Method for failure detection of injectors in an internal combustion engine, control unit and system for carrying out a method

Abstract

The invention relates to a method for detecting the failure of injectors in an internal combustion engine, comprising the following steps: measuring a crank angle signal; transforming the crank angle signal into the frequency range by means of a discrete Fourier transformation; switching off each injector once and in a sequential manner; detecting and storing an angle of the harmonic of the 0.5th order of the Fourier-transformed crank angle signal for each switched-off injector once and in a sequential manner; continuous detection and storage of an angle and an amount of the harmonic of the 0.5th order of the Fourier-transformed crank angle signal; continuous comparison of the continuously detected amount with a predetermined threshold value, and determining a failure of the injector when the amount exceeds the predetermined threshold value; comparing the continuously detected angle with the angles stored for each switched-off injector when a failure of the injector is detected, and identifying the failed injector with an injector, for which a matching, stored angle is found.

Claims

1. A method for failure detection of injectors in an internal combustion engine, including the steps of: measuring a crank angle signal; transforming said crank angle signal into a frequency range using discrete Fourier-transformation; sequentially turning off each of a number of injectors one time; sequentially capturing and storing one time an angle of the harmonic of the 0.5th order of said Fourier-transformed crank angle signal for each said turned off injector; continuously capturing and storing an angle and an amount of the harmonic of the 0.5th order of said Fourier-transformed crank angle signal; continuously comparing said continuously captured amount with a predetermined threshold value and detecting an injector failure if said continuously captured amount exceeds said predetermined threshold value; and comparing said continuously captured angle with said sequentially captured angles stored for each said turned off injector, if said injector failure has been detected, and identifying said failed injector as an injector for which a stored sequentially captured angle corresponds.

2. The method according to claim 1, wherein: said sequentially captured angles are stored in a look-up table.

3. The method according to claim 1, wherein: said sequential capture and storing of said angles for each said turned off injector is performed after a start of the internal combustion engine or after a start of the method.

4. The method according to claim 1, wherein: at least one action is taken when said injector failure is detected and said failed injector is identified, whereby said at least one action is selected from a group of measures consisting of issuing a warning message to a driver or operator, interrupting an energizing of said failed injector, reducing a performance of the internal combustion engine, and shutting off the internal combustion engine.

5. The method according to claim 1, wherein: said continuously captured and stored angle and amount of the harmonic of the 0.5th order of said Fourier-transformed crank angle signal is initially stored when an initial injector failure is detected, before said angles for each said turned off injector are sequentially captured and stored one time, immediately after a start of the internal combustion engine or of the method; after capture and initial storing of said continuously captured and stored angle and amount, said injectors are turned off sequentially one time, and for each injector an amount and an angle of the harmonic of the 0.5th order of the crank angle signal is captured and compared with said initially stored continuously captured and stored angle and amount; and a failed injector is identified by a correspondence between said amount and angle captured for said turned off injector and said initially stored continuously captured and stored angle and amount.

6. The method according to claim 5, wherein: at least one action is taken when said injector failure is detected and said failed injector is identified, whereby said at least one action is selected from a group of measures consisting of issuing a warning message to a driver or operator, interrupting an energizing of said failed injector, reducing a performance of the internal combustion engine, and shutting off the internal combustion engine.

7. The method according to claim 1, wherein: the method is performed by an engine control unit; said crank angle signal is captured by a crank shaft sensor; and said engine control unit is initially synchronized to work cycles of the internal combustion engine using a cam shaft signal.

8. The method according to claim 1, wherein: the method is performed at one operating point of the internal combustion engine under load or no-load.

9. An engine control unit for an internal combustion engine, said engine control unit implementing a series of steps, said series of steps comprising: measuring a crank angle signal; transforming said crank angle signal into a frequency range by way of discrete Fourier-transformation; sequentially turning off each of a number of injectors one time; sequentially capturing and storing one time an angle of the harmonic of the 0.5th order of said Fourier-transformed crank angle signal for each said turned off injector; continuously capturing and storing an angle and an amount of the harmonic of the 0.5th order of said Fourier-transformed crank angle signal; continuously comparing said continuously captured amount with a predetermined threshold value and detecting an injector failure if said continuously captured amount exceeds said predetermined threshold value; and comparing said continuously captured angle with said sequentially captured angles stored for each said turned off injector, if said injector failure has been detected, and identifying said failed injector as an injector for which a stored sequentially captured angle corresponds.

10. A system to detect injector failure in an internal combustion engine, comprising a detection device designed to capture a crank angle signal; a converter designed to transform said crank angle signal into a frequency range by way of discrete Fourier transformation; a switching device designed to sequentially turn off a number of injectors of the internal combustion engine; a first memory device designed to capture and store an angle of the harmonic of the 0.5th order of said crank angle signal for each said turned off injector; a second memory device designed to continuously capture and store an angle and an amount of the harmonic of the 0.5th order of said crank angle signal; a first comparison device designed to continuously compare said amount stored in said second memory device with a predetermined threshold value, said first comparison device being further designed so that it detects an injector failure when said amount exceeds said predetermined threshold value; a second comparison device designed to compare said angle stored in said second memory device with each said angle stored in said first memory device when said injector failure occurs, said second comparison device being further designed so that it identifies said failed injector as an injector for which an angle stored in said first memory device corresponds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing, wherein:

(2) The FIGURE shows a flow diagram of one embodiment of the method.

(3) Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

(4) Turning now to the FIGURE, in a first step 1 the method for failure recognition of injectors is initiated. This may occur together with or immediately after the start of the internal combustion engine. In a second step 3 an amount and an angle of a harmonic of the 0.5th order of a crank angle signal that was transformed by way of discrete Fourier transformation into the frequency range are captured and possibly stored in a third memory device. A retrieval step 5 follows, which verifies if the amount initially stored in step 3 is greater than a predetermined threshold value.

(5) If this is not the case, then there is clearly no initially failed injector and the method proceeds further to retrieval step 7. Here it is verified if a first memory device has already been initialized. The first memory device may be newly initialized after each new start of the internal combustion engine. It is, however, not absolutely necessary to re-initialize the first memory device if the method is halted during running operation of the internal combustion engine and, after a certain waiting period, is started again. But, it is certainly possible to re-initialize the first memory device, whereby it can also be erased at the end of the process, so that it must be newly initialized upon restart of the engine. In an alternative embodiment it is of course also possible that the memory device is not re-initialized after each new start of the internal combustion engine, but that the values filed in particular in the lookup-table are used for a predetermined number of uses of the internal combustion engine. If the first memory device is not yet initialized the method proceeds to step 101. Otherwise, if an initialized first storage device or respectively a look-up table that is filled with data is already available, the method proceeds to a step 9.

(6) Initialization of the first memory device and/or assignment of data to the look-up table is described next. For this purpose a number of cylinders of the internal combustion engine and thereby also the number of injectors of the internal combustion engine is first determined in step 101. In one embodiment of the method the internal combustion engine includes exactly one injector per cylinder. It is however also possible that more than one injector per cylinder can be provided. The method described below is then modified accordingly. For the sake of simplicity, only the arrangement wherein the internal combustion engine only includes one injector per cylinder is described here. The determined number of cylinders is stored and a running variable is set to value 0.

(7) Afterwards it is verified in retrieval step 103 whether the current value of the running variable is less than the stored number of cylinders. If this is the case, the method proceeds to a step 105, in which a first injector is turned off if the running variable shows a value of 0, in which a second injector is turned off if the running variable shows a value of 1, and so on. Thus always one and only one injector that is clearly assigned to the current value of the running variable is turned off. In a subsequent step 107 an angle of the harmonic of the 0.5th order is captured and filed in the first memory device or respectively the look-up table, and is assigned to the only turned off injector according to the current value of the running variable. In a following step 109 the relevant injector that is assigned to the current value of the running variable is turned on again.

(8) In a subsequent step 111 the value of the running variable is increased by an amount of 1. The process returns to retrieval step 103 where it is again verified whether the new value of the running variable is still less than the stored number of cylinders. If this is still the case, the sequence of steps 105 to 111 is repeated. In other words, a loop around retrieval step 103 and steps 105 to 111 is cycled until for each individually turned off injector an angle of the harmonic of the 0.5th order has been captured and stored. The first time the running variable shows a value which is consistent with the number of cylinders, the appropriate loop for all injectors will have been cycled, the first loop having started for the first injector with value 0 for the running variable. Therefore, the loop will have occurred for the last injector when the running variable shows a value that is consistent with the number of cylinders, reduced by 1.

(9) If, therefore the running variable shows a value for the first time in retrieval step 103 that is identical to the number of cylinders, the method proceeds to step 9. As already explained, the method also proceeds directly from retrieval step 7 to step 9 if initialization of the first memory device, or respectively placement of data in the look-up table can be foregone. In step 9 an amount as well as an angle of the harmonic of the 0.5th order of the Fourier transformed crank angle signal is captured and may be stored in a second memory device. In retrieval step 11 it is verified if the amount captured and stored in step 9 is greater than the predetermined threshold value. If this is not the case then there is clearly no injector failure and the process returns to step 9, where again an amount and an angle of the harmonic of the 0.5th order is captured and stored. Thereby it becomes clear that no loop occurs here, wherein an amount and an angle of the harmonic of the 0.5th order is continuously captured and stored. This is continued until it is determined in retrieval step 11 that the current captured and stored value is greater than the predetermined threshold value. In this case there is an injector failure and the method proceeds to step 13, where the angle captured in step 9 is compared individually with the angles stored in the first memory device or respectively the lookup-table that are respectively assigned to individually turned off injectors.

(10) In retrieval step 15 it is finally verified whether, within the scope of a predetermined tolerance, or respectively error range, a conforming angle has been found. If this is not the case, it is determined in step 17 that there is clearly an error, wherein the failed injector has not been recognized. In this case the method returns to step 9 and the continuous capture and storage of the amount and the angle of the harmonic of the 0.5th order of the Fourier transformed crank angle signal resumes. If in contrast a conforming angle has been detected, then the failed injector can at the same time be identified by way of the values on file in the first memory device or respectively the lookup-table. The failed injector is then output in step 19 and/or measures are taken whereby for example a warning message is issued to a driver or operator of the internal combustion engine, energizing of the failed injector is interrupted, performance of the internal combustion engine is reduced, and/or the internal combustion engine is shut off. After this, the method concludes preferably in step 21.

(11) If an initially failed injector has been detected in step 5, because the initially captured value for the amount of the harmonic of the 0.5th order is greater than the predetermined threshold value, the method does not proceed to retrieval step 7, but rather to step 201. In this step, the number of cylinders is determined, analogously to the procedure in step 101, and the value 0 is assigned to a running variable. Reference is made in this respect to the explanations given for step 101. In both steps 201 and 101 deviating starting values for the running variable are possible. The method is then modified accordingly. In retrieval step 203 it is verified analogously to retrieval step 103 whether the running variable is smaller than the number of cylinders. This is typically the case on a first accessing of retrieval step 203, because the running variable was previously set to value 0 in step 201. In step 205 one injector to which the current value of the running variable is assigned is turned off. In regard to the assignment of the injectors to the values of the running variable we refer to the explanations already given in connection with retrieval step 103 and steps 105 to 111. Note that in step 205 only one single injector that is clearly assigned to the current value of the running variable is selectively turned off.

(12) In a step 207 an amount and an angle of the harmonic of the 0.5th order are captured according to the operating condition of the internal combustion engine with the currently turned off injector that is assigned to the current value of the running variable. In retrieval step 209 the thus determined values for the amount and the angle which are assigned to the current value of the running variable are compared with the values that were initially determined and stored in step 3. If these values coincide, possibly within a predetermined tolerance range or respectively error range, the failed injector is the one currently turned off because no change in regard to the values that are assigned to the harmonic of the 0.5th order resulted. In this case, the method proceeds to step 19 because the initially failed injector has been recognized. The already described procedures may then be implemented and the process concludes in step 21. If, in contrast the values that are assigned to the current value of the running variable do not coincide in retrieval step 209 with the values that were initially measured in step 3, then clearly the injector that was turned off was not the failed injector.

(13) In this case, the injector that was turned off at the current value of the running variable is turned on again in step 211, and the count of running variable is increased by 1 in a step 213, in other words its amount is increased by 1. The process then returns to retrieval step 203 where it is again verified whether the current value of the running variable is less than the number of cylinders. A loop then occurs here which will cycle until either the initially failed injector has been identified, or until all injectors have been turned off individually, without the failed injector having been identified. Only in this last example does the running variable assumes a value which is consistent with the number of cylinders in retrieval step 203. In all other cases the loop ends earlier in retrieval step 209 because the failed injector has been identified with the process therefore moving on to step 19. Since in the last case the loop was cycled erroneously because an injector failure was detected in retrieval step 5, but thereupon no failed injector was identified, the method then reverts to step 201, where again the number of cylinders is determined. Then a new cycle of retrieval step 203 or respectively steps 205 to 209 or also 211 and 213 follows until the failed injector has successfully been identified.

(14) Exemplary values are indicated in Table 1 which can be stored in the first memory device for identification of injectors assigned to individual cylinders. Table 1 is in this respect an example of a lookup-table. The illustrated values were measured for a 12-cylinder V-engine and in this regard represent exemplary values for entering data into a lookup-table. Table 1 is only intended to illustrate that it is in fact possible to clearly determine by way of an angle of the harmonic of the 0.5th order which injector has failed. It is evident that this angle in fact clearly indicates an individually turned off, or respectively failed injector.

(15) In the left column of Table 1 the respective injector is clearly identified in regard to the cylinder assigned to it. In a V-engine differentiation is made between the two cylinder banks which are arranged in a geometric in V-shaped angle opposite one another and which are identified by the letters A and B. The twelve cylinders are therefore consecutively numbered with identification A1 to A6 for the cylinders of the A-bank and identification B1 to B6 for the cylinders of the B-bank. Exactly one injector is thereby allocated to each cylinder. The typical angles of the harmonic of the 0.5th order of the Fourier transformed crank angle signal are entered in the right column for the individually turned off injectors that are identified in the left column.

(16) It is thereby shown that the individual values of the angles for the individual injectors are typical, so that these are clearly definable via the angle values.

(17) TABLE-US-00001 TABLE 1 Injector Angle [] A1 261.6 A2 141.7 A3 20 A4 200.6 A5 319.4 A6 81.5 B1 216.5 B2 96.9 B3 334.7 B4 156.1 B5 275.6 B6 36.1

(18) Overall it is shown that with the assistance of the method, the engine control unit and the system injector failure recognition is simple and quick, whereby in particular detection of defective injectors during running operation of the internal combustion engine without having to turn off the cylinder, which could disrupt operation, is possible. It is readily possible to identify a defective injector and to thereby exchange it in a targeted manner. Moreover, it is not necessary to run test sequences outside of the normal operation of the internal combustion engine, since the method facilitates virtually on-line monitoring during running engine operation.

(19) While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.