EP2449238B1 - Method and apparatus for controlling an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a method for operating an internal combustion engine according to the preamble of claim 1. The invention further relates to a computer program, an electrical storage medium and a control and / or regulating device.

From the market, for example, internal combustion engines are known in which gasoline from injectors is injected directly into respective combustion chambers. Such injection valves have a valve needle, which is actuated, for example, by an electromagnetic actuator. In order to calculate an optimum injection amount of fuel in a precise amount, various methods are known in which i.a. Control information for the injection valves, such as. Ansteuerbeginn, Ansteuerdauer and / or Ansteuerende be determined. The more precisely this information is available, the more accurate a metering can be controlled by the control and / or regulating device, with delay times also being taken into account when opening and closing the valve needle.

Disclosure of the invention

Object of the present invention is to develop a method of the type mentioned, which further optimizes the fuel injection via the injectors.

This object is achieved by a method having the features of claim 1. Further solutions are specified in the independent claims that relate to a computer program, an electrical storage medium and a control and / or regulating device. Advantageous developments of the invention are specified in subclaims. In addition, important features for the invention can be found in the following description and in the drawings. These features may be important for the invention both alone and in different combinations, without being explicitly referred to again.

With the aid of the method according to the invention, an opening delay time of the injection valve is determined. In this case, individual, differing inaccuracies of the valve elements, a valve seat and possibly also a magnet armature are taken into account, which lead to the opening delay time being subject to tolerances. The basic structure of the actuated by the electromagnetic actuator injectors is not relevant to the inventive method, i. the valve elements can both be firmly connected to the armature, or they can have a magnetic armature, which has a certain axial play with respect to the valve element.

A valve opening duration is composed of a drive duration, less the opening delay time, and (after the completion of the drive time) a closing time. So it is purely mathematical: $$\mathrm{Valve}\ddot{\mathrm{O}}\mathrm{ffnungsdauer}=\mathrm{control\; period}-\ddot{\mathrm{O}}\mathrm{ffnungsverzugszeit}+\mathrm{closing\; time}$$

The method according to the invention is based on the idea of determining that actuation duration at which a stroke movement of the valve element is no longer or just not possible and the valve thus remains closed. Thus, there is no valve opening time and no closing time. By changing the above-mentioned formula for this case, the formula is reduced purely mathematically in: $$\ddot{\mathrm{O}}\mathrm{ffnungsverzugzeit}=\mathrm{control\; period}$$

This means that for this case, the thus determined activation duration corresponds to the opening delay time, which can be regarded as constant irrespective of the actual activation duration during the driving operation in the simplest case.
The closing of the injection valve can be easily determined by various known methods, for example by means of sensors and / or by analysis of electrical or electromagnetic parameters. Some of these are already implemented to control and regulate the injectors. This therefore does not represent an additional cost factor.

The inventive method is particularly effective when the drive time is successively reduced until a closing of the injector just can not be determined, or the drive time is successively increased until a closing of the injector can be determined, and that the opening delay time for the Injection valve is determined from the time from the start of control until the last time or first closing. In order to reduce the determination time, in a first step of the method, a greater temporal jump can be made in the vicinity of the critical point and then approach the critical activation duration in small steps, in which the lifting and closing movement of the valve element is just recognized or straight again is not recognized. It can be taken into account that with a minimal opening of the valve element, the closing can not be diagnosed and thus the diagnosed actuation time deviates from an exact value. For this purpose, for example, in the control and / or regulating device, the determined value of the activation duration can be correspondingly corrected by empirically found adaptation values, for example from a test or test field. It is also conceivable to approach the critical activation duration from both sides and then to form the exact critical activation time from both determined values according to a predetermined algorithm (for example by forming an average value).

In the method according to the invention it is provided that the electrical operating variable is a time derivative (gradient) of a voltage of a magnetic coil of the electromagnetic actuator, and that is concluded from a minimum of the gradient on a closing of the injection valve. By placing the valve element in a valve seat of the injector is the decaying electrical voltage of the electromagnetic actuator is influenced by a change in the mutual induction caused by the change in movement of the valve element, so that it comes to a saddle-like voltage curve, wherein the inflection point of the course corresponds to the touchdown point of the valve element. For reliable detection of the placement of the valve element, the time derivative (gradient) of the voltage curve is advantageous because the saddle-like course is transformed into an easily diagnosed minimum. In this case, only the first occurring minimum is to be considered after completion of the drive time, since, for example, by bouncing the valve element or the anchor later more minima can be generated. Alternatively or additionally, it is possible to detect the placement of the valve element in a second derivative of the function, which has a zero point when closing the valve element. The implementation of the derivation of the voltage curve is possible in the control and / or regulating device easily and at low cost.

In order to obtain reliable values about the opening time delay at all times, and to detect a drift or deterioration of the injection valve as a result of wear, the method is repeated (for example in each case after a specific operating time or a certain number of operating cycles) during operation of the internal combustion engine.

It is also advantageous that the method can be carried out during operation of the internal combustion engine with multiple injections, in which case the change in the activation duration is carried out only in a single injection and compensated by changes in the control period of at least one other individual injection substantially torque and / or exhaust gas neutral. This means that the method does not disturb the operation of the internal combustion engine.

The method may also be performed in a coasting operation of the engine with a late firing angle. This has the advantage that, for example, a fuel pressure can be freely varied as needed for a determination of the pressure dependence of the opening delay time. The injection time can be increased gradually from the safe non-opening state of the injection valve to the first opening. Thus, an impairment on the exhaust gas is minimal. If the activation is assigned a later firing angle, the combustion of the injected fuel takes place substantially neutral in terms of torque. This measure also serves to ensure that normal operation of the internal combustion engine is not hindered by the method.

The knowledge of the exact opening delay time makes it possible to take this into account in a control and / or regulation of the injection valve. As a result, the fuel metering and the overall control and / or regulation of the fuel injection can be further refined (cf formula (1)). The dispersion of the injection amount from one injection valve to the other is - when the opening delay time is determined for all injectors of an internal combustion engine - reduced, which saves fuel and causes a homogenization of the operation of the internal combustion engine.

Furthermore, it is proposed that the method be carried out for different fuel pressures and that a characteristic map be formed from the results of the method. This can then be used for example for a controlled or controlled operation of the fuel injection valves.

Figur 1

eine schematische Darstellung einer Brennkraftmaschine mit mehreren Einspritzventilen;

Figur 2

eine schematische Darstellung eines Einspritzventils aus Figur 1;

Figur 3

zwei Diagramme, in denen einerseits ein Ansteuerstrom des Einspritzventils aus Figur 2 und andererseits deren Auswirkung auf einen Hub des Einspritzventils über der Zeit aufgetragen ist;

Figur 4

drei Diagramme, in denen der Ansteuerstrom, der Hub und die Ableitung der Spulenspannung über der Zeit aufgetragen sind (während eines Normalbetriebs der Brennkraftmaschine);

Figur 5

drei Diagramme ähnlich zu Figur 3, aber mit einer gegenüber Figur 3 verkürzten Ansteuerung;

Figur 6

drei Diagramme ähnlich zu Figur 4, aber mit einer gegenüber Figur 4 nochmals verkürzten Ansteuerung; und

Figur 7

ein Flussdiagramm eines Verfahrens zum Betreiben der Brennkraftmaschine von Figur 1.

Hereinafter, an embodiment of the invention will be explained in more detail with reference to the drawing. Show it:

FIG. 1

a schematic representation of an internal combustion engine with a plurality of injection valves;

FIG. 2

a schematic representation of an injector FIG. 1 ;

FIG. 3

two diagrams in which on the one hand a drive current of the injection valve FIG. 2 and on the other hand its effect on a stroke of the injector over time is plotted;

FIG. 4

three diagrams in which the drive current, the stroke and the derivative of the coil voltage over time are plotted (during normal operation of the internal combustion engine);

FIG. 5

three diagrams similar to FIG. 3 but with one opposite FIG. 3 shortened control;

FIG. 6

three diagrams similar to FIG. 4 but with one opposite FIG. 4 again shortened control; and

FIG. 7

a flowchart of a method for operating the internal combustion engine of FIG. 1 ,

Detailed description

An internal combustion engine carries in FIG. 1 overall, the reference numeral 10. It comprises a tank 12 from which a conveyor system 14 promotes fuel in a common rail 16. To this several injectors 18a to 18d are connected, which inject the fuel directly into them associated combustion chambers 20a to 20d. The operation of the internal combustion engine 10 is controlled or regulated by a control and regulating device 22 which, among other things, also controls the injection valves 18a to 18d.

In FIG. 2 By way of example, the injection valve 18a is shown in greater detail. It comprises an electromagnetic actuator 24, which in turn comprises an electromagnetic coil 26 and a magnet armature 30 on a valve needle 28. The armature 30 is presently firmly connected to the valve needle 28. It is also possible that there is a certain axial play between magnet armature 30 and valve needle 28.

The injection valve 18a basically operates as follows: The injection valve 18a is in FIG. 2 shown in a closed state, ie, the valve needle 28 abuts against a valve seat 32. At the electromagnetic coil 26, an electrical voltage ("drive voltage") is applied to an actuation of the armature 30 via the control of the control and regulating device 22 and an output stage, which energizes the coil 26 and the valve needle 28 with appropriate strength and duration from the valve seat 32 lifts.

FIG. 3 shows a schematic diagram of such a control of the injection valve 18a (as an exemplary example) and the effect on an opening time of the injector 18 over time. The FIG. 3 consists of two diagrams, the upper diagram shows the timing of a drive current I and the lower diagram shows the resulting stroke H of the injection valve 18 a.

The course of the drive current I in the upper diagram shows an initially rapid increase (see reference numeral 40), which is then kept constant over a certain period of time, in order then to drop by about half (see reference numeral 42). This current level is maintained until the end of the control period t _i . The end of the activation period t _i is characterized in that the current I is switched off (see reference numeral 44).

In the lower diagram it can be seen that the valve needle 28 of the injection valve 18a lifts off after the beginning of the activation only after a certain opening delay time t ₁₁ (compare reference number 46). If the valve needle 28 has reached its maximum stroke, a lesser drive current I is sufficient to maintain this level. If the drive current I is switched off, the valve needle 28 returns to the valve seat 32, but also with a delay (see reference numeral 48). The period of time from the switching off of the drive current I until complete closure is defined as the closing time t _from the valve needle 28. The entire valve opening duration is identified by T _op . Purely mathematically, then: $${\mathrm{T}}_{\mathrm{operating\; room}}={\mathrm{t}}_{\mathrm{i}}-{\mathrm{t}}_{\mathrm{11}}+{\mathrm{t}}_{\mathrm{from}}$$

The FIGS. 4 to 6 show three scenarios when operating the injector 18 at different drive durations t _i . Each figure shows three diagrams. The upper diagram shows in each case the course of the drive current I, the middle diagram shows the course of the valve lift H and the lower diagram shows the course of a temporally first derivative ("time gradient") of the coil voltage after completion of the control decaying voltage UM to the solenoid 26 ,

FIG. 4 shows a scenario as it takes place, for example, in a normal operation. The drive current I and the stroke H of the valve needle 28 correspond to the known, procedure described above. It can be seen from the lower diagram that the course of the first derivative of the voltage U _{M has} a minimum 50 which marks the time at which the valve needle 28 is placed in the valve seat 32. The minimum 50 is due to a change in the voltage curve at the magnetic coil 26, which has a saddle-like course at the time of placement of the valve needle 28. This comes from the change in movement when placing the valve needle 28 and the associated change in the mutual induction in the solenoid 26th

FIG. 5 shows a scenario with a slightly shortened drive time t _i . Due to the short duration of the activation duration t _i , the maximum stroke of the valve needle 28 is no longer reached. As a result, the valve opening duration T _{op is} shortened. By placing the valve needle 26 in the valve seat 32, the course of the first derivative of the voltage U _M again has the minimum 50.

In FIG. 6 is the Ansteuerdauer t _i further shortened, in such a way that the valve needle 26 can no longer lift out of the valve seat 32. As a result, the course of the first derivative of the voltage U _{M has} no minimum. The valve opening duration T _op and the closing time t _ab are not present, ie mathematically = 0.

If the two zero values are used in the abovementioned formula for the definition of the valve opening duration T _op , then, in the event that the actuation duration t _{i is} so short that the valve needle 28 has just not lifted off, after a conversion of the formula: $${\mathrm{Activation\; time\; t}}_{\mathrm{i}}=\ddot{\mathrm{O}}{\mathrm{opening\; delay\; t}}_{\mathrm{11}}$$

This means that the opening delay time t _{11 can be} determined by the principle of a successive shortening of the activation period. An accurate knowledge of the opening delay time t ₁₁ enables the control and regulation of the single-point valves 18a to 18d and thereby to refine the entire injection method.

• Ausgangspunkt ist ein normaler Fahrbetrieb mit der durch die Steuer- und Regeleinrichtung 22 vorgegebene Ansteuerdauer t_i (Bezugszeichen 100). Danach überprüft die Steuer- und Regeleinrichtung 22 in Schritt 110, ob die äußeren Bedingungen der Brennkraftmaschine 10 eine Verkürzung der Ansteuerdauer t_i für zumindest ein Einspritzventil 18 zulassen, ohne dass der Fahrbetrieb der Brennkraftmaschine 10 beeinträchtigt wird. Dies wäre bspw. in einem Schubbetrieb gegeben. Ist dies möglich, wird für das ausgewählte Einspritzventil 18 in Schritt 120 die Ansteuerdauer t_i reduziert. Gleichzeitig wird die erste Ableitung des Spannungsverlaufs U_M für die zugeordnete Magnetspule 26 gebildet. Wird ein Minimum 50 im Verlauf der ersten Ableitung erkannt (Bezugszeichen 130), wird die Ansteuerdauer t_i weiter reduziert (Sprung nach Schritt 120). Ist ein Minimum nicht mehr erkannt, ist die kritische Ansteuerdauer t_i erreicht. In diesem Fall wird in Schritt 140 die Öffnungsverzugszeit t₁₁ aus der Differenz aus Ansteuerbeginn und Ansteuerende berechnet. Eventuell können noch Korrekturfaktoren mit einfließen. In Schritt 150 wird das vermessene Einspritzventil 18 in der Steuer- und Regeleinrichtung gekennzeichnet, damit beim nächsten Messzyklus ein anderes Einspritzventil 18 ausgewählt werden kann.

One possible method for determining the opening delay time t ₁₁ is in FIG. 7 shown:

• The starting point is a normal driving operation with the control time t _i predetermined by the control and regulating device 22 (reference numeral 100). Thereafter, the control and regulating device 22 checks in step 110 whether the external conditions of the internal combustion engine 10 allow a shortening of the actuation period t _i for at least one injection valve 18, without affecting the driving operation of the internal combustion engine 10. This would be, for example, given in a push operation. If this is possible, the activation period t _{i is} reduced for the selected injection valve 18 in step 120. At the same time, the first derivative of the voltage curve U _M for the associated magnetic coil 26 is formed. If a minimum 50 is detected in the course of the first derivation (reference numeral 130), the actuation duration t _{i is} further reduced (jump to step 120). If a minimum is no longer detected, the critical drive time t _{i is} reached. In this case, in step 140, the opening delay time t _{11 is} calculated from the difference between the drive start and drive end. Optionally, correction factors can also be incorporated. In step 150, the measured injection valve 18 is identified in the control device, so that another injection valve 18 can be selected at the next measurement cycle.

Claims (13)

1. Method for operating an internal combustion engine (10), in which fuel passes into at least one combustion chamber (20) by means of at least one injection valve (18) comprising an electromagnetic actuation device (24), characterized in that an electrical operating variable of the injection valve (18), characterizing closing of a valve element (28) of the injection valve (18), is analyzed for different actuation periods of the injection valve (18), in that the actuation period is determined during which closing of the valve element (28) can still just be detected or can firstly be detected, and in that the opening delay of the injection valve (18) is determined from this actuation period.
2. Method according to Claim 1 or 2, characterized in that the actuation period is reduced successively until closing of the injection valve (18) can just no longer be detected or the actuation period is increased successively until closing of the injection valve (18) can be detected, and in that the opening delay for the injection valve (18) is determined from the time from the start of actuation up to the last or first closing.
3. Method according to one of the preceding claims, characterized in that the electrical operating variable is a time gradient of a voltage of a coil (26) of the electromagnetic actuation device (24), and in that closing of the injection valve (18) is closed from a minimum of the gradient.
4. Method according to one of the preceding claims, characterized in that the method is carried out repeatedly while the internal combustion engine (10) is operating.
5. Method according to Claim 5, characterized in that it is carried out while the internal combustion engine (10) is operating with multiple injections, wherein the change in the actuation period is carried out as an individual injection, and is compensated essentially mutually in terms of torque and/or exhaust gas by changing the actuation period of at least one other individual injection.
6. Method according to one of Claims 5 or 6, characterized in that it is carried out in an open operation of the internal combustion engine (10) with a late ignition angle.
7. Method according to one of the preceding claims, characterized in that the opening delay is set to be equal to the actuation period at the last-detected or first-detected movement of the valve element (28).
8. Method according to one of the preceding claims, characterized in that the determined opening delay is taken into account during open-loop and/or closed-loop control of the injection valve (18).
9. Method according to one of the preceding claims, characterized in that in the case of an internal combustion engine (10) with a plurality of injection valves (18), the opening delay is determined for all the injection valves (18).
10. Method according to one of the preceding claims, characterized in that it is carried out for different fuel pressures and a characteristic diagram is formed from the results of the method.
11. Computer program, characterized in that it is programmed for application in a method according to one of the preceding claims.
12. Electrical storage medium for an open-loop and/or closed-loop control device (22) of an internal combustion engine (10), characterized in that a computer program for application in a method of Claims 1 to 10 is stored in said storage medium.
13. Open-loop and/or closed-loop control device (22) for an internal combustion engine (10), characterized in that it is programmed for application in a method according to one of Claims 1 to 10.

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