Control means and method for operating an internal combustion engine

Abstract

A method for operating an internal combustion engine is described in which a combustion air ratio () is determined and used to determine a deviation of this combustion air ratio from an in particular default or determined set point combustion air ratio. Spontaneous ignition of the internal combustion engine are detected based on the determined deviation () and used to control the operation of the engine.

Claims

1. A method for operating an internal combustion engine, in particular of a passenger car, with the steps: assigning a detection window to a cylinder arrangement, in particular a cylinder (1) of the internal combustion engine, wherein the detection window comprises a predetermined crank angle range (w.sub.c1, . . . , w.sub.c4); determining, in a controller, a combustion air ratio () in the detection window; determining, in the controller, a deviation () of this combustion air ratio () from a predetermined set point combustion air ratio (.sub.d); integrating, over the detection window, the deviation () of the combustion air ratio () from the predetermined set point combustion air ratio (.sub.d) to determine an integrated deviation (S), detecting, with the controller, a spontaneous ignition event of the internal combustion engine based on the integrated deviation (S); and adjusting a controlling operation of the internal combustion engine with the controller in response to the spontaneous ignition event and based on the integrated deviation (S).

2. The method according to claim 1, wherein further comprising detecting the spontaneous ignition event of the internal combustion engine when the integrated deviation (S) deviates from a predetermined limit value (SPI) by at least a predetermined amount (M).

3. The method according to claim 2, wherein at least one of the combustion air ratio () and the integrated deviation (S) are determined for a cylinder-specific arrangement.

4. The method according to claim 3, further comprising determining the air ratio () is determined with a lambda probe configured to measure a given cylinder of the internal combustion engine.

5. The method according to claim 1, wherein controlling operation of the internal combustion engine when a spontaneous ignition event is detected comprises taking a protective measure selected from the group consisting of enriching a fuel-air mixture of the internal combustion engine, enrichment and enabling a knock control suppression.

6. A computer program product comprising engine control unit having a program code stored on a non-transitory medium that is readable by the engine control unit and configured to carry out the method according to claim 1.

7. A control apparatus for an internal combustion engine, in particular of a passenger car, with: a combustion air ratio detector configured to determine a combustion air ratio () during a detection window of a cylinder arrangement, in particular a cylinder (1) of the internal combustion engine, wherein the detection window comprises a predetermined crank angle range (w.sub.c1, . . . , w.sub.c4); a comparator having an integrator, the comparator configured to determine a deviation () of the combustion air ratio () from a predetermined set point combustion air ratio (.sub.d) and the integrator configured to integrate the deviation () of the combustion air ratio () from the predetermined set point combustion air ratio (.sub.d) to determine an integrated deviation (S); a detector configured to detect a spontaneous ignition event of the internal combustion engine based on the integrated deviation (S) and; an engine controller configured to execute a protective measure selected from the group consisting of enriching a fuel-air mixture of the internal combustion engine, enrichment and enabling a knock control suppression based on the spontaneous ignition event and the integrated deviation (S).

8. The control apparatus of claim 7 wherein the combustion air ratio detector comprises at least one lambda probe.

9. The control apparatus according to claim 7 wherein the comparator is further configured to detect when the integrated deviation (S) deviates from a predetermined limit value (SPI) at least by a predetermined amount (M).

10. The control apparatus according to claim 7, wherein the combustion air ratio detector of a cylinder arrangement is assigned to a cylinder of the internal combustion engine.

11. A motor vehicle comprising an internal combustion engine and a control apparatus according to claim 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements.

(2) FIG. 1 a pressure curve in four cylinders (bottom), a determined and a predetermined combustion air ratio (middle) and an integral (top) of a deviation between determined and predetermined combustion air ratio of the internal combustion engine of FIG. 2 over a crankshaft angle;

(3) FIG. 2 a part of an internal combustion engine of a passenger car with a control apparatus according to an embodiment of the present disclosure; and

(4) FIG. 3 a method according to an embodiment of the present disclosure for operating the internal combustion engine of FIG. 2, as it is carried out by the control apparatus of FIG. 2.

DETAILED DESCRIPTION

(5) The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

(6) An internal combustion engine having a cylinder 1 with a moveable piston 2, an inlet 3 and an exhaust outlet 4 are exemplarily shown. A lambda probe 5 is arranged with the engine, which may in a modification (not shown) be arranged centrally for all cylinders, for example in an exhaust manifold. The lambda probe 5 detects and transmits a combustion air ratio (), to a control apparatus in the form of an engine control unit or ECU 6.

(7) FIG. 1 shows a pressure curve in four cylinders over a crankshaft angle (). Evident is the curve of the pressure in a first cylinder (p.sub.c1), second cylinder (p.sub.c2), third cylinder (p.sub.c3) and fourth cylinder (p.sub.c4) which is typical for the combustion. Here, an undesirable stochastic pre-ignition occurs in the first cylinder as is noticeable from the severe increase of the pressure (p.sub.c1).

(8) FIG. 1 shows in the middle a predetermined combustion air ratio (.sub.d), which exemplarily is constant in particular in a crank angle range (w.sub.c1). Plotted above this is the actual combustion air ratio () as it is detected by the lambda probe 5. It is noticeable that it substantially follows the predetermined combustion air ratio (.sub.d) in the crank angle ranges w.sub.c4, w.sub.c2 and w.sub.c3.

(9) As a consequence of the stochastic pre-ignition in the first cylinder, the lambda probe 5 however detects a significant enrichment, i.e. a dropping of the combustion air ratio () in the crank angle range (w.sub.c1). Accordingly, temporary deviations (.sub.n=(.sub.n).sub.d(.sub.n) are obtained here over the crankshaft angle () for discrete crankshaft angles (.sub.n) or crankshaft angle intervals (.sub.n.sub.n1), of which one is exemplarily drawn in in FIG. 1.

(10) In order to detect the stochastic pre-ignition from these deviations (.sub.n) or by means of the lambda probe 5, the ECU 6 carries out the method described in the following with the help of FIG. 3. To this end, the detection windows drawn in FIG. 1 are predetermined in the form of crank angle ranges (w.sub.c1 to w.sub.c4), which, assigned to the respective cylinders, are shifted in particular by a predetermined interval against the top dead center of these. As explained above, the combustion air ratio () in the crank angle range (w.sub.c1) substantially results from the combustion in the first cylinder, so that the significant deviation (.sub.n) is correspondingly reflected here as a consequence of the stochastic pre-ignition in this cylinder, in the crank angle range (w.sub.c4) substantially from the combustion in the fourth cylinder, in the crank angle range (w.sub.c3) substantially from the combustion in the third cylinder and in the crank angle range (w.sub.c2) substantially from the combustion in the second cylinder. In another internal combustion engine, the combustion air ratio can also result from the combustion in multiple cylinders, so that the detection windows are then assigned to these cylinders. Equally, each cylinder can be assigned a separate detection window also here in an embodiment in such a manner that only a stochastic pre-ignition in this cylinder causes a corresponding deviation of the combustion air ratio () from the predetermined combustion air ratio (.sub.d) in this detection window.

(11) In a first step S10, when the crankshaft continues rotating into a new detection window (w.sub.ci), an integral value (S) and a scanning value (n) are initialized. Following this, at discrete crank angle intervals or at discrete crankshaft angles (.sub.n,) in each case in a step S20, the scanning value (n) is incremented (n=n+1), the respective combustion air ratio (.sub.n) determined by the lambda probe 5, from this through a deviation determining means 6.1 of the ECU 6 a difference (.sub.n) between the default set point combustion air ratio (.sub.dn=(.sub.n)) and this combustion air ratio (.sub.n) determined, and the latter integrated (S=S+.sub.n) through an integrator means of the deviation determining means 6.1 by addition to the integral value (S) initialized at the outset.

(12) Then, in a step S30, a comparison means of spontaneous ignition detector 6.2 of the ECU 6 compares this integrated deviation (S) with a predetermined limit value (SPI). If the integrated deviation S deviates by a predetermined amount (M), which like the predetermined limit value SPI is indicated in FIG. 1, from the limit value (SPI) or if the integrated deviation (S) exceeds the limit value (SPI), shown as Y at S30, by at least the predetermined amount (M), the spontaneous ignition detector 6.2 detects spontaneous ignition in that cylinder of the internal combustion engine, which is assigned to the current detection window (w.sub.ci), in the exemplary embodiment in the first cylinder.

(13) Following this, a protection means 6.3 of the ECU 6 in a step S40 carries out a protective measure in that it lowers the default set point combustion air ratio (.sub.d) in a working cycle next but one to a predetermined lower value (.sub.p), thus enriching the mixture. This is schematically indicated in FIG. 1. If the integrated deviation (S) does not exceed the predetermined limit value (SP1) by at least the amount (M), shown as N in S30, the spontaneous ignition detector 6.2 does not detect any spontaneous ignition and step S40 is skipped.

(14) In a following step S50 it is checked if a new detection window (w.sub.ci+1) has started, i.e. the crankshaft angle has entered a new crank angle range (w.sub.ci+1). For as long as this is not the case (S50:N), the method returns to step S20 so that in particular the differences (.sub.n) are continued to be integrated into the integrated deviation (S). As soon as a new detection window w.sub.ci+1 has started (S50:Y), the method returns to step S10, where in particular integral value (S) and scanning value n are reset or initialized.

(15) This is shown at the top of FIG. 1, where .sub.n is computed as follows:
.sub.n=.sub.0+.sub.2+ . . . =[.sub.d(.sub.0)(.sub.0)]+[.sub.d(.sub.1)(.sub.1)]+ and illustrated for the successive detection windows (w.sub.c4, w.sub.c2, w.sub.c1, w.sub.c3), the predetermined limit value (SP1) and the predetermined amount (M). It is evident that as a consequence of the stochastic pre-ignition in the first cylinder, e.g. the significant pressure increase (PC1) the combustion air ratio () in the assigned detection window (w.sub.c1) likewise significantly deviates from the default set point combustion air ratio (.sub.d) and accordingly the integral of this deviation exceeds the predetermined limit value (SP1) by more than the amount (M). Based on this exceeding of the limit value (SP1) by the integrated deviation (.sub.n) the ECU 6 detects a stochastic pre-ignition in the first cylinder and can carry out appropriate protective measures.

(16) Although in the preceding description exemplary embodiments were explained it is pointed out that a multiplicity of deviations is possible. Accordingly, a medium value (.sub.n/n) of the determined combustion air ratios (.sub.n) of one or multiple preceding detection windows can also be used as a set point combustion air ratio (.sub.d) can also be used instead of a set point combustion air ratio (.sub.d) predetermined by an emission control. It is additionally pointed out that while at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment is only an example, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims and their legal equivalents.