KR101201995B1 - A method for controlling an internal combustion engine - Google Patents

Abstract

The present invention relates to a method for controlling an internal combustion engine having at least two cylinders in the case of irregular operation caused by combustion problems, the method comprising the following steps: a first time of operation of the internal combustion engine Measuring a segment time of the first cylinder during the interval T1 (100), transmitting a corresponding first signal as a first actual value to the controller (300), a second time interval of the operation of the internal combustion engine ( Detecting a pressure change in the second cylinder during T2) (200), transmitting a corresponding second signal as a second actual value to the controller (400), and wherein the first and second actual values are respectively transmitted to the controller. Varying (500) operating parameters (600) of one or more cylinders by the controller based on the first and second signals when deviating from the stored setpoint value.

Description

A method for controlling an internal combustion engine {A METHOD FOR CONTROLLING AN INTERNAL COMBUSTION ENGINE}

The present invention relates to a method for controlling an internal combustion engine having at least one cylinder in case of irregular operation caused by combustion problems.

The combustion problem in an internal combustion engine may for example be the occurrence of so-called knocking combustion. With knocking combustion, ignition of the fuel / air mixture normally occurs first through sparking of the spark plugs, and a flame front is formed in a conventional manner. In general, the high temperature and pressure increase in the cylinder may allow self-ignition to occur at different points of the cylinder with the creation of the second flame front, which is overheated in an undesired manner. The two flame fronts can then collide with each other and cause a unique knocking noise.

In the case of undesired excessive heating of the cylinder, so-called ignition by premature ignition or hot flash can occur, which initiates ignition in an undesired way before the actual ignition point. Another combustion problem, premature ignition, can have a more destructive effect than knocking combustion, because premature ignition causes the temperature in the piston head to rise too high, thereby reaching the melting point of the piston material after a few seconds and thus causing the piston to Can be destroyed. In the case of premature ignition, the ignition point can no longer be controlled by the engine controller. Parts that undergo excessive heating in this manner include discharge valves, spark plugs, sealing parts and surfaces surrounding the combustion chamber and deposits on these parts.

To prevent the occurrence of combustion problems, for example knocking combustion, for example, publication DE 10 2006 015 662 A1 has proposed the use of so-called knock sensors to detect noise in internal combustion engines, in which case each combustion Noise to the cycle forms a cylinder-individual signal. Thereby, when there is knocking due to premature ignition, i.e. when the current signal value for such a cylinder exceeds a predetermined setpoint value, the monitored cylinder is switched off, i.e. for example fuel supply to this cylinder. This is stopped.

In addition, the combustion problem can manifest itself in a change in the so-called segment time of the crankshaft. Segment time describes the time required by the crankshaft during the working cycle of the individual cylinders to pass a predetermined angle.

For example, in publication DE 19544720 C1, the measurement of segment time for the detection of irregular operation is described. Here, after the measured segment time is subjected to the measured segment time and to the calibration factor reflecting the mechanical inaccuracy of the rotational speed sensor for the measurement of the segment time, an irregular running value is determined and compared with a predetermined setpoint value. do. Based on this comparison, corresponding changes are then made to the operating parameters of the individual cylinders, thereby suppressing irregular running.

It is known that the disadvantages of the methods described in the prior art are the inability to achieve proper recognition of different forms of combustion problems.

It is therefore an object of the present invention to avoid the disadvantages of the prior art and to provide an improved method for controlling an internal combustion engine having one or more cylinders with irregular operation caused by combustion problems.

This object is met by the features of claim 1.

To this end, the present invention provides a method for the recognition of ignition by hot light emission of a spark-ignition internal combustion engine having at least one cylinder connected to a crankshaft, the method comprising the following steps: Operation of the internal combustion engine Measuring the rotational speed of the crankshaft during the compression cycle of the cylinder during the first time interval T1 of the process, detecting the knock signal during the operating cycle of the cylinder during the second time interval T2 of the operation of the internal combustion engine 200, and recognizing ignition when the rotational speed of the crankshaft is slow compared to the reference value and knocking combustion is perceived based on the knock signal.

To this end, the present invention proposes a method comprising the following steps: measuring a segment time of a first cylinder during a first time interval T1 of an operation of an internal combustion engine, a second of an operation of an internal combustion engine Detecting a knock signal of the second cylinder during the time interval T2, in which the first cylinder precedes the second cylinder in the ignition sequence.

The advantage of the present invention is that in each case based on the cylinder, the measurement of the segment time and the detection of pressure fluctuations provide a relatively reliable recognition of both the combustion problem caused by premature ignition and the combustion problem caused by knocking combustion. Is the point. If there is a deviation from the measurement of the segment time in the time interval T1 and the individual setpoint value with the knock signal in the time interval T2, then during operation of the internal combustion engine, the first time interval T1 is the second time interval. Preceding T2, it can be concluded that there is premature ignition in the second cylinder.

Preferably, the second time interval T2 is divided into a plurality of time intervals, thereby detecting the occurrence of knocking combustion in at least one of the time intervals. Thereby, the start and / or duration of the individual time intervals can be changed.

The following relate to an internal combustion engine having a spark ignition comprising at least two cylinders. In the firing sequence, the first cylinder is ahead of the second cylinder. The internal combustion engine may be a four stroke or two stroke engine. The invention is also applicable to an internal combustion engine having two or more cylinders, for example four, six or eight cylinders.

1 shows a schematic diagram of a pressure curve P with normal combustion in the combustion chamber of the second cylinder according to the crankshaft position in degrees KW. Also, this graph shows the knock sensor signal KS of the conventional knock sensor, and in this example, the knock sensor signal KS extends almost horizontally and flatly because no knocking combustion occurs.

The maximum position of the graph P, ie the maximum pressure in the combustion chamber, consists of the position of the crankshaft immediately after the top dead center (TDC) of the piston movement shown in FIG. 1 by the vertical dashed line.

2 shows a schematic diagram of a pressure curve P with knocking combustion in a second cylinder. The pressure fluctuations formed in the combustion chamber lead to significant pressure fluctuations, which are plotted (superimpose) and recorded by the knock sensor, which results in a vibrational knock sensor signal KS corresponding to the pressure fluctuations.

2 also shows a time interval T2, in which pressure variations in the corresponding combustion chambers are sensed. It is clearly shown that the time interval T2 is chosen such that any knocking or occurring pressure fluctuations during combustion in the second cylinder can be recorded.

3 shows a schematic diagram of a pressure curve P with knocking combustion caused by premature ignition. It is clear here that in FIG. 2 there are a plurality of time intervals T2 ', T2 "replacing the time interval T2, whereby the pressure fluctuations at a relatively initial position in the combustion chamber caused by premature ignition in this way The time interval T2 as shown in Fig. 2 is only recorded at a very late time point. The start and duration of the time intervals T2 ', T2 "can be optionally changed. . The time interval can be arranged before and after the top dead center (TDC) of the second cylinder, preferably after TDC (T2 ") and preferably before (T2 ').

However, in many cases, the early ignition is moved to a much earlier time position relative to the top dead center (TDC), whereby the time gap between the occurrence of the TDC and the early ignition is very large and no pressure fluctuations occur anymore and time The combustion problem caused by knocking combustion from the gap T2, T2 'or T2 "can no longer be recognized.

As a result, it is necessary to find another method for the recognition of combustion problems. This is achieved by measuring the segment time of the first cylinder preceding the second cylinder in the combustion sequence as described, for example, in publication DE 195 44 720 C1. Segment time is to be understood as meaning a defined angular degree, ie the temporal duration required by the crankshaft to rotate by a predetermined segment. In the case of a six-cylinder four-stroke internal combustion engine, the cylinder segment may for example be 120 °. The segment time of the cylinder is the time required by the crankshaft to cover a fixed 120 °. The cylinder segment may for example be a work cycle, which is the combustion cycle of the individual cylinders where the aspirated fuel is burned. The cylinder segments of the individual cylinders are assigned to the individual cylinders and are formed by corresponding markings on the crankshaft. In the event that premature ignition occurs in the compression cycle of the second cylinder n, the segment time of the first cylinder changes, allowing the premature ignition to occur quite early with respect to the crankshaft position and a change to the segment time. May be related to the cylinder n-1 which is temporarily in front of the cylinder which is a problem in the combustion sequence. However, in order, to accurately recognize the occurrence of premature ignition, a change to the segment time must be specified for the second cylinder n. Thus, the time interval T1 is set in the compression cycle of the second cylinder n, during which the theoretical angles (set point values) covered by the angular distances (actual values) actually covered by the crankshaft are covered. Are compared. This is measured using, for example, the segment time of the first cylinder during the combustion cycle of the first cylinder. If premature ignition occurs, the piston of the first cylinder is braked during the combustion cycle by premature ignition in the induction cycle of the second cylinder, thus resulting in an extended segment time for the first cylinder. Since the deviation of the segment time from the set point may contribute to the mechanical error, since the changed segment time is not an integral proof of the occurrence of premature ignition independently, the additional condition used for the occurrence of premature ignition is It may be the occurrence of knocking combustion in the combustion process, whereby knocking combustion at the changed segment time and time interval T2 (or T2 ', T2 ") at time interval T1 since premature ignition and knocking combustion are dependent on each other. It is possible to determine that there is an early ignition for combustion in the second cylinder when all are recorded, instead of evaluating the segment time of the first cylinder, it is possible to evaluate the rotational speed of the crankshaft in the compression cycle of the second cylinder. In the case of ignition by high temperature incident light, the rotation speed of the crankshaft is set to Is reduced by the predetermined value to be compared with the bit values using the segment time of the first cylinder, it has the advantage that this information is available and by monitoring for the fire ignition times has already been acquired in the control device.

4 schematically shows a method according to the invention in the form of a flow routine. Corresponding to the measurement of the segment time of the first cylinder in the time interval T1 caused by premature ignition or the detection of the pressure fluctuation in the time interval T2 caused by knocking combustion in the second cylinder 100, 200. , The corresponding first and second signals are recorded. In step 300 or 400, the first or second signal is output and optionally stored as a first or second actual value for the controller, in which case they are the corresponding set points stored in the controller in step 500. The values are compared. The set point value corresponds to the segment time of the first cylinder with normal combustion in the second cylinder and to the knock signal with normal combustion in the second cylinder. If there is no deviation from the set point value, return to the beginning of the routine of steps 100 and 200. If there is a deviation from the set point value, the operating parameters of the cylinder in question are correspondingly changed in step 600, in which case the change in the operating parameters is interrupted to the fuel supply, reduced boost pressure, fresh -Reduction in gas filling or cooling of the corresponding cylinder by fuel, thereby eliminating irregular running caused by combustion problems.

Early ignition may occur in the compression cycle of the first cylinder, thus resulting in a decrease in the speed of the cylinder. Ignition by hot light emission may occur well before the ignition point of the first cylinder. For example, the speed reduction is noticed from the longer segment time of the first cylinder preceding the second cylinder in ignition.

If knocking combustion for the second cylinder is now recognized and the extended segment time is measured for the first cylinder, this is evidence of ignition by hot flash for combustion in the second cylinder.

According to the selected embodiment, if knocking combustion for the second cylinder is perceived both in the time interval after the TDC and in the time interval before the TDC, ignition by hot light emission is recognized. Thereby, different thresholds for perception of knocking combustion can be used for the time interval before the TDC and the time interval after the TDC.

According to this embodiment, different thresholds may be used for the recognition of extended segment time. For example, the lower the threshold for recognition of knocking combustion, the longer the extension time and thereby the segment time must be extended, which is evidence of ignition by high temperature light emission called premature ignition.

The following describes the invention with reference to the drawings.

1 is a schematic diagram of a pressure curve with normal combustion in a combustion chamber depending on the crankshaft position.

2 is a schematic diagram of a pressure curve with knocking combustion in the combustion chamber according to the crankshaft position.

3 is a schematic diagram of a pressure curve with knocking combustion generated by premature ignition in the combustion chamber according to the crankshaft position.

4 is a schematic diagram of a method according to the invention.

Claims (7)

A method of detecting ignition by incandescent in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft, Measuring the rotational speed of the crankshaft during the compression cycle of the cylinder within a first time interval T1 of the operation of the internal combustion engine, Detecting a knock signal during the working cycle of the cylinder in the second time interval T2 of the operation of the internal combustion engine (200), and -Recognizing ignition by hot light emission of the cylinder when the rotational speed of the crankshaft is slow compared to a reference value and knocking combustion is perceived based on the knock signal. A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft. The method of claim 1, The internal combustion engine comprises two or more cylinders, In the ignition sequence, the first cylinder precedes the second cylinder, Measuring (100) the segment time of the working cycle of the first cylinder within a first time interval T1 during the compression cycle of the second cylinder, and Detecting a knock signal during the working cycle of the second cylinder within a second time interval T2, Recognizing ignition by high temperature light emission of the second cylinder when the segment time of the working cycle of the first cylinder is extended compared to the reference value and when knocking combustion is recognized in the second cylinder based on the knock signal, A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft. The method of claim 1, Knocking is perceived when the knock signal is above a predetermined threshold, A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft. The method of claim 2, When the segment time of the working cycle of the first cylinder is extended by a predetermined time interval compared to the set point value, the ignition by the high temperature light emission is recognized, A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft. The method of claim 2, The second time interval T2 is divided into a plurality of time intervals T2 ', T2 ", ..., and at least one of the plurality of time intervals T2', T2", ... A time interval exists before the top dead center of the second cylinder, and a time interval of one of the plurality of time intervals T2 ', T2 ", ... exists after the top dead center of the second cylinder, A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft. The method according to any one of claims 2, 4 and 5, The method for recognizing ignition by hot flashing further comprises changing 600 an operating parameter for the second in-cylinder combustion process, In the case of an internal combustion engine having a plurality of cylinders, measuring the segment time (100), detecting a pressure change to detect the knock signal (200), and changing the operating parameter (600), Performed individually for each cylinder, A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft. The method of claim 6, Varying the operating parameter 600 Reduction or interruption of fuel supply to the second cylinder, reduction of boost pressure in the second cylinder, reduction of fresh-gas filling of the second cylinder, and current operating point of the internal combustion engine At least one of cooling the second cylinder by increased fuel supply in comparison with A method of recognizing ignition by hot light emission in a spark-ignition internal combustion engine having one or more cylinders connected to a crankshaft.

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