Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
  • F02D41/221—Safety or indicating devices for abnormal conditions relating to the failure of actuators or electrically driven elements
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/02—Circuit arrangements for generating control signals
  • F02D41/14—Introducing closed-loop corrections
  • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
  • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
  • F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
  • F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
  • F02M65/006—Measuring or detecting fuel leakage of fuel injection apparatus
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02D—CONTROLLING COMBUSTION ENGINES
  • F02D41/00—Electrical control of supply of combustible mixture or its constituents
  • F02D41/22—Safety or indicating devices for abnormal conditions
  • F02D2041/224—Diagnosis of the fuel system
  • F02D2041/225—Leakage detection
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/40—Engine management systems

Definitions

• the invention relates to a method for detecting leaks in fuel injection valves of an internal combustion engine, in particular an internal combustion engine with direct fuel injection, a control device for controlling such an internal combustion engine and a computer program for controlling a computer-controlled control device for such an internal combustion engine.
• Disclosure of the invention It is therefore an object of the invention to improve the detection of leaks in injection valves of an internal combustion engine and, in particular, to be able to reliably detect leaks in the workshop environment and to be able to assign them cylinder-specifically.
• a method for detecting leaks in fuel injection valves, in particular in high-pressure injection valves, of an internal combustion engine, in particular an internal combustion engine with direct fuel injection, with at least one cylinder the following steps are provided: starting the internal combustion engine; Operating the internal combustion engine until it has reached a predetermined operating temperature; Activation of a measuring sensor system which is at least partially arranged in or on an exhaust gas tract of the internal combustion engine; Switching off the internal combustion engine; Waiting for a specified downtime; after the predefined standstill period has elapsed: activating the starter with deactivated fuel injection and ignition in order to pump the contents of the at least one cylinder into the exhaust gas tract;
• the method can be stored in the software of the engine control and can be started by the workshop tester by connecting a workshop tester or a diagnostic tester to the vehicle.
• the workshop tester is connected to the vehicle via interfaces in the engine control software, so-called ATS interventions, which enable actuation specifications via actuators on the coupled workshop tester.
• ATS interventions which enable actuation specifications via actuators on the coupled workshop tester.
• the procedure in the workshop tester stored and carried out via ATS interventions in the engine control.
• the method according to the invention makes it possible to assign a leakage from fuel injection valves, in particular from high-pressure injection valves, unambiguously, reliably and in a standardized manner to the corresponding fuel injection valve.
• This is achieved by first bringing the fuel supply system to operating temperature by starting and operating the internal combustion engine, which changes the viscosity of the fuel. Due to the heating, the fuel becomes more fluid and can therefore escape through smaller leaks than viscous fuel. This means that leakage defects - if any - are more pronounced.
• the operational readiness of the measuring sensors is established, which is then activated. Heating the internal combustion engine to a predetermined operating temperature before activating the measuring sensor system prevents damage to the measuring sensor system from occurring.
• the internal combustion engine By activating the starter with deactivated fuel injection and ignition, the internal combustion engine is operated by the starter as an “air pump” which pumps the contents of the at least one cylinder into the exhaust tract. At least one signal is then recorded with the measuring sensor system for a predetermined measuring period and then evaluated in a further step in order to detect a leak in at least one fuel injection valve of the internal combustion engine.
• the measuring sensor system comprises a lambda probe (I-probe), in particular a broadband lambda probe, arranged in an exhaust gas tract of the internal combustion engine.
• the lambda probe is an oxygen partial pressure sensor, which is also characterized by cross-sensitivity to hydrocarbons (HC).
• a broadband lambda probe is a variant of a simple lambda probe that is specially designed for use in internal combustion engines Direct fuel injection was developed. Broadband lambda probes can be used reliably in a l-value range of 0.8 and higher.
• the specified standstill period comprises a period of at least 1 to 10 minutes, in particular a period of at least 5 minutes. However, periods of more than 10 minutes are also conceivable.
• the idle period of the internal combustion engine is used to ensure that a detectable amount of fuel collects in the corresponding cylinder in the event of a leak.
• the specified period of at least 1 to 10 minutes is to be regarded as an example and results from a compromise of a sufficiently long period of time to collect a detectable amount of fuel in the corresponding cylinder on the one hand and an economically justifiable period for a workshop to carry out the method according to the invention on the other.
• the specified measurement period comprises a period of at least 1 to 10 seconds, in particular a period of at least 2 seconds. However, the measurement period can also be longer than 10 seconds.
• the specified period is based on an assumption of the time that the internal combustion engine needs to empty the combustion chamber of each fuel injector in "air pump" mode.
• the evaluation of the at least one recorded signal of the measuring sensor system comprises the comparison of a period of time up to a first rise in the signal after the activation of the starter with a predefined period threshold value and / or the comparison of a gradient of the signal with a predefined gradient. Threshold.
• the respective threshold values are vehicle-specific values that are stored in the software of the respective engine control.
• a leak is detected in at least one fuel injection valve if the time period up to a first rise in the signal is greater than the predefined time duration threshold value and / or the gradient of the signal is less than the predefined gradient threshold value.
• An air package from a cylinder with a leak-free fuel injection valve contains pure, so to speak fresh, air and causes a strong initial increase in the signal.
• An air packet from a cylinder with a A leaked fuel injector contains a fuel-air mixture and causes a weaker initial rise in the signal than an air packet from a cylinder with a leak-free fuel injector.
• the evaluation of the at least one recorded signal from the measuring sensor system can therefore also include comparing the signal with a predetermined signal threshold value.
• the time period up to the first rise of the signal is therefore preferably compared with a predetermined time period threshold value.
• the predetermined duration threshold value corresponds to the length of time that a fresh air packet needs from the exhaust valves of the internal combustion engine to the measuring sensors. This duration threshold value is vehicle-dependent, since the arrangement of the measuring sensors can vary. If the measured duration is greater than the duration threshold, this air packet comes from a fuel injection valve that is prone to leakage.
• the comparison of a slope of the signal with a predefined slope threshold value is relevant for determining leaks after the first increase. If the measured slope of the signal is less than the specified slope threshold value, this corresponds to a weakening of the slope of the signal and one speaks of a so-called "plateau detection", since this weakening of the slope of the signal can form a kind of plateau when the slope increases attenuates almost zero.
• the slope threshold value can be different depending on whether the first increase comes from a fuel injection valve with or without a leak. Therefore, either different threshold values have to be stored, or the first leaked fuel injection valve has to be replaced or repaired and then the method has to be carried out again.
• the evaluation of the at least one signal further comprises determining and determining a distance between the activation of the starter and the detection of a leak in at least one fuel injection valve identify the at least one defective fuel injection valve based on the distance thus determined.
• the interval between the activation of the starter and the detection of a leak in at least one fuel injection valve depends on the geometry of the exhaust tract, in particular the distance between the outlet valves and the measuring sensors.
• the interval between the activation of the starter and the detection of a leak is determined by means of the engine position, in particular the angle of rotation of a crankshaft of the internal combustion engine, when the leak is detected relative to the engine position during the standstill period.
• the engine position is particularly suitable as a relevant variable for measuring the distance, since the combustion engine is operated as an "air pump” in this process, which pushes individual air packets into the exhaust gas tract. In this way, the origin of the air packets can be determined in relation to the individual cylinders and thus the associated fuel injection valves.
• the motor position is independent of speed fluctuations, such as can be caused, for example, by fluctuations in the battery voltage.
• An alternative way of determining the first rise in the signal, also referred to as the first characteristic, and the attenuation of the rise in the signal, also referred to as the second characteristic, is to derive it from an integrated or differentiated (lambda) signal curve.
• the first characteristic can be seen in the integrated signal curve as a change from a linear to an exponential slope.
• the second characteristic can be seen in the integrated signal curve as a change from a strong exponential slope to a linear or weak exponential slope.
• the first characteristic can be seen as the first change to a positive value.
• the second characteristic is in the differentiated waveform as Decline to a lower value, in some cases even to the zero line, or as a local minimum, recognizable. Similar relationships can also be derived for further transformations of the original (lambda) signal curve.
• the size of the signal from the measuring sensor system is a measure of the extent of the leakage. In this way, the extent of the leak can be recognized on the basis of the signal curve.
• Embodiments of the invention also include a control device for controlling an internal combustion engine, the control device being designed to carry out the method according to the invention.
• the control device has a memory element which is designed to store engine-specific values.
• the object of the invention is also achieved by a computer program for controlling a computer-controlled control device for an internal combustion engine, the computer program being designed to control the control device in such a way that it executes the method according to the invention.
• Such a computer program can be installed, for example, on a workshop diagnostic device or a workshop tester, which can be connected to the control unit of the internal combustion engine via the so-called ATS intervention interfaces. If there is an existing connection, the method according to the invention can be started via the workshop tester and the results can be output on the workshop tester after the entire method has been run through.
• FIG. 1 shows schematically a vehicle with an internal combustion engine with cylinders with fuel injection valves, a starter, an exhaust tract with measuring sensors, and a control unit;
• FIG. 2 shows a flow diagram of a method according to the invention
• FIG. 3 shows an exemplary test sequence with qualitative signal profiles, as it is generated according to the method according to the invention
• FIG. 4 shows a section of a diagram of an exemplary defect measurement in which, on the one hand, the engine speed and, on the other hand, the measurement signal generated over time are shown;
• FIG. 5 shows a partial range of time of the diagram from FIG. 3 in an enlarged illustration, only the generated measurement signal being shown;
• FIG. 6 shows the same time part of the diagram as FIG. 4, the engine speed and the engine position being shown.
• FIG. 1 schematically shows the structure which makes it possible to carry out a method according to the invention in a workshop environment on a vehicle 2.
• vehicle 2 has an internal combustion engine 4, a starter 6 for starting the internal combustion engine 4 and an exhaust tract 8, which is shown in abbreviated form in FIG.
• the internal combustion engine 4 has, for example, four cylinders 10, each of which has a fuel injection valve 12.
• the fuel injection valves 12 are connected to a fuel line (“rail”) 14 for supplying fuel.
• a measuring sensor system 16 is arranged on the exhaust tract 8, which in the exemplary embodiments described below is designed as a broadband lambda probe.
• the measuring sensor system 16 is coupled to a control device 18 of the internal combustion engine 4 for signal transmission.
• the control device 18 has at least one so-called ATS intervention interface 20, via which a diagnostic device, such as a workshop tester 22, is detachably coupled to the control device 18.
• the control unit also has a memory element 21 which is designed to store engine-specific values
• FIG. 2 shows a sequence of the method according to the invention on the basis of a flowchart according to an exemplary embodiment of the invention and
• FIG. 3 shows an example of a test sequence which qualitatively over time the curves of a measurement signal 24 generated by the method and a speed 26 of the internal combustion engine 4 (see FIG. 1) represents. The method is described below with reference to FIGS. 2 and 3.
• the procedure is started first. This can be carried out, for example, by the workshop tester 22 coupled to the control unit 18 of the internal combustion engine 4, as is shown by way of example in FIG.
• a first step S1 of the method the internal combustion engine 4 is started and then operated, in particular at idle, until an optimal operating temperature for the internal combustion engine 4 is reached (step S2).
• the warming up of the internal combustion engine 4, and in particular of the fuel supply system has the effect, among other things, that the viscosity of the fuel increases, as a result of which any leakage defects that may be present are more pronounced.
• the operational readiness of the measuring sensor system 16, in particular a (broadband) lambda probe is thereby established.
• the measuring sensor system 16 is then activated (step S3) and the internal combustion engine 4 switched off (step S4) in order to produce an inactive vehicle state. In this state, if fuel injection valves 12 are prone to leakage, a defect-relevant and detectable amount of fuel accumulates in the associated cylinder 10.
• the operational readiness of the measuring sensor system 16 is maintained, as is the case, for example, in the stop mode of the start / stop operation of the internal combustion engine 4.
• a predetermined downtime in particular in the range from 1 to 10 minutes, for example 5 minutes, is awaited during which the internal combustion engine 4 remains deactivated (step S5).
• step S6 starter 6 is activated in step S6 with deactivated fuel injection and ignition.
• the internal combustion engine 4 is operated by the starter 6 as an “air pump”.
• the measuring sensor system 16 for example a broadband lambda probe, is arranged in the exhaust tract 8 (see FIG. 1).
• the measuring sensor system 16 records the content of the respective cylinder 10 by measuring technology and generates a corresponding measurement signal 24, which is recorded in step S7.
• the size of the measurement signal 24 is, on the one hand, a measure of whether there is a defect, i.e., a leak, and, on the other hand, a measure of the extent of the leakage.
• the measurement signal 24 is then evaluated (step S8).
• the measurement result which contains the statement as to whether and, if so, which fuel injection valve 12 has a leak, is output to an output device such as, for example, the coupled workshop tester 22 (see FIG. 1).
• the contents of a cylinder 10 with a leak-free fuel injection valve 12 have pure air, so to speak fresh air, and cause a strong first rise 24A of the measurement signal 24 (see FIG. 3).
• the contents of a cylinder 10 with a leaked fuel injection valve 12 corresponds to an air-fuel mixture and causes a weak first rise 24B of the measurement signal 24.
• the content of the cylinder 10 with the leakage fuel injection valve 12 causes a weakening of the already existing rise of the measurement signal 24 or a plateau 28 in the course of the measurement signal 24 over time (see also Figure 5).
• FIGS. 4 to 6 show time diagrams of the measurement signal acquisition using the example of a broadband lambda probe as measurement sensor system 16.
• FIG. 4 shows a section a time diagram over a last time range of the measurement signal acquisition, showing on the one hand the course of the sensed signal 24 of the measuring sensor system 16 and on the other hand the course of the engine speed 26.
• FIGS. 5 and 6 show a partial section relevant for defect detection from the time range shown in FIG. 4 in an enlarged illustration.
• FIG. 5 shows the course of the measurement signal 24
• FIG. 6 shows the course of the engine speed 26 and the course of the engine position 30, for example measured as the angle of rotation of the crankshaft of the internal combustion engine 4.
• the course of the measurement signal 24 is strongly influenced by the geometry of the exhaust tract 8, in particular by the distance between the exhaust valves of the cylinders 10 of the internal combustion engine 4 and the measurement sensors 16.
• a first characteristic 32 is the first increase in the course of the measurement signal 24 after the activation of the starter 6. This first characteristic 32 is also referred to as “lambda increase detection”. With the aid of this first characteristic 32, the period of time, also referred to as the running time, is determined which the contents of the cylinders 10, also referred to below as air parcels, require from the exhaust valves of the internal combustion engine 4 to the measuring sensor system 16.
• the first air packet that is recorded by the broadband lambda probe comes from a cylinder 10 with a fuel injection valve 12 that is prone to leakage.
• a second characteristic 34 is a weakening of the slope of the measurement signal 24, that is to say a plateau 28 in the measurement signal 24, which indicates a fuel injection valve 12 that is prone to leakage.
• the associated defective fuel injection valve 12 is determined from the time interval ⁇ t of the second characteristic 34 from the first characteristic 32 in the engine position 30, e.g. measured via the angle of rotation of the crankshaft of the internal combustion engine 4 (see Figure 6), taking into account the engine position above Determined standstill of the internal combustion engine 4 during the standstill period. In this way, the cylinder 10 with the leaked fuel injection valve 12 can be clearly identified.
• Using the engine position to identify a cylinder 10 with a leaked fuel injection valve 12 is particularly suitable because the internal combustion engine 4 is operated as an "air pump" in this process, which pushes individual air packets into the exhaust tract 8 and thus the origin of the air packets based on the cylinder 10 and thus on the fuel injection valves 12, can be determined.
• the motor position is independent of speed fluctuations, as can occur, for example, due to fluctuations in the battery voltage, and is therefore more reliable.
• the two characteristics 32, 34 can also be derived from a course of an integrated or differentiated measurement signal 24 of the broadband lambda probe, which are not shown in the figures.
• the first characteristic 32 can be recognized as a change from a linear to an exponential slope of the course.
• the second characteristic 34 is shown as a change from a strong exponential slope to a weak exponential or a linear slope.
• the first characteristic 32 can be identified as the first change to a positive value.
• the second characteristic 34 is recognizable as a decrease to a lower value, in some cases even to the zero line, or as a local minimum. Similar relationships can also be derived for further transformations of the course of the original measurement signal 24 of the measurement sensor system 16.
• the “pinpointing” on the individual cylinders is determined by the distance between the activation of the starter 6 and the detection of fuel components in an air package by the measurement sensor system 16 and the course of the measurement signal 24.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
• Combined Controls Of Internal Combustion Engines (AREA)

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• 2020
  • 2020-03-20 DE DE102020203628.4A patent/DE102020203628A1/de active Pending
• 2021
  • 2021-01-26 WO PCT/EP2021/051702 patent/WO2021185501A1/de active Application Filing
  • 2021-01-26 CN CN202180022335.1A patent/CN115280006B/zh active Active

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