Title of Invention

METHOD AND DEVICE FOR KNOCK CONTROL IN THE EVENT OF THE PHASE SENSOR FAILING

Abstract

A method and a device for the electronic spark control in the event of the failure of the phase detector, which, if the double ignition mode is not activated, carry out the normal electronic spark control individually for each cylinder. If the double ignition mode is activated in the event of the failure of the phase detector, the electronic spark control is carried out using a measure that is not individually performed for each cylinder. Such a cylinder non-individual measure could be a retarded ignition security adjustment or an electronic spark control with a knock recognition threshold for all cylinders.

Full Text

Method and device for knock control in the event of the phase sensor failing Prior art The invention relates to a method and a device for the knock control of an internal combustion engine according to the generic part of the independent claims, In an internal combustion engine abnormal combustion processes, known as knocking, can occur as a result of self-ignition of the fresh mixture not yet overtaken by the flame front. Owing to the increased thermal load and the pressure waves occurring, more persistent knocking may result in damage to the combustion chamber components. An important parameter affecting . the susceptibility of an internal combustion engine to knocking is the ignition point. Knocking combustion occurs if the fuel-air mixture present in the combustion chamber is ignited prematurely. Once a knocking phenomenon in the internal combustion engine has been detected, therefore, one possible way of preventing this in subsequent combustion is to retard the ignition point. Over-retarded ignition is associated with a loss of efficiency, for which reason a form of knock control is used in internal combustion engines, which firstly detects whether knocking combustion has occurred. This element of knock control is known as knock-sensing. A second element of knock control is adjustment of the ignition advance angle. Knock control of this type is disclosed, for example, by International Patent Application PCT/DE 91/00170. Other control variables, however, can also be adjusted in order to reduce an internal combustion engine's susceptibility to knocking, such as the fuel-air mixture, the charge, the compression ratio and the engine operating range. Individual-cylinder knock control, in which both the knock-sensing and the adjustment of the ignition advance angle are performed separately for each cylinder, is also known. Structural differences between the cylinders and an unequal distribution of the knock sensors, together with the associated knock signals specific to particular cylinders, lead to cylinder-specific differences in the knock control, so that with individual-cylinder knock control the susceptibility to knocking is reduced whilst at the same time optimizing the efficiency. If the phase sensor, which delivers signals controlling the synchronization of the ignition and the knock control, should fail, new demands are placed on the knock control hitherto applied to individual cylinders. Owing to the possibility of damage to the internal combustion engine, the knock control in such an event should function with the utmost reliability and with great accuracy in order to achieve maximum efficiency. Advantages of the invention The method according to the invention and the device according to the invention have the advantage that the knock control is configured differently as a function of the activation of dual-spark ignition. Non-individual -cylinder measures affecting the knock control are activated as an emergency strategy. Since this may vary during the operating time of the internal combustion engine or after restarting, it is also advantageous that the method according to the invention and the device according to the invention adapt themselves to the operating condition of the internal combustion engine at any given time. Maximum combustion efficiency and high knock control reliability can thus be achieved. For example, the method according to the invention allows optimum knock control to be performed despite the failure of the phase sensor, where it has been possible to restore synchronization by some other measure. Other advantages revealed by the exemplary emibodiments of the invention relate to the special non-individual-cylinder measures employed therein. They afford great reliability in preventing knocking phenomena through selection of the knock-sensing threshold or selection of the ignition advance angle. A further refinement of the invention is obtained by integrating the method and device according to the invention with the various non-individual-cylinder measures into a universal control unit, which selects a special non-individual-cylinder measure according to internal combustion engine type and operating condition. This universal control unit can be used for various types of internal combustion engine corresponding to the generic part of. the independent claims, and selects the non-individual-cylinder measure most suitable in each' case. Drawing The exemplary embodiments of the invention are represented in drawings and explained in more detail in the following description. Figure 1 shows a schematic diagram of the structure of a 4-cylinder internal combustion engine with ignition control unit and knock control. Figure 2 shows a time sequence, which illustrates the ignition points of a 4-cylinder internal combustion engine. Figure 3 shows a flow chart, which illustrates the procedure according to the invention should the phase sensor fail, and Figure 4 shows a flow chart, which illustrates a further exemplary embodiment of the procedure adopted by a universal control unit. Description of the exemplary embodiments Figure 1 represents an internal combustion engine having 4 cylinders. An internal combustion engine having more or fewer than 4 cylinders has a structure similar to Figure 1• The internal combustion engine in Figure 1 contains an ignition control unit 10, which is connected to a rotational-speed sensor 20 and a phase sensor 30. The ignition control unit 10 operates the ignition coils 4 0 each assigned to a cylinder 1 to 4. The ignition control unit 10 and hence the ignition coils 4 0 are connected by way of ignition control cables 45 to the spark plugs 50 numbered 1 to 4, the ignition coils 40 each being connected to a correspondingly numbered spark plug. In other words^ spark plug 1 is assigned to cylinder 1, spark plug 2 to cylinder 2, spark plug 3 to cylinder 3 and spark plug 4 to cylinder 4. Also assigned to the internal combustion engine is a knock control device 60, which is connected to the ignition control unit 10 and to one or more knock sensors 70. It is possible to combine the ignition control unit 10 and the knock control device 60 in one engine/universal control unit, Furthermore, the knock control is also connected to the rotational-speed sensor 20 and to the phase sensor 30. The knock control provides an angle signal for the ignition, in order to prevent the occurrence of knocking and at the same time to permit operation of the engine close to the knock limit. The rotational-speed sensor 20 measures the rotational speed of the crankshaft. The presence of a mark also allows the rotational-speed sensor to determine . when the crankshaft has completed one revolution. The phase sensor 30 measures the completion of one revolution of the camshaft. In the course of a four-stroke cycle the crankshaft rotates twice, that is through 720 degrees- It is not possible to distinguish from this whether the crankshaft is in the angle range from 0 to 360 degrees or in the angle range from 3 60 to 720 degrees, that is to say it is not possible to determine in what stroke of the four-stroke cycle of an internal combustion engine a cylinder is currently engaged. The camshaft rotates once during the same period, that is through 360 degrees. It is therefore possible, by means of the signal from the phase sensor 30, to determine in which phase of the four-stroke cycle each cylinder is engaged. Figure 2 illustrates, by means of a time sequence, the firing order of the cylinders with the associated crank angle degrees for a 4-cylinder internal combustion engine. In the time sequence, certain points are identified by vertical dashes. Below the time sequence the position of the crankshaft in degrees corresponding to these points in time is correlated with the said points in time. The cylinder at ignition top dead centre at the respective point in time is indicated above the time sequence. The top dead centre will hereinafter be referred to as TDC. Since the four-stroke cvcle extends over two crankshaft revolutions, the piston reaches TDC, the piston reversal point, twice, the first time at the start of the induction stroke. This TDC is termed the overlap TDC, The piston reaches TDC for the second time at the start of the power stroke. This TDC is termed ignition TDC. The mixture present in the combustion chamber is only ignited at the ignition TDC and is burned during the power stroke. The signal from the rotational-speed sensor 20 alone only permits identification of the so-called cylinder groups at TDC at any given time. For example, in the 4-cylinder internal combustion engine cylinders 1 and 4 or cylinders 2 and 3 will be at TDC at the same time. It is not possible to detect just by the signal from the rotational-speed sensor which cylinder of the cylinder groups is at ignition TDC, The signals from phase and rotational-speed sensors, however, are also significant for knock control. The noises generated by the combustion processes in the cylinders of the internal combustion engine and detected by the knock sensor or knock sensors 70 and deliver corresponding electrical signals to the knock control device 60 [sic] . The noise's are picked up within a certain time window after the ignition, the so-called measuring window, which is typical of the occurrence of knocking processes. On the basis of the clock pulse emanating from the rotational-speed sensor 20 and the phase sensor 30, the timing of the measuring window can . be corrected and the electrical signals assigned to a cylinder of the internal combustion engine. The knock control device 50 contains a storage medium, which stores a threshold value for each cylinder. If the ratio of the integrated noise signal from the respective combustion process to background noise signal assigned to a cylinder exceeds this so-called knock-sensing threshold of the associated cylinder, the knock control device 60 senses that knocking has occurred during the combustion in this cylinder. The background noise signal is obtained from a mean value for the integrated noise signals over a certain number of firings occurring previously, for example 16. If knocking has been detected, the knock control device 60 sends measures to the ignition control unit 10 in order to prevent knocking in subsequent combustion sequences. These are, in particular, individual-cylinder measures, retardation being undertaken, for example, only for that cylinder in which knocking has just occurred. If the phase sensor 30 should fail for unknown reasons, the ignition control unit 10 can no longer detect which cylinder is just at ignition TDC. There is therefore a risk of the internal combustion engine failing. One possible measure that can be taken by the control unit in order to prevent failure of the internal combustion engine is to institute dual-spark ignition, which means that each cylinder is fired at each TDC. This ensures that ignition always occurs at ignition TDC. The function of the ignition control unit 10 may include measures that allow it to detect, even without a signal from the phase sensor 30, whigh TDC pertains to the power stroke. A first exemplary embodiment of the method according to the invention is shown in the form of a flow chart in Figure 3. In this it is assumed that the phase sensor 30 has failed. If the question 75 as to whether dual-spark ignition has been activated is answered negatively, the method progresses to the knock control 77 of individual cylinders. Here the synchronization may either be correct, that is .to say the internal combustion engine may happen to be running correctly, or it was possible to achieve synchronization by some other measure despite the phase sensor having failed. If the question 75 is answered affirmatively, that is to say dual-spark ignition is in operation, a non-individual-cylinder measure 7 9 influencing further knock control is activated. In this case the knock control is not in a position to identify a noise signal as the knocking of a specific cylinder and/or to effect knock control of individual cylinders. In the event of a failure of the phase sensor 30 and the activation of dual-spark ignition, therefore, a non-individua1-cylinder measure must be instituted. One example of a non-individual-cylinder measure, for example, may be to set a uniform knock- sensing threshold for all cylinders. Owing to the engine damage caused by knocking, a threshold is selected, which reliably detects any knocking. This takes account of combustion knock being erroneously detected in too many firings, which leads to the operation of individual cylinders far from the knock limit, As another measure, the same pre-set ignition advance angle, at which no knocking occurs, can be set for all cylinders. This measure is referred to as safety retardation. Such a fixed ignition advance angle may either be a fixed angle independent of engine parameters such as load, torque demand or temperature, or it may be a fixed value dependent on engine parameters. The fixed angle may also be made up of a value angle and a differential value, the so-called differential ignition advance angle. Ignition advance angle and differential ignition advance angle may be angles dependent upon or independent of engine parameters. In this case the non-individual-cylinder measure consists of fixing the said differential ignition advance angle for all cylinders. Such fixed ignition advance angles or differential ignition advance angles are fixed before commissioning of the internal combustion engine and are contained in the memory of the ignition control unit 10. This measure results in the operation of all cylinders far from the knock limit. Should dual-spark ignition not be activated, however, in the method according to the invention individual-cylinder knock control is performed, which is the usual method in normal engine operation. Figure 4 represents a further exemplary embodiment of a method according to the invention in the form of a flow chart. Such a method can be used in a universal knock control, which can be employed in various types of internal combustion engines differing in the number of cylinders and the number of knock sensors. As in the preceding example, it is again assumed that the phase sensor has failed. Similarly, the question 75 concerning the activation of dual-spark ignition is put first. If the question 75 is answered negatively, the method again progresses to the measure 7 7 of individual-cylinder knock control• If the question 75 is answered affirmatively, that is to say dual-spark ignition is being performed, further differentiation according to the characteristics of the internal combustion engine is necessary, in order to institute the correct non-individual-cylinder measure. The method then next progresses to the question 8 6 concerning the existence of an odd number of cylinders. If the number of cylinders of the internal combustion engine is an odd number, that is to say the question 8 6 is answered affirmatively, the method progresses to the measure 88 of safety retardation for all cylinders. In the case of an odd number of cylinders, the dual-spark ignition causes ignition actually to take place at the ignition TDC of this cylinder, the other ignition at the overlap TDC, no other cylinder being at the ignition TDC at this time. Knock control and hence adjustment of the measuring window continues, however, at the frequency of single- spark ignition. Although the internal combustion engine is running correctly, the absence of phase information makes the synchronization between ignition and measuring window of the knock control unreliable, that is to say it is not certain whether the measuring window is set after the ignition TDC. Safety retardation must therefore be adopted. If the question 86 is answered negatively, that is to say there is an even number of cylinders, then if one cylinder is right at the overlap TDC the second cylinder of a group of cylinders is situated right at the ignition TDC, since the ignition advance angles of the cylinders in a cylinder group always differ by a crank angle of 360 degrees, Despite the presence of dual-spark ignition, given an even number of cylinders the synchronization between combustion and measuring window is now correct. The method now progresses to next a question 90, as to whether the system contains one or more knock sensors. Should a plurality of knock sensors belong to the system, measure 88, safety retardation for all cylinders, is again accomplished. In this, noises are received from different knock sensors. Owing to the absence of phase information it is not possible to assign the knock control evaluation path to a knock sensor, thereby making safety retardation fop all cylinders necessary. If only one knock sensor is present in the system, the method arrives at the measure 92, knock-sensing with a single threshold for all cylinders. As already noted, with an even number of cylinders the measuring window of the knock sensor can be correctly timed in relation to the ignition. The assignment of this measuring window to the single knock sensor is also assured. Knock-sensing may therefore still be performed. Since assignment to a specific cylinder of a cylinder group is not possible, however, one knock-sensing threshold is used for all cylinders. This single knock-sensing threshold replaces the cylinder-specific knock-sensing thresholds, which are used in normal knock control. It generally constitutes the minimum for cylinder-specific thresholds, since knocking is to be detected with the utmost reliability. In the method according to the invention contained in the exemplary embodiment, therefore, individual-cylinder knock control is performed without the activation of dual-spark ignition, and on the activation of dual-spark ignition either the measure of safety retardation is instituted or one knock-sensing threshold is used for all cylinders, the measure adopted being dependent on the structure of the internal combustion engine and of the knock control system. Neither of these measures acts on individual cylinders. Whilst with the safety retardation measure knock-sensing is no longer performed and a fundamental retardation of the ignition advance angle occurs, by means of knock-sensing with one threshold for all cylinders it is still possible for knock control to be performed, which may possibly result in increased combustion efficiency. Should the engine be of a type, however, such that the knock-sen sing measure with one threshold for all cylinders cannot be accomplished, the reliable achievement of knock-free combustion through safety retardation is to be preferred to the achievement of high efficiency. Claims 1. Method for the knock control of an internal combustion engine with multiple cylinders, to each of which an ignition coil (40) is assigned for generating an ignition spark for a spark plug (50) arranged in each of the cylinders, it being determined by a signal from a rotational-speed sensor (20) in which cylinder a piston is at the top dead centre, it being determined by a signal from a phase sensor (30) which cylinder is engaged in a power stroke, a knock control signal being generated for each signal individually in the presence of a rotational-speed sensor signal and a phase sensor signal, it being possible to activate dual-spark ignition in the event of a failure of the phase sensor, which ignition produces an ignition spark in each cylinder at each top dead centre, characterized in that, in the event of the phase sensor failing with dual-spark ignition activated, an emergency knock control strategy is adopted, which includes a non-individual-cylinder measure, and in that, in the event of the phase sensor failing with dual-spark ignition inactivated, the normal individual-cylinder knock control is adopted. 2. Method according to Claim 1, characterized in that a pre-set ignition advance angle or differential ignition advance angle is adopted as non-individual -cylinder knock control measure. 3. Method according to Claim 1, characterized in that a uniform knock-sensing threshold for the detection of knocking combustion is adopted as non-individual-cylinder knock control measure for all cylinders. 4 . Method according to Claims 2 and 3, characterized in that an appropriate non-individual-cylinder measure is selected in a universal control unit as a function of parameters corresponding to the structure of the internal combustion engine with knock control. 5, Method according to Claim 4, characterized in that the said parameters are the number of cylinders and the number of knock sensors. 6. Device for the knock control of an internal combustion engine with multiple cylinders, to each of which an ignition coil (40) is assigned for generating an ignition spark for a spark plug (50) arranged in each of the cylinders, a rotational- speed sensor (20) being assigned to the internal combustion engine and serving to detect th.e top dead centre of a cylinder, a phase sensor (30) being assigned to the internal combustion engine and serving to detect the cylinder engaged in the power stroke, the knock control generating an individual knock control signal for each cylinder when the rotational-speed sensor (20) and the phase sensor (30) are functioning correctly, there being a device for generating dual-spark ignition in the event of a failure of the phase sensor, which device produces an ignition spark in each cylinder at each top dead centre, characterized in that, in the event of the phase sensor failing with dual-spark ignition activated, the knock control device is operated with an emergency knock control strategy, which includes a non-individua1- cylinder measure, and in that, in the event of the phase sensor failing with dual-spark ignition inactivated, the knock control device generates the normal individual-cylinder knock control signal. 7. Device according to Claim 6, characterized in that in the knock control device a pre-set ignition advance angle or differential ignition advance angle is relayed to the ignition control unit (10) as non-individual-cylinder measure. 8. Device according to Claim 6, characterized in that in the knock control device a uniform knock-sensing threshold for all cylinders is implemented as non-individual-cylinder knock control measure. 9. Device according to Claims 7 and 8, characterized in that the appropriate non-individual-cylinder measure is selected in a universal control unit as a function of parameters corresponding to the structure of the internal combustion engine with knock control. 10. Device according to Claim 9, characterized in that the said parameters are the number of cylinders and the number of knock sensors. 11. Method for the knock control of an internal combustion engine with multiple cylinders substantially as herein described with reference to the accompanying drawings. 12. Device for the knock control of an internal combustion engine, with multiple cylinders substantially as herein described with reference to the accompanying drawings. Dated this 23 day of August 2001

Documents:

in-pct-2001-1177-che-abstract.pdf

in-pct-2001-1177-che-claims duplicate.pdf

in-pct-2001-1177-che-claims original.pdf

in-pct-2001-1177-che-correspondence others.pdf

in-pct-2001-1177-che-correspondence po.pdf

in-pct-2001-1177-che-description complete duplicate.pdf

in-pct-2001-1177-che-description complete original.pdf

in-pct-2001-1177-che-drawings.pdf

in-pct-2001-1177-che-form 1.pdf

in-pct-2001-1177-che-form 19.pdf

in-pct-2001-1177-che-form 26.pdf

in-pct-2001-1177-che-form 3.pdf

in-pct-2001-1177-che-form 5.pdf

in-pct-2001-1177-che-pct.pdf