|Title of Invention||
METHOD FOR IGNITION CONTROL
|Abstract||The proposal is for a method for ignition control in which the load gradient is determined. The load gradient is compared with a first specifiable dynamic threshold and the ignition control variable is retarded by adding to it an adaptable dynamic lead if the load I gradient exceeds the first dynamic threshold (l.DYN- SCHW). If the load gradient (drl) exceeds a second specifiable dynamic threshold (2.DYN-SCHW) and no knock , occurs, the dynamic lead output is reduced, moving the ignition back in the direction of advance.|
Method for ignition control
The invention relates to a method for determining the ignition control variables for an internal combustion engine when acceleration occurs.
A method of this kind is already known from "Bosch Techni$che Unterrichtung, Kombrniertes Zund- und Benzineinsprit2system mit Lambda-Regelung, Motronic" [Bosch Technical Instruction, Combined Ignition and Petrol Injection System with Lambda Closed-Loop Control, Motronic] (1987722011, KH/VDT--Q9.895-DE) ,
With this known ignition control device, the various operating parameters, such as engine speed, load/ pressure and temperature, are detected by means of corresponding sensors on the periphery of the internal combustion engine and are then passed to the control device. The sensor signals detected are processed in associated sensor-signal conditioning circuits or units, it being possible for these conditioning circuits to be arranged either outside the control device or in the control device itself» An arithmetic unit of the control device then determines the corresponding ignition control variable, inter alia on the basis of the available signals^ preferably on the basis of the engine-speed signal and load signal. An ignition map plotted against engine speed and load is stored in the control device for the purpose of carrying out this determination. The characteristic maps have, for example, been determined beforehand by application" on an engine test bed in accordance with optimum operating conditions. This determination of the ignition control variable is assigned a knock control system that brings about a retardation of the ignition point away from the knock limit after knocking combustion in this cylinder. The determination of the ignition point is furthermore assigned an additive adjustment of the ignition point taken from the characteristic map to adjust the previously determined
ignition point as a function of a dynamic process that occurs. With the incorporation of a so-ca]-lad dynamic lead, the ignition point is retarded. This additive adjustment is then cut back over time and the ignition point is adjusted back in the direction of the mapped ignition point. The additive adjustment ensures that the ignition point is nor too close to the knock limit, thereby avoiding knock. Finally, the adaptation of the ignition point has the effect that, in the event of acceleration, a maximum torque is provided. In the case of very sharp acceleration, which would lead to a step change in the ignition point and hence to a deterioration in the running characteristics, this change is carried out slowly and only m cases in which a rapid change is absolutely essential, e, g. at the transition from part load to full load, does the control device allow a rapid step change.
Advantages of the invention
In contrast with the known method, the method according to the invention with the features of the main claim has the advantage that through the introduction of a second dynamic threshold, above which the dynamic lead is adapted in the direction of advance, the operation of the internal combustion engine meets the requirements that a low dynamic threshold should be defined for the outputting of the lead and a high dynamic threshold should be defined for adaptation in the direction of advance. This improves the interaction between the adaptation and outputting of the dynamic lead and hence the effectiveness of the latter.
Advantageous developments and improvements of the method given in the main claim are possible by means of the measures presented in the subclaims.
It is particularly advantageous to determine the two dynamic thresholds by application and to store them in a memory. A further advantage is obtained by storing the dynamic lead to be output in a map plotted
against load and engine speed when the first dynamic threshold is exceeded. This allows the change in the ignition point to be adapted very effectively to the current operating state. Finally, a further advantage is obtained in the stepwise reversal of the adaptation of the dynamic lead in the direction of advance since this results in gentler running characteristics and hence more refined running.
Exemplary embodiment of the invention are illustrated in the drawing and explained in greater detail in the description which follows. In the drawing:
Figure 1 shows the basic structure of the control device for carrying out the method according to the invention, and Figure 2 shows a program flow diagram for carrying out the method according to the invention.
Description of the exemplary embodiments
Figure 1 shows the basic structure of a control unit for determining the ignition control variable. Here, the operating parameters detected by sensors, such as engine speed n, reference mark BM, temperature T, pressure p etc,/ are fed to a control device 10 as input variables 11. The control device 10 is furthermore supplied with the signal of at least one knock sensor KS 12. The control device 10 contains means 13 for knock detection* to which the knock signal is fed. The occurrence of knocking combustion is detected in a known manner by comparison with a standardised reference level as already described in numerous publications, and it is therefore not necessary to go into this in detail again here. Also provided in the control device is a dynamic-process detection stage 14, which evaluates the engine-speed signal n or the position of the throttle valve for example and in this way determines whether the internal
combustion engine is in a dynamic state. Also arranged in the control device 10 is an ignition control unit 15, the output signal of which is feci to an external output stage not indicated explicitly in Figure 1, In the control device 15, the ignition point is taken from a characteristic map using the current operating parameters, as described at the outset, and the output stage is then activated accordingly. If knocking combustion has been detected in the cylinder to be activated, the ignition point for this specific cylinder is retarded. After a predetermined number of knock-free combustions in this cylinder, the ignition point is brought back to the mapped ignition point again in steps. Dynamic states are detected in the dynamic-process detection stage 14. This dynamic sr.ate is detected by means of the opening angle of the throttle valve, for example, indicating whether the driver intends to initiate a change in load.
Figure 2 shows the basic flow diagram for ignition control when a dynamic process occurs. In a first working step 20, the current load gradient drl i$ acquired. This load gradient drl is compare;d in a subsequent inquiry 21 with a first specifiable dynamic threshold 1,DYN-SCHW. If the load gradient drl is greater than this first specifiable dynamic threshold. I.e. drl In an inquiry 23, a check is then made to determ.ine whether the load gradient drl acquired in working step 20 is greater than a second specifiable dynamic threshold 2.DYN-SCHW. If drl > 2,DYN-SCHW, the YES output leads to an inquiry 24, in which a check is made to determine whether knock KL has occurred with
the currently output ignition angle. If no knock process is determined in the evaluated coinbastions of the dynamic phase r the no output of the: inquiry 24 leads to an inquiry 25. Her«5, a check is made to determine whether a specifiable number of knock-free combustions has already occurred with the ignition control variable determined by the knock control 3ys^tem. If this is the case/ the dynamic lead wkrdya output is reduced in each case by an increment in a working step 2 6 following the yes output, thus adjusting the ignition back in the direction of advance and hence closer to the knock limit. Operation closer to the knock limit also means better torque and hence higher efficiency.
If the inquiry 23 as to wheth&r the load gradient has also exceeded the second specifiable dynamic threshold 2,DYN-SCHW has resulted in the answer no, the no output of this inquiry 23 leads to an inquiry 27, in which the combustions on [sic] the dynamic phase are once again monitored for the occurrence of knock. If knock KL is detected, the yes output of the inquiry 27, like the yes output of inquiry 24, leads to a subsequent inquiry 28. Here, the knock event KL detected is assessed by ascertaining and assessing the intensity of the knock event:. In the case of a knock event that has exceeded a specifiable intensityp the currently used dynamic lead wkrdya is increaseci by a specifiable amount in a subseqiaent working step 29, thus retarding the ignition overall.
Finally, the no outputs of the inquiry 21, indicating that the load gradient drl is less than the first dynamic threshold l.DYN-SCKW, the inquiry 27, indicating that no knock has been detected, th& inquiry 28/ indicating that the knock detected was of low intensity, and the inquiry 25, indicating that only a single or very few knock-free combustions were detected, are passed to a working step 30* Here, it is determined that the dynamic lead wkrdya stored in the memory will be retained. The program flow diagram is
then executed again to evaluate the next dynamic phase, a dynamic phase comprising a specifiable number of combustion cycles• Adaptation itself takes place once par dynamic phase.
If there is a change in load, i.e. in the case of a dynamic process, it is necessary ro adjust the ignition point in such a way as to give a maximum torque. In practice/ this means that: the ignition control variable must be advanced* At tne same rime, a very large advance in the ignition control variable results in an increased tendency to knock. The method according to the invention therefore provides a possibility that cleverly combines contradictory requirements for knock-free operation of the internal combustion engine and as high a torque as possible for good efficiency of the internal combustion engine.
The definition of a first: dynamic threshold for the load gradient ensures that: brief and extremely small changes in load do not lead to the ignirion being retarded. This means that high efficiency is maintained. In the method according to the invention, the- dynamic lead output when the first dynamic threshold is exceeded is adapted on the basis of the current operating conditions and then stored in a memory until alteration of the dynamic lead is necessary, allowing it to be read out of Che memory when the internal combustion engj.ns is operated in thas range again and to be used to retard the ignition. There are two distinct possibilities for adapting the dynamic lead. On the one hand, the dynamic lead can be increased^ meaning that the ignition is retarded further, or the dynamic lead can be reduced, meaning that the ignition is advanced in the direction of the knock limit. The dynamic lead is reduced if the load gradient has exceeded the second dynamic threshold and a specifiable number of knock-free combustions has taken place. In this case, it is assumed that the "safety margin" with respect to the knock limit brought about by the dynamic lead is too large, and the
ignition can be advanced in steps. If rhe second dynamic threshold has not been exceeded by the load gradient, the intensity of knock events that occur needs to be checked. If there is a very severe tendency towards knock/ the dynamic lead is increased, with the result that the ignition is retarded further and hence moved away from the knock limit.
1, Method for ignition control for an internal
combustion engine when a change m load occurs, having
the following steps:
- determination of an ignition control variable from a stored characteristic map on the basis of detected operating parameters,
- acquisition of the load gradient (drl)
- comparison of the acquired load gradient with a specifiable first dynamic threshold (1.DYN-SCHW) and outputting of a specifiable dynamic lead (wkrdya) that retards the ignition control variable if the load gradient exceeds the specifiable first dynamic threshold (1.DYN-SCHW),
^ comparison of the acquired load gradient (drl) with a specifiable second dynamic threshold (2.UYN-SCHW) and stepwise adaptation of the dynauiic lead (wkrdya) ; resulting in advancing of the ignition control variable if the load gradient exceeds the specifiable second dynamic threshold (2.DYN-SCHW) ana if there is a specifiable proportion of knock-free combustions in the dynamic phase.
2, Method for ignition control according to Claim 1/ characterised in that the dynamic lead (wkrdya) is increased in steps if knock events (KL) that exceed a specifiable knock intensity occur.
3, Method for ignition control according to one of the preceding claims, characterized in that the first and the second dynamic threshold are determined by application.
4, Method for ignition control according to one of the preceding claims/ characterised in that the dynamic lead (wkrdya) is taken from a characteristic map.
5, Method for ignition control according to one
of the preceding claims, characterised in that the
adapted dynamic lead (wkrdya) is in each case stored in
the memory as a new learned value.
6. Method for ignition control for an internal combustion engine substantially as hereinbefore described with reference to the accompanying drawings.
|Indian Patent Application Number||IN/PCT/2000/794/CHE|
|PG Journal Number||50/2007|
|Date of Filing||08-Dec-2000|
|Name of Patentee||M/S. ROBERT BOSCH GMBH|
|Applicant Address||Postfach 30 02 20 D-70442 Stuttgart|
|PCT International Classification Number||F02P 5/152|
|PCT International Application Number||PCT/DE99/01404|
|PCT International Filing date||1999-05-10|