Method for adapting a common-rail injection system of an internal combustion engine

Abstract

In a method for adapting at least one injector of an injection system, in particular of a common-rail injection system of an internal combustion engine of a motor vehicle, where injections take place based on a characteristics map with at least two input variables and at least one output variable, a transition is carried out into a learning mode in which only discrete values are permitted for one of the at least two input variables of the characteristics map.

Claims

1. A method for adapting at least one injector of an injection system of a motor vehicle, in which injections are performed based on a characteristics map that provides at least one output variable based on at least two input variables, the method comprising: transitioning, by processing circuitry, into a learning mode in which only discrete values are permitted for one of the at least two input variables of the characteristics map; and updating, by the processing circuitry, the characteristics map during the learning mode; and adapting an activation period of the at least one injector of the injection system of the motor vehicle, in which injections are performed based on the characteristics map that provides the at least one output variable based on the at least two input variables.

2. The method of claim 1, wherein the transitioning is performed when correction parameters for the updating must be ascertained.

3. The method of claim 1, wherein one of the at least two input variables of the characteristics map is adjusted only in discrete stages.

4. The method of claim 3, wherein only predefined values for which discrete check points are provided in the characteristics map are used for the discrete stages.

5. The method of claim 1, further comprising: ascertaining a value of the one input variable to be provided during normal operation, wherein, the updating includes setting whichever one of the permitted discrete values that is closest to an ascertained value as a setpoint value of the one input variable.

6. The method of claim 1, wherein a hysteresis is provided at each of a plurality of switchover points between respective pairs of the permitted discrete values.

7. The method of claim 1, wherein an entirety of the characteristics map is generated from multiple characteristic curves formed using discrete values of the one input variable.

8. The method of claim 1, wherein the transitioning is performed only if predefined boundary conditions, which can influence the behavior of the at least one injector of the injection system, are within limits predefined as normal for a driving operation.

9. The method of claim 1, wherein the injection system is a common-rail injection system of an internal combustion engine of a motor vehicle.

10. The method of claim 1, wherein the injection system is a common-rail injection system and the one variable is a rail pressure.

11. The method of claim 10, wherein the one variable is a setpoint value of the rail pressure.

12. A non-transitory computer-readable medium having a computer program, which is executable by a processor, comprising: a program code arrangement having program code for adapting at least one injector of an injection system, in which injections are performed based on a characteristics map that provides at least one output variable based on at least two input variables, by performing the following: transitioning into a learning mode in which only discrete values are permitted for one of the at least two input variables of the characteristics map; and updating the characteristics map during the learning mode; and adapting an activation period of the at least one injector of the injection system of the motor vehicle, in which injections are performed based on the characteristics map that provides the at least one output variable based on the at least two input variables.

13. An electronic control device comprising processing circuitry, wherein the processing circuitry is configured to perform a method for adapting at least one injector of an injection system, in which injections are performed based on a characteristics map that provides at least one output variable based on at least two input variables, the method comprising: transitioning into a learning mode in which only discrete values are permitted for one of the at least two input variables of the characteristics map; and updating the characteristics map during the learning mode; and adapting an activation period of the at least one injector of the injection system of the motor vehicle, in which injections are performed based on the characteristics map that provides the at least one output variable based on the at least two input variables.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flowchart that illustrates a method according to an example embodiment of the present invention.

(2) FIG. 2 shows, using the example of a rail pressure setpoint value, a connection between the setpoint value of a variable which is to be established for discrete values in a learning mode during normal operation (x axis) as well as during the learning mode (y axis), according to an example embodiment of the present invention.

(3) FIG. 3 shows a variant of the connection shown in FIG. 1 including an extension by the hysteresis loops provided at the switchover points, according to an example embodiment of the present invention.

(4) FIG. 4 shows an a processing structure of a pilot-controlled correction for adapting an individual injector behavior, according to an example embodiment of the present invention.

DETAILED DESCRIPTION

(5) The example embodiment illustrated in FIG. 1 of the method according to the present invention is described using the example of a characteristics map of a common-rail injection system of an internal combustion engine of a motor vehicle in which the activation period is stored as an output variable as a function of the desired injection duration and the rail pressure as input variables. It is understood that the principles described herein and the method described herein are in general also applicable in the case of other characteristics maps or in the case of other injection systems having corresponding characteristics maps.

(6) It is initially checked 100 whether the correction parameters which are necessary for the adaption or correction of an individual injector have not been yet ascertained at all or must be re-ascertained, since a predefined maintenance interval was exceeded. If one of these conditions is met, the normal driving operation of the motor vehicle is switched to learning mode 105. In this example embodiment, the learning mode differs from the normal operation only in that the rail pressure is no longer predefined in such a way that it is continuously adjustable as a function of the desired injection quantity and the rotational speed of the internal combustion engine, but such that the setpoint value of the rail pressure may have only exactly predefined discrete values. These predefined values are preferably identical to the pressure values for which base points are already provided in the characteristics map which is to be adapted or subsequently corrected.

(7) The above-mentioned limitation to discrete values takes place according to the present example embodiment in that initially a rail pressure p.sub.rail,n (see FIG. 2, reference numeral 200) to be provided during normal driving operation is ascertained 110 and then the (discrete) value which is closest to it and which is permissible in the learning mode is determined and used 115 as rail pressure value p.sub.rail,setpoint (see FIG. 2, reference numeral 205).

(8) In order to avoid a frequent switchover between two discrete rail pressure values, the characteristic curve shown in FIG. 2 and having the rail pressure setpoint value p.sub.rail,n during normal operation as the input variable (x axis) and the rail pressure setpoint value p.sub.rail,setpoint during learning mode as the output variable (y axis) can in each case be provided with a hysteresis 305 at switchover points 210, 300 (see FIG. 3).

(9) In the described example embodiment, it is achieved overall that during the learning mode only the setpoint injection duration is still continuously adjusted and the measured values can be unambiguously assigned to a characteristic curve activation period=f (injection duration) at a fixed rail pressure in each case, the entire characteristics map possibly being made up of multiple characteristic curves of this type at discrete rail pressure values in each case.

(10) Since the deviation between the rail pressure selected in the learning mode and that provided during normal operation is relatively small in each case if the stages of the characteristic curve shown in FIGS. 2 and 3 are accordingly fine and, in addition, the injected fuel quantity itself is not changed by the learning mode, the learning mode or the transition from normal operation to learning mode remains unnoticed by the vehicle driver and can thus be maintained in the driving operation until a sufficient amount of measured values for a precise adaption or subsequent correction of the characteristics map is available. It is thus possible to switch any time from normal mode to learning mode during the driving operation (see FIG. 1, reference numeral 105), if necessary, so that the learning mode is not limited to exceptional situations during the driving operation.

(11) According to one variant, the learning mode is enabled only when certain boundary conditions, which may influence the injector behavior, are within limits that are normal for the driving operation so that measured values which are influenced by certain boundary conditions are not taken into consideration when correcting the characteristics map. The above-mentioned boundary conditions can be, for example, the cooling water temperature or the fuel temperature present in the internal combustion engine.

(12) One example embodiment of a processing structure for subsequent multiplicative and additive correction of the output variable of a characteristics map is illustrated in FIG. 4. According to this structure, the activation period AD.sub.0 415 which is necessary for such an injector is initially ascertained on the basis of a two-dimensional application characteristics map 400 for a mean-valued injector from a setpoint value of injection duration T.sub.open 405 and an actual value of rail pressure p.sub.rail,actual 410. Subsequently, a multiplicative correction factor K.sub.m 425 is, in turn, determined as a function of the above-mentioned actual value of rail pressure p.sub.rail,actual 410 from a first adaption characteristic curve 420.

(13) Furthermore, an additive correction factor K.sub.+ 435 is also determined as a function of the actual value of rail pressure p.sub.rail,actual 410 from a second adaption characteristic curve 430.

(14) Activation period AD.sub.korr 450 which is adapted to the individual injector behavior is computed on the basis of the two correction factors 425, 435 determined in this manner according to the relationship [AD.sub.korr=K.sub.m*AD.sub.0+K.sub.+] with the aid of a multiplicative linking point 440 and an additive linking point 445. The base points of the first and the second adaption characteristic lines have been in this case determined beforehand based on the method according to the present invention, i.e., during the above-mentioned learning mode. Starting values for correction factors K.sub.m and K.sub.+ prior to a learning process which is carried out for the first time are:
K.sub.m(p.sub.rail,actual)=1 and
K.sub.+(p.sub.rail,actual)=0.

(15) It is to be noted that the above-described learning mode may also be accordingly applied to determine adaption parameters for other variables than the ones described here as an example.

(16) The method described above can be implemented in the form of a control program for an electronic control device for controlling an internal combustion engine or in the form of one or multiple corresponding electronic control units (ECUs).