DE102004038733A1 - Method and device for operating an internal combustion engine - Google Patents

Abstract

A method and a device for operating an internal combustion engine (1) are proposed, which enable leakage detection without air mass meter. In this case, a first value for an air mass flow to the internal combustion engine (1) from at least two operating variables of the internal combustion engine (1) is modeled. A second value for the air mass flow to the internal combustion engine (1) is determined from a pressure difference across a component (5) of an air supply (10) to the internal combustion engine (1). The two values for the air mass flow are compared with each other. If the two values for the air mass flow deviate by more than a predetermined threshold, an error is detected.

Description

The The invention relates to a method and a device for Operating an internal combustion engine according to the preamble of the independent claims.

It are already methods and apparatus for operating an internal combustion engine known in which a value for an air mass flow to the engine of at least two Operating variables of Internal combustion engine is modeled. In these at least two operating sizes of Internal combustion engine is, for example, the pressure upstream a throttle and the position of the throttle.

Farther it is known in the case of supercharged internal combustion engines that in case of leakage downstream a compressor in an air supply of the internal combustion engine of Boost pressure drops. An existing charge pressure control then causes the closing a bypass valve around a turbine in an exhaust line of the internal combustion engine, which drives the compressor in the air supply via a shaft. On This way, a pre-set boost pressure setpoint can be reached again become. The turbine rotates faster, because it also the power for compression the leakage air must apply. There is a risk of overspeeding. In supercharged internal combustion engines are usually air mass meter for measuring the air mass flow to the internal combustion engine or the Air filling in the Combustion chamber of the internal combustion engine used. The upstream of the Compressor's built-in air mass meter measures the sum the leakage air and the air that ultimately enters the internal combustion engine flows. With the help of the pressure sensor upstream of the throttle, the measures the boost pressure, and the position of the throttle can also be the Air mass flow of the air ultimately flowing into the internal combustion engine model. By comparing the measured by the air mass meter Air mass flow with the modeled air mass flow can be Detect if a leak between the air mass meter and the Pressure sensor is present.

Advantages of invention

The inventive method and the device according to the invention for operating an internal combustion engine having the features of the independent claims In contrast, the advantage that a second value for the air mass flow to the engine from the pressure difference over one Component of an air supply to the internal combustion engine is determined that the two values for the Air mass flow are compared with each other and that at a amount difference of the two values for the air mass flow by more than a predetermined threshold Error is detected. In this way, the error or a leak can be in the air supply even then detect if no air mass meter is available for measuring the air mass flow.

By in the subclaims listed activities are advantageous developments and improvements of the main claim specified method possible.

Especially just lets the first value for the air mass flow from an intake manifold pressure and an engine speed model.

Also let yourself the first value for the air mass flow simply from a pressure in the air supply upstream a performer and an opening degree modeling of the performing element.

The Accuracy in determining the second value for the air mass flow let yourself increase, if the second value for the air mass flow is corrected.

A such correction leaves very easy and precise dependent from the difference between the first value and the second value for the Perform air mass flow.

Especially easy and precise to carry out the correction by means of a regulation.

The Accuracy in determining the first value for the air mass flow let yourself increase, if the first value for the air mass flow dependent from a temporal pressure change Corrected upstream of a power element in the air supply becomes.

One Another advantage arises when the two values the air mass flow mark at different points of the air supply. In this way is it possible a leak between these different parts of the air supply to recognize.

drawing

An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description. Show it 1 a schematic view of an internal combustion engine and 2 a functional diagram for explaining the inventive method and apparatus of the invention.

description of the embodiment

In 1 features 1 an internal combustion engine, which may be formed for example as a gasoline engine or as a diesel engine. In the following, by way of example, assume that the internal combustion engine 1 is designed as a gasoline engine. The gasoline engine 1 includes a cylinder block 110 with one or more cylinders, each comprising a combustion chamber. Representing is in 1 the combustion chamber of a cylinder of the cylinder block 110 shown schematically. This combustion chamber will have an in 1 not shown inlet valve fresh air from an air supply channel 10 , which is also referred to below as the air supply, fed. The flow direction of the fresh air in the air supply 10 is in 1 indicated by arrows. The fresh air is first from an air filter 5 in the air supply 10 cleaned by the dust contained in the intake air. A differential pressure sensor 55 Determines the pressure difference between the air inlet and the air outlet of the air filter 5 in the air supply 10 adjusts itself and passes the measurement result to a motor control 20 further. Such differential pressure sensors are already well known to the skilled person. Downstream of the air filter 5 is in the air supply 10 a compressor 45 arranged, which is the gasoline engine 1 supplied fresh air compressed. Downstream of the compressor 45 is in the air supply 10 a pressure sensor 50 arranged the pressure in the air supply 10 measures and the measurement result to the engine control 20 forwards. Downstream of the pressure sensor 10 is in the air supply 10 a performing element 15 , formed in this example as a throttle valve, arranged. Thus, the pressure sensor detects 50 the pressure in the air supply 10 upstream directly in front of the throttle 15 , The throttle 15 turn is from the engine control 20 driven. In the following, it will be assumed by way of example that the gasoline engine 1 driving a vehicle, with a driver at an in 1 not shown accelerator pedal can specify a driver's request, that of the engine control 20 in a default value for the opening degree of the throttle valve 15 is implemented. The engine control 15 then causes the throttle 15 for setting this predetermined opening degree. The compressed and optionally throttled fresh air supplied to the combustion chamber in this way is via an injection valve 60 mixed with fuel. It is according to 1 shown that the fuel through the injector 60 injected directly into the combustion chamber. Alternatively, the fuel may already be in the air supply 10 downstream or upstream of the throttle 15 be injected. At the same time, the injection valve becomes 60 also from the engine control 20 controlled, for example, to comply with a predetermined air / fuel mixture ratio. The air / fuel mixture formed in this way is from a spark plug 65 ignited. Also the spark plug 65 can from the engine control 20 be controlled, for example, to realize a suitable ignition timing. This can, for example, with regard to a torque reserve to be set or with regard to the heating of a possibly present catalyst in the exhaust system of the gasoline engine 1 be predetermined. The resulting during the combustion of the air / fuel mixture in the combustion chamber exhaust gas is a in 1 not shown exhaust valve in an exhaust line 70 pushed out. The flow direction of the exhaust gas in the exhaust system 70 is in 1 also marked by arrows. In the exhaust system 70 is according to 1 a turbine 70 arranged, the exhaust gas mass flow in the exhaust system 70 is driven. The turbine 75 in turn drives over a wave 80 the compressor 45 for compression of the gasoline engine 1 to be supplied fresh air. The compressor 45 , the turbine 75 and the wave 80 form in this example an exhaust gas turbocharger.

The double arrow in 1 between the throttle 15 and the engine control 20 indicates that there is also a position feedback, ie that a measuring device in the throttle valve 15 For example, in the form of a potentiometer, the position of the throttle 15 recorded and to the engine control 20 feeds back. This measurement is also called αdk. The from the pressure sensor 50 upstream of the throttle 15 detected pressure value is referred to as pvdk and the differential pressure sensor 55 determined pressure difference across the air filter 5 is called dplufi. A control of a bypass around the turbine 75 the turbocharger is in 1 not shown for reasons of clarity and can be carried out in a manner known to those skilled in the art.

In 2 The method according to the invention and the device according to the invention are now described in greater detail on the basis of a functional diagram. This function diagram can be software and / or hardware in the engine control 20 be arranged or implemented. In the process, the pressure from the differential pressure sensor 55 measured pressure difference dplufi a determination unit 30 supplied, which is formed in this example as a characteristic and the differential pressure dplufi converted into a corresponding air mass flow mslufiuk. The characteristic 30 describes the relationship between the pressure drop across the air filter 5 and the associated air mass flow through the air filter 5 , This characteristic 30 can be determined for example on a test bench. Instead of the characteristic 30 can also be used a map, in addition to the pressure difference dplufi as another input variable, the temperature of the air in the air supply 10 in the Area of the air filter 5 receives, this temperature measured for example by a temperature sensor or with the help of various operating variables of the gasoline engine 1 can be modeled in a manner known to those skilled in the art. Output of the then instead of the characteristic 30 used map is in turn the air mass flow mslufiuk through the air filter 5 which, however, has higher accuracy considering the air temperature. The map can also be determined, for example, on a test bench. The thus determined in dependence on the differential pressure dplufi air mass flow mslufiuk through the air filter 5 is then in a first multiplier 90 multiplied by a correction factor fkmslufi, being a product in the output of the first multiplication element 90 a corrected air mass flow mslufi results. This correction is also optional and takes into account, for example, increasing contamination of the air filter 5 , Such increasing pollution leads to an increase in the drag coefficient of the air filter 5 , The correction value fkmslufi is the output of a very slow-running integrator 85 , whose input with the difference from the corrected air mass flow mslufi and a modeled air mass flow msdk through the throttle valve 15 which may optionally be dynamically corrected, where the dynamically corrected modeled air mass flow through msdkk in 2 is shown. The modeled air mass flow msdk through the throttle 15 is in a modeling unit 25 from the pressure pvdk upstream of the throttle 15 and the position, ie, the opening degree αdk of the throttle valve 15 modeled in the art known manner. Alternatively, the modeled air mass flow msdk through the throttle 15 also in a known manner from the intake manifold pressure downstream of the throttle 15 and the engine speed of the gasoline engine 1 be modeled. The intake manifold pressure can be measured by an intake manifold pressure sensor or by various operating variables of the gasoline engine 1 be modeled in the art known manner. The engine speed of the gasoline engine 1 For example, by a in 1 for clarity, not shown speed sensor in the region of the cylinder block 110 be measured.

The following relationship is in the comparison of the air mass flow mslufiuk determined by the differential pressure dplufi by the air filter 5 with the modeled air mass flow msdk through the throttle 15 to consider: that the air filter 5 supplied air mass is equal to that via the throttle 15 to the cylinder block 110 outgoing air mass plus the air mass change in what is referred to as storage and within the air supply 10 formed space between the outlet of the air filter 5 and the throttle 15 , The air mass change in this memory is proportional to the pressure change dpvd / dt in this memory. The proportionality constant is denoted by K here. The temporal pressure change dpvd / dt can be derived from the measuring signal of the pressure sensor 50 determine. In the addition point 100 will be the one of the modeling unit 25 modeled air mass flow msdk through the throttle 15 is added to the product of the proportionality constant K and the temporal pressure change dpvd / dt in said memory, so that the dynamically correct air mass flow msdkk at the output of the addition element 100 results. this is comparable to the corrected value mslufi of the air mass flow. In this case, the modeled and optionally dynamically corrected value msdkk for the air mass flow represents a first value for the air mass flow and the value mslufi based on the pressure difference dplufi here also optionally corrected for the mass air flow represents a second value for the air mass flow. In a subtraction element 105 the second value mslufi for the air mass flow is subtracted from the first value msdkk for the air mass flow. The resulting difference becomes the integrator 85 supplied on the input side, which then forms in the manner described, the correction or adaptation factor fkmslufi, with which the drift in the conversion between the differential pressure dplufi and the resulting air mass flow mslufiuk is corrected by the gradual contamination of the air filter 5 arises. Thus, the conversion of the differential pressure dplufi into the air mass flow mslufiuk can thus be adapted with the aid of the modeled and optionally dynamically corrected air mass flow msdkk.

The proportionality For example, K can be determined by means of a series of measurements on a test bench become.

Furthermore, according to the invention, it is now provided that the output of the subtraction element 105 in a second multiplier 95 multiplied by the factor-1 to obtain a sign reversal of the difference. As a result, the difference becomes positive when the over the differential pressure sensor 55 determined air mass flow mslufi exceeds the modeled value msdkk. This inverted difference becomes a comparator 35 supplied together with a threshold value S. The comparison element 35 includes an error detection unit 40 containing both the inverted difference at the output of the second multiplier 95 as well as the threshold value S are supplied. Exceeds the inverted difference at the output of the second multiplier 95 the threshold value S, the error detection unit generates 40 an error signal E_leck and outputs this, for example, to a display device for reproducing the detected error and / or to an emergency running unit, which in known in the art an emergency operation of the gasoline engine 1 starts, at For example, by blanking one or more cylinders of the cylinder block 110 or in the last consequence by switching off the gasoline engine 1 ,

So if suddenly a leak, for example, downstream of the compressor 45 and upstream of the throttle 15 occurs, then is from the compressor 45 one part of the air is blown into the open, the other part flows over the throttle 15 towards the cylinder block 110 from. The sum of the leakage air mass flow flowing out into the atmosphere and that via the throttle valve 15 towards the combustion chamber of the cylinder block 110 outgoing air mass flow corresponds to the total air mass flow, previously through the air filter 5 had flowed. Thus, from the pressure drop or the pressure difference dplufi above the air filter 5 still with the help of the characteristic curve 30 the air mass flow mslufiuk or, after correction with the factor flcmslufi, the corrected air mass flow mslufi, which filters the total air mass flow through the air 5 equivalent. The dependent on the pressure pvdk in front of the throttle 15 and the opening degree αdk of the throttle valve 15 determined air mass flow msdk through the throttle 15 deviates now considerably from that through the air filter 5 flowing mass air flow. In this case, the inverted difference exceeds the output of the second multiplier 95 the threshold S, causing a fault or leakage in the air supply 10 is recognized. Of course, the threshold S is suitable to choose. This can be selected, for example, on a test bench so that it takes into account tolerances that result from the different determination of the second value mslufi and the first value msdkk for the air mass flow, but at the occurrence of a leak in the air supply 10 between the compressor 45 and the throttle 15 definitely exceeded.

The inventive method and the device according to the invention is a leakage detection in the air supply 10 without the use of an air mass meter possible.

The process of increasing pollution of the air filter 5 usually takes place slowly. That's why it can be at the integrator 85 to act accordingly a very slow-running integrator.

The from the pressure sensor 50 in front of the throttle 15 detected pressure pvdk is at the same time the boost pressure from the compressor 45 is effected.

The position of the throttle 15 is represented by the throttle angle αdk.

The significant deviation of the air mass flow msdk through the throttle 15 from the air mass flow mslufiuk through the air filter 5 in the case of leakage, it is no longer possible to use the dynamic correction K · dpvd / dt in the addition element 100 correct because the memory described above is no longer present due to the leak in this form and the correction based thereon can no longer provide reliable results.

It is therefore crucial for leak detection if the two values for the air mass flow are at different points in the air supply 10 be determined so that a dazwi rule lying leak can be detected. In this case, the differential pressure instead of the air filter 5 be detected via another component of the air supply, such as a charge air cooler. Instead of multiplication by the second multiplier 95 can also quite generally a magnitude of the difference at the output of the subtraction element 105 be used.

By the first multiplication element 90 , the subtraction element 105 and the integrator 85 a control loop or a regulation is realized.

Claims (9)

Method for operating an internal combustion engine ( 1 ), wherein a first value for an air mass flow to the internal combustion engine ( 1 ) from at least two operating variables of the internal combustion engine ( 1 ) is modeled, characterized in that a second value for the air mass flow to the internal combustion engine ( 1 ) from the pressure difference across a component ( 5 ) an air supply ( 10 ) to the internal combustion engine ( 1 ), it is determined that the two values for the air mass flow are compared with one another and that an error is detected when more than a predetermined threshold value is deviated from the two values for the air mass flow. Method according to claim 1, characterized in that that the first value for the air mass flow from an intake manifold pressure and an engine speed is modeled. A method according to claim 1, characterized in that the first value for the air mass flow from a pressure in the air supply ( 10 ) upstream of a performance element ( 15 ) and from an opening degree of the performing element ( 15 ) is modeled. Method according to one of the preceding claims, characterized characterized in that the second value for the air mass flow corrected becomes. A method according to claim 4, characterized gekenn characterized in that the correction is performed depending on the difference between the first value and the second value for the mass air flow. Method according to claim 4 or 5, characterized that the correction is carried out by means of a regulation. Method according to one of the preceding claims, characterized in that the first value for the air mass flow depending on a temporal pressure change upstream of a Leistungsing element ( 15 ) in the air supply ( 10 ) is corrected. Method according to one of the preceding claims, characterized in that the two values, the air mass flow at different points of the air supply ( 10 ). Contraption ( 20 ) for operating an internal combustion engine ( 1 ), whereby modeling means ( 25 ) are provided, which have a first value for an air mass flow to the internal combustion engine ( 1 ) from at least two operating variables of the internal combustion engine ( 1 ), characterized in that the means of investigation ( 30 ) are provided, which has a second value for the air mass flow to the internal combustion engine ( 1 ) from the pressure difference across a component ( 5 ) an air supply ( 10 ) to the internal combustion engine ( 1 ) determine that comparison means ( 35 ) are provided, which compare the two values for the air mass flow with each other, and that error detection means ( 40 ) are provided, which detect an error in a magnitude deviation of the two values for the air mass flow by more than a predetermined threshold.