EP1517023B1 - Method for preadjusting the throttling of the suction air in an internal combustion engine - Google Patents

Description

The present invention relates to a method for presetting the fresh air supply throttling in an internal combustion engine, in particular in a diesel engine, which is equipped with a control circuit for controlling the throttling of the fresh air air supply, a method for regenerating an exhaust gas purification device of an internal combustion engine, and an internal combustion engine.

In order to reduce harmful emissions from internal combustion engines, arranged in the exhaust system particulate filters are used. For example. In a diesel engine, a particulate filter (DPF, Diesel Particulate Filter) collects the soot produced in the diesel engine. In this case, carbonaceous filter residues accumulate, which increase the flow resistance for the exhaust gases passing through the particle filter. Therefore, such a particulate filter must be regenerated from time to time so that the fuel consumption of the engine does not increase undesirably due to the flow resistance. The regeneration is carried out by an oxidation process, ie by burning the filter residues. However, the carbon contained in the filter residues ignites only at relatively high temperatures of about 550 ° C, unless the combustion process undergoes catalytic support. However, such high exhaust gas temperatures are only achieved when the engine is operated at high load or in the high speed range. In order to ensure regeneration of the particulate filter under all operating conditions, so even if the engine is not operated under high load or in the high speed range, therefore, the possibility must be created, if necessary, the exhaust gas temperature sufficient for the regeneration of the particulate filter Increase value.

Various approaches have been proposed in the prior art for increasing the exhaust gas temperature. A measure for increasing the exhaust gas temperature is, if appropriate in interaction with further measures, the throttling of the fresh air supply of the engine, as described, for example, in EP 1 205 647, EP 1 296 050 and EP 1 304 458.

The said procedures have in common that a precise control of the throttling is necessary to the high exhaust gas temperature even in non-stationary operation of the engine, d. H. In the transition between different operating conditions, eg. When driving in city traffic with frequent idling and frequent braking operations to maintain. The previous control strategies for throttling the fresh air supply typically consist of a control term, also called Voreinstellterm, which allows a rapid readjustment of the throttling, as well as a Regelterm be compensated by the error in the steady operation of the throttling. A corresponding control is described in WO 03/012559 A1. The control term set during the development process specifies a throttle position or the duty cycle of an actuator associated with the throttle.

Aging phenomena of the adjusting device of the throttle, for example, a negative pressure-adjusting device can lead to significant deviations in the throttling positions associated with a duty cycle in the same throttle devices. Likewise, due to manufacturing tolerances significant deviations in the effective flow cross sections may occur at identical throttle positions. Therefore, throttle control may be well set for one engine (with nominal throttle characteristics), whereas in other engines, due to (summed) manufacturing tolerances with identical throttle adjustment signal, it will result in higher or lower throttle flow. A lower flow, ie a stronger throttling, can lead to instabilities in the combustion process in the engine or lead to problems when driving (especially at throttle plates with low leakage rate), whereas too high a flow, ie a lower throttling, has a negative effect on the achievable exhaust gas temperature when regenerating the particulate filter, which makes the regeneration of the particulate filter difficult. The importance of the last point should not be underestimated. In particular, considering the regeneration characteristics of catalytic filtration systems or particulate filters in which regeneration occurs without additional fuel injection, it can be seen that reducing the exhaust gas temperature by 10-20 ° C is doubled due to the exponential dependence of the regeneration rate on the exhaust gas temperature the required regeneration time can lead.

From DE 38 16 520 A1 a method for adapting a pilot value of a lambda control is known. In this method, the value of a pilot variable in a calibration procedure is determined such that the effect of at least one predictor is minimized.

It is an object of the present invention to provide an improved method for regenerating a particulate filter in the exhaust system of an internal combustion engine.

Another object of the present invention is to provide an improved internal combustion engine.

The first object is achieved by a method according to claim 1 for presetting the fresh air supply throttling in an internal combustion engine, and the second object by an internal combustion engine according to claim 12. The dependent claims represent advantageous developments of the invention.

In the inventive method for regenerating a particulate filter in the exhaust system of a equipped with a control circuit for regulating the throttling of the fresh air supply internal combustion engine increasing the Exhaust gas temperature by throttling the fresh air supply, a control signal of the control loop is combined with a preset signal to a throttling adjusting throttle signal. The method according to the invention is characterized in that a calibration of the presetting signal is carried out on the basis of the actuating signal.

The invention is based on the following considerations:

If a sufficiently adjusted throttle system had nominal throttle characteristics, then the preset signal would represent the correct throttle signal, i. H. there would be no need for regulation. In fact, however, errors occur that are due in particular to manufacturing tolerances or aging phenomena in components. The control circuit therefore serves to compensate for these errors during stationary operation of the throttling by means of a control signal to be combined with the presetting signal.

The inventive calibration of the preset signal based on the control signal now makes it possible to take into account the manufacturing tolerances or aging phenomena already in the preset signal and thus to reduce the contribution of the control signal to the throttle signal. The result is a preset signal adapted to the characteristics present in the respective engine. As a result, due to the improved presetting signal, the method according to the invention makes possible an improved control of the fresh air supply, in particular in non-stationary operation of the internal combustion engine.

With the improved control of the fresh air supply, in particular improved strategies for regenerating particulate filters in the exhaust system of the internal combustion engine can be realized.

The method according to the invention enables an adaptive control strategy for the throttling, in which the preset signal is constantly updated, ie to the current tolerances or aging phenomena is adapted. In one embodiment of the invention, therefore, a repeated calibration of the preset signal based on the control signal. The Adjustment can be considered as a "learning process" in which the throttling "learns" to consider changing tolerances or aging phenomena. The adaptive control strategy may obviate position sensors for the throttle. In addition, the manufacturing costs for the throttling and adjusting device can be reduced, since less stringent requirements can be made of the specifications for the manufacturing tolerances.

In one embodiment of the method according to the invention, the calibration takes place on the basis of a correction term determined from the actuating signal and the preset signal. In a development that is easy to implement, the correction term can be determined in particular on the basis of an offset to be added to the presetting signal and based on the actuating signal.

• den Wert des Stellsignals abzüglich eines positiven Grenzwertes, falls der Wert des Stellsignals größer als der Grenzwert ist,
• durch den Wert des Stellsignals zuzüglich des Grenzwertes, falls der Wert des Stellsignals kleiner als das Negative des Grenzwertes ist, und
• durch den Wert Null, falls der Betrag des Stellsignals kleiner als oder gleich dem Grenzwert ist.

The offset can be defined in particular by

• the value of the actuating signal less a positive limit value if the value of the actuating signal is greater than the limit value,
• by the value of the actuating signal plus the limit value if the value of the actuating signal is less than the negative of the limit value, and
• by the value zero, if the amount of the actuating signal is less than or equal to the limit value.

By means of the limit value, a range can be defined in which the control signal can vary without a calibration of the preset signal. Ie. Calibration takes place in the presence of such a limit value only if the errors associated with the tolerances and / or aging phenomena exceed an unacceptable level defined by the limit value.

The correction term can be given in one embodiment of the method, in particular by the offset itself. If the correction term is given by the offset itself, a rapid response of the preset signal takes place on the offset, ie there is a rapid calibration. If a big one Offset is present, but it can lead to a large jump in the preset signal. Alternatively, the correction term can therefore also be given by a fraction of the offset, the calibration then taking place in a plurality of calibration steps corresponding to the number of fractions. This avoids large jumps in the preset signal.

Before calibrating the preset signal, a check can be made as to whether the control loop is in a stationary operating state, wherein the calibration of the preset signal only takes place when a stationary operating state of the control loop is detected. Thereby, erroneous calibration in a non-stationary state can be avoided. In one embodiment, the stationary operating state can be determined if selected engine parameters, for example, over a predetermined period of time are almost constant.

The determination of the presetting signal for the throttling can take place on the basis of a mapping rule which supplies a value for the presetting signal as a function of engine parameters of the internal combustion engine. Possibly. Corrections for ambient and / or engine conditions may be added to the presetting signal thus determined. In the prior art, the determination of the preset signal is generally based on such a mapping rule. The calibration of the preset signal can therefore be realized in a simple manner by updating the mapping rule. During calibration, either the entire mapping rule can be updated, ie the mapping rule for all engine parameters is updated, or the part of the mapping rule whose motor parameters correspond to the stationary operating state can only be updated. The inventive method for presetting the Frischluftzufuhrdrosselung in an internal combustion engine can be used in particular as part of a method for regenerating a particulate filter while increasing the exhaust gas temperature in the exhaust system of an internal combustion engine by throttling the fresh air supply.

• eine Drosseleinrichtung zum Drosseln der Frischluftzufuhr,
• einen Regelkreis, der zur Ausgabe eines Stellsignals zum Regeln der Drosselung der Frischluftluftzufuhr ausgestaltet ist,
• eine Steuereinheit, die zur Ausgabe eines Voreinstellsignals zum Voreinstellen der Drosselung der Frischluftluftzufuhr ausgestaltet ist,
• einer Kombiniereinheit, die zum Erzeugen eines die Drosselung einstellenden Drosselsignal anhand einer Kombination des Voreinstellsignals mit dem Stellsignal ausgestaltet ist,
• einen im Abgassystem angeordneten Partikelfilter, welcher unter Erhöhung der Abgastemperatur durch Drosselung der Frischluftzufuhr regenerierbar ist,
• eine Regenerationseinrichtung zum Regenerieren des Partikelfilters durch Drosselung der Frischluftzufuhr unter Erhöhung der Abgastemperatur, und
• eine Kalibriereinheit zum Kalibrieren des Voreinstellsignals, die zum Ausführen des erfindungsgemäßen Verfahrens zum Regenerieren eines Partikelfilters ausgestaltet ist.

An inventive internal combustion engine comprises:

• a throttle device for throttling the fresh air supply,
• a control circuit which is designed to output a control signal for regulating the throttling of the fresh air supply,
• a control unit which is designed to output a presetting signal for presetting the throttling of the fresh air air supply,
• a combining unit which is designed to generate a throttling adjusting throttle signal based on a combination of the preset signal with the actuating signal,
• a particle filter arranged in the exhaust system, which can be regenerated by increasing the exhaust gas temperature by throttling the fresh air supply,
• a regeneration device for regenerating the particulate filter by throttling the fresh air supply while increasing the exhaust gas temperature, and
• a calibration unit for calibrating the preset signal, which is designed to carry out the method according to the invention for regenerating a particle filter.

Fig. 1

zeigt die typische Struktur einer Steuerung/Regelung für die Drosselung der Frischluftzufuhr in einem Verbrennungsmotor.

Fig. 2

stellt das erfindungsgemäße Verfahren anhand eines Flußdiagramms dar.

Further features, advantages and features of the invention will be explained below with reference to an embodiment with reference to the accompanying drawings.

Fig. 1

shows the typical structure of a controller for throttling the supply of fresh air in an internal combustion engine.

Fig. 2

illustrates the method according to the invention with reference to a flow chart.

For a better understanding of the invention, the typical structure of a control / regulation for the fresh air supply throttle 1, hereinafter referred to as throttle, in an internal combustion engine will first be described with reference to FIG. By means of the throttle 1, the intake pressure is adjusted in the intake manifold of the engine.

The control comprises a controller which outputs a control signal or preset signal u_ff for influencing the throttle 1. The determination of the presetting signal u_ff takes place on the basis of a calibrated mapping rule 3 which outputs the actuating signal u_ff as a function of the engine speed 2 and the engine torque 4. The value for the presetting signal u_ff determined on the basis of the mapping rule 3 can be corrected by means of a correction unit 5 as a function of further operating states 6 of the motor.

In addition, the control / regulation comprises a control loop with a controller 7, which outputs a control signal u_fb for influencing the throttle 1. The controller 7 generates the control signal u_fb in response to the deviation map_error of the actual pressure map measured in the intake manifold from a target value map_ref. The setpoint map_ref for the intake manifold pressure is determined by means of a calibrated mapping instruction 9 which outputs the setpoint map_ref as a function of the engine speed 2 and the engine torque 4. By means of a setpoint correction unit 11, in order to take into account ambient conditions and further engine operating conditions 12, the setpoint determined using the mapping rule 11 can be corrected before the deviation map_error of the actual pressure map in the intake manifold from the setpoint value map_ref is determined. The deviation map_error is finally input to the controller, which calculates the control signal u_fb on the basis of the deviation map_error.

In the control system, the control signal u_fb is added to the presetting signal u_ff in order to obtain a throttle signal u as a setting signal actuator_cmd for the actuator of the throttle 1. As shown in FIG. 1, the throttle signal u may still undergo scaling in an optional scaling unit 13, so that the scaled throttle signal represents the actual adjustment signal actuator_cmd for the actuator of the throttle 1.

In the prior art, the control is to allow rapid adjustment of the throttle 1 in the non-stationary operation of the engine, while the control in stationary operation of the engine correcting errors takes over due to aging effects or manufacturing tolerances.

In the method according to the invention, the control signal u_fb of the control is now used to repeatedly calibrate the preset signal u_ff, for example by means of an offset ff_offset and thus to adapt the preset signal u_ff to changed operating conditions of the engine, for example due to aging phenomena. The thus adjusted or updated preset signal u_ff then enables a more precise setting of the throttling.

A possible procedure for calibrating the preset signal u_ff will be described below with reference to the flowchart shown in FIG.

After the process has been designed in step 20, a query is first of all made in step 22 as to whether regulation of the throttle takes place. If this is answered in the negative, the method returns to its starting point. If the query for the control is affirmative, the next step 24 is a query whether the calibration of the preset signal is permitted. If not, the process returns to its starting point. Both conditions, d. H. Regulating the throttle and allowing calibration must be met before the actual calibration procedure can begin in step 26. If no regulation of the throttle takes place, the necessary information for calibrating the preset signal u_ff is not available. By means of the second condition, it is possible to take account of switching off the calibration, for example during the warm-up phase of the engine or in operating states of the engine in which calibration is not necessary, for example during the high-load operation of the engine.

Although in the present embodiment, the query whether a control of the throttle takes place before the query whether the calibration of Preseinstellsignals is allowed, however, this order is arbitrary and can be reversed just as well If both conditions are met, a query is made in step 26 as to whether the control and / or the engine are in a stationary state. A stationary state of the engine can be detected, for example, by setting limit values for the derivatives of the engine speed and the torque, at which a stationary state of the engine is reached or fallen below.

A stationary state of the engine is strictly speaking characterized in that the engine speed and the torque are constant, d. H. the derivatives of the engine speed and the torque after time have the value zero. Therefore, the set limits should be close to zero. The closer the limit values are to zero, the more precisely a stationary state is reached when the limit values are undershot. The limit values should therefore be chosen in particular as a function of how exactly the stationary state must be reached in order to allow a meaningful calibration of the preset signal u_ff.

A steady state of the control is given when the control signal u_fb has reached a steady state (constant) value, i. H. the deviation map_error of the actual pressure map in the intake manifold has reached zero from the nominal value map_ref. For reasons of practicability, it is sufficient if the deviation map_error has reached or fallen below a limit value close to zero. The limit value should be chosen depending on how exactly the stationary state of the control must be reached in order to allow a meaningful calibration of the preset signal u ff.

If the described values and possibly the values of further relevant signals are constant over a certain period of time, the presence of the stationary state is determined in step 26. The period of time over which the constancy must be present can be chosen freely. However, choosing it too long may result in infrequent stationary conditions, so calibration can rarely occur. As a rule, the duration is a few seconds.

If the stationary state is not detected in step 26, if the steady state is not detected in step 26, the process returns to its starting point. If, on the other hand, the presence of a stationary state is detected, the offset ff_offset to be added to the presetting signal u_ff is next computed in step 28.

The calculation of the offset ff_ofsett takes place as follows: Assuming that the presetting signal has the value u_ff = x% and the actuating signal has the value u_fb = y%. In the ideal case, ie without disturbances or altered parameters of the throttle, u_fb = 0, but in the presence of disturbances or altered characteristics of the throttle not. The offset in the presence of disturbances or changed characteristics is now determined so that essentially u_fb = 0 is produced, ie the preset signal assumes the value u_ff = x% + y%. In the present embodiment, strict u_fb = 0 does not have to be strict. Instead, a range defined by a value α is permitted, in which the value y% of the actuating signal u_fb may move without an offset being added to the preset signal. The value of the offset ff_offset is then calculated as follows: ff_offset = y - α for y> α y + α for y <-α 0 for | y | ≤ α where α is an adjustable value, which is typically about 3% to 5%.

In step 30, following the calculation of the offset, a correction term for the calibrated mapping rule 3 (FIG. 1) is calculated, which outputs the control signal u_ff in dependence on the engine rotational speed 2 and the engine torque 4. In step 32, the calibrated mapping rule 3 is then updated or corrected on the basis of the correction term.

The correction term can be, for example, the total value of the offset ff_offset calculated in step 28. In an alternative embodiment of the method For example, the updating, ie the correction, of the calibrated mapping rule 3 can be carried out in increments which are limited in their increment. For example, if the value of the preset signal is 50% in the basic calibration, although it should be 65% under the current operating conditions to achieve the desired degree of throttling (as set in the target map_ref), updating will occur in one embodiment of the mapping rule from 50% to 65% in a single update step, whereas updating the calibrated mapping rule 3 in the alternative embodiment is done in several small update steps, such as three steps of 5% per step.

The updating of the calibrated mapping rule 3 can relate to the entire calibrated mapping rule 3, ie. H. there is an updating of the calibrated mapping rule 3 for all engine parameters. Alternatively, however, only an updating of that part of the calibrated mapping rule 3 whose motor parameters correspond to the stationary operating state can take place.

After updating the calibrated mapping rule, the calibration of the preset signal is completed and the method returns to its initial state. If a timer is used to detect the steady state in step 26, it is reset before returning to the initial state.

The method according to the invention can be realized both in the form of a hardware solution and in the form of a software solution.

Claims (12)

1. Method for regenerating a particle filter in the exhaust system of an internal combustion engine which is equipped with a control circuit for controlling the throttling of the fresh air supply, by increasing the exhaust gas temperature by throttling the fresh air supply, and an actuation signal (u_fb) of the control circuit being combined with a presetting signal (u_ff) to form a throttle signal (u) which sets the throttling,
   characterized in that,
   the presetting signal (u_ff) is standardized by means of the actuation signal (u_fb).
2. Method according to Claim 1,
   characterized in that,
   the presetting signal is standardized repeatedly by means of the actuation signal.
3. Method according to Claim 1 or 2,
   characterized in that,
   the standardization is carried out by means of a correction term which is determined from the actuation signal (u_ff) and the presetting signal (u_ff).
4. Method according to Claim 3,
   characterized in that,
   the correction term is determined by means of an offset (ff_offset) which is to be added to the presetting signal (u_ff) and is based on the actuation signal (u_fb).
5. Method according to Claim 4,
   characterized in that,
   the offset is defined by the value of the actuation signal (u_fb) minus a positive limiting value (α), if the value of the actuation signal (u_fb) is greater than the limiting value (α),

   - by the value of the actuation signal (u_fb) plus the limiting value (α), if the value of the actuation signal (u_fb) is less than the negative of the limiting value (α), and

   - by the value zero, if the absolute value of the actuation signal (u_fb) is less than or equal to the limiting value (α).
6. Method according to Claim 4 or 5,
   characterized in that,
   the correction term is provided by the offset (ff_offset).
7. Method according to Claim 4 or 5,
   characterized in that,
   the correction term is given by a fraction of the offset (ff_offset) and the standardization is carried out in a plurality of standardization steps which correspond to the number of fractions.
8. Method according to one of Claims 1 to 7,
   characterized in that,
   before the standardization of the presetting signal (u_ff) a check is carried out to determine whether the control circuit is in a steady operating state and the standardization of the presetting signal (u_ff) takes place only if a steady operating state of the control circuit is detected.
9. Method according to one of Claims 1 to 8,
   characterized in that,
   the presetting signal (u_ff) is determined by means of a mapping rule which supplies a value for the presetting signal (u_ff) as a function of engine parameters of the internal combustion engine, and in that the mapping rule is updated in order to standardize the presetting signal (u_ff).
10. Method according to Claim 9,
    characterized in that,
    for the standardization, the mapping rule is updated for all the engine parameters.
11. Method according to Claim 8 and Claim 9,
    characterized in that,
    for the standardization, that part of the mapping rule whose engine parameters correspond to the steady operating state is updated.
12. Internal combustion engine having

    - a throttle device for throttling the fresh air supply,

    - a control circuit which is designed to output an actuation signal (u_fb) for controlling the throttling of the fresh air supply,

    - a control unit which is designed to output a presetting signal (u_ff) for presetting the throttling of the fresh air supply, and

    - a combination unit which is designed to generate a throttle signal (u) which sets the throttling by combining the presetting signal (u_ff) with the actuation signal (u_fb),

    - a particle filter arranged in the exhaust system, which can be regenerated by increasing the exhaust temperature by throttling the fresh air supply, and

    - a regeneration device for regenerating the particle filter by throttling the fresh air supply by increasing the exhaust temperature,

    characterized by a standardization unit for standardizing the presetting signal (u_ff) which is designed to carry out the method for regenerating a particle filter according to one of Claims 1 to 11.

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