DE19525815B4 - Method for detecting the load signal of an internal combustion engine - Google Patents

Abstract

method for detecting the load signal of an internal combustion engine by means of a arranged in the intake manifold sensor, wherein the intake manifold pressure (ps) using one behind the throttle valve of the internal combustion engine (1) arranged Pressure sensor (3) detects and after a height as well as the internal and external Considering exhaust gas recirculation Correction is converted into a load signal (tl), characterized that the intake manifold pressure (ps) is taken into account for the external exhaust gas recirculation Correction of the load signal (tl) reduced by a pressure component (pKagr) that of the exhaust gas pressure (pa), the rotational speed (n) of the internal combustion engine (1) and the duty cycle (τagr) one Exhaust gas recirculation valve (2) depends.

Description

The The invention relates to a method for detecting the load signal of a Internal combustion engine according to the preamble of patent claim 1.

From the DE 195 08 505 A1 a device for calculating the intake air amount of an internal combustion engine is known. An apparatus for calculating an amount of air supplied to a cylinder of an internal combustion engine will be described. The cylinder is supplied with air via an air intake passage. Gas is removed from the cylinder via an air outlet duct. Both of these include an intake valve which, both controlled and alternately and selectively open and closed by an intake valve drive mechanism corresponding to crankshaft rotation, simultaneously open to open the ducts leading to the cylinder during a valve overlap phase. In order to vary a setting of the driven valve, a variable valve timing mechanism controls an operation setting of the valve driving mechanisms with respect to the crankshaft in accordance with an engine running state. The calculation device comprises a first detection device for detecting the crankshaft speed. A second detection device detects an intake pressure in the air intake passage. A third detection means detects the operation setting of the valve driving mechanisms. A determination device determines an operation adjustment according to the detected crankshaft speed and operation setting. A first calculating means calculates the amount of air supplied to the cylinder depending on the crankshaft rotational speed, the intake pressure and the operating setting adjustment. From the DE 38 07 175 A1 already a method and a system for controlling the fuel injection rate in an internal combustion engine known. A method for controlling the fuel injection rate in an internal combustion engine according to the intake pressure and the engine speed will be described. The method includes determining the intake pressure using the time period after changing the throttle opening as a variable and calculating a basic injection duration according to the intake pressure and the engine speed calculated in this manner. The fuel injection takes place by means of a system according to this method. In the system, the steady state intake pressure suction pressure is determined from the throttle opening degree and the engine speed, thus correcting certain intake pressure by taking a response delay of the intake pressure s in a transient period and determining the basic injection duration from the corrected intake pressure and the engine speed. According to this method, since the injection rate is set according to the engine speed and the actual intake pressure that can be predetermined with high accuracy, the fuel injection rate can be controlled in very close accordance with the injection rate required by the engine.

From the DE 39 32 420 C2 are known a control device for a in the intake system of an air-compressing injection internal combustion engine arranged throttle element. In this case, an actuator for actuating the throttle element is provided, which is controlled by an electronic control unit which at least one of the current engine speed, the current engine load and a suction pressure downstream of the throttle element corresponding measured value signal is supplied, wherein the throttle element in low load and speed ranges held in the open position and in medium and high load and speed ranges in an open position and is adjusted at each operating point of the internal combustion engine to that open position corresponding to a determined from a load and speed-dependent map taking into account the intake pressure value. An atmospheric pressure sensing sensor and an intake air temperature sensing sensor are provided which are connected to the electronic control unit. The intake pressure downstream of the throttle element is the controlled variable, wherein a basic value of the controlled variable is corrected as a function of atmospheric pressure and intake air temperature such that the set point decreases linearly with decreasing atmospheric pressure by a correction value but the correction value is no longer output below a predetermined limit value for the atmospheric pressure. so that the throttle element is transferred to its fully open position and that the correction of the target value in the low intake air temperature range is reduced up to a first intake air temperature value with increasing intake air temperature is kept constant from this first intake air temperature value to a second intake air temperature value and from this second intake air temperature value is increased again with increasing intake air temperature, wherein the second Ansauglufttemperaturwert is greater than the first.

Out the publication "mixture formation in gasoline engines "H. P. Lenz, Springer-Verlag Vienna, New York, 1990, it is known that be supplied by an electronic control unit control pulses whose Duration of the absolute intake manifold pressure, of the engine speed, as well depends on further correction variables.

From the DE 42 14 648 A1 a system for controlling an internal combustion engine is known. A system for controlling an internal combustion engine, in particular a self-igniting internal combustion engine, which comprises a turbocharger and exhaust gas recirculation means, is described. This system comprises means for forming an air quantity signal, based on the rotational speed, the amount of fuel to be injected, an exhaust gas recirculation signal and a comparison of the power of the compressor and the power of the turbine For determining the load signal of an internal combustion engine is initially substantially sucked by the internal combustion engine fresh air mass, for example by an air mass meter detected. Depending on this measured fresh air mass then a load signal, ie the injection time is determined. This type of detection of the load signal of an internal combustion engine requires a technically complex and therefore costly air mass meter arranged in the intake manifold in front of the throttle valve.

The Detecting the load signal by means of such air mass meter proves especially in smaller and cheaper vehicles as a disadvantage, or not necessary.

task The invention is therefore a method for detecting the load signal an internal combustion engine to convey, in the simple way arranged by means of a suction pipe, technically less expensive and therefore inexpensive sensor the sucked fresh air mass and thus the load signal of the internal combustion engine detected can be.

Advantages of invention

The Task is in a method according to the preamble of the claim 1 according to the invention the features of claim 1 solved.

Especially It is advantageous that the Intake manifold pressure with the help of a behind the throttle valve of the internal combustion engine arranged technically simple and thus cheap pressure sensor detected can be, and that this so grasped Intake manifold pressure after a height as well as internal and possibly external exhaust gas recirculation Correction is converted directly into a load signal.

Basically the measured by a pressure sensor behind the throttle intake manifold pressure from a pressure share together, the sucked fresh air mass is attributable to a pressure component caused by due to valve overlaps inevitable internal exhaust gas recirculation caused is and a pressure proportion by the possibly existing external exhaust gas recirculation caused becomes.

to Determination of fresh air mass, it is now necessary, by caused the internal and external exhaust gas recirculation pressure increase from the actual, the sucked fresh air mass attributable Separate pressure. In other words, the sucked total mass a fresh air portion and a residual gas content, and it is one Separation of the residual gas content, for example, in the case of Internal exhaust gas recirculation through valve overlaps is caused, necessary from the fresh air portion.

This is advantageously by the inventive method possible.

advantageous embodiments The invention are the subject of the dependent claims.

So For example, it is advantageous that the intake manifold pressure to order one with a height factor weighted sum of ambient pressure and exhaust back pressure reduced becomes. This allows up easy way the correction of the altitude influence and by caused the internal exhaust gas recirculation Pressure increase.

Farther It is advantageous in the case of an existing external exhaust gas recirculation the Intake manifold pressure to reduce a pressure fraction, the exhaust gas pressure, the speed of the internal combustion engine and the duty cycle of a Exhaust gas recirculation valve depends. In this way, the pressure increase resulting from the external exhaust gas recirculation is eliminated. Advantageously, this pressure component is just like the exhaust back pressure each taken from a map.

Furthermore are advantageously provided further correction maps, for example, for consideration due to delivery grade influences of charge influences depend on the speed and the intake manifold pressure in the load signal, or to compensate for temperature influences in the load signal of the Temperature of the engine and the intake temperature depend.

The Method is advantageously used in an electronic circuit, for example in a digital computer, a programmable logic circuit, an analog computer and the like. executed.

 drawing

Embodiments of the invention will be explained in more detail in connection with the drawing and the description below. Show it:

1 schematically a first variant of an electronic circuit for implementing the method;

2 a second variant of an electronic circuit for implementing the method and

3 schematically the arrangement of the pressure sensor in the intake manifold of an engine.

description the embodiments

Of the The basic idea of the present invention is a method for detecting the load signal of an internal combustion engine by means of a to arrange arranged in the intake manifold sensor, wherein the sucked Fresh air share by means of a simple, arranged behind the throttle pressure sensor detected and which makes it possible the so captured Intake manifold pressure under consideration one the height as well as internal and possibly external exhaust gas recirculation Correction to convert directly into a load signal.

The Procedure can be best explained in conjunction with the drawing.

3 schematically shows an internal combustion engine 1 with a gas mass flow flowing into it 1a and with a gas mass flow out of this 1b , with an external, through an exhaust gas recirculation valve 2 shown exhaust gas recirculation 2a , In the intake manifold after the throttle valve (not shown) is a pressure sensor 3 arranged. This pressure sensor 3 detects not only the intake fresh air, but also a residual gas content, which is present for example due to internal or external exhaust gas recirculation. Thus, always the existing residual gas content of the internal exhaust gas recirculation caused for example by unavoidable valve overlaps, which cause that always a part of the exhaust gas expelled is sucked in again.

How out 1 shows, first, the voltage value of the intake manifold pressure sensor 3 sampled in 1 ms raster. The sampled values are in a computing unit 4 that is part of an electrical circuit 5 is converted into an averaged intake manifold pressure p _s . The thus determined intake manifold pressure p _s is then simultaneously a first map 6 , a third map 8th and a circuit unit 11 supplied for multiplication by a factor F _ps . In addition, the intake manifold pressure of a circuit unit 12 supplied, which will be described below.

In the first map 6 is determined depending on an externally detected speed n of the exhaust back pressure pabg. This one is in an adder 14 added to the ambient pressure pu and a multiplier 16 supplied in which the sum multiplied by an altitude factor fho, which is essentially the difference of an actually detected ambient pressure and a normalized ambient pressure multiplied. From the multiplier 16 a signal processed in this way arrives at another multiplier 18 in which it is multiplied by another constant factor, the residual gas fraction Fprgs. The thus-processed signal of the residual gas pressure prgs output from the multiplier enters a subtractor 20 in which the difference of the corrected intake pipe pressure pskor, that of the multiplier 11 is output and the residual gas pressure prgs is formed and another subtractor 22 is supplied.

Another part of the multiplier 16 output exhaust pressure pa passes into the subtractor 12 in which the difference pa-ps of the exhaust gas pressure pa and the intake manifold pressure ps is formed. This difference signal pa-ps reaches a second characteristic map 7a , in which also the duty cycle τagr of the exhaust gas recirculation valve 2 , which is essentially a measure of the opening area of the exhaust gas recirculation valve 2 represents, is fed.

From the second map 7a an output signal p * agr reaches another multiplier 24 in which this factor 26 is multiplied, which corresponds to the quotient of a predetermined standard speed n _o and the rotational speed n of the internal combustion engine.

From the multiplier 24 _Then , a signal p _{Kagr representing} the pressure fraction caused due to the external exhaust gas recirculation reaches the subtractor 22 by taking from the signal supplied by the subtractor 20 is withdrawn.

In this way, in the first subtractor 20 for the height and the internal exhaust gas recirculation taking into account correction of the intake manifold pressure p _s by a height factor f _ho weighted sum of ambient pressure p _u and exhaust back pressure p _abg reduced while in the subtractor 22 the thus reduced by this signal manifold pressure p _s is then reduced to the external exhaust gas recirculation taken into consideration correction of the load signal to the pressure proportion p _KAGR, the n from the exhaust pressure P _a, the rotational speed of the engine and the duty ratio τ _EGR of the exhaust gas recirculation valve 2 depends. The signal thus obtained is finally in a further multiplier 28 multiplied by a constant 1 / K _DS , which is essentially the stoichiometric air ratio, cylinder number, the fuel mass per time, the stroke volume and a warm temperature taken into account, and it is obtained in this way directly the load signal t _l .

How out 1 further, a third correction map may be provided 8th be provided that depends on the speed n and the intake manifold pressure p _s to take into account degrees of inflow due to Aufladseinflüssen in the load signal t _l . The map that this third correction 8th taken signal is in a multiplier 30 multiplied by the load signal t _l .

Finally, there may be a fourth correction map 9 be provided, which depends on the temperature of the load signal from the temperature of the engine T _mot and the intake temperature T _ans to compensate for. This fourth map 9 taken signal is in a multiplier 32 with the multiplier 30 output signal multiplied. The output signal of the entire electronic circuit 5 , which may be a digital computer, for example, is now the actual, corrected in the manner described load signal t _l . The described method for generating a load signal t _{l on} the basis of the measured intake manifold pressure p _s is based on the following equation t l = 1 / K as * [f ps * p s - f PRGS * (P u + p abg ) * f ho - p * agr * n O / N] where f _{ps is} a constant that depends on the following rule of the isentropic exponent χ and the compression ratio ε. f ps = (χ * (ε - 1) + 1) / (χ * (ε - 1)) and the constant f _{prgs is} a constant which depends on the isentropic exponent and the compression ratio ε according to the following equation. f PRGS = 1 / (χ * (ε - 1))

The pressure increase p * _agr is a function of the difference p _a -p _s of the exhaust gas pressure p _a and the intake manifold pressure p _s and the duty cycle τ _{agr of} the exhaust gas recirculation valve and is in the manner described the second map 7 taken.

A second variant of the method is based on the 2 explained. It is different from that 1 explained method only in that of the multiplier 16 output exhaust pressure p _a on the one hand a circuit unit 13 is supplied, in which the quotient p _s / p _a from the intake manifold pressure p _s and the exhaust pressure P _{a is} formed, which in turn the map 7b on the other hand, and that the exhaust gas pressure p _a on the other hand, a multiplier 15 is supplied by the with the from the map 7b is multiplied and multiplied by the quotient n _o / n.

In this case, in contrast to the above-mentioned method and thus the signal p * _agr , the map depends on the difference between the quotient p _s / p _a and the duty cycle τ _{agr of} the exhaust gas recirculation valve.

Claims (7)

Method for detecting the load signal of an internal combustion engine by means of a sensor arranged in the intake manifold, wherein the intake manifold pressure (ps) is determined with the aid of a throttle valve of the internal combustion engine ( 1 ) arranged pressure sensor ( 3 ) is detected and converted into a load signal (tl) according to a height and the internal and external exhaust gas recirculation, characterized in that the intake manifold pressure (ps) to the correction of the load signal (tl) taking into account the external exhaust gas recirculation by a pressure component (pKagr) is reduced by the exhaust gas pressure (pa), the speed (n) of the internal combustion engine ( 1 ) and the duty cycle (τagr) of an exhaust gas recirculation valve ( 2 ) depends. Method according to claim 1, characterized in that that the intake manifold pressure (ps) to the height and the internal exhaust gas recirculation take into account Correction of the load signal (tl) by one with an altitude factor (fho) weighted sum of ambient pressure and exhaust gas back pressure (pu + pabg) is reduced. A method according to claim 2, characterized in that the exhaust back pressure (pabg) a first map ( 6 ) is taken. Method according to one of the preceding claims, characterized in that the dependence of the pressure component (pKagr) on the exhaust gas pressure (pa) and the duty cycle (τagr) a second correction map ( 7a . 7b ) is taken. Method according to one of the preceding claims, characterized in that for the consideration of feed grade influences due to charge influences in the load signal (tl) a third of the rotational speed (n) and the intake manifold pressure (ps) dependent third correction map ( 8th ) is provided. Method according to one of the preceding claims, characterized in that for compensation of temperature influences in the load signal (tl) a fourth correction map dependent on the temperature of the internal combustion engine (Tmot) and the intake temperature (Tans) ( 9 ) is provided. Method according to one of the preceding claims, characterized in that it is in a electronic circuit ( 5 ) is executed, for example, in a digital computer.