DE4001477A1 - System controls engine knocking - modifying specified characteristics of each working point when knocking is detected - Google Patents

Abstract

The system modifies the specified chartacterisations for each working point when engine knocking is detected by a modification figure so that the short-term regulation for each working point refers to a new ignition point specification (specified characteristics plus modification figure). Within a given repetitive observation interval, the modification figure is determined depending on whether or not knocking is detected. The modification figure is determined by measuring control excursions from short-term control and normalising these excursions so that they are independent of angular speed and load. USE/ADVANTAGE - Reduces engine knocking. Stable control.

Description

The invention relates to a knock control of a spark ignition th internal combustion engine according to the preamble 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. Since the Location of the knock limit of operating parameters, especially the Fuel quality, temperature and air pressure depends, it is known, a knock control in the manner of a Short-term regulation.

When knocking events occur, the stored characteristic map read by each one step to a control stroke to a value for one current ignition timing in the direction of the late ignition men. If there is no further knocking events, the Value for the current ignition point gradually in again  Back in the direction of early ignition based on the map leads.

This short-term regulation is thus at the level of the filed related map specifications. With unfavorable operating parity meters, especially if the fuel quality is poor the knock limit was relatively far from the map specification conditions, so that the control with correspondingly large control strokes and large control bandwidth is operated. This is for the Stability of the scheme unfavorable, so that relatively many knocking burns with sometimes violent knockers in Purchase must be made. The short-term continues regulation with certain regulation strokes for a straight danger an operating point with a certain speed and load. If this operating point is left and another operating point is approached, usually also changes from the map output, which is then the new Operating point corresponds. With that also the short-term adjust the regulation to these new circumstances. At unfavorable transition conditions must rela tiv many knocking burns with sometimes violent Knockers are accepted until the short-term rain optimally adjusted to the new operating point Has. This is especially the case when the knock limit is relatively far from the map and the Regulation with relatively large control strokes must be operated. Overall, this increases the internal combustion engine Bela exposed and acoustic comfort is also through sometimes very audible knockers disturbed.

It is also known several, predetermined and from the beginning to store certain maps and, if necessary, for To make available. For this purpose it is known, for example, from a specific map that the operation with super power is assigned by changing the plug in the motor space to pass to a second, predetermined map, the to be used when operating with normal fuel. This ent speaks a manual long-term adjustment.  

It is also known to switch such a map as Lang time adjustment to be carried out automatically when a large number of knocking events is registered. With this order circuits are in any case one of predefined, global change or withdrawal of the Ignition point for the entire engine map. So that will be Reference level for short-term regulation only by one be agreed, global amount postponed, this postponed exercise as a rough adaptation to changing conditions. The statements made above for short-term control, esp especially with regard to the control stability and the increased to number of knocking events, therefore also hit here in relation towards the differently adjusted levels.

In contrast, the object of the invention is the number of Knock events decrease and knock control in total to hold together more stable.

This object is achieved with the features of claim 1.

According to claim 1, a long-term adjustment is carried out in this way led that the map for each operating point knocking events occurring by an adjustment value of the Knock limit is withdrawn away or modified so that the short-term control for each operating point to a new one Ignition timing specification (map specification plus adjustment value) or a different level. The adjustment values who depending on the knocking events occurring semi-determined, repetitive observation time interval valle determined.

The determination of the adjustment values is done in this way carried out that currently occurring control strokes from the short time control recorded and via a first weighting map in standardized control strokes that are independent of speed and load be standardized. For this are in the first weighting map Valuation variables filed, which refer to a certain Value (100% value) engine-specific the intensity of the on  handles knock control for knocking burns for a specific operating point or for a map area play. The weighting map thus corresponds in structure and the assignment of the map for the ignition timing and for normalization the control strokes for a be agreed operating point or map area with the corresponding corresponding valuation values from the first weighting map mul multiplied. It can therefore occur in one observation period vall, which is said to have at least about 500 firings, ver different operating points are approached, each for the long-term adaptation of usable, standardized control stroke quantities be preserved.

These recorded, standardized control strokes are added up and averaged to a single standardized control stroke average. This standardized control stroke mean value is a standardized measure for how the short-term regulation must be adapted in order to low control strokes and thus stable control and less Rule bandwidth to work cheaply. From the standardized rule stroke mean can thus be according to requirements and A normalized adjustment value. It is advantageous to process only a single value.

The normalized adjustment value is a single value that like therefore on the different circumstances of the individual operating points or map areas got to. This is done using a second weighting map des, with regard to its structure and function as well of the stored evaluation variables in principle the first wich performance map corresponds. The normalized adjustment value is in addition for a current operating point with the filed for it th valuation variables from the second weighting map strikes, so that thereby current adjustment values for the load and speed-dependent operation points will be earned.

The special advantages of the long-term described above Adaptation is that after just one observation period  interval adjustment values for the entire map for ver stand, that is, the long-term adjustment very intervenes quickly. For the determination of the standardized values can be different be in an observation time interval drive points are approached. Calculations, case differences doses and, if necessary, storages are standardized with the few ten values feasible so that the required electronic components can be designed easily and inexpensively.

According to claim 2, everyone is in the observation time interval occurring control stroke recorded for further processing. To Claim 3, it is also possible to only the control strokes that exist at the time of a knock event.

As is known, the knock limit is not a precisely defined limit ze, but to be seen as a statistical limit, depending on knockers the quality of the present combustion events above or below the determined statistics knock limit can occur. Since the location of the Knock limit is not a precisely defined variable anyway, is proposed with claim 4, a standardized adaptation value to be formed only if a newly determined nor Mated control stroke mean value greater than or equal to a fixed is set threshold. In addition, a new, standardized adaptation should be solution value or correction value for an existing one earlier adjustment value the control stroke average minus that Value for a specified threshold. In order to it is ensured that the short-term regulation is the possibility has to regulate based on this new level and not by an adaptation value of the long-term adaptation that is too large is practical table is blocked.

Instead of a case distinction over a threshold in the standardized values according to claim 4 can be a case distinction also with the current adjustment values according to Claim 5 can be made. A current new one should Adjustment value or correction value for an existing one earlier current adjustment value can only be formed if  the newly determined adjustment value is greater than or equal to one agreed definable threshold.

Since the two weighting maps in principle have the same radio tion, namely to evaluate current sizes or a nor attributed size to current sizes, with An Say 6 a simpler embodiment thereby proposed conditions that only one weighting map is provided with which both the standardization of the control strokes and the feedback the normalized adjustment value into current adjustment values is carried out. With two independent weighting maps are, on the other hand, more options for intervention given more precise adjustment.

If the knock limit gradually, e.g. at night ken of better quality fuel, back towards to the original map specification should also the adjustment values are adjusted again and adjusted. This is achieved with the features of claim 7 by if there is no or a few knock events, the norm te adjustment value gradually by a certain return size is withdrawn. A desired quick return is achieved with the features of claim 8.

For a quick dismantling of a possibly too large long current value when changing to a new operating point or another map area is proposed with claim 9 an existing adjustment value until the occurrence of a Knock event back via the short-term control algorithm to take. Which then occurs when a knock event occurs The difference to the map specification should be the first adjustment value for this operating point or map area will.

According to claim 10 is in the adjustment with a new adaptation adjustment of a new control stroke made that the previous control stroke by the difference between the previous and the new adjustment value  is changed. This avoids a jump in the regular strokes the one that would otherwise be corrected via the short-term control had to.

The long-term adjustment should only be in knocking reel vanten area, that is, in the upper map area, active be. Accordingly, it is only necessary to the wich performance maps in relation to the upper map area lay.

The current adjustment is expedient according to claim 12 values formed cylinder-selectively, the fixed weighting maps but can be made uniform for all cylinders be educated.

There is a possibility that with specific internal combustion machine unique map areas exist in which none knocking burns occur or only a very slight Knock tendency is present. There it can lead to the loss of the contractor fit, although for the other knock-relevant Map areas a long-term correction is necessary. Around Here To remedy and improve is a requirement 13 suggested that knock at the transition from a first relevant map area in a second map area without Knock tendency the adaptation value of the first map area saved and when restarting this first map area is taken over again. If according to claim 14, however an adjustment value was determined in the second map area, this should be included in the first map area if this adjustment value is greater than that for the first map area stored adjustment value. In order to the greater tendency to knock in the first map area Rech worn. The area boundaries between the first and second map areas can advantageously according to claim 15 are obtained from the weighting maps in such a way that the area boundaries are placed where small and same valuation variables (e.g. 10%) are stored. With this measure can also limit the lower map  be determined by the knock control is inactive.

It can be complex for a specific type of internal combustion engine be the assessment parameters in the weighting maps determine, because extensive tests and test programs the individual operating points or map areas required are. Manufacturing tolerances also make it possible that internal combustion engines of the same type are proprietary ten that determine from the general engine-specific weighted and stored weighting maps are not optimal be written. Also through long-term changes over the Life of the internal combustion engine can change occur so that the fixed weighting maps with their Be valuation variables are no longer optimally applicable. In a particularly preferred embodiment according to claim 16 therefore proposed to store the stored assessment parameters in a Correct kind of self-learning process. For this, the current control strokes of short-term control with a specific Threshold value compared and if these control strokes despite the Long-term adjustment are above the threshold that corresponds Corrected the relevant valuation variables automatically until the threshold is again fallen below.

The invention is explained in more detail with reference to the 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 in which the adjustment of a reference level (LZ) registered for a short-term regulation,

Fig. 3 is a diagram showing the basic limit position of the knock and illustrates the basic course of the values for the control strokes,

Fig. 4 is a flow chart values to determine the matching illustrates

Fig. 5 is a representation of a map matrix,

Fig. 6 matrix a representation of an associated weighting characteristic map.

In Fig. 1 the dependence of the torque on the ignition timing α _{z is} specified. 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 , that is at maximum, with no knocking burns occurring.

The curve 4 represents approximately the half-load range, is more strongly curved and the knock limit 2 has moved closer to the maximum point 5 , in which the internal combustion engine is operated optimally. With appropriate control, there is no risk of knocking burns here either.

Curve 6 represents the full load range, the knock limit 2 being before the maximum, that is to say in the region between curves 4 and 6 , knocking events are to be expected with optimized operation, so that the knock control is also active for this region. On the curve 6 , the optimal operating point 7 is shown, which is just before the knock limit 2 . The double arrow 8 is intended to indicate the approaching of the ignition point at this point 7 with the aid of the short-term 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 9 for the ignition timing from a stored map at a certain operating point. This map specification 9 is selected so that the internal combustion engine is operated under normal operating conditions close to the knock limit and thus isolated knocking events can occur. This state is shown in the time interval I, where with the aid of a short-term control known per se and not explicitly described, this map specification when knocking events occur (K) by one step to a control stroke for a current ignition timing (represented by curve 10 ) in Direction "late" is withdrawn. If there is no further knocking events, the value for the current ignition point is then brought back to the map specification 9 by one step in the direction of the early ignition.

Due to changes in operating parameters, for example after refueling and gradual mixing with a poorer quality fuel, knocking events increasingly occur in time interval II. Thus, the current ignition points (curve 2 ) are successively moved away from the original map 9 in the "late" direction. At such a level, at a distance LZ from the characteristic field specification 9 , which corresponds to a changed knock limit, the short-term control then settles again, as is shown in time interval III. The determination of the value LZ is explained in more detail in connection with FIG. 4. If another operating point is approached, a new value LZ is also available for a new operating point, so that the control immediately continues without further transient processes.

In Fig. 3, the torque or the load is plotted against the speed in a horizontal plane, curve 11 showing the full load curve, curve 12 delimiting the area over which knocking events are to be expected when the internal combustion engine is operating optimally (compare Fig. 1) and a curve 13 at a distance from curve 12 delimits an area downwards in which the knock control is not required and is therefore inactive.

To the top, the amount of control strokes in Fig. 3 by way of example shown on four speed points. It can be seen that the control stroke 14 must be greater in full-load operation (curve 11 ) than in the direction of part-load operation, that is to say that the knock control must intervene more strongly in the full-load range. In order to show the basic course, a linear rise (straight line 15 ) is drawn in FIG. 3, a more precise and adapted curve can be determined here for a special cylinder. The control stroke 14 corresponds, for example, to an operation with fuel of lower quality, the small right control stroke 16 (dashed line) corresponds to operation with a fuel of better quality.

In Fig. 5, a graph 17 is shown, are summarized in which a respective number of adjacent operating points in map regions 18. In the present case, the map 17 is designed as a 16 × 16 matrix with 16 load and 16 speed support points and corresponds in principle to the horizontal surface from FIG. 3. The center line 19 corresponds approximately to the curve 13 from FIG. 3, that is, it separates the area below the half-load area in which the knock control is not activated.

FIG. 6 shows a weighting map 20 which is assigned to the map 17 from FIG. 5. Since the knock control below the line 19 is not activated, the weighting map 20 can only be assigned to the upper part of the map 17 with only half of the support points. The characteristic map area 18 thus corresponds to the weighting map area 21 . In these weighting characteristic map areas, the evaluation variables relating to a certain value (100% value) are stored, with which a current control stroke can be standardized. These evaluation variables correspond to the engine-specific intensity of the intervention of the knock control and thus in principle the upward-drawn course of the control stroke intervention in FIG. 3.

The determination of the adaptation values LZ is shown schematically in FIG. 4:
The current control strokes Rh are recorded in a unit 22 and a standardized control stroke Rh _{n is} formed in each case via a first weighting map, for example the weighting map 20 from FIG. 6, it being possible to travel in the entire map. These standardized control strokes Rh _n are fed to a unit 23 in which averaging takes place:

where N = number of ignitions is for which an observation interval is set.

A single standardized control stroke mean value _{n has} thus been formed from a multiplicity of standardized control strokes Rh _n .

This mean _n is also examined in unit 23 according to the following case distinction:

• 1. LZ _{alt n} = 0: This means that in the event that there is no old, standardized adaptation value (LZ _{alt n} = 0), a new adaptation value is only formed if _{new n is} greater than or equal to a defined threshold.
• 2. LZ _{alt n} <0: If an earlier adjustment value already exists (LZ _{alt n <0} ), this is corrected in the "late" direction if _{new n is} greater than or equal to a threshold. If this value is less than a threshold, the old adjustment value is gradually reduced by the amount ΔLk. The size of the threshold and ΔLk are adjustable parameters.

The normalized adaptation value LZ _{new n} formed according to the above case distinction is fed to a unit 24 which essentially contains a second weighting map with the same structure as in FIG. 6. There, the standardized adaptation value LZ _{n is} modified to the load-dependent and speed-dependent current long-term value LZ for each approached operating point or map area.

For a self-learning process for correcting the evaluation variables stored in the weighting characteristic diagrams or units 22 and 24 , the arrangement shown in broken lines is added. For this purpose, the current control strokes Rh and the current adaptation values LZ are supplied to a unit 25 . There it is examined whether, despite the long-term adjustment, control strokes of the short-term control occur that exceed a certain threshold. If this case occurs, the stored evaluation variables in the weighting maps are corrected automatically, which is shown schematically with the dashed lines 26 and 27 .

In the map of Fig. 5 knocking relevant map areas I are shown as well as a singular characteristic field area II, occur in which no knocking combustion or Klopfnei supply is very low. These areas are separated by a border line 28 .

These map areas I and II with the boundary line 28 also occur accordingly in the weighting map according to FIG. 6. If such map areas II are present in a specific internal combustion engine, it is expedient to take special measures at the transition from map areas I to map areas II and vice versa in order to avoid "unlearning" the adaptation values in areas in which knocking does not occur the. For this purpose, the normalized adaptation value of area I is stored at the transition from map area I to map area II and is thus available for further utilization when returning to area I.

Claims (16)

1. Knock control of a spark-ignited internal combustion engine,
with a short-term control, in which a map for the ignition timing is made at a specific operating point of the internal combustion engine from a map that is stored as a function of operating parameters,
when knocking events (K) occur, this characteristic map is modified and withdrawn by one step to a control stroke (Rh) to a value for a current ignition point in the "late" direction and
if there is no further knocking events (K), the value for the current ignition point is brought back one step to a control stroke (Rh) in the "early" direction towards the map, and
characterized by an additional long-term adjustment,
that the long-term adjustment is carried out in such a way
that the map specification for each operating point in the event of knock events (K) being withdrawn or modified by an adjustment value (LZ) away from the knock limit, so that the short-term control for each operating point is based on a new ignition timing specification (map specification plus adjustment value) or is related to a different level,
that the adaptation values (LZ) are determined as a function of the knocking events (K) occurring within certain, repeating observation time intervals,
that to determine the adaptation values (LZ), current control strokes (Rh) occurring from the short-term control are recorded and standardized via a first weighting map (unit 22 ) into control strokes (Rh _n ) that are standardized in each case independent of speed and load,
whereby in the first weighting map (unit 22 ) assigned to the corresponding areas of the permanently stored map ( 17 ) are stored in each case related to a specific value (100% value), with which the current control stroke (Rh) multiplies or nor is weighted and the evaluation variables reflect engine-specific the intensity of the intervention of the knock control in knocking combustion for a certain operating point or for a map area ( 18 ),
that the standardized control strokes (Rh _n ) are summed up for all operating points approached in an observation time interval and averaged to a single standardized control stroke value ( _s ),
that a single standardized adaptation value (LZ _n ) for long-term adaptation is formed from the standardized control stroke mean value ( _n ),
that this normalized adaptation value (LZ _n ) is subjected to evaluation variables from a second weighting map (unit 24 ), the second weighting map corresponding to the first weighting map in terms of structure and function and with regard to the stored rating values and thus via the second weighting map from the standardized Adaptation value (LZ _n ) current adaptation values (LZ) are formed for the respective load and speed-dependent operating points. 2. knock control according to claim 1, characterized in that that everyone occurring in the observation time interval Control stroke (Rh) is recorded for further processing. 3. knock control according to claim 1, characterized in that each control stroke (Rh) at the time of a knock nisse in the observation interval for further processing processing is recorded. 4. knock control according to one of claims 1 to 3, characterized in that a new, standardized adaptation value (LZ _{new n} ) is formed only when the newly determined, standardized control stroke mean value ( _{new n} ) is greater than or equal to a threshold (S ), whereby the new standardized adaptation value (LZ _{new n} ) or correction value for an already existing previous adaptation value (LZ _{old n} ) corresponds to the control stroke mean value ( _{new n} ) minus the value for the threshold (S): 5. knock control according to one of claims 1 to 3, characterized in that a current new adjustment value (LZ _new ) or correction value for an already existing previous current adjustment value (LZ _old ) is formed only if the newly determined adjustment value (LZ) is greater or is equal to a certain threshold (S). 6. knock control according to one of claims 1 to 5, characterized in that only one weighting map is provided with which the normalization of the control strokes (Rh) and the feedback of the normalized adjustment value (LZ _n ) is carried out in current adjustment values (LZ). 7. knock control according to one of claims 1 to 6, characterized in that in the absence or a few (Schwel le S) knocking events (K) within at least one observation period, the normalized adjustment value (LZ _{alt n} ) in the direction of the original map step by step a certain feedback variable (Δ Lk) is reset to a new, standardized adaptation value (LZ _{new n} ). 8. knock control according to claim 7, characterized in that in the absence of knock events (K) within of at least two consecutive observation times intervals the amount of the feedback variable (Δ Lk) for one faster return is increased. 9. knock control according to one of claims 1 to 8, characterized in that when changing to a new operating point or another map area, a pre-existing adaptation value (LZ) until the occurrence of a knocking event is canceled via the short-term control algorithm and
that the then existing difference to the map specification is adopted as the first adjustment value for this operating point or map area. 10. knock control according to one of claims 1 to 9, characterized in that when adapting to a new adjustment value (LZ _new ) to avoid a jump also an adaptation of a new control stroke (Rh _new ) thereby it follows that the previous control stroke ( Rh _old ) is changed by the difference between the previous (LZ _old ) and new adjustment value (LZ _new ): Rh _new = Rh _old + LZ _old -LZ _new . 11. knock control according to one of claims 1 to 10, characterized characterized that the long-term adjustment only in the knock relevant area is active. 12. Knock control according to one of claims 1 to 11, characterized characterized that the current adjustment values (LZ) be formed cylinder-selectively, the fixed weighting maps are common to all cylinders. 13. Knock control according to one of claims 1 to 12, characterized in that for the case of first, knock-relevant map areas (I) and second singular map areas (II), in which no knocking conditions occur or a very small tendency to knock before is, a normalized adaptation value (LZ _n ) of the first map area (I) is stored during the transition from a first map area (I) to a second map area (II) and is taken over again when this first map area (I) is restarted. 14. Knock control according to claim 13, characterized in that when determining a normalized adaptation value (LZ _n ) in a second map area (II) this value is also adopted for the first map area (I) if this adjustment value is greater than that for the first map area (I) is stored adjustment value. 15. knock control according to claim 13 or 14, characterized in that area boundaries (boundary line 28 ) for between the first and second map areas from the or the weighting maps are adopted in such a way that the area boundaries are detected where small and the same evaluation values (e.g. 10%). 16. Knock control according to one of claims 1 to 15, characterized in that in the event that despite the long-term adaptation current control strokes (Rh) of the short-term control are determined, which lie above a certain threshold value, which in the or the weighting characteristics ( Units 22 and 24 ) stored evaluation variables in a self-learning process are automatically corrected (unit 25 ) until the current control strokes (Rh) are below the threshold.