied by the volume deviation and the adder 213 be supplied.

According to the preferred embodiment of the invention shown here, this method, which is known per se, will now be expanded so that it is now also possible at operating points at which no cylinder equalization has hitherto been possible. There is an additional block for that 310 provided, the mass correction _value q _{cor is} supplied. In a conversion element 311 First, a conversion, again in particular temperature-dependent, into a volume correction value v _{cor occurs} . This is then in a filter member 312 , For example, a PT1 element, temperature-dependent filtered. In particular, high-frequency components are discarded here. The storage then takes place in an integrator 313 , which in turn is controlled in particular temperature-dependent. The integrator 313 Over time, it takes over from the control element 201 output value, so that the control output of the limb 201 with time goes to zero and for the output of the limb 313 over time goes against the volume correction value v _cor .

In the particularly preferred embodiment of the invention shown here, this desired volume correction value now becomes a transfer function with the same correction map 214 corrected, which is also used for injector balancing. As a result, therefore, the invention can be implemented particularly easily. According to the wording of the claims, in this embodiment, as the (first) correction map for the cylinder equalization, the (second) correction map for the injector quantity adjustment is used.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19527218 A1 [0004]
• DE 2004010412 A1 [0004]
• DE 10215610 A1 [0014]

Claims (12)

Method for correcting an injection quantity quantity for an injector ( 109 ) of an internal combustion engine, wherein the size indicative of an injection quantity for the injector ( 109 ) is corrected for at least a first operating point using a correction value (q _cor ), wherein the correction value (q _cor ) for the at least one first operating point is determined by a closed-loop control, characterized in that the size indicative of an injection quantity for at least a second operating point using the correction value (q _cor ) for the at least one first operating point and a transfer function ( 214 ), the transfer function ( 214 ) converts the correction value (q _cor ) for the at least one first operating point into the correction value (q _{cor ''} ) for the at least one second operating point. The method of claim 1, wherein the injection quantity indicative size is a desired injection mass or a target injection volume. The method of claim 1 or 2, wherein the correction value (q _cor ) for the at least one first operating point is determined by a speed-based cylinder equalization method. Method according to one of the preceding claims, wherein the at least one first operating point for a cylinder equalization is suitable. Method according to one of the preceding claims, wherein the transfer function includes extra and / or interpolation. Method according to one of the preceding claims, wherein the transfer function has a first operating point-dependent correction map ( 214 ) includes. Method according to claim 6, wherein the correction map ( 214 ) is a correlation map of an injector balance method. Method according to claim 6 or 7, wherein in the correction map ( 214 ) operating point-dependent weighting factors are included. Method according to one of the preceding claims, wherein the quantity characterizing the injection quantity is additionally determined at least for the second operating point using a second correction map ( 214 ) is corrected for the first operating point mathematically linked volume correction value (v _cor ), wherein the second correction map ( 214 ) provides a transfer between the first operating point and the second operating point. The method of claim 9, wherein the volume correction value (v _cor ) is determined injector-individual by comparing desired injection volume and actual injection volume. Method according to a combination of claim 9 or 10 with claim 6, 7 or 8, wherein the first correction map and the second correction map are identical. Arithmetic unit which is adapted to carry out a method according to one of the preceding claims.

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