DE4205888C2 - Cylinder-selective knock control of a spark-ignited internal combustion engine - Google Patents

Description

The invention relates to a cylinder-selective knock control a spark ignition internal combustion engine according to the generic term of claim 1.

For the optimized operation of a spark ignition internal combustion engine machine it is necessary to depend on the ignition timing speed and load. It is known in a map of an electronic engine control device Map specifications depending on the speed and load put out for a current ignition timing will read.

Another well-known optimization regarding a gerin fuel consumption and low pollutant emissions is achieved in that the internal combustion engine in the higher Load range is operated close to the knock limit. The location The knock limit depends on operating parameters, in particular fuel quality, temperature and air pressure and it is known to perform knock control.

In a known method for knock detection (DE 40 06 992 A1) a knock sensor output signal becomes a peak Signal and an average signal with a threshold ver like. The comparison is made in a knock determining element Result evaluated and determined whether a knock before lies.  

In a known knock control (DE 40 01 474 A1) the Occurrence of knocking events from the stored code Map field readout field by one rule each step to a control stroke to a value for a current one Ignition timing in the direction of late ignition withdrawn. At the If there are no knock events, the value for the current ignition timing step by step towards Early ignition is attributed to the map specification. A such short-term regulation is of additional sluggishness here long-term regulation overlaid.

In addition, the under are for further optimization different conditions on the individual cylinders visible and the knock control carried out cylinder-selectively. There are the knock events and a corresponding Control stroke determined for each individual cylinder.

Such a cylinder-selective knock control exists a possible source of error in that noise, e.g. B. by a valve noise of an incorrectly working Hydraulic tappet, fake knocking events and the rule electronics that are actually not available are available. This will cause the affected cylinder Control stroke constantly increased and thus the ignition angle in the direction Late ignition may be withdrawn until it stops. An opti Male adjustment and regulation is no longer possible, what however not according to the actual circumstances would be required.

Another accident can occur in that at a cylinder-selective knock control for a specific cylin which, for example due to a larger noise spectrum, knockers in a cylinder are not recognized. For such a "deaf" cylinder will actually occur knock events the ignition angle caused by the knocking rain not withdrawn. The affected cylinder is thus operated in a danger zone where damage is caused by mechanical overload with the risk of destruction  stands.

It is also known to provide a plurality of knock sensors on internal combustion engines with a plurality of cylinders; e.g. B. for an internal combustion engine with six cylinders to use a first knock sensor for cylinders 1 to 3 and a second knock sensor for cylinders 4 to 6 . If a knock sensor failure is detected, it has been customary to retract the ignition angle for the cylinders affected by the failure of a knock sensor to a predetermined stop for safety reasons to protect the internal combustion engine in a type of emergency operation knock control. Knock control and adjustment of the ignition angle of the affected cylinders for optimization is no longer possible.

In a similar known method (DE 40 34 523 A1) determined with a cylinder-selective knock control whether knock detection due to interference may be incorrect is. Again, there is a possible incorrect knock Detection in the manner of an emergency run knock control regulation suppressed for the cylinder concerned, so that there is no more optimization.

The object of the invention is a generic Develop knock control so that with cylinder-specific Disorders an at least partially, optimized adjustment of the assigned ignition angle for the person concerned Cylinder remains intact.

This task is carried out with the characteristic features of the contractor spell 1 solved.

According to claim 1, the value of the cylinder-selective is determined th control strokes for a particular cylinder with a Coupling area compared whether this value within this Kop range. The coupling area is made up of one agent value of the control strokes of other cylinders plus a specified one Deviation formed. In the event that the cylinder-selective  determined control stroke of the cylinder under consideration not in the head range, the map specification is not determined by the telten control stroke, but coupled with one with this mean belt coupling stroke for a current ignition timing withdrawn. This comparison is made for each of the cylinders with a coupling area in connection with an average other cylinder performed. The invention lies in the Understanding that the control strokes of the individual cylinders a basic principle for a cylinder-selective knock control have the same behavior, i.e. for example poor fuel quality all cylinder selective rule strokes are relatively large and all cylinder-selective, current Ignition times are relatively far from the map specification lie. The control strokes determined cylinder-selectively can only have a maximum deviation from one another.  

If now in the event of an accident, for example due to a major noise spectrum, a cylinder has become "deaf" is, d. that is, knock events for that cylinder no longer exist would be known, the cylinder-selective knock control would Do not retard the ignition timing so that this cylinder in an area at high risk of overload would practice. According to the invention, however, it is now recognized that at the determined control stroke of a "deaf" cylinder not in the head pel range, based on other cylinders, so that then not for the knock control of this cylinder Control stroke (this would be the rule for a completely deaf cylinder stroke equals zero), but a coupling control stroke is used, which is based on the average of the control strokes of other cylinders and with a change in this mean, too is changed so that even for a deaf cylinder largely optimized knock control outside of a hazard zone is feasible.

In the opposite case, if for a particular cylinder Knocking events are determined by noise, e.g. B. due to valve noise when the Hydro is not working correctly pestle, which actually did not occur, becomes the withdrawn further than necessary. In the worst Traps become very many knockers that actually do not exist events determined, causing the ignition for this cylinder reduced to a lower, maximum control stop would. According to the invention, however, it is also recognized here that the Control stroke for this incident on a cylinder outside the to the other cylinders related coupling area and therefore for a largely optimized, further knock control this cylinder whose control stroke as a coupling control stroke to the Average from other cylinders is coupled.

As a coupling control stroke if the control stroke of the cylinder under consideration that is not in the coupling area, then the formed one could Mean or the mean plus a certain, pre-determined given size and allowable for the internal combustion engine be applied. However, is advantageous according to claim 2  Value of the coupling control stroke of a limit of the coupling area equated. According to claim 3 is then the over step through the coupling area through the considered control stroke in the "late" direction, the "late limit" as the value for the paddock control stroke output. This would be the case if by one Incident for a cylinder, the control stroke in the "late" direction runs away incorrectly. In the event of a deviation in the control stroke over the coupling area in the direction of "early" would then "Early limit" of the coupling area as the coupling control stroke give.

According to claim 4, the coupling area is thus a kind of fen most around the mean, with a maximum Ab softening around the mean, as with an order proper operation as a deviation for the control stroke considered towards "late" and towards "early".

Especially in the event that the limits of the coupling area are also output as coupling control strokes, d. H. each one considered control stroke when the coupling belt is exceeded depending on its borders, it can vary depending on Conditions to be advantageous, a smaller deviation in Approval "early" than direction "late", because in Rich tion "early" is the critical area for overload.

When considering a particular cylinder, according to An Proposition 6 for a suitable averaging the control strokes of all other cylinders. This will on the one hand one for a comparison and detecting a malfunction coupling area applicable to the detection of knocking events formed and on the other hand this one cylinder in the event of a fault the mean value formed by all other cylinders couples.

When executing a generic, cylinder-selective ven knock control with several known knock sensors ren, a knock sensor are multiple cylinders for one assigned cylinder-selective detection of knock events,  the failure of a knock sensor being processed direction is recognizable. Previously, if a sol knock sensor the control strokes for the cylinders concerned for security reasons at most to a non-optimized loading be richly reduced. According to claim 5 is now under Proposed use of the basic idea according to the invention if a knock sensor fails, a coupling to the center value of the control strokes of the intact knock sensor (s) orderly cylinders. Overall, the Brenn engine even with certain disturbances in the detection system for the knocking events further in one for the burning engine harmless and uncritical and largely still optimized ignition angle range operated.

The invention is explained in more detail with reference to a drawing.

Show it

Fig. 1 is a diagram showing the position of the knock limit in Depending ness of the load and of the ignition angle,

Fig. 2 is a diagram illustrating the proper function of a cylinder-selective knock control for one cylinder,

Figure 3 is a diagram showing strokes, the averaging of the rule illustrates the other cylinder.,

Fig. 4 is a diagram showing the coupling of a faulty control for one cylinder to the control of the other cylinder and

Fig. 5 is an illustration for the coupling in the event of a knock sensor failure.

In Fig. 1, the dependence of the torque of the ignition timing adjustment α _z indicated. At low load, curve 1 is relatively flat and knock limit 2 is far from the maximum of curve 1 . The internal combustion engine is expediently operated at point 3 , ie at maximum, with no knocking burns occurring.

The curve 4 represents approximately the half-load range, is more curved and the knock limit 2 has moved closer to the maximum point 5 , in which the internal combustion engine is operated optimally.

Curve 6 represents the full-load range, knock limit 2 being before the maximum, ie knock events are to be expected in the region between curves 4 and 6 with optimized operation, so that the knock control is active in this area in particular. On the curve 6 , the optimal operating point 7 is located , which is just before the knock limit 2 . The double arrow 8 is intended to indicate the approach of the current ignition timing at this point 7 with the help of the knock control.

In the diagram in FIG. 2, the value of the ignition angle α _{z is} plotted with the direction of early ignition over the time axis pointing to the right. The horizontally running, dashed line corresponds to a map specification α _v for the ignition timing from a stored map at a specific operating point for a first cylinder (cylinder 1 ). This map specification α _v is selected so that the internal combustion engine or the cylinder 1 is operated under normal operating conditions close to the knock limit and thus knocking events can occur occasionally. This state is shown in the time interval a, where with the help of the knock control known per se, this map specification when knocking events occur (K) by one step (late correction value SK) on a control stroke for a current ignition point (represented by the curve 9 ) is withdrawn towards "late". If there is a further lack of knockers, the value for the current ignition point is then brought back one step (early correction value FK) in the direction of early ignition to the characteristic map specification α _v .

Due to changes in operating parameters, for example after refueling and gradual mixing with a poorer quality fuel, knocking events occur more and more in the time interval b. Thus, the current ignition times (curve 9 ) are successively moved further away from the original map specification α _v in the "late" direction (arrow 10 ). The knock control then levels off again at a lower level, as is shown in the time interval c.

A current control stroke R _h1 for the cylinder 1 under consideration is shown in FIG. 2. This control stroke R _h1 is compared with a coupling area KB (see FIG. 4) to determine whether its value is still within this coupling area KB.

The position of the coupling area KB is variable overall and is determined by the position of the mean value _h2-6 (in the present exemplary embodiment, a six-cylinder internal combustion engine is assumed). The averaging is shown schematically in FIG. 3.

From Fig. 4 it can be seen that the position and size of the coupling area KB is determined by the mean value _h2-6 and a maximum deviation formed on both sides and by the values -A and + A.

In Fig. 4, three different cases are shown:
In area a of FIG. 4, the control stroke R _h1 lies within the coupling area KB. This means that there are no recognizable faults for the cylinder-selective knock control of the cylinder 1 and the knock control works properly.

In contrast, in region b of FIG. 4, no control stroke R _{h1 is} output for cylinder 1 , although the mean value _{h2-6 of} the other cylinders and thus the coupling region KB are relatively far away from the map specification α _v . From this it can be seen that there is a malfunction in the detection of knocking events for the cylinder 1 , since it is not possible for the cylinder 1 directly at the map specification α _v and the other cylinders in a region regulated back in the "late" direction operate. Knock events are therefore not recorded for cylinder 1 , although these must be present (based on the consideration of the other cylinders). The cylinder 1 would thus operate without reducing the ignition point in a zone with the risk of damage and destruction. According to the invention, a coupling control stroke R _{h1 (-A)} is therefore output and the cylinder 1 is thus pulled out of the danger zone. This coupling control stroke R _{h1 (-A)} corresponds to the upper limit (early limit) of the coupling area KB.

In area c of FIG. 4, a malfunction in the detection of knocking events for cylinder 1 is shown, where if too many (actually non-existent) knocking events are detected, so that the control stroke R _{h1 may run} down as far as it will go . By comparison with the mean value _h2-6 or the _{coupling area} KB it is recognized that this large withdrawal of the ignition for the cylinder 1 is due to a fault. When leaving the coupling area KB beyond the lower limit, a coupling control stroke R _{h1 (+ A)} corresponding to the value for the lower limit (late limit) of the coupling area KB is therefore further output and the knock control for the cylinder 1 at the mean value _{h2- 6 of} the other cylinders coupled. This means that the cylinder 1 will continue to operate despite the malfunction in the detection of the knockers in a largely optimized area.

In connection with Fig. 5, an internal combustion engine with six cylinders and two knock sensors is considered, wherein a knock sensor for cylinder-selective detection of the Klopfereig nit for cylinders 1, 2, 3 and a second knock sensor to the cylinders 4, 5, 6 is associated. It is now the case that the knock sensor for the cylinders 1 , 2 , 3 has fallen out. So far, the knock control for these Zy cylinder had to be moved back to the lower stop for safety reasons.

According to the invention shows a mean value is in accordance. 5 formed _h4-6 of the control strokes of the other cylinders 4 to 6, the knock sensor is operating properly. Coupled to this mean value _h4-6 and increased by a small safety _distance + A, coupling hubs R _{h1 (+ A)} , R _{h2 (+ A)} and R _{h3 (+ A)} are the same for cylinders 1 , 2 and 3 Output size. This ensures that, on the one hand, in spite of a knock sensor, the cylinders concerned are not operated in any endangered area and, on the other hand, extensive optimization, coupled to the mean value of the other cylinders, is retained.

Claims (7)

1. Cylinder-selective knock control of a spark-ignited internal combustion engine with several cylinders,
with an output level corresponding to a map (α _v ), which is output from a map that is stored as a function of operating parameters as a default for the ignition point at a specific operating point of the internal combustion engine,
when knocking events (K) occur, these cylinders are selected, that is to say assigned to each cylinder, and the map specification (α _v ) is cylinder-selectively one step at a time through a late correction value (SK) to a cylinder-selective control stroke (R _h ) to a value for current ignition timing in the direction of "late" is modified and withdrawn and
if knocking events (K) are still absent, the value for the current ignition point is led one step at a time through an early correction value (FK) to a control stroke (R _h ) in the "early" direction,
characterized,
that the value of the control stroke (R _h1 ) determined for a specific cylinder (cylinder 1) is compared with a coupling area (KB),
wherein the coupling area (KB) is formed from an average of the control strokes ( _h2-6 ; _h4-6 ) of other cylinders (cylinders 2 to 6; cylinders 4 to 6) plus a defined deviation (+ A; -A) and
that if the cylinder-selectively determined control stroke (R _h1 ) of the cylinder under consideration (cylinder 1) is not in the coupling area (KB), the map specification α _v ) is not about the determined control stroke (R _h1 ) but about one with this mean value coupled coupling control stroke (R _{h1 (+ A)} ; R _{h1 (-A)} ) is withdrawn for a current ignition timing. 2. Cylinder-selective knock control according to claim 1, characterized in that the value of the coupling control stroke (R _{h1 (+ A)} ; R _{h1 (-A)} ) corresponds to a limit of the coupling area (KB). 3. Cylinder-selective knock control according to claim 2, characterized in that when the Koppelbe range (KB) is exceeded by the control stroke (R _h1 ) in the direction "late" or "early" the value of the respectively exceeded limit as a coupling control stroke (R _{h1 ( + A)} or R _{h1 (-A)} ) is output. 4. Cylinder-selective knock control according to one of claims 1 to 3, characterized in that the coupling area (KB) as a window through the mean ( _h ) increases by a maximum deviation (+ A) in the "late" direction and / or ver by one maximum deviation (-A) is formed in the "early" direction. 5. Cylinder-selective knock control according to claim 4, characterized characterized that the deviation (+ A) towards "late" is greater than the deviation (-A) in the "early" direction.   6. Cylinder-selective knock control according to one of claims 1 to 5, characterized in that when considering a specific cylinder (cylinder 1) the mean ( _h2-6 ) from the control strokes (R _h2 ; R _h3 ... R _h6 ) of all others ren cylinder (cylinders 2 to 6) is formed. 7. cylinder-selective knock control according to one of claims 1 to 5,
with a plurality of knock sensors, a knock sensor being assigned several cylinders for a cylinder-selective detection of knock events and the failure of a knock sensor being ascertainable,
characterized,
that in the event of a knock sensor failure (failure of the knock sensor for cylinders 1, 2, 3), the mean value ( _h4-6 ) for the coupling area (KB) from control strokes (R _h4 , R _h5 , R _h6 ) of the other, at least one intact Knock sensor assigned cylinders (cylinders 4, 5, 6) is formed.