DE102014209194A1 - Method and device for controlling an internal combustion engine - Google Patents

Abstract

A method is proposed for controlling an internal combustion engine by means of at least one injector, in which a noise quantity characterizing the noise emission of the internal combustion engine is determined. This checks whether the value of the noise quantity exceeds a limit value and that, when the limit value is exceeded, it is checked whether deviations from an expected value occur during the opening and / or closing behavior of the injector. That a control variable of the injector is corrected with a correction value until the noise size reaches a minimum.

Description

State of the art

The invention is based on a device or a method according to the preamble of the independent claims.

From the EP 416,265 a method for controlling an internal combustion engine is known in which the duration of the drive pulse for the injectors of a common rail injection system is determined in certain operating states, in which just uses the pilot injection. Based on a feedback signal, it is detected that a pre-injection takes place or does not take place. As feedback signals, structure-borne noise and combustion chamber pressure are used.

Disclosure of the invention

Advantages of the invention

The device according to the invention and the method according to the invention with the features of the independent claim have the advantage that a cost-effective method for reducing the radiated structure-borne noise or sound of multiple injections is provided. Furthermore, the connections of different tolerances and drifts are significantly reduced.

According to the invention, it is provided that a noise quantity characterizing the noise emission of the internal combustion engine is determined, that checks whether the value of the noise quantity exceeds a limit value and that, when the limit value is exceeded, it is checked whether the opening and / or closing behavior of the injector deviates from an expected value occur. Subsequently, a drive quantity of the injector is corrected with a correction value until the noise size reaches a minimum. In this case, a correction value for the corresponding control variable is preferably changed, that is increased or decreased, until a minimum for the noise quantity is found. With this correction value, the drive quantity is then corrected during further operation of the internal combustion engine.

According to the invention, a minimum search is carried out in which the correction value is determined at which the lowest noise emissions occur, or a minimum occurs in the course of the noise emissions above the correction value.

It is particularly advantageous if the drive quantity is a variable which influences the edge steepness of the drive signal of the injector and / or a quantity quantity. The size that influences the edge steepness is preferably the charging current or the discharge current with which the piezoelectric actuator is charged or discharged. The quantity size serves to control the injector. This may be, for example, an internal quantity that corresponds to the amount of fuel to be injected. However, it can also act as a derived variable, such as the driving time. The actuation duration denotes the time duration for which the respective injector is actuated with a drive signal for metering fuel. That is, it is particularly advantageous if the variable which corrects the edge steepness of the drive signal and / or the quantity quantity.

In a particularly advantageous embodiment, it is provided that, when the internal combustion engine is at operating temperature, the quantity is increased until the noise quantity reaches a minimum. For this purpose, the correction value is increased and checked whether the noise emission is reduced. If this is not the case, then the correction value and thus the quantity size is no longer increased.

Alternatively, it is advantageous that with cold internal combustion engine, the quantity size is reduced until the noise size reaches a minimum. For this purpose, the correction value is reduced and checked whether the noise emission is reduced. If this is not the case, then the correction value and thus the quantity size is no longer reduced.

If this reduction of the quantity does not lead to a reduction of the noise size, it is advantageous that the quantity size is increased until the noise size reaches a minimum.

It is particularly advantageous if, with a small exhaust gas recirculation rate, the edge steepness is increased until the noise size reaches a minimum. This is advantageous because at low exhaust gas recirculation, the noise emission is sensitive to small changes in edge steepness.

It is particularly advantageous if a deviation during needle closing and / or when needle opening is detected from the expected value, the opening and / or closing behavior of the injector is corrected. It is particularly advantageous if it is first checked whether there is a deviation during needle closing and / or needle opening, and only when these deviations have been corrected is the minimum search for the noise emissions carried out.

In a particularly simple embodiment, it is provided that the closing behavior is checked by means of a zero-quantity calibration.

In a further aspect, the invention relates to program code together with processing instructions for creating a computer program executable on a controller, in particular source code with compiling and / or linking instructions, the program code providing the computer program for performing all the steps of one of the described methods, if according to the processing instructions be converted into an executable computer program, so in particular compiled and / or linked. This program code can be given in particular by source code, which are downloadable, for example, from a server on the Internet.

Short description of the drawing

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

1 the essential elements of an internal combustion engine,

2 a flow chart of the method according to the invention, and

3 . 4 u. 5 in each case a flowchart of a method step of the method according to the invention.

Embodiments of the invention

In the 1 are the essential elements of an internal combustion engine shown. With 100 is called the internal combustion engine. This comprises four cylinders in the illustrated embodiment. Each cylinder is an injector 101 to 104 assigned. At the internal combustion engine is at least one sensor 120 arranged, the a signal P relating to a characteristic of the combustion in at least one of the cylinders to a control unit 150 transmitted. The control unit 150 acts on the injectors 101 to 104 with control signals.

The device according to the invention is not limited to use in an internal combustion engine with four cylinders. It can be performed on any number of cylinders.

Modern internal combustion engines are equipped with sensors 120 equipped, which can detect a knocking of the internal combustion engine. Such sensors 120 work according to different principles. In a first embodiment, a knock sensor is provided, which comprises a seismic mass whose signal is examined with the aid of filters and a digital signal processor on the typical for the knock spectral components. This correspondingly filtered signal can be used as a noise quantity. One or more of these sensors can detect combustion in each of the cylinders. In some cases, this acoustic process can lead to false signals due to other mechanical influences.

In a further embodiment, a combustion chamber pressure sensor 120 intended. This combustion chamber pressure sensor evaluates the pressure in the cylinder. In this case, the pressure increase of the compression, the ignition and possibly the reflective pressure waves of a combustion is detected for each individual cylinder. This size is used as the noise size.

In a third embodiment is an ion sensor 120 intended. Between the ignitions, a DC voltage of about 400 volts is applied to the spark plugs. The measurement of the current flow simultaneously provides information about pressure, temperature and ion density. Tapping is indicated by ion current spikes, which are filtered out, counted and evaluated as a noise quantity according to certain criteria.

Knock sensors are particularly advantageous because they have the advantage over combustion chamber pressure sensors that no further holes in the cylinder head are necessary and that a sensor can measure several cylinders. This results in low sensor and ECU costs.

Due to tolerances and drifts of the air system and / or the injection system of the internal combustion engine, in particular in the region of the combustion chamber of the individual cylinders avoidable noise emissions occur. These can be largely compensated by the procedure described below.

In the 2 essential elements of the procedure according to the invention are shown. In a first step 200 The noise emissions are recorded as noise size G of the internal combustion engine. In a first embodiment, the output signal of a structure-borne sound sensor is used for this purpose. In a further embodiment, a variable is calculated from the signal of a combustion chamber pressure sensor, which characterizes the noise emission G of the internal combustion engine. For this purpose, for example, the gradient of the combustion chamber pressure or the derivative of the combustion chamber pressure over time or over the angular position of the crankshaft or the camshaft can be used. Alternatively, other signals may be used which characterize the noise emission of the internal combustion engine.

The course of the noise quantity G over time, the angular position of the crankshaft or camshaft, which characterizes the noise emissions can, in an advantageous embodiment, also be compared with a reference noise signal waveform determined offline at an earlier time. This comparison is preferably carried out at specific operating points of the internal combustion engine. Preferably at the same engine temperature and the same injection pattern. If an allowable tolerance band is exceeded, the causative cylinder is determined first. The measurement window can be limited to the crankshaft angle range which is relevant for the relevant implementation of the injections and acoustics.

In a second step 210 it is checked whether the noise quantity G of the internal combustion engine is greater than a threshold value S. If this is not the case then the program ends and it will be re-entered at a later date 200 continued. If the noise quantity G is greater than the threshold value S, then step follows 220 ,

In step 220 the tolerances of the needle closing behavior of the injectors are checked and corrected if necessary.

Does the needle closing behavior of the injector, i. the valve needle of the injector closes and / or opens faster or slower than the other injectors, this has the consequence that more or less fuel is metered with the same drive signal. Furthermore, this has the consequence that the injection sooner or later, i. not done at the scheduled time. Overall, this has the consequence that increased noise emissions occur.

The closing behavior can be determined by known methods and given if corrected. For this purpose, along with the reference noise signal waveforms at certain operating points of the internal combustion engine and the associated needle movement curves are measured and stored. The opening behavior and / or the closing behavior are measured. Corresponding methods for determining the needle opening and / or closing behavior can be realized via the sensor properties of piezo actuators (NCC = Needle Closing Control) or by additional piezo sensor elements (NCS = Needle Closing Sensor). In case of deviations of the needle closing behavior from the standard behavior, the opening and / or closing behavior is corrected by correcting the electrical control signal of the respective injector. In this case, the current and / or the voltage are measured and features sought in the waveform of the current and / or the voltage, which correlate with the needle closing and / or needle opening.

At high exhaust gas recirculation rates, the case may occur in the case of small injection quantities that there is no ignition and thus no combustion. The injected fuel is converted at the next subsequent injection. This has the consequence that in this subsequent combustion, a high pressure gradient in the combustion chamber and thus increased noise occurs. According to the invention, it is therefore provided that different procedures are carried out depending on the exhaust gas recirculation. In step 230 Therefore, it is checked whether the exhaust gas recirculation rate EGR is greater than a threshold SAGR. If this is not the case, then step 240 ,

It is particularly advantageous if the method described below is carried out only below a specific exhaust gas recirculation rate SAGR

In step 240 the opening rate and the slope of the injectors are checked and corrected if necessary.

A small slope of the charging or discharging process results in a flat opening rate. This can lead to a high ignition delay with small injection quantities. In particular, with a small injection quantity, this can lead to the fuel quantity being converted only with the subsequent injection. This results in a higher pressure gradient of the combustion pressure in this next injection. This causes a negative influence on the noise. In an advantageous embodiment, it is therefore provided that the procedure for checking for excessive ignition delay, as described below.

The property of piezo injectors is used in that the charge and discharge edges can be changed by means of the size of the charge or discharge pulses. A large charge pulse or a large charging current results in a steep increase in the voltage at the piezoelectric actuator. This increase in voltage is also referred to as the charging edge. Accordingly, a large discharge pulse or a large discharge current results in a steep drop in the voltage at the piezoelectric actuator. This drop in voltage is also referred to as the discharge edge. A steep charging edge or a steep discharge edge has a faster opening or closing of the piezoelectric actuator result. A parameter for the speed of opening or closing the piezoelectric actuator is the opening rate or the closing rate. The opening rate corresponds to the inverse of the opening time or the closing time. In the Opening time or the closing time is the time between the start of the charging or the discharging process and the opening or closing of the piezoelectric actuator.

If the permissible noise tolerance band is exceeded, the loading edge is incrementally reduced. If, in a further reduction of the steepness charging edge, there is a further increase in the noise emission, in particular due to the combustion pressure gradient, the injection type is not responsible for the overshoot. Thereafter, the charging edge is incrementally increased. If there is a further increase in the steepness of the charging edge to a decrease in noise emission, in particular due to the combustion pressure gradient, the injection type is responsible for the excess. The new gradient is stored injector specific in the controller and used in the following injections.

A corresponding procedure is in 3 exemplified. In a first step 300 the correction value K is initialized to the value dx. Then in step 310 the charging current I is reduced by the correction value K. That is, the slope of the charging edge is reduced. The subsequent query 320 checks if the noise quantity G increases. If this is not the case, then the procedure ends in step 330 and the query follows 230 , If the query detects an increase in the noise level, then step follows 340 , In step 340 the charging current I is increased by the value K. The subsequent query 350 checks whether the noise emission decreases. If this is the case, then in step 370 the correction value K is increased by the value dx. Then follow again step 340 , Recognizes the query 350 in that the noise emission does not decrease, the process ends in step 360 and the determined correction value K is stored. This is followed by a query 230 ,

The procedure was described using the charging current as an example. According to the invention, another variable which influences the steepness of the charging edge and / or the discharge edge can also be correspondingly corrected. It is essential that a variable influencing the edge steepness of the drive signal of the injector be corrected accordingly.

Will in step 230 If the exhaust gas recirculation rate EGR is detected to be greater than a threshold value SAGR, the step follows 250 , In the subsequent process, there is an incremental increase in a quantity quantity until it comes to implementation of the injection again. As a result, a significant noise reduction is achieved.

In this case, a distinction is made between two approaches, which depend essentially on the temperature of the internal combustion engine. Therefore, in step 250 checks whether the internal combustion engine has reached its operating temperature. If this is the case, then in step 260 the process for the internal combustion engine is executed in the warm operating state. If not, it will be in step 270 the procedure for a cold internal combustion engine worked off.

The procedure in step 270 will be described below on the basis of 4 described in detail. According to the invention, it has been recognized that in a cold internal combustion engine, the noise emissions increase both in the case of an excess quantity and in the case of a reduced quantity. If an increased or a lower fuel quantity is attributed due to tolerances and / or drifting, increased noises occur in both cases.

Therefore, according to the invention, the procedure for the minimum noise search is as follows: the quantity is reduced incrementally. If this results in a lower noise level, the amount is reduced until it again results in a noise deterioration. The last amount corresponding to the noise minimum is stored.

If a greater level of noise occurs at the beginning of the reduction in quantity, the search continues through an increase in volume. The amount is increased incrementally as long as there is an improvement in noise. If the noise value deteriorates again, the last quantity value / activation duration corresponding to the noise minimum or the activation duration difference from the applied value is stored.

If a greater noise level results with the beginning of the increase in quantity, the search is aborted, since the noise minimum and the quantity / activation duration already correspond.

In the starting step 400 a correction value K is set to the value dx. Subsequently, in step 405 reduces the applied amount M0 by the value K. This means that the applied injection quantity M0 is reduced by the correction value K. In the subsequent query 410 it is checked whether the noise emission has decreased.

If this is the case, then in step 415 the value of the correction value K is increased by dx. In the subsequent step 420 the applied amount M0 is reduced by the value K. That is, the applied amount M0 is reduced by the value K. In the subsequent step 425 it is checked whether the noise emission has reduced. If so, it will be in step 415 the correction value K further increases and thus reduces the injection quantity. Recognizes the query 425 that the noise emission has not decreased, so in step 430 the correction value K is reduced by dx. Thus, the correction value corresponds to the value at which the lowest noise emissions occur.

Will in step 410 recognized that the noise emissions do not decrease, so in step 440 the correction value K is increased by the value dx. In the subsequent step 445 the injection amount M is increased by the value K. That is, the applied amount M0 is increased by the value K. The subsequent query 450 Checks if the noise emission decreases. If this is the case, then in step 440 the correction value K is increased by the value dx. Recognizes the query 450 that the increase in the amount does not result in a reduction of the noise, so in step 460 the correction value is reduced by the value dx.

The procedure in step 260 will be described below on the basis of 5 described in detail. According to the invention, it has been recognized that the noise emissions increase in the case of a low-powered internal combustion engine. If a lower fuel quantity is attributed due to tolerances and / or drifts, increased noise occurs in both cases.

Therefore, according to the invention, the procedure for the minimum noise search is as follows. The amount is increased incrementally as long as there is an improvement in noise. If there is no further improvement or if the noise value deteriorates again, then the last quantity value / activation duration corresponding to the noise minimum or the activation duration difference to the applied value is stored.

This procedure is in 5 detailed as a flowchart.

In the starting step 500 a correction value K is set to the value dx. Subsequently, in step 510 the value of the correction value K is increased by dx. In the subsequent step 520 the injection amount M is increased by the value K. This means that the correction value K is added to the applied quantity M0. In the subsequent step 530 it is checked whether the noise emission has reduced. If so, it will be in step 510 the correction value K further increases and thus reduces the injection quantity. Recognizes the query 530 that the noise emission has not decreased, so in step 540 the correction value K is reduced by dx. Thus, the correction value corresponds to the value at which the lowest noise emissions occur.

In a particularly advantageous embodiment it is provided that the height of the correction value is limited. It is preferably provided that it is checked for each change of the correction value K whether the amount of the correction value is greater than a maximum permissible threshold value. Alternatively, it can also be provided that every time the correction value K is increased, it is checked whether it is greater than a threshold value and whether it is smaller than a threshold value each time the correction value is reduced.

If the threshold for the correction value is reached, an error is detected. This can be stored, for example, in the fault memory and lead in the service for replacement of the injector.

In modern injection systems usually several injectors are installed. The described method is performed for each injector. Furthermore, it is provided in modern injection systems that an injection process is divided into several partial injections. This means that several partial injections take place during a combustion cycle. It is preferably provided that the method is carried out for all partial injections which contribute to the moment of the internal combustion engine. These are the split injections, commonly referred to as pilot injection and / or main injection. In this case, the pilot injection and / or the main injection can also be divided into a plurality of partial injections. It is particularly advantageous if the method is applied to all these partial injections.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• EP 416265 [0002]

Claims (12)

A method for controlling an internal combustion engine by means of at least one injector, wherein a noise emission of the internal combustion engine characterizing noise is determined that checks whether the value of the noise exceeds a threshold value and that is checked when the limit is exceeded, whether in the opening and / or closing behavior of the Injector deviations from an expected value occur, and that a control variable of the injector is corrected with a correction value until the noise size reaches a minimum. A method according to claim 1, characterized in that a the edge steepness of the drive signal of the injector and / or a quantity quantity for controlling the injector is corrected with the correction value. A method according to claim 2, characterized in that when operating the internal combustion engine, the quantity size is increased until the noise size reaches a minimum. A method according to claim 2, characterized in that with cold internal combustion engine, the quantity size is reduced until the noise size reaches a minimum. A method according to claim 4, characterized in that when the internal combustion engine, the quantity size is increased until the noise size reaches a minimum, if a reduction in the quantity size has no reduction in the noise size. A method according to claim 2, characterized in that at low exhaust gas recirculation rate, the edge steepness is increased until the noise size reaches a minimum. A method according to claim 1, characterized in that the opening and / or closing behavior of the injector is corrected when a deviation in needle closing and / or needle opening is detected by the expected value. Claim according to claim 7, characterized in that the closing behavior is checked by means of a zero quantity calibration. A computer program configured to perform all the steps of one of the methods of any one of claims 1 to 8. A machine readable storage medium storing the computer program of claim 9. A controller adapted to perform all the steps of one of the methods of any one of claims 1 to 8. Program code along with processing instructions for creating a computer program executable on a controller, the program code providing the computer program of claim 9 when converted into an executable computer program according to the processing instructions.

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