DE102008008209A1 - Method for diagnosing intake-manifold switching in internal combustion engine, involves adjusting length of suction manifold in different operating areas in different manner - Google Patents

Abstract

The method involves adjusting length of a suction manifold (5,10) in different operating areas in different manner. The multiple values for characteristic factors (ps,ml) are identified for determining the air charge in the combustion chamber of an internal combustion engine (1) during the predetermined time or crank angle intervals, that an amplitude of the characteristic factor is determined from the identified values of the characteristic factor, by which the amplitude is compared with a predetermined threshold. An independent claim is included for a device for diagnosing an intake-manifold switching in an internal combustion engine.

Description

State of the art

The The invention relates to a method and a device for Diagnosis of a suction pipe changeover in an internal combustion engine according to the preamble of the independent claims.

From the DE 197 27 669 B4 is already a method for monitoring the function of a Saugrohrklappe for intake manifold switching an internal combustion engine known. In this case, the intake manifold pressure is calculated on the basis of the speed detected by a means for detecting the rotational speed and the air mass flow detected by a means for detecting the air mass flow for at least two different Saugrohrklappenstellungen and measured simultaneously by a means for detecting the pressure. The differences of the calculated and measured intake manifold pressures are formed at the different intake manifold flap positions and evaluated for a diagnosis of the intake manifold flap.

Disclosure of the invention

Advantages of the invention

The inventive method and the invention Device for diagnosing a Saugrohrumschaltung in an internal combustion engine with have the features of the independent claims In contrast, the advantage that during a given Time or crank angle interval multiple values for one for determining the air charge in the combustion chamber of the internal combustion engine characteristic size can be determined that from the determined values of the characteristic size an amplitude of the characteristic size determined is that the amplitude compared with a predetermined threshold and that depending on the comparison result an error with regard to the set intake pipe length is recognized. In this way, the diagnostic effort is significantly reduced and it's not a comparison between a calculated and a measured one Intake manifold pressure required, it is also not necessary to Intake manifold pressure both to calculate, as well as to measure.

Consequently it is the subject of the independent claims Also not required, both the intake manifold pressure and the air mass flow to measure the internal combustion engine.

By the measures listed in the dependent claims are advantageous developments and improvements of the main claim specified method possible.

Especially It is advantageous if the predetermined time or crank angle interval an intake stroke is selected accordingly. In this way the reliability of error detection is increased.

Advantageous is still if during the given time or Kurbelwinkelintervalls the characteristic size in a regular grid, preferably in a 1ms raster, is sampled. This will ensure that enough values of the characteristic size for reliable fault detection stand.

One Another advantage arises when as a characteristic size the intake manifold pressure or an air mass flow to the engine is selected. This way you can have a sufficiently large amplitude of the characteristic size realize a reliable error detection.

Advantageous is still, if from the determined values of the characteristic Size is an absolute maximum and an absolute one Minimum are determined and if from the difference between the absolute Maximum and the absolute minimum the amplitude of the characteristic Size is determined. That way the amplitude of the characteristic quantity very simple and inexpensive to determine.

Advantageous is still, if the error only under given operating conditions, preferably with respect to engine speed and / or engine load, the Internal combustion engine is detected. This way will too a sufficiently large amplitude of the characteristic Size for a reliable Error detection ensured.

Advantageous is there when the given operating conditions by a Throttle angle determined above a predetermined threshold become. In this way, a sufficiently large amplitude the characteristic size for one reliable fault detection regarding the engine load ensured.

Advantageous is still, if the given operating conditions by a Engine speed above a predetermined upper threshold or below a predetermined lower threshold, the smaller is determined as the predetermined upper threshold. On This will be sufficient in view of the engine speed large amplitude of the characteristic size for Ensured reliable error detection.

Another advantage results from the fact that the error is detected when the amplitude of the characteristic size of the predetermined threshold worth falls below. Thus, an insufficient charging effect at the set intake pipe length and thus an error for the adjustment of the intake pipe length is detected in a simple manner.

drawing

One Embodiment of the invention is in the drawing shown and in the following description in more detail explained. Show it:

1 a schematic view of an internal combustion engine and

2 a functional diagram for explaining the device according to the invention and the method according to the invention.

Description of the embodiment

In 1 features 1 an internal combustion engine, which is designed for example as a gasoline engine or as a diesel engine. The internal combustion engine 1 includes one or more cylinders, of which in 1 illustrated by way of example and with the reference numeral 75 is marked. About an air supply 40 becomes the combustion chamber of the cylinder 75 Fresh air supplied. The flow direction of the fresh air in the air supply 40 is with arrows in 1 characterized. It is in the air supply 40 a throttle 45 arranged whose position the air mass flow to the cylinder 75 influenced and by a motor control 15 is controlled, for example, depending on a torque to be converted. In the event that the internal combustion engine 1 drives a vehicle, the torque to be converted, for example, correspond to a driver's request, for example, according to an accelerator pedal position. A measuring device 50 , for example in the form of a throttle valve potentiometer, detects the current position of the throttle 45 in the form of a throttle angle wdk and gives the measured value to the engine control 15 from. Upstream of the throttle 45 is according to 1 an air mass meter 25 , For example, in the form of a hot-film air mass meter, the current air mass flow ml to the cylinder 75 measures and the reading to the engine control 15 forwards. Downstream of the throttle 45 goes the air supply 40 in a first suction pipe 5 or in a second suction pipe 10 depending on the position of a first intake manifold flap 55 and a second intake manifold flap 60 above. As shown 1 are the first intake manifold flap 55 and the second intake manifold flap 60 in a position shown in solid, in which the second suction pipe 10 is shut off and thus the air supply to the cylinder 75 only over the first intake manifold 5 that is larger and longer than the second intake manifold 10 is done. On the other hand, are the first intake manifold flap 55 and the second intake manifold flap 60 each in its dashed line position, then the first suction pipe 5 shut off and the air only passes through the second intake manifold 10 and the air supply 40 to the cylinder 75 , The intake manifold flaps 55 . 60 are doing from the engine control 15 either driven so that they are both simultaneously in their solid position and thus the second suction pipe 10 shut off, or that they are both at the same time in their dashed position and thus the first intake manifold 5 Shut off. Downstream of the two intake manifold flaps 55 . 60 is in one of the two taurus ears 5 . 10 common Saugrohrabschnitt 8th through which the air is independent of the position of the intake manifold flaps 55 . 60 always to the cylinder 75 is fed, an intake manifold pressure sensor 20 arranged, which measures the current intake pipe pressure ps and the measured value to the engine control 15 forwards. Although in 1 both the intake manifold pressure sensor 20 , as well as the Luftmassehmesser 25 are shown, it is sufficient for the invention, if either only the intake manifold pressure sensor 20 or just the air mass meter 25 is provided. Via an inlet valve 65 the fresh air is then the combustion chamber of the cylinder 75 fed. The fuel supply to the combustion chamber of the cylinder 75 and in the case of the gasoline engine the ignition is in 1 not shown for reasons of clarity. The combustion of the air / fuel mixture in the combustion chamber of the cylinder 5 formed exhaust gas is via an exhaust valve 70 in an exhaust system 80 the internal combustion engine 1 pushed out. intake valve 65 and exhaust valve 70 For example, in the manner known in the art via one or more camshafts or, as in 1 indicated by direct control of the engine control 15 be adjusted by means of an electro-hydraulic or an electromagnetic valve drive. In the area of the cylinder 75 is a crank angle sensor 85 arranged, which detects the current crank angle KW and by temporal differentiation of the current crank angle KW, the current engine speed nmot and to the engine control 15 forwards.

The through the first intake manifold flap 55 and the second intake manifold flap 60 realized Saugrohrumschaltung between different intake manifold lengths serves to increase the performance of the internal combustion engine 1 , In this case, the respective intake pipe length is so on the internal combustion engine 1 tuned that with the throttle fully open 45 a pressure wave is generated in the currently used intake manifold, the maximum then just at the inlet valve 65 arrives when this closes. This charging effect provides an increase in performance. The adaptation of the intake manifold length to the internal combustion engine 1 however, it is optimal only for a certain engine speed range. In order to obtain the described charging or resonance effect with pressure waves in different engine speed ranges, the Suction tube length with the help of the intake manifold flaps 55 . 60 switched in the manner described. In this way, for each engine speed ranges, the respective optimal intake pipe length can be selected for the desired charging effect. In the present example 1 can the Saugrohrlange for two different engine speed ranges to the internal combustion engine 1 be adapted, namely using the first suction pipe 5 or the second suction pipe 10 ,

In 2 is a functional diagram for explaining the method according to the invention for a diagnosis of Saugrohrumschaltung shown. The functional diagram represents a device for diagnosing the intake manifold changeover and is, for example, software and / or hardware in the engine control 15 implemented. In the following, it is assumed that the measured values for the intake manifold pressure ps are evaluated for the diagnosis so that the air mass meter 25 is not required. In an analogous manner, however, instead of the signal of the intake manifold pressure sensor 20 also the signal of the air mass meter 25 be evaluated with the measured values ml, so that in this case the intake manifold pressure sensor 20 not needed.

According to 2 are only those components of the engine control 15 shown, which are required for the diagnosis of Saugrohrumschaltung and which form the device for the diagnosis of Saugrohrumschaltung. Thus, the diagnostic device includes the engine controller 15 an amplitude detection unit 30 , the signal ps with the current measured values of the intake manifold pressure from the intake manifold pressure sensor 20 is supplied. The amplitude detection unit 30 is also from the crank angle sensor 85 supplied the crank angle signal KW with the current crank angle. The amplitude determination unit evaluates this 30 the signal ps of the intake manifold pressure sensor 20 Only for those crank angle KW off, in an intake stroke of the cylinder 75 lie, these crank angle in the amplitude detection unit 30 are known and have been determined in the expert be known manner. Further, from the crank angle sensor 85 the speed signal nmot with the current values for the engine speed a first comparator 90 supplied to the diagnostic device and there with a predetermined upper threshold NDSUO a first threshold value memory 105 and a predetermined lower threshold NDSUU of a second threshold memory 110 compared. If the respective current value for the engine speed nmot is above the predefined upper threshold value NDSUO or below the predefined lower threshold value NDSUU, then the first comparator outputs 90 a set signal, otherwise a reset signal. The output signal of the first comparator 90 is doing on an AND gate 125 guided. The signal wdk of the throttle potentiometer 50 with the current values for the throttle angle wdk becomes a second comparator 95 supplied to the diagnostic device and there compared with a threshold value WDKDSU for the throttle angle, in a third threshold value memory 115 is stored. If the respective current value wdk of the throttle valve angle lies above the threshold value WDKDSU for the throttle valve angle, then the second comparator outputs 95 a set signal, otherwise a reset signal. Here is the output of the second comparator 95 also on the AND gate 125 guided. The AND member 125 outputs a set signal at its output when its two input signals are set, and otherwise a reset signal. The output signal of the AND gate 125 becomes the amplitude detection unit 30 fed. The evaluation of the intake manifold pressure signal ps in the amplitude determination unit 30 only takes place when the amplitude detection unit 30 a set signal from the AND gate 125 receives. Thus, an evaluation of the intake manifold pressure signal ps in the amplitude detection unit 30 only when the current throttle angle wdk is greater than the predetermined threshold value WDKDSU for the throttle angle and at the same time the current engine speed nmot is either greater than the predetermined upper threshold NDSUO or less than the predetermined lower threshold NDSUU, the predetermined lower threshold NDSUU being smaller as the predetermined upper threshold NDSUO. In addition, the intake pipe pressure signal ps in the amplitude detection unit 30 for example, only evaluated when the cylinder 75 located in an intake stroke and the amplitude detection unit 30 receives the characteristic for the intake stroke values for the crank angle KW.

The determination of the amplitude amp of the intake manifold pressure signal ps in the amplitude determination unit 30 can be done in a simple way as follows: The intake manifold pressure ps is from the intake manifold pressure sensor 20 in a predetermined regular grid, for example in a 1 ms time grid, sampled and the sampled values as Saugrohrsignal ps to the amplitude detection unit 30 forwarded. From the received sampled intake manifold pressure values ps, the amplitude determination unit determines 30 the absolute maximum and the absolutely minimum intake manifold pressure within one intake stroke. The amplitude amp of the oscillation of the intake pipe pressure signal ps is determined by the amplitude determining unit 30 formed from the difference between the absolute maximum detected intake manifold pressure and the absolute minimum detected intake manifold pressure. This can for example be done as follows: At the beginning of the intake stroke is in the amplitude detection unit 30 the first of the intake manifold pressure sensor 20 Receive intake manifold pressure value equal to a minimum value psampu and set equal to a maximum value psampo for the intake manifold pressure. When the next from the intake manifold pressure sensor 20 in the amplitude detection unit 30 If the intake manifold pressure is greater than psampo, psampo will be overwritten with the new value. When the next one of intake manifold pressure sensor 20 However, if the intake manifold pressure received is less than psampu, psampu will be overwritten with the new value. This process is continued until the end of the intake stroke. At the end of the intake stroke, the amplitude amp = psampo-psampu is then formed from the difference between the then present maximum value psampo and the then present minimum value psampu. The value psampo present at the end of the intake stroke represents an absolute maximum of the intake manifold pressure values sensed during the intake stroke. The psampu value present at the end of the intake stroke represents an absolute minimum of the intake manifold pressure values sensed during the intake stroke 30 determined amplitude amp of the intake manifold pressure signal ps during an intake stroke is an optional filter provided 100 , For example, a low-pass filter, supplied for averaging. The filtered amplitude signal ampf is then a comparison and detection unit 35 fed. Alternatively, it may also refer to the use of the filter 100 be waived. Filtering through the filter 100 should avoid that at high engine speeds with low measured values of the intake manifold pressure even a single evaluation on an output clock triggers an error message. The filter is initially initialized to an initial value that is characteristic of a healthy state. The comparison and detection unit 35 is from a fourth threshold memory 125 a predetermined threshold AMPDSU supplied to the amplitude. The comparison and detection unit 35 compares the filtered amplitude ampf to the predetermined threshold value AMPDSU for the amplitude. Represents the comparison and detection unit 35 determines that the filtered amplitude ampf is less than the predetermined threshold value AMPDSU for the amplitude, it outputs at its output a set error signal F, otherwise a reset error signal F. In the case of a set error signal F has the comparison and detection unit 35 an error in the adjustment of the intake pipe length and thus an error in the adjustment of the intake manifold flaps 55 . 60 detected, since the amplitude of the intake pipe pressure ps is too low at the set intake manifold and thus the desired charging effect is not achieved.

A sufficiently large amplitude of the intake manifold pressure signal ps for a reliable fault detection is only under certain operating conditions of the internal combustion engine 1 achieved with respect to engine speed and / or engine load. These operating conditions can be determined, for example, on a test bench and / or in driving tests. These operating conditions are in the Funktionsdiagamm after 2 given by the predetermined threshold value WDKDSU for the throttle angle with respect to the engine load, and by the predetermined upper threshold NDSUO and the predetermined lower threshold NDSUU for the engine speed and are present when the current throttle angle wdk greater than the predetermined threshold WDKDSU for the throttle angle and the current engine speed nmot is either greater than the predetermined upper threshold NDSUO or less than the predetermined lower threshold NDSUU, in other words, when the output of the AND gate 125 is set. The operating condition for the load thus becomes apparent in the example 2 a current throttle angle wdk greater than the predetermined threshold WDKDSU for the throttle angle described. The predetermined threshold value AMPDSU for the amplitude of the intake pipe pressure signal ps is then for the described load and speed range, in which the output signal of the AND gate 125 is set, example, applied to a test bench and / or driving tests such that only for amplitudes amp or filtered amplitudes ampf greater than or equal to the predetermined threshold AMPDSU, there is a sufficient charging effect and thus a perfect intake manifold switching, amp for amplitudes or filtered amplitudes ampf below the predetermined threshold AMPDSU but no sufficient charging effect and thus an error in the Saugrohrumschaltung exists. Because only with correct position of Saugrohrumschaltung, ie with the correct position of the first intake manifold flap 55 and the second intake manifold flap 60 forms a sufficiently large amplitude in the pressure wave of the intake manifold pressure for the desired charging effect.

If instead of the intake manifold pressure signal, the signal of the air mass meter with corresponding samples for the mass air flow ml is also used in an appropriate time grid, can its amplitude in the same way as for the intake manifold pressure described, evaluated.

Intake manifold pressure ps and air mass flow ml each represent a characteristic for determining the air charge in the combustion chamber of the internal combustion engine size, ie, a size on the basis of the air charge in the combustion chamber of the internal combustion engine 1 can be determined. For the described diagnosis of Saugrohrumschaltung therefore described in the same way as for the intake manifold pressure ps and the air mass flow ml any other for determining the air charge in the combustion chamber of the internal combustion engine 1 characteristic size are used, since it evaluates in the same way generated bare vibrations during the intake stroke.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19727669 B4 [0002]

Claims (10)

Method for diagnosing a suction pipe changeover in an internal combustion engine ( 1 ), in which the length of the suction tube ( 5 . 10 ) is set differently in different operating ranges, characterized in that a plurality of values for a determination of the air charge in the combustion chamber of the internal combustion engine during a predetermined time or crank angle interval ( 1 ) characteristic variable (ps, ml) can be determined that an amplitude (amp) of the characteristic variable is determined from the determined values of the characteristic quantity (ps, ml), that the amplitude (amp) is compared with a predetermined threshold value (AMPDSU) and that an error with regard to the set intake pipe length is detected as a function of the comparison result. Method according to claim 1, characterized in that that the predetermined time or crank angle interval an intake stroke is selected accordingly. Method according to one of the preceding claims, characterized in that during the predetermined time or crank angle interval the characteristic size (ps, ml) in a regular grid, preferably in a 1 ms raster, is scanned. Method according to one of the preceding claims, characterized in that the characteristic size of the intake manifold pressure (ps) or an air mass flow (ml) to the internal combustion engine ( 1 ) is selected. Method according to one of the preceding claims, characterized in that from the determined values of the characteristic Size (ps, ml) is an absolute maximum and absolute Minimum and that the difference between the absolute maximum and the absolute minimum the amplitude (amp) the characteristic size is determined. Method according to one of the preceding claims, characterized in that the error only at predetermined operating conditions, preferably in terms of engine speed (nmot) and / or engine load (wdk), the internal combustion engine ( 1 ) is recognized. Method according to Claim 6, characterized that the given operating conditions through a throttle angle (wdk) determined above a predetermined threshold value (WDKDSU) become. Method according to claim 6 or 7, characterized that the given operating conditions by an engine speed (nmot) above a given upper threshold (NDSUO) or below a predetermined lower threshold (NDSUU), which is smaller than the predetermined upper threshold (NDSUO). Method according to one of the preceding claims, characterized in that the error is detected when the amplitude (amp) falls below the given threshold (AMPDSU). Contraption ( 15 ) for the diagnosis of a Saugrohrumschaltung in an internal combustion engine ( 1 ), in which the length of the suction tube ( 5 . 10 ) is differently adjustable in different operating ranges, characterized in that first determination means ( 20 . 25 ) are provided, which during a predetermined time or crank angle interval a plurality of values for determining the air charge in the combustion chamber of the internal combustion engine ( 1 ) characteristic size (ps, ml), that second investigative means ( 30 ) are provided, which determine from the determined values of the characteristic quantity (ps, ml) an amplitude (amp) of the characteristic quantity (ps, ml) that comparison and recognition means ( 35 ) are provided, which compare the amplitude (amp) with a predetermined threshold (AMPDSU) and recognize as a function of the comparison result equal an error with regard to the set intake pipe length.