DE102019001677B4 - Method for predicting the condition of an injector - Google Patents

Abstract

Method for predicting the state of an injector (7) in a common rail system, in which a deviation of a target operating point from an actual operating point of the injection is calculated based on the individual accumulator pressure (pE), in which an abstracting function is derived from a plurality of deviations in the operating point as well as their parameters are determined, a time development of the parameters of the abstracting function is observed, in which a condition prognosis of the injector (7) is made based on the time development of the parameters and a maintenance recommendation is made, in which based on the position of the actual operating point in an injector map (11) an area (Bi) of the injector map (11) is determined, based on the deviations of the operating point for each area (Bi) an area-specific abstracting function and their area-specific parameters are determined, in which a time development of area-specific parameters of abstrahi The maintenance recommendation is made on the basis of a summary of all area-specific temporal developments of the parameters, in which a Gaussian normal distribution is determined as the abstracting function and a mean value and a standard deviation are determined as the parameters of the abstracting function and in which an envelope curve as a summary of all area-specific normal distributions is calculated, the area of which is determined and the maintenance recommendation is defined via an area portion in the impermissible value range.

Description

The invention relates to a method for predicting the condition of an injector in a common rail system, in which a target / actual deviation of an operating point of the injection is calculated using the individual accumulator pressure, in which an abstracting function and its parameters are determined from a plurality of deviations from the operating point, a Temporal development of the parameters of the abstracting function is observed and in which a condition prognosis of the injector is made based on the temporal development of the parameters and a maintenance recommendation is made.

From the DE 10 2004 006 896 A1 a common rail system with individual accumulators is known in which the injection is assessed on the basis of the measured individual accumulator pressure. For this purpose, a target / actual deviation of the start of injection is determined and compared with a tolerance band. This applies mutatis mutandis to the end of the injection. If both the start of injection deviation and the end of injection deviation are within the tolerance band, the injector is fault-free. If the start of injection deviation or the end of injection deviation is outside the tolerance band, the injector is assessed as faulty and either the control parameters of the injector are adjusted or the injector is deactivated. The reference describes a purely reactive system in which an exchange of the injector is initiated in a fixed time interval or only after a malfunction is detected.

The DE 10 2012 204 319 A1 describes a method for determining a functional state value for a fuel supply system, in which a speed deviation of an actually installed low-pressure fuel pump compared to a calibrated fuel pump is calculated, then the progression of the deviation is determined and a functional state is calculated from this. Based on the development of the functional state over time, a state prognosis is made and a maintenance recommendation is made.

The DE 10 2016 218 278 A1 discloses a method for operating a solenoid valve for fuel metering, in which the opening duration, the mass flow through the opened solenoid valve and the leakage flow are determined and stored. The saved values are the basis for estimating the service life of the solenoid valve.

The US 2017/0082053 A1 describes a method for identifying a defective injector by detecting the influence of an injecting injector on the speed. A mean value is then calculated from the speed changes of all injectors and the deviation from the mean value is determined for each injector. A defective injector can then be identified using a standard deviation calculated individually for the injector with a subsequent limit value observation.

Finally from the DE 10 2016 119 043 A1 a method for determining an injector precision is known in which a degree of dispersion is calculated from injection quantity values, in particular on the basis of the variance or standard deviation among the injection quantity values.

The invention is based on the object of developing a method for determining the state of an injector with an early indication of its malfunction.

This object is achieved by the features of claim 1. The refinements are presented in the subclaims.

The method according to the invention now provides that an abstracting function and its parameters are determined from a plurality of deviations in the operating point, for example the duration of energization of the injector, and the development of the parameters of the abstracting function over time is observed. Based on the development of the parameters over time, a condition forecast of the injector is made and a maintenance recommendation is made. A normal distribution or an exponential function can be used as an abstracting function. In the case of a normal distribution, the parameters then correspond to the mean value and the standard deviation.

Furthermore, the method provides that, based on the position of the actual operating point in an injector characteristic diagram, an area of the injector characteristic diagram is selected and, for example, a normal distribution is selected as an abstracting function for each area. On the basis of the development over time of the area-specific parameters of the abstracting functions, an envelope curve is calculated from the area-specific normal distributions, with a maintenance action being defined via the area portion in the impermissible value range.

The invention offers the known advantages of a condition-based maintenance, that is, the injector is simply no longer exchanged rigidly at predetermined maintenance intervals, but depending on the respective wear. The forecast, in turn, offers the advantage of early procurement of spare parts, including early commissioning of the service personnel. Overall, there is therefore a higher degree of availability of the internal combustion engine, combined with a corresponding one Cost advantage for the operator. In addition, the process can be applied retrospectively in the electronic control unit as a program supplement without changing the sensors.

• 1 ein Systemschaubild,
• 2A,B einen Verlauf des Einzelspeicherdrucks,
• 3 einen Programm-Ablaufplan,
• 4 ein Injektor-Kennfeld,
• 5 einen Ausschnitt des Injektor-Kennfelds und
• 6 mehrere Zustandsdiagramme.

A preferred embodiment is shown in the figures. Show it:

• 1 a system diagram,
• 2A, B a course of the individual accumulator pressure,
• 3 a program schedule,
• 4th an injector map,
• 5 a section of the injector map and
• 6th several state diagrams.

The 1 shows a system diagram of an electronically controlled internal combustion engine 1 with a common rail system and individual accumulators. The common rail system comprises the following mechanical components: a low pressure pump 3 for pumping fuel from a fuel tank 2 , a variable suction throttle 4th to influence the flow of fuel flowing through, a high-pressure pump 5 to deliver the fuel under pressure increase, a rail 6th to store the fuel and injectors 7th for injecting the fuel into the combustion chambers of the internal combustion engine 1 . In the illustrated embodiment, the individual memory 8th in the injector 7th integrated as an additional buffer volume. The one from the injector 7th The fuel to be injected is taken from the individual reservoir 8th taken. The feed line from the rail 6th to single storage 8th is designed in such a way that just enough fuel comes out of the rail during the injection pause 6th in the individual storage 8th is promoted that the individual storage 8th is filled again at the beginning of the new injection. The feed line therefore has a defined hydraulic resistance.

The mode of operation of the internal combustion engine 1 is controlled by an electronic control unit 10 certainly. The electronic control unit 10 contains the usual components of a microcomputer system, for example a microprocessor, I / O modules, buffers and memory modules (EEPROM, RAM). In the memory modules are those for the operation of the internal combustion engine 1 relevant operating data in maps / characteristics or applied as engine models. The electronic control unit uses this to calculate 10 the output variables from the input variables. In the 1 the following input variables are shown as examples: the rail pressure pCR, which is determined by means of a rail pressure sensor 9 is measured, an engine speed nMOT, the individual accumulator pressure pE and an input variable ON. The input variable EIN summarizes the output specified by the operator and the other sensor signals, for example the charge air pressure of an exhaust gas turbocharger. In the 1 are as output variables of the electronic control unit 10 a PWM signal to control the suction throttle 4th , a signal ve for controlling the injector 7th (Start of injection / end of injection) and an output variable AUS. The output variable AUS is representative of the other control signals for controlling and regulating the internal combustion engine 1 , for example for a control signal for activating a second exhaust gas turbocharger in the case of register charging.

The 2 consists of the two 2A and 2 B which show the individual accumulator pressure pE over time t. In the 2A a target injection course is shown as a dash-dotted line, while the solid line indicates an actual injection course. The curves also apply in an analogous manner to a course over a crankshaft angle. A target fuel volume and the injection time / start of injection are calculated in a known manner from the output specification of the operator. The target fuel volume and the rail pressure then define an injection duration and ultimately an energization duration with which the injector is activated. Like in the 2A shown, the electronic control unit initiates an injection at a first point in time t1 and then deactivates the injection at a point in time t2. The time period t1 / t2 corresponds to an energization duration BD. The curve of the individual accumulator pressure pE corresponds to this injection event with a target injection start SB (SL) and a target injection end SE (SL). Due to signal transit times, tolerances or aging effects, however, the actual course of the injection deviates from the specification. The electronic control unit determines the actual course of the injection from the measured individual accumulator pressure pE. In the 2A this is shown as the actual start of injection SB (IST) and the actual end of injection SE (IST). The electronic control device now adapts the actual curve to the target curve by changing the current supply duration BD. The adjusted course is in the 2 B shown accordingly. The method can also be implemented in an analogous procedure by adapting the start of injection.

In the 3 the process is shown in a program flow chart. At S1 the individual accumulator pressure pE is read in within a predetermined time window or crankshaft angle range. The injection duration and from this the energization duration BD are determined from the individual accumulator pressure. At S2, the actual operating point of the injection is derived from the control variables of the injection and assigned to an operating range of an injector characteristic diagram. Among the control variables of the injection are the energization duration BD, der Understand rail pressure pCR and fuel volume VKr. An injector map 11 is for an ideal injector in the 4th shown. In this characteristic diagram, the energization duration BD is shown in milliseconds on the abscissa and the fuel volume VKr to be injected is shown in cubic millimeters on the ordinate. The injector map 11 shows six operating ranges Bi with the reference symbols B1 to B6, the operating ranges B1 to B3 characterizing the ballistic operation of the injector. The parallel lines within the injector map 11 correspond to the rail pressure pCR. In step S2, a deviation dBD of the energization duration is calculated and an area Bi of the injector characteristic diagram 11 assigned. For example as point B in area B6. The further description is now based on FIG 5 . The 5 shows a section of the injector map 11 the 4th , more precisely, the area B6. A family of straight lines is shown which defines the maximum adjustment range of the energization duration BD. The family of straight lines is limited by a straight line with the reference value RV = -100% and a straight line with the reference value RV = + 100%. The dash-dotted straight line with the reference value RV = 0% corresponds to the ideal injector characteristic. In the ideal case, point B lies on the straight line with the reference value RV = 0%. Due to aging effects, however, point B can, for example, lie on the straight line with the reference value RV = -75%. In the 5 this corresponds to point C. It applies to point C that the energization duration BD compared to the ideal value, point B, was shortened by 75% of the maximum permissible correction of -100% in order to inject the specified amount of fuel. An injection event in area B6 is therefore counted with minus seventy-five percent as a discrete value. This applies analogously to point D, that is to say, an injection event in area B6 is counted with plus twenty-five percent. Point E is outside the adjustment range.

In the 3 the injection event for data reduction is counted in a class following S3 at S4. The operating point C is therefore counted in the minus seventy-five percent class as a discrete value. An area-specific abstracting function is then determined from the count values of the area at S5. The further explanation is based on a Gaussian normal distribution as an abstracting function. Step S5 therefore describes the transition from discrete numerical values to a mathematical function. The parameters of a Gaussian normal distribution are the mean My and the standard deviation sigma. At S5, the change in these parameters is then observed during a predefinable period t. From the change in these parameters within this time period t, a future target value can be forecast within a time period tx, S6. The state prognosis is therefore determined via extrapolation. My (t + tx) applies to the future mean value and Sigma (t + tx) applies to the standard deviation. A typical value for tx is 3000 operating hours. Then at S7 a statistical forecast is calculated as a weighted calculation of the information from all areas B1 to B6. For this purpose, the envelope curve of the area-specific normal distributions is formed, the area of which is calculated and how large the area is outside the permissible area. A check is then made at S8 to determine whether the area outside the permissible range, reference symbol VALUE, is greater than a first limit value GW1, for example 2%. If this is not the case, query result S8: no, normal operation remains set as the operating mode, S9, and the flow chart is continued at S14. If it was found at S8 that the calculated area VALUE is greater than the first limit value GW1, then at S10 a maintenance recommendation is displayed to the operator. Subsequently, at S11 it is checked whether the area VALUE is greater than a second limit value GW2, for example 5%. If this is not the case, query result S11: no, the program sequence is continued at S14. Otherwise, a power-reduced operation of the internal combustion engine is initiated at S12 and this is indicated to the operator. Maintenance is initiated at S13. Maintenance can be initiated automatically by informing the service technician of the maintenance date and the procurement of spare parts. It is then checked at S14 whether the operator has initiated an engine stop. If this is not the case, the program flow chart branches to point A. Otherwise the program flow chart is ended.

The 6th includes the 6A to 6E , in which the procedure is shown again. In the 6A to 6D three examples are drawn. The figures on the left side of the drawing correspond to one another. Accordingly, the figures in the middle of the drawing page correspond to one another and the figures on the right-hand side of the drawing correspond to one another. The 6A shows the injection events counted in classes as a bar chart, so shows the bar chart 12th the number n1 in the first area B1 of the injector map. The bar chart shows accordingly 13th the number n2 for the second area B2 and the bar chart 14th the number n3 for the third area B3. From the column chart 12th ( 6A) can be a normal distribution 15th ( 6B) as an abstracting function. As parameters of the normal distribution 15th the mean My1 (solid line) and the standard deviation Sigma1 (dash-dotted line) are defined and their curves are determined over time t ( 6C ). The development over time can then be forecast for a point in time tx in the future, for example tx = 3000 operating hours. The predicted mean value and the predicted standard deviation are the parameters for a predicted normal distribution 18th , please refer 6D . The 6D shows how the normal distribution 15th of the first area B1 will in future be in the direction of the normal distribution 18th changed. In the same way, they become a bar chart 13th the normal distribution 16 , the future development of the parameters ( 6C ) and the predicted normal distribution 19th certainly. For the column chart 14th of the third area B3, the normal distribution then results 17th and the predicted normal distribution 20th ( 6D ). The further method now consists in creating an envelope curve from the forecast parameters or the forecast normal distributions of all areas in a first step 21st and their area are added. The area is calculated from the sum of the predicted normal distributions. In a second step, it is then checked how large the area portion, based on the total area, is which is outside the permissible range. In the 6E this area portion, which lies outside the range of -100%, is marked with the reference symbol VALUE. The stepped maintenance recommendation described above is then based on the area share VALUE. In the 3 this corresponds to queries S8 and S11.

List of reference symbols

1

Internal combustion engine

2

Fuel tank

3

Low pressure pump

4th

Suction throttle

5

high pressure pump

6th

Rail

7th

Injector

8th

Single storage

9

Rail pressure sensor

10

Electronic control unit

11

Injector map

12

Bar chart, first area

13th

Bar chart, second area

14th

Bar chart, third area

15th

Normal distribution, first area

16

Normal distribution, second area

17th

Normal distribution, third area

18th

Predicted normal distribution, first range

19th

Predicted normal distribution, second area

20th

Predicted normal distribution, third area

21st

Envelope curve

Claims (3)

Method for predicting the state of an injector (7) in a common rail system, in which a deviation of a target operating point from an actual operating point of the injection is calculated based on the individual accumulator pressure (pE), in which an abstracting function is derived from a plurality of deviations in the operating point as well as their parameters are determined, a time development of the parameters of the abstracting function is observed, in which a condition prognosis of the injector (7) is made based on the time development of the parameters and a maintenance recommendation is made, in which based on the position of the actual operating point in an injector map (11) an area (Bi) of the injector map (11) is determined, based on the deviations of the operating point for each area (Bi) an area-specific abstracting function and their area-specific parameters are determined, in which a time development of area-specific parameters of abstrahi The maintenance recommendation is made on the basis of a summary of all area-specific temporal developments of the parameters, in which a Gaussian normal distribution is determined as the abstracting function and a mean value and a standard deviation are determined as the parameters of the abstracting function and in which an envelope curve as a summary of all area-specific normal distributions is calculated, the area of which is determined and the maintenance recommendation is defined via an area portion in the impermissible value range. Procedure according to Claim 1 , characterized in that the deviation of the operating point is determined from a duration of energization. Procedure according to Claim 1 , characterized in that the deviation of the operating point is determined from a start of injection.

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