DE102004057261A1 - Internal combustion engine e.g. petrol engine, operating method for motor vehicle, involves evaluating signal quality for identification of installation location of solid borne sound sensor, where engine works in defined operating condition - Google Patents

Abstract

The method involves providing a signal for controlling and/or regulation of an internal combustion engine (10) by a solid borne sound sensor (22a-22c). A signal quality, which depends on the distance of the sensor from a combustion chamber of cylinders is evaluated for identification of an installation location of the sensor. The engine works in a defined operating condition for the identification of the location of the sensor. Independent claims are also included for the following: (1) computer program; (2) internal combustion engine.

Description

The The invention relates to a method for operating an internal combustion engine with several cylinders, in which at least one structure-borne sound sensor is a signal supplies which for used a control and / or regulation of the internal combustion engine becomes. The invention further relates to a computer program, an electrical Storage medium for a control and / or regulating device of an internal combustion engine, a control and / or regulating device for an internal combustion engine, and an internal combustion engine.

From the DE 195 47 167 A1 and DE 197 09 395 A1 It is known to use structure-borne sound sensors for knock control in an internal combustion engine. Such a knock control makes sense, since the efficiency of an internal combustion engine close to the knock limit (at a late ignition angle) is optimal. By "knocking" is meant an uncontrolled form of combustion which can cause damage in the internal combustion engine. To prevent damage by knocking, a safety margin is provided between the current operation and the knock limit. The knock limit is detected during operation of the internal combustion engine.

Acoustic emission sensors detect the knocking combustion occurring in the combustion chamber of a cylinder typical sounds and thus allow the determination of the current knock limit. The usage from such structure-borne sound sensors has about it addition, the advantage that, for example, in diesel internal combustion engines the structure-borne sound signal obtained also for the calibration, regulation and optimization of a pre-injection can be used. In internal combustion engines with multiple cylinders or less favorable Arrangement of the cylinder also several such structure-borne sound sensors are used.

Of the Location of a structure-borne sound sensor on the engine block of the internal combustion engine is in appropriate investigations for the Internal combustion engine type set so that it for its associated cylinder one possible good signal-to-noise ratio. To prevent the structure-borne sound sensors incorrectly connected and / or used in incorrect installation locations are currently being provided mechanically a swap protection. An incorrect assignment of the received signals to the corresponding ones Acoustic emission sensors has due to the damping properties the engine block of the internal combustion engine, a significant deterioration the signal quality resulting in all, on structure-borne noise based regulatory and diagnostic functions. A incorrect assignment of the signal received can be specific to gasoline engines the knock control impossible let and lead to a total loss of the internal combustion engine. Of the mechanical swap protection can, for example, different Plug shapes, different cable lengths, and / or different types of structure-borne sound sensors include. However, this reduces the production quantities of a sensor and requires special measures for example, in warehousing.

task The present invention is the cost of the use of structure-borne sound sensors at To reduce internal combustion engines.

These Task is characterized by a method of the type mentioned by solved, that at least one signal property, which depends on the distance the sensor from the sound production site, in particular a combustion chamber a cylinder, depends, is evaluated to identify the installation location of the sensor. For a computer program, an electrical storage medium, a control and / or control device and an internal combustion engine is the Asked task solved accordingly.

Advantages of invention

According to the invention can a special marking or design of the individual structure-borne sound sensors be waived without the risk that the received Signals to the wrong sensor or incorrect installation location of a sensor be assigned. Thus, you can identical sensors, for example, also uniformly directly plugged Acoustic emission sensors, be used. these can subsequently produced in larger quantities are and are easier to store. Thus, the total costs for the Use of structure-borne sound sensors reduced.

Of the Invention is based on the finding that the properties a signal of a structure-borne sound sensor with increasing distance of the place where the sound is generated is, from the place where the structure-borne sound sensor is placed, change. For example takes the signal strength respectively.

amplitude with increasing distance between combustion chamber and sensor. But also the frequency spectrum, which is detected by the structure-borne sound sensor, depends on the corresponding distance of the structure-borne sound sensor from the combustion chamber, in which the sound-generating event takes place.

It should be noted explicitly that the inventive method also brings advantages in the use of a single structure-borne sound sensor. In internal combustion engines having a plurality of cylinders, a plurality of positions may be provided on which such a structure-borne noise sensor can be arranged. Thanks to the method according to the invention, the actual installation location of the sensor can be clearly defined.

The inventive method is advantageously at the first start of the internal combustion engine performed after their preparation. Furthermore, the inventive method should carried out when, for example, a structure-borne sound sensor replaced has been.

In an advantageous embodiment of the method according to the invention it is suggested that for the evaluation of the signal properties in the range of low frequencies, especially in the range of half the crankshaft frequency up to half ignition frequency, be used. Which by a compression and / or expansion in a combustion chamber caused strains in the engine block of the internal combustion engine generate low-frequency vibrations whose amplitude coincides with Increasing distance from the combustion chamber particularly significantly reduced. An evaluation of the signal properties in the range of low frequencies leads therefore to particularly meaningful Results. A possibility, To obtain these lower frequencies is to use of lowpass and / or bandpass filters.

Especially It is advantageous if the method according to the invention is a plausibility check includes, when tested is whether the determined installation location of a structure-borne sound sensor with that Fitting location matches, not the other structure-borne sound sensors was assigned. This can improve the reliability of identification of the installation site in the presence of multiple structure-borne sound sensors clearly elevated become.

Further it is suggested that for the identification of an internal combustion engine in a defined Operating state works in gasoline engines, preferably in one Operating condition in which knocking can not occur. hereby will prevent the internal combustion engine as long as the installation locations are not identified, damaged during operation.

A advantageous variant of the method provides that the signal of a Borne sound sensor is evaluated in the frequency domain. This has advantages in such Internal combustion engines in which the vibrations detected by the sensor have multiple shares of different frequencies. Indeed the signal of the structure-borne sound sensor must have a larger period measured, so over several periods are recorded.

In concrete training for this purpose, it is proposed that the signal a structure-borne sound sensor evaluated by a Fourier transform for specific frequencies and comparing the actual result with predetermined target results which is in advance for certain installation locations were determined. One such method is easy to program. The camshaft frequency and its integer Multiples up to half the ignition frequency can thereby be safely evaluated. Alternative to a Fourier transformation can also be the use of bandpasses will be realized. From the (possibly normalized) amplitude and phase position the o.g. Frequencies can safely affect the structure-borne sound signal amplitude for individual Cylinder closed, thus determining the installation location of the sensor become. Similar Methods for frequency evaluation are e.g. in the detection of misfires used from the signal of a speed sensor.

alternative The signal of a sensor can also be evaluated in the time domain. This is programmatically easy to implement.

In concrete training for this purpose, it is proposed that same Signal properties, preferably the (possibly normalized) amplitudes or gradients at any given time or at a time certain crank angle or in a specific time or crank angle window within the working cycles of the respective cylinders are determined and the obtained actual value group with predetermined target value groups is compared, which in advance for certain installation locations were determined.

special reliable Results are achieved when the specific time or crank angle or the particular time or crank angle window is chosen so that possible low high frequency signal components are present.

The Signal evaluation is further facilitated when the difference signals two times or two crank angle or two time or Crank angle window to be evaluated.

drawings

following become particularly preferred embodiments the present invention with reference to the accompanying Drawing closer explained.

In show the drawing:

1 a schematic representation of an internal combustion engine having a plurality of cylinders and three structure-borne sound sensors;

2 a flowchart of a method for identifying the installation location of a structure-borne sound sensor on the basis of a evaluation in the time domain;

3a to 3c Diagrams in which the signal of the three structure-borne sound sensors for the respective cylinders are respectively plotted during the compression and during the expansion stroke;

4a to 4c Diagrams similar 3 the averaged signals from which the high frequency vibration components are eliminated;

5 a table of the three quadruplicates corresponding to the three installation locations of the structure-borne sound sensors;

6 a flowchart of a method for identifying the installation location of a structure-borne sound sensor on the basis of an evaluation in the frequency domain; and

7 a diagram in which the signal of two structure-borne sound sensors is plotted against the crank angle, which for the method of 6 is used.

description the embodiments

An internal combustion engine used in a motor vehicle, not shown, carries in 1 altogether the reference sign 10 , Here are in 1 only some components of the internal combustion engine 10 represented, which are of particular importance in the present case.

The internal combustion engine 10 includes four cylinders 12a to 12d in whose combustion chambers the fuel is directly from injectors 14a to 14d is injected. Ignites the fuel-air mixture in the combustion chambers of spark plugs 16a to 16d , In operation of the internal combustion engine 10 will be an in 1 Not shown crankshaft set in motion, whose angular position and speed of a sensor 18 is detected. The position of an in 1 also not shown camshaft is a camshaft sensor 19 detected.

An engine block in which the cylinders 12a to 12d are present, bears the reference numeral 20 , Between the two cylinders 12a and 12b is at a mounting location 21a a first structure-borne sound sensor 22a arranged between the two cylinders 12b and 12c at a place of installation 21b a second structure-borne sound sensor 22b and between the two cylinders 12c and 12d at a place of installation 21c a third structure-borne sound sensor 22c , The sensors 18 . 19 and 22 deliver their signals to a control device 24 , This also controls the injectors 14a to d and, in the Otto internal combustion engine shown here by way of example, the spark plugs 16a see you.

The structure-borne sound sensors 22a to 22c be in the present embodiment in normal operation of the internal combustion engine 10 used to detect a knocking combustion (in a diesel engine, the structure-borne sound sensors would be used to calibrate a pilot injection, which is mainly the noise comfort). The injectors 14a to 14d and the spark plugs 16a to 16d are doing by the control and regulating device 24 so driven that a knocking combustion in the cylinders 12a to 12d just does not happen yet. As a result, a maximum efficiency of the internal combustion engine 10 allows without the internal combustion engine 10 can be damaged by a knocking combustion.

Based on the signals from the structure-borne sound sensors 22a to 22c can be in the control 24 to determine which of the cylinders 12a to 12d just about tapping. The injectors 14a to 14d and the spark plugs 16a to 16d Thus, cylinder-selectively can be controlled so that in each cylinder 12a to 12d , in the corresponding operating state of the internal combustion engine 10 , just no knocking occurs.

For a reliable cylinder-selective knock control, it is necessary that in the control and regulating device 24 incoming signals of the individual structure-borne sound sensors 22a to 22c clearly the appropriate installation locations 21a to 21c can be assigned. Only then can a sensor 22a to 22c be used for the evaluation. In other words, before during normal operation of the internal combustion engine 10 a cylinder-selective knock control can be performed, the actual installation locations 21a to 21c the structure-borne sound sensors 22a to 22c from the control and regulating device 24 be identified. For this purpose, a method is used, which now in particular with reference to the 2 to 5 will be explained in detail.

The procedure starts in a starting block 26 , In a block 28 is queried whether the installation locations 21a to 21c the structure-borne sound sensors 22a to 22c to be identified. This is usually before the first startup of the internal combustion engine 10 after their production or after replacement of a structure-borne sound sensor 22a to 22c of the Case. Is the answer in the block 28 yes, the internal combustion engine 10 in the block 30 Initially operated so that a knocking combustion in the cylinders 12a to 12d can be excluded. This is at the in 1 illustrated gasoline internal combustion engine then the case when a sufficient safety margin of the ignition angle is maintained at a firing angle critical for knocking combustion, which by a corresponding control of the spark plugs 16a to 16d is realized. In a diesel internal combustion engine, not shown, such an operating state is realized by a comparatively long pre-injection of fuel through the injectors 14a to 14d is realized. For both types of internal combustion engine such an operating state could also include a non-fired operation, for example a coasting operation or an operating state in which a starter causes the crankshaft of the internal combustion engine to rotate.

While the internal combustion engine 10 in the block 30 is operated in a mode "Knock excluded", are in the block 32 from the structure-borne sound sensors 22a to 22c Signals detected and in the control and regulating device 24 cached (from here is the procedure in 2 for reasons of clarity, only for the structure-borne sound sensor 22a shown in detail). In this case, those signals are particularly interesting, based on structure-borne noise, during a compression and during an expansion phase of a cylinder 12a to 12d is generated in this, and here again those signal components with low frequencies in the range of the camshaft frequency and their integer multiples up to half the ignition frequency.

Such low-frequency vibrations, for example, by strains in the engine block 20 caused and subject to a particularly significant path-dependent damping. The amplitudes of these vibrations thus decrease with the distance from the cylinder 12a to 12d in which they have been produced, clearly off. This also results from the 3a to 3c in which for the three sensors 22a to 22c which are plotted towards the end of a compression stroke (crank angle from 90 ° to 180 °) and at the beginning of an expansion stroke (crank angle from 180 ° to 270 °). Each with a crank angle of 180 ° is the piston of the considered cylinder 12a to 12d in the upper dead center between compression and expansion stroke.

While in the 3a to 3c the signals are plotted as they are actually from the structure-borne sound sensors 22a to 22c to the control and regulating device 24 are transmitted in the 4a to 4c the corresponding signals after a band or low pass filtering are shown, by which the high-frequency signal components are eliminated. This bandpass filtering is done in the flowchart of 2a in the block 34 , It is of course important for an evaluation that the low frequencies of half the crankshaft frequency to half the ignition frequency is not filtered out or by the structure-borne sound sensors 22a to 22c be suppressed. Because it is exactly those frequencies that are due to the in 2 evaluated procedures are evaluated.

In a block 36 An assignment of individual areas of the detected signal to the corresponding cylinders takes place 12a to 12d , Such an assignment is possible because of the signals of the angle sensors 18 and 19 the control and regulating device 24 it is known which of the cylinders 12a to 12d is just at the end of the compression or at the beginning of the expansion stroke, in which the characteristic low-frequency wave is generated. In a block 38 Then, a value group is formed, the amplitudes of the individual cylinders 12a to 12d associated signal curves at a certain crank angle includes (this crank angle is in the 4a to 4c indicated by a dashed line. In particular, if such a discrete crank angle corresponding to the line 40 is used, it is advantageous if this crank angle is chosen so that of the structure-borne sound sensors 22a to 22c to the control and regulating device 24 output signal comprises a few high-frequency signal components.

In the present exemplary embodiment, such a value group has four values, that is, it is an actual value quadruple. This will now be in a block 42 compared with predetermined desired-value quadruples, the advance for the type of internal combustion engine used and the individual installation locations 21a to 21c were determined. For the present embodiment, these predetermined value quadrips are in 5 tabulated. For the individual values, no normal value is used, but a relative normalized value based on a cylinder-specific signal. The letter "H" denotes a comparatively high amplitude, the letter "M" denotes a medium, and the letter "L" denotes a comparatively small amplitude.

One recognizes immediately that according to 4a for the structure-borne sound sensor 22a obtained actual-value quadruple the in 5 for the installation location 21a specified set value quadruple corresponds and in the same way, the two structure-borne sound sensors 22b and 22c the installation locations 21b and 21c can be assigned. The in the block 44 successful assignment of the installation locations 21a to 21c to the individual structure-borne sound sensors 22a to 22c will be in the control unit 24 stored and for the subsequent knock control in the normal drove the internal combustion engine 10 used. The procedure ends in the block 46 ,

In the exemplary embodiment just described, the value quadruples were determined for a specific crank angle. But it is also possible to select a crank angle range, as in the 3a to 3c exemplified by the two dashed lines 48a and 48b is indicated. For the formation of the actual value quadruple, the mean values obtained for such a range can then be used. The range can also be very large, for example, from 120 ° to 240 ° crank angle, or relatively small, for example, from 140 ° to 160 ° crank angle or even smaller, as in the 3a to 3c shown.

Furthermore, the difference between two evaluation windows can also be used to form the actual value quadruple. Such a second evaluation window is in the 3a to 3c by dashed lines 50a and 50b indicated. A possibility (not shown) for forming the actual value quadrupole also consists of, after a low-pass filtering for suppressing high-frequency interference components, the gradients of the cylinders 12a to 12d to determine assigned signals and to form from these gradients the value quadruple. In particular, areas with strong signal changes, for example from 150 ° to 170 ° crank angle or from 190 ° to 210 ° crank angle come into question.

The in connection with the 2 to 5 The methods explained relate to the so-called "time range". Alternatively, an evaluation in the frequency domain is possible, as now with reference to the 6 and 7 is explained. Such function blocks and waveforms, which are equivalent to function blocks and waveforms of the 2 to 5 , the same reference numerals. They are not explained again in detail.

Instead of the direct determination of the amplitudes at a certain crank angle or in a specific crank angle range, the signals of the structure-borne sound sensors 22a to 22c in an evaluation in the frequency domain over a longer period, for example, recorded over three cycles, such as 7 is apparent. The signal detected by a structure-borne sound sensor is then in a block 52 subjected to a Fourier transform (FFT) and determined for each structure-borne sound sensor, the corresponding Fourier spectrum at the camshaft frequency and their multiples up to half the ignition frequency. The obtained actual Fourier spectrum is in the block 42 compare with target Fourier spectra, which in advance for the in 1 shown type of internal combustion engine and for the installation locations 21a to 21c were determined.

At the in 6 shown method is before the end block 46 in a block 54 another plausibility check in the block 44 completed identification of the installation locations 21a to 21c the structure-borne sound sensors 22a to 22c carried out. In this case, it is checked, for example, for the sensor 22c Determined installation location 21c coincides with that location, the other sensors 22a and 22b was not assigned.

There the evaluation methods described above on the relative comparison the signal of a structure-borne sound sensor for the single cylinder based, the specified methods have a comparatively high robustness or a low sensitivity to differences in the sensor gain, across from Scatters of background noise from one internal combustion engine to another, etc. The specified Procedure allows It therefore also, in the same internal combustion engine structure-borne noise sensors different manufacturers and / or different structure-borne sound sensor types to use. Preferably, the methods shown become idle the internal combustion engine performed. It is understood that if individual types of structure-borne sound sensors the for needed the evaluation suppress too low frequencies, to carry out the said identification method, the internal combustion engine for a short time even higher Speed can be operated.

Claims (14)

Method for operating an internal combustion engine ( 10 ) with several cylinders ( 12 ), in which at least one structure-borne sound sensor ( 22 ) provides a signal which is for a control and / or regulation of the internal combustion engine ( 10 ), characterized in that at least one signal characteristic which depends on the distance of the structure-borne sound sensor ( 22 ) from the sound generation location, in particular a combustion chamber of a cylinder ( 12 ), for identification ( 44 ) of the installation site ( 21 ) of the structure-borne sound sensor ( 22 ) is evaluated ( 42 ). Method according to claim 1, characterized in that for the evaluation ( 42 ) the signal properties in the range of low frequencies, in particular in the range of half the crankshaft frequency up to half the ignition frequency can be used. Method according to one of the preceding claims, characterized in that it has a plausibility check ( 54 ), in which it is checked whether the determined installation location ( 21 ) of a structure-borne sound sensor ( 22 ) with that installation location ( 21 ), the other structure-borne sound sensors ( 22 ) has not been assigned. Method according to one of the preceding claims, characterized in that for the identification ( 44 ) an internal combustion engine ( 10 ) operates in a defined operating state, in gasoline engines preferably in an operating state in which knocking can not occur. Method according to one of the preceding claims, characterized in that the signal of a structure-borne sound sensor ( 22 ) is evaluated in the frequency domain ( 52 ). Method according to Claim 5, characterized in that the signal of a structure-borne sound sensor ( 22 ) by a Fourier transformation ( 52 ) is evaluated for specific frequencies and the actual result is compared with predetermined target results ( 42 ), which in advance for certain installation locations ( 21 ) were determined. Method according to one of claims 1 to 4, characterized in that the signal of a structure-borne sound sensor ( 22 ) is evaluated in the time domain ( 38 ). A method according to claim 7, characterized in that same signal properties, preferably the amplitudes or slopes, at a certain time or at a certain crank angle or in a specific time or crank angle window within the working cycles of the respective cylinder ( 12 ), determined ( 38 ) and the resulting actual value group is compared with predetermined target value groups ( 42 ), which in advance for certain installation locations ( 21 ) were determined. A method according to claim 8, characterized in that the specific time or the specific crank angle ( 40 ) or the specific time or crank angle window is selected so that as few high-frequency signal components are present. Method according to one of the preceding claims, characterized in that the difference signals of two time or angle ranges ( 48 . 50 ) be evaluated. Computer program, characterized in that it programmed for use in a method according to any one of the preceding claims. Electrical storage medium for a control and / or regulating device ( 24 ) an internal combustion engine ( 10 ), characterized in that on it a computer program for use in a method of claims 1 to 10 is stored. Control and / or regulating device ( 24 ) for an internal combustion engine ( 10 ), characterized in that it is programmed for use in a method according to one of claims 1 to 10. Internal combustion engine ( 10 ), in particular for a motor vehicle, with a control and / or regulating device ( 24 ) programmed for use in a method according to any one of claims 1 to 10.