EP1517023A1 - Method for preadjusting the throttling of the suction air in an internal combustion engine - Google Patents

Abstract

Method for regenerating a particle filter in an exhaust gas system of a combustion engine, which has a control loop for regulating the throttling of the fresh air supply to it, by increasing the exhaust gas temperature by throttling the fresh air supply. According to the method, an input signal (ufb) to the control loop is combined with a preset input signal (uff) to form a throttling signal (u), whereby calibration to determine the preset input signal is achieved using the current input signal. The invention also relates to a corresponding combustion engine.

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 regulating the Choking the fresh air supply is equipped, a method for Regenerating an exhaust gas purification device of an internal combustion engine, as well as an internal combustion engine.

To reduce harmful emissions from internal combustion engines, In the exhaust system arranged particle filters are used. For example. collects in a diesel engine a particulate filter (DPF, diesel particulate Filter) the soot produced in the diesel engine. Thereby gather carbonaceous filter residues, the flow resistance for the increase the exhaust gas passing through the particulate filter. Therefore, such a Particulate filters can be regenerated from time to time to reduce fuel consumption the engine is not due to the flow resistance in undesirably increased. The regeneration is done by a Oxidation process, d. H. by burning the filter residues. The in the Filter residues contain carbon but does not ignite until relatively high temperatures of about 550 ° C, if the combustion process no receives catalytic support. Such high exhaust gas temperatures are However, only achieved when the engine at high load or high Speed range is operated. To regenerate the particulate filter under all operating conditions, even if the engine is not included high load or in the high speed range, ensure Therefore, the possibility must be created, if necessary, the Exhaust gas temperature to one for the regeneration of the particulate filter to increase sufficient value.

In the prior art, various approaches to increasing the Exhaust temperature has been proposed. A measure to increase the Exhaust gas temperature is doing, possibly in conjunction with others Measures, the throttling of the fresh air supply of the engine, as it is, 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 maintain the high exhaust gas temperature also in the non-stationary operation of the engine, d. H. at the transition between Different operating conditions, eg. When driving in city traffic with frequent idle operation and frequent braking events, maintained can. The previous control strategies for throttling the Fresh air intake typically consist of a control term, too Preset term called the rapid resetting of the throttling allows, as well as a Regelterm, by the error in stationary operation the throttling are compensated. The tax term, which 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, eg. One Vacuum adjusting device can be the same throttle devices to significant deviations in one work cycle lead assigned throttle positions. Likewise, due to Manufacturing tolerances significant deviations in the effective Flow cross sections occur at identical throttle positions. Therefore can be a throttle control for a motor (with nominal Throttle characteristics) are well set, whereas in others Motors due to (summed) manufacturing tolerances at identical Adjustment signal for throttling to a higher or lower flow through the throttle. A lower river, d. H. a stronger one Throttling, can cause instabilities in the combustion process in the engine or lead to problems during driving (especially with throttle plates with low leakage rate), whereas too high a flow, i. H. a lower one Throttling, negative effects on the achievable exhaust gas temperature when regenerating the particulate filter, which has the regeneration of the Particulate filter difficult. The meaning of the last point should not be underestimated. In particular, considering the regeneration characteristics catalytic filtration systems or particle filters in which the Regeneration without additional fuel injection is considered to realize that decreasing the exhaust gas temperature by 10-20 ° C because the exponential dependence of the regeneration rate on the exhaust gas temperature lead to a doubling of the required regeneration time can.

It is therefore an object of the present invention to provide an improved process for presetting the fresh air supply throttling in an internal combustion engine to make available.

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

Yet another object of the present invention is to provide a to provide improved combustion engine.

The first object is achieved by a method according to claim 1 to Presetting the fresh air supply throttling in an internal combustion engine, the second object by a method according to claim 12 for Regenerating a particulate filter in the exhaust system of an internal combustion engine and the third task by an internal combustion engine after Claim 13 solved. The dependent claims represent advantageous Further developments of the invention.

In the inventive method for presetting the Frischluftzufuhrdrosselung in an internal combustion engine, which is equipped with a control circuit for Rules of throttling the fresh air supply is equipped, a Control signal of the control loop with a preset signal to a the Throttling adjusting throttle signal combined. The invention Method is characterized in that a calibration of the preset signal done on the basis of the control signal.

The invention is based on the following considerations:

Would a sufficiently adjusted throttling system be nominal Have throttle characteristics, the preset signal would be the correct Represent throttle signal, d. H. there would be no need for regulation. In fact, however, errors occur, in particular on manufacturing tolerances or aging of components are. The control circuit is therefore used in stationary operation of the throttling these errors by means of a to be combined with the preset signal To balance the actuating signal.

The calibration according to the invention of the preset signal on the basis of Control signal now allows the manufacturing tolerances or aging phenomena already to be considered in the preset signal and so the Reduce contribution of the control signal to the throttle signal. The result is a adapted to the present in each motor parameters preset signal. As a result, the inventive method allows due to the improved preset signal especially in non-stationary Operation of the internal combustion engine improved control of Fresh air.

With the improved control of the fresh air supply can in particular also 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 again and again updated, d. H. to the current tolerances or aging phenomena is adapted. In one embodiment of the invention therefore takes a repeated calibration of the preset signal based on the control signal. The Adaptation can be viewed as a "learning process" in which the throttling "learns" changing tolerances or aging phenomena account. The adaptive control strategy can be position sensors make redundant for the throttle. In addition, the Production costs for the throttling and adjusting device are reduced, because less stringent requirements for the specifications for the Manufacturing tolerances can be made.

In one embodiment of the method according to the invention that takes place Calibrate using one of the control signal and the preset signal determined correction terms. In an easy-to-implement training the correction term can in particular be based on a presetting signal to be added and based on the control signal offsets determined become.

• 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, an area can be defined in which the Adjusting signal may vary without any calibration of the preset signal he follows. Ie. a calibration takes place in the presence of such Limit value only if that with the tolerances and / or aging phenomena accompanying error is no longer acceptable, by exceed the limit defined measure.

The correction term can in one embodiment of the method in particular be given by the offset itself. If the correction term is replaced by the Offset itself is given, there is a rapid response of the preset signal on the offset, d. H. There is a quick calibration. If a big one Offset, but it can be a big jump in the Preset signal come. Alternatively, the correction term can therefore also be given by a fraction of the offset, with the calibration then in several, corresponding to the number of fractions calibration steps he follows. This avoids large jumps in the preset signal.

Before calibrating the preset signal, a check may be made take place, whether the control loop in a stationary operating condition with calibration of the preset signal taking place only when a stationary operating state of the control loop is detected. This may cause erroneous calibration in a non-stationary state be avoided. In one embodiment, the stationary operating state be determined if selected engine parameters, eg. About 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, und
• eine Kalibriereinheit zum Kalibrieren des Voreinstellsignals, die zum Ausführen des erfindungsgemäßen Verfahrens zum Voreinstellen der der Frischluftzufuhrdrosselung 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 combination unit, which is designed to generate a throttling adjusting throttle signal based on a combination of the preset signal with the actuating signal, and
• a calibration unit for calibrating the presetting signal, which is designed to carry out the method according to the invention for presetting the fresh air supply throttling.

In addition, it can also be arranged in particular in the exhaust system Particulate filter and a regeneration device for regenerating the Include particulate filter while throttling the fresh air supply.

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, first with reference to FIG. 1 typical structure of a control for the fresh air supply throttle 1, hereafter referred to as throttle, in an internal combustion engine described. By means of the throttle 1, the intake pressure in the intake manifold of the engine.

The controller includes a controller that receives a control signal or Preset signal u_ff for influencing the throttle 1 outputs. Determining the preset signal u_ff is based on a calibrated Mapping rule 3, the control signal u_ff depending on the Engine speed 2 and the engine torque 4 outputs. The basis of the Abbildungsvorschrift 3 determined value for the preset signal u_ff can by means of a correction unit 5 as a function of others Operating conditions 6 of the engine are corrected.

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 setpoint map_ref. The setpoint map_ref for the pressure in Intake manifold is based on a calibrated mapping rule 9 determines the setpoint map_ref as a function of the engine speed 2 and the engine torque 4 outputs. By means of a setpoint correction unit 11 may be to enter ambient conditions and other engine operating conditions 12 take into account the setpoint determined using the mapping rule 11 get a correction before the deviation map_error of the actual Pressure map in the intake manifold of the desired value map_ref is determined. The Deviation map_error is finally entered into the regulator, which is on the basis of the deviation map_error that control signal u_fb calculated.

In the control system, the control signal u_fb becomes the preset signal u_ff added to a throttle signal u as a setting signal actuator_cmd for to get the actuator of the throttle 1. As shown in Fig. 1, the Throttle signal u in an optional scaling unit 13 is still a scale so that the scaled throttle signal is the actual tuning signal actuator_cmd for the actuator of the throttle 1 represents.

In the prior art, the control is used to quickly adjust the To allow throttle 1 during 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 occur.

In the method according to the invention, the control signal u_fb now becomes the control used to the preset signal u_ff bspw. By means of an offset ff_offset especially to calibrate repeatedly and so the preset signal u_ff to changed operating conditions of the engine, eg. Due to Aging phenomena, adapt. The thus adapted or updated presetting signal u_ff then allows a more precise setting throttling.

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

After the process has been designed in step 20, takes place first in step 22, a query whether a regulation of the throttle takes place. If this is answered in the negative, the method returns to its starting point back. If the answer to the rule is affirmative, the next is Step 24 is a query of whether to allow the calibration of the preset signal is. If not, the process returns to its starting point. Both Conditions, d. H. Regulation of the throttle and allowance of the calibration, must be met before the actual calibration procedure in Step 26 can begin. If no regulation of the throttle takes place, stands the necessary information for calibrating the preset signal u_ff not to disposal. By means of the second condition, turning off the Calibration, for example during the warm-up phase of the engine or at Operating conditions of the engine, in which a calibration is not necessary, such as during high load operation of the engine.

Although in the present embodiment, the query whether a Regulation of the throttle takes place, before interrogating whether to calibrate the Preset signal is allowed, however, this order is arbitrary can be chosen and can be turned around as well

If both conditions are satisfied, a query is made in step 26 as to whether the control and / or the engine in a stationary State are. A stationary state of the engine can be, for example. by establishing limits for the engine speed and the derivative Torque are set when they reach or fall below a stationary state of the engine is present.

A stationary condition of the engine is strictly speaking characterized from that the engine speed and the torque are constant, d. H. the Derivation of the engine speed and the torque after the time Have zero value. Therefore, the set limits should be close to zero lie. The closer the limits are to zero, the more accurate is one steady state when falling below the limits reached. The Limits should therefore be chosen in particular depending on it How exactly the steady state must be reached to a allow meaningful calibration of the preset signal u_ff.

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

If the described values and possibly the values of other relevant signals are constant over a certain period of time, the presence is in step 26 of the stationary state. The period of time over which the constancy must be available, can be chosen freely. If, however, they are elected too long This may result in infrequent stationary conditions being detected so that calibration can rarely be done. Usually amounts to the duration of a few seconds.

If the steady state is not detected in step 26, it will Procedure back to its starting point. If, on the other hand, this is the case a steady state is detected, then next in step 28 the offset ff_offset to be added to the preset signal u_ff is calculated.

wobei α ein einstellbarer Wert ist, der typischerweise bei ca. 3% bis 5% liegt.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:

where α is an adjustable value, which is typically about 3% to 5%.

In step 30, which follows the calculation of the offset, the Calculating a correction term for the calibrated mapping rule 3 (Fig. 1), the control signal u_ff in response to the engine speed 2 and the motor torque 4 outputs. In step 32, the calibrated Mapping instruction 3 is then updated on the basis of the correction term or corrected.

The correction term can, for example, the total value of the calculated in step 28 Offsets be ff_offset. In an alternative embodiment of the method can updating, d. H. correcting, calibrating Figure 3 in steps that follow in their increment are limited above. If, for example, the value of the preset signal is 50% in the basic calibration, although under the current operating conditions Should be 65% to the desired degree of throttling (as in the Setpoint map_ref is set), so takes place in the one Configuration updating the mapping rule from 50% to 65% in a single update step, whereas updating the calibrated mapping rule 3 in the alternative embodiment in several small update steps, for example, in three steps to each 5% per step.

Updating the calibrated mapping rule 3 may save the entire relate to calibrated mapping rule 3, d. H. there is an update the calibrated mapping rule 3 for all engine parameters. alternative However, it may just be an update of that part of be performed calibrated mapping rule 3, the motor parameters of the correspond stationary operation state.

After updating the calibration mapping rule that is Calibration of the preset signal stops and the process returns to its Initial state back. If to determine the steady state in Step 26 is using a timer, this will be before returning to the Initial state reset.

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. In a software solution, for example, the following algorithm can be used:

Claims (14)

Method for presetting the fresh air supply throttling in an internal combustion engine, which is equipped with a control circuit for regulating the throttling of the fresh air air supply, wherein a control signal (u_fb) of the control loop is combined with a presetting signal (u_ff) to a throttling signal adjusting the throttling (u),
characterized in that
a calibration of the preset signal (u_ff) based on the control signal (u_fb) takes place. Method according to claim 1,
characterized in that
the calibration of the presetting signal is repeated on the basis of the actuating signal. Method according to claim 1 or 2,
characterized in that
the calibration takes place on the basis of a correction term determined from the actuating signal (u_ff) and the presetting signal (u_ff). Method according to claim 3,
characterized in that
the correction term is determined on the basis of an offset (ff_offset) to be added to the presetting signal (u_ff) and based on the actuating signal (u_fb). Method according to claim 4,
characterized in that
the offset is defined by
the value of the control signal (u_fb) less a positive limit value (α), if the value of the control signal (u_fb) is greater than the limit value (α), by the value of the control signal (u_fb) plus the limit value (a) if the value of the control signal (u_fb) is less than the negative of the limit value (α), and by the value zero, if the magnitude of the control signal (u_fb) is less than or equal to the limit value (α). Method according to claim 4 or 5,
characterized in that
the correction term is given by the offset (ff_offset). Method according to claim 4 or 5,
characterized in that
Correction term is given by a fraction of the offset (ff_offset) and that the calibration takes place in several calibration steps corresponding to the number of fractions. Method according to one of claims 1 to 7,
characterized in that
before calibrating the presetting signal (u_ff), a check is made as to whether the control loop is in a stationary operating state and the calibration of the presetting signal (u_ff) takes place only when a stationary operating state of the control loop is detected. Method according to one of claims 1 to 8,
characterized in that
the determination of the presetting signal (u_ff) takes place on the basis of a mapping rule which delivers 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 to calibrate the presetting signal (u_ff). Method according to claim 9,
characterized in that
to calibrate an updating of the mapping rule for all engine parameters is done. Method according to claim 8 and claim 9,
characterized in that
for calibration, an updating of that part of the mapping rule is carried out whose motor parameters correspond to the stationary operating state. Method for regenerating a particulate filter in the exhaust system of an internal combustion engine while increasing the exhaust gas temperature by throttling the fresh air supply to the internal combustion engine,
characterized in that
presetting the fresh air supply throttling according to one of the preceding claims Internal combustion engine with a throttling device for throttling the fresh air supply, a control circuit which is designed to output a control signal (u_fb) for regulating 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 air supply, and a combination unit which is designed to generate a throttling adjusting throttle signal (u) based on a combination of the preset signal (u_ff) with the actuating signal (u_fb), characterized by a calibration unit for calibrating the preset signal (u_ff) configured to carry out the method for presetting the fresh air supply restriction according to any one of claims 1 to 11. Internal combustion engine according to claim 13, further comprising a in Exhaust system arranged particulate filter and a regeneration device for regenerating the particulate filter according to the method according to claim 12.

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