DE102019110108A1 - Method for operating an internal combustion engine and engine control device - Google Patents

Abstract

A method for operating an internal combustion engine is provided in which, in the event that knocking in a cylinder of the internal combustion engine is detected (12), an ignition point for the cylinder is shifted (16) to a later point in time by a predefined standard value (18) determines whether an increase in cooling of the cylinder and / or a fuel / air mixture fed into the cylinder is possible, and in the event that the increase in cooling is possible, a cooling output for cooling by a predefined output increment is increased (20) and essentially at the same time an ignition point for the cylinder is shifted by a predefined ignition angle increment to an earlier point in time (22). The safety-oriented shift (16) of the ignition point at a later point in time by the standard value is at least partially reversed in the case of additional cooling by the ignition angle increment in order to be able to limit the shift of the ignition angle to the extent necessary to avoid knocking, see above that an efficient operation of an internal combustion engine with little knock is made possible.

Description

The invention relates to a method for operating an internal combustion engine and an engine control device with the aid of which knocking in a cylinder of the internal combustion engine of a motor vehicle can be avoided.

In order to achieve the highest possible efficiency in an internal combustion engine, the maximum cylinder pressure during the combustion of a fuel / air mixture in the cylinder should be shortly after top dead center. In particular, if the internal combustion engine has a high demand and / or the ignition point is too early, an unfavorable ignition of the fuel / air mixture in the cylinder can occur, which leads to a behavior of the cylinder known as “knocking”, in which, for example, audible high-frequency vibrations in the Cylinder pressure curve occur, which can lead to damage.

Out EP 2 700 804 A1 It is known to inject water into the cylinder when knocking occurs in a cylinder of an internal combustion engine of a motor vehicle and / or to postpone an ignition point for the cylinder to a later point in time.

There is a constant need to operate an internal combustion engine with a high degree of efficiency and essentially knock-free.

It is the object of the invention to indicate measures which enable an efficient operation of an internal combustion engine with little knocking.

The object is achieved according to the invention by a method with the features of claim 1 and a motor control device with the features of claim 10. Preferred embodiments of the invention are specified in the dependent claims and the following description, each of which individually or in combination represent an aspect of the invention can.

According to the invention a method for operating an internal combustion engine is provided in which, in the event that knocking is detected in a cylinder of the internal combustion engine, an ignition point for the cylinder is shifted by a predefined standard value to a later point in time, it is checked whether an increase in a Cooling of the cylinder and / or a fuel / air mixture conducted into the cylinder is possible, and in the event that the increase in cooling is possible, a cooling power for the cooling is increased by a predefined power increment and essentially simultaneously an ignition point for the Cylinder is shifted by a predefined ignition angle increment to an earlier point in time.

By shifting the ignition point to a later point in time, knocking can usually be prevented well. The crankshaft angle can be used as a predefined standard value by an amount ΔKW ⁺ of 0.5 ° ΔKW ⁺ 5.0 °, in particular 1.5 ° ΔKW ⁺ 4.5 ° and preferably ΔKW ⁺ 3.0 ± 0.5 ° can be shifted to a later point in time, the predefined standard value preferably being selected differently depending on the current operating behavior of the motor vehicle engine. As a result, a higher standard value can be selected for an operating point considered to be critical and a lower standard value can be selected for carrying out the method in an operating point considered less critical. However, this also allows the maximum cylinder pressure during combustion to be shifted at a later point in time, which is further away from top dead center, as a result of which the efficiency is reduced and the efficiency of the operation of the internal combustion engine of a motor vehicle decreases. This can be at least partially compensated for by increasing the cooling capacity. In this case, use is made of the knowledge that at the moment in which the cooling capacity is increased, the predefined standard value for the standard shift in the ignition time to a later point in time may be too large. The predefined standard value is dimensioned in particular for the case that further cooling is not possible, so that knocking can be safely eliminated as quickly as possible. However, if further cooling is still possible, the cooling can make a contribution to preventing knocking, this contribution making it possible to shift the ignition time to an earlier point in time, which correlates with this contribution. The actually provided shift of the ignition point in time by the predefined standard value at a later point in time is at least partially reversed in the event that the cooling has been increased by the predefined ignition angle increment. As a result, the ignition angle can only be shifted at a later point in time as is absolutely necessary taking into account the effect of the increased cooling. The safety-oriented shift of the ignition point at a later point in time by the standard value is at least partially reversed in the case of additional cooling by the ignition angle increment in order to be able to limit the shift of the ignition angle to the extent necessary to avoid knocking, so that more efficient Operation of an internal combustion engine with little knock is made possible.

The increase in the cooling capacity can in particular be carried out without a stored correction data field. As a result, it is not necessary to correct and / or use an ignition map, thereby regulating the ignition point and / or the cooling capacity can take place quickly. This can reduce the number of knocking events occurring in the cylinder. In addition, it is also possible to use fuels that have a lower knock resistance, for example fuels with an octane rating of less than 98 RON. Since knocking is at least partially avoided by increasing the cooling capacity and thus less or even not at all due to a shift in the ignition point, Knocking can be prevented with almost no significant reduction in the performance of the internal combustion engine.

The increase in the cooling capacity can in particular take place as a function of the selected predefined ignition angle increment, which is preferably selected differently as a function of the current operating behavior of the motor vehicle engine. Depending on the current operating behavior of the motor vehicle engine, an amount ΔKW ^- of 0.5 ° ΔKW ^- 4.0 °, in particular 1.0 ° ΔKW ^- 3.0 ° and preferably ΔKW ^- 2 can be used for the predefined ignition angle increment , 0 ± 0.5 ° can be specified. The amount ΔKW ^{- of} the predefined ignition angle increment to shift the ignition point to an earlier point in time by a difference amount of at least 0.5 ° smaller than the amount ΔKW ^{+ of} the predefined standard value to shift the ignition point to a later point in time is particularly preferred. The shifting of the ignition point to an earlier point in time can in particular take place in several partial steps, as long as the cooling capacity can still be increased. To increase the cooling capacity, in particular the flow rate of the coolant can be increased by 3% to 10%, in particular by 4% to 7% and preferably by 5% ± 0.5%, based on the maximum flow rate at the selected ignition angle increment. This enables the available maximum possible increase in the flow rate to be used moderately for shifting the ignition point to an earlier point in time without fear of an unstable overshoot of the regulation of the ignition point with the aid of the adaptation of the cooling output. The increase in the flow rate and the shift of the ignition point in time to an earlier point in time can in particular be repeated several times in order to control an operating point which is particularly close to the knock limit.

In particular, in the event that knocking is still detected in the cylinder, the steps shifting the ignition timing for the cylinder by the predefined standard value to a later point in time, checking whether an increase in cooling of the cylinder and / or that in the cylinder guided fuel / air mixture is possible, and in the event that the increase in cooling is possible, increasing the cooling power for the cooling by the predefined power increment and essentially simultaneously shifting the ignition timing for the cylinder by the predefined ignition angle increment earlier time repeated. If the previous control intervention is not sufficient to prevent knocking, the ignition timing can be shifted again. If an increase in the cooling output is still possible in this loop pass, the cooling output can be increased again and the shift in the ignition angle by the ignition angle increment can be reversed. If an increase in the cooling capacity is not possible, for example because a maximum cooling capacity provided for this purpose has already been reached, the ignition angle remains shifted by the standard value without partial compensation being undertaken. The multiple pass makes it possible to provide smaller amounts for the standard value as well as for the predefined power increment of the increase in the cooling power and the ignition angle increment correlating with the power increment, so that a correspondingly finer regulation is possible. The internal combustion engine can thus be operated particularly close to the knock limit, so that the maximum cylinder pressure during combustion can be present as soon as possible after top dead center.

In the event that knocking is no longer detected in the cylinder, the cooling capacity is preferably reduced. In particular, the previously shifted ignition point is retained when reducing the cooling capacity. When the knocking that has occurred has disappeared again, the cooling power can first be reduced in order to reduce an unnecessarily high flow rate of a coolant, in particular water. As a result, a pump output for delivering the coolant can be reduced. An improvement in the situation that led to the knocking can initially be used by a sudden or gradual reduction of the cooling capacity to the original value before the knocking. For example, the cooling carried out over a certain period of time may have resulted in a temperature of an inner wall of the cylinder being reduced sustainably, as a result of which the risk of knocking has also been sustainably reduced in the subsequent operation. The increased cooling capacity is no longer required in this situation.

It is particularly preferred that all the increases in the cooling capacity that have previously been made are withdrawn simultaneously. The energy consumption required to increase the cooling capacity can be reduced particularly quickly as a result. This is particularly useful if the increased cooling capacity is maintained for a rather longer period of time before the cooling capacity can be reduced.

In a further embodiment, the cooling output is reduced by the predefined output increment in each case until knocking is detected again in the cylinder or all previous increases in cooling output have been withdrawn. The cooling capacity can thereby be reduced to the same extent as it was previously increased. This makes it easier to regulate an optimal value for the cooling capacity at which the internal combustion engine can be operated particularly close to the knock limit. This is particularly useful if the increased cooling capacity is maintained for a rather shorter period of time before the cooling capacity can be reduced.

In particular, a predefined waiting time is waited for before the cooling capacity is reduced. It can thereby be ensured that the increase in the cooling capacity can achieve an effect in the cylinder. It can be taken into account here that the increase in the cooling capacity can only influence the situation in the cylinder with a certain dead time and with a more integral control behavior. An unstable oscillation of a control loop implemented with the aid of the method can thereby be avoided. The waiting time can be selected in particular as a function of the operating point and / or the operating behavior and / or the outside temperature or other influencing factors. For example, a longer waiting time can be specified for operation at an operating point that is considered to be critical and a shorter waiting time at an operating point that is considered to be less critical. A suitable waiting time t can for example be 0.05 s t 1.0 s, in particular 0.1 s t 0.7 s, preferably 0.2 s t 0.5 s and particularly preferably t = 0, 3 s ± 0.05 s.

Preferably, after all previous increases in the cooling capacity have been withdrawn, the ignition point for the cylinder is shifted to an earlier point in time. An improvement in combustion also achieved through the previously increased cooling capacity in the cylinder can be used by shifting the ignition point at an earlier point in time. The internal combustion engine can thus be operated particularly close to the knock limit. If knocking is detected at an earlier point in time during the shift in the ignition point, the method can be started again.

Particularly preferably, the ignition point for the cylinder is shifted to an earlier point in time until a predefined starting value for the ignition point is reached or a knocking in the cylinder is detected. A shift in the ignition point beyond the originally provided, possibly speed-dependent and / or load-dependent output value is thereby avoided. In spite of shifting the ignition timing to an earlier point in time, knocking can be avoided.

In particular, in order to increase the cooling, in particular exclusively, a water rate of a charge air cooler is increased. By increasing the water rate of the charge air cooler, the cooling capacity of the charge air cooler can be increased accordingly. As a result, the temperature of the fuel / air mixture entering the cylinder can be reduced, whereby knocking can already be avoided. The coolant used for the intercooler, in particular water, can be part of a closed cooling circuit, so that the water is not consumed when the cooling is increased, in contrast to water injection into the cylinder. The coolant of the charge air cooler can be cooled, for example, via an air-cooled front cooler.

The invention also relates to an engine control device for operating an internal combustion engine with means for executing the method, which can be designed and developed as described above. The safety-oriented shift of the ignition point at a later point in time by the standard value with the help of the engine control device is at least partially reversed in the case of additional cooling by the ignition angle increment, in order to be able to limit the shift of the ignition angle to the extent necessary to avoid knocking, so that an efficient operation of an internal combustion engine with little knock is made possible. The engine control device can in particular be connected to a knock sensor for detecting knocking in the cylinder. In addition, the engine control device can be connected to a feed pump for setting a cooling capacity for cooling the cylinder and / or for cooling a fuel / air mixture for the cylinder, the feed pump in particular being part of a closed cooling circuit for operating a charge air cooler. The engine control device can also be connected to an adjusting device for controlling an ignition point in the cylinder. In particular, a flow meter for the mass flow delivered by the feed pump is connected to the motor control so that the motor control device can check whether the maximum intended cooling capacity has already been set and whether an increase in the cooling capacity is still possible at all. In addition, it is possible that in the engine control device, possibly variable values for the predefined standard value for shifting the ignition point in time to a later point in time, the predefined power increment for increasing the cooling and the predefined Ignition angle increments for shifting the ignition point to an earlier point in time are stored.

• 1: eine schematische Darstellung eines Regelkreises für ein Verfahren zum Betrieb eins Verbrennungsmotors.

In the following, the invention is explained by way of example with reference to the attached drawing using a preferred exemplary embodiment, the features shown below being able to represent an aspect of the invention both individually and in combination. It shows:

• 1 : a schematic representation of a control loop for a method for operating an internal combustion engine.

The in 1 shown control loop 10 an engine control device has an initial check carried out with the aid of a knock sensor 12 on whether knocking occurs in a monitored cylinder of an internal combustion engine of a motor vehicle. If no knocking is detected, the control loop will do so 10 The illustrated procedure is not triggered and the engine control provided for normal operation remains. When the initial review 12 has shown that there is knocking, is in the control loop 10 a first loop 14th go through, in which first a shift 16 of an ignition point in time to a later point in time by a predefined standard value, in that an ignition angle for the ignition point for igniting the fuel / air mixture introduced into the monitored is shifted closer to top dead center.

A review is then carried out 18th whether the cooling of the cylinder and / or the fuel / air mixture can be increased. If this is the case, because, for example, a maximum provided water rate for a charge air cooler has not yet been reached, an increase follows 20th the cooling capacity by a predefined capacity increment, with also a shift 22nd of the ignition point at an earlier point in time by a predefined ignition angle increment that correlates with the predefined power increment. An ignition point shifted by the standard value without taking into account a knock avoidance effect achieved by the cooling can be at least partially reversed by the predefined ignition angle increment that correlates with the predefined power increment, so that an unnecessarily large shift in the ignition point is avoided. When the review 18th that results in an increase 20th the cooling capacity is no longer possible, the process steps are increasing 20th the cooling capacity and the displacement 22nd of the ignition point skipped by the ignition angle increment, so that it is at the shift 16 of the ignition point remains around the standard value to a later point in time.

A new check is then carried out 24 whether the knocking in the cylinder is still present. If it does, it does the first loop 14th done again by repeating the shift 16 of the ignition point takes place at a later point in time by the standard value and, if necessary, the increase again 20th the cooling capacity and the simultaneous shift 22nd of the ignition timing is carried out at an earlier point in time by the ignition angle increment.

When re-checking 24 if there is no knocking in the cylinder, a predefined waiting time is awaited and then a reduction 26th the previously increased cooling capacity. Another check then takes place 28 whether there is knocking. If this is not the case, termination may occur 30th of the procedure and return to normal operation. In this case, the adjustment of the ignition point can be left to the regular standard engine control. If the further review 28 however, if knocking is still present, a second loop formed thereby 32 the procedure with the start of the first loop 14th be carried out again. In this case it may be the reduction 26th the cooling performance was carried out too early and / or too strong and the cooling performance by running through the first loop 14th is regulated again to a suitable value at which the knocking disappears again.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• EP 2700804 A1 [0003]

Claims (10)

Method for operating an internal combustion engine, in which in the event that knocking is detected in a cylinder of the internal combustion engine (12), an ignition point for the cylinder is shifted by a predefined standard value to a later point in time (16), it is checked (18) whether an increase in cooling of the cylinder and / or a fuel / air mixture fed into the cylinder is possible, and In the event that the increase in cooling is possible, a cooling capacity for the cooling is increased by a predefined capacity increment (20) and an ignition point for the cylinder is shifted to an earlier point in time (22) essentially at the same time by a predefined ignition angle increment. Procedure according to Claim 1 , in which, in the event that knocking is still detected (24) in the cylinder, the steps of shifting (16) the ignition timing for the cylinder by the predefined standard value at a later point in time, checking (18) whether an increase in a Cooling of the cylinder and / or the fuel / air mixture guided into the cylinder is possible, and in the event that the increase in cooling is possible, increasing (20) the cooling power for the cooling by the predefined power increment and essentially shifting it simultaneously (22) of the ignition point for the cylinder can be repeated at an earlier point in time by the predefined ignition angle increment. Procedure according to Claim 1 or 2 , in which, in the event that knocking in the cylinder is no longer detected (24), the cooling capacity is reduced (26). Procedure according to Claim 3 , in which all previously made increases in cooling capacity are withdrawn at the same time. Procedure according to Claim 3 , in which the cooling capacity is reduced (26) by the predefined capacity increment in each case until a knocking in the cylinder is detected again (28) or all previous increases in the cooling capacity are canceled. Method according to one of the Claims 3 to 5 , during which a predefined waiting time is awaited before a reduction (26) of the cooling capacity is carried out. Method according to one of the Claims 3 to 6 , in which, after all previously made increases in the cooling capacity have been withdrawn, the ignition point for the cylinder is shifted to an earlier point in time. Procedure according to Claim 7 , in which the ignition point for the cylinder is shifted to an earlier point in time until a predefined output value for the ignition point is reached or a knocking is detected in the cylinder. Method according to one of the Claims 1 to 8th , in which for the increase (20) of the cooling, in particular exclusively, a water rate of a charge air cooler is increased. Motor control device for operating an internal combustion engine with means for carrying out the method according to one of the Claims 1 to 9 .

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