Method for determining a leak in a high-pressure area of ​​a fuel supply system

Abstract

Method for determining a fuel leakage (112) in a high-pressure area of ​​a fuel supply system (100) for an internal combustion engine (140) of a vehicle, wherein a profile (210) of a pressure (202) is provided in a high-pressure storage tank (130) of the fuel supply system (100), wherein in one or more sections (220) of the process a value for a pressure drop (240) is determined, wherein in one or in each of the several sections the vehicle is operating in overrun mode, no fuel is injected into the internal combustion engine (140), and no fuel is supplied to the high-pressure accumulator (130), and where, based on one or more values, information (312) about the leakage is determined.

Description

[0001] The present invention relates to a device for detecting a fuel leakage in a high-pressure area of ​​a fuel supply system for an internal combustion engine of a vehicle, as well as a computing unit and a computer program for carrying it out. Background of the invention

[0002] In modern internal combustion engines, fuel is supplied via fuel injectors, which receive fuel from a high-pressure storage tank, also known as a rail or common rail. High-pressure pumps are used to transfer fuel from a fuel tank to the high-pressure storage tank; these pumps are supplied with fuel via a low-pressure pump.

[0003] From DE 101 36 706 B4, a diagnostic device for high-pressure fuel supply systems of internal combustion engines is known. An abnormal condition is detected when the delivery rate setpoint of the high-pressure pump rises above a limit value and remains above it for a certain period of time. This increases the reliability of the diagnosis and avoids misinterpretations due to noise.

[0004] German patent DE 10 2010 020 852 B4 discloses a diagnostic system for high-pressure fuel systems that detects faults in a high-pressure pump or pressure sensor. Based on the distributor pressure during engine cranking, a fault is diagnosed if the pressure falls below a threshold value that depends on the coolant temperature and ethanol content.

[0005] Patent DE 10 2015 207 961 B4 discloses a method and a system for detecting continuous injection in internal combustion engines. Continuous injection is detected when the high pressure in the injection system drops within a specific time interval without a control valve having been activated. The test starts when the high pressure falls below a target value. Disclosure of the invention

[0006] According to the invention, a method for determining a leakage, a computing unit, and a computer program for carrying it out, comprising the features of the independent claims, are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

[0007] The invention relates to the operation of a fuel supply system for a vehicle's internal combustion engine, and in particular to the detection of leaks in the high-pressure section. Despite, for example, ever-improving manufacturing processes, leaks in the fuel supply system are unavoidable; escaping or excess fuel is then usually routed to the fuel tank via return lines. Particularly in the high-pressure section—especially at the fuel injectors and the high-pressure accumulator—a leak can not only lead to fuel loss but also to unnecessary refueling, which requires additional energy. Furthermore, certain functions that rely on the current high-pressure pressure may malfunction, especially if the leak is too large.However, determining such a leak is not yet possible, or at least not with sufficient accuracy.

[0008] However, leakage, or rather its specific value, can be relevant for various functions, such as determining the fuel's elastic modulus or detecting coking. This is particularly true for diesel fuel.

[0009] Against this background, it is proposed to provide a pressure profile in the high-pressure accumulator of the internal combustion engine; for this purpose, the pressure can be detected or determined using a suitable sensor. For example, a pressure sensor, which is usually already present on the high-pressure accumulator, can be used, which can be read by an engine control unit. The pressure profile is preferably detected or determined via an angle or crankshaft angle of the internal combustion engine (i.e., synchronized with the crankshaft angle), since any rotational speed effects then have no influence.

[0010] The pressure profile is typically regulated to a specific value. While fuel is drawn from the high-pressure storage tank by the fuel injectors, thus lowering the pressure, the high-pressure pump replenishes the high-pressure storage tank with fuel, thereby increasing the pressure.

[0011] It is now proposed that the pressure or pressure profile be considered for one or more specific sections of the curve, specifically during which the vehicle is in overrun mode, no fuel is injected into the internal combustion engine, and no fuel is supplied to the high-pressure accumulator. In the case of several such sections, a longer period of overrun mode can be selected, during which overrun mode applies for the entire duration. Within this period, corresponding sections should then be selected during which no fuel is supplied to the high-pressure accumulator. It should also be noted that the curve does not necessarily have to be continuous or quasi-continuous; rather, the relevant sections are sufficient.Nevertheless, in practice there will be a continuous or quasi-continuous process in which the relevant sections can then be selected or determined accordingly.

[0012] In each of these sections, a pressure drop value is determined; for example, a pressure value can be determined at the beginning and end of the section, and the difference between these values ​​is then calculated. This can also be done using average values. As has been shown, the pressure drop in such sections is an indicator of leakage because other specific pressure changes do not occur.

[0013] Based on one or more values, information about the leakage is then determined, preferably including information about the leakage level. In one embodiment, a reference value for the leakage of a reference fuel supply system can be provided, with the leakage level then being determined based on the one or more values ​​and the reference value. The reference value can, for example, be obtained from a corresponding characteristic map that provides comparative values ​​for various conditions such as pressures in the high-pressure accumulator, temperatures, and the like. This allows a ratio of actual to nominal leakage to be determined.

[0014] It is advantageous to determine a pressure drop value at each of several sections of the data flow, i.e., to have multiple measurements. The number of sections or values ​​can be, for example, more than ten, more than 20, or even more than 50. Based on these multiple values, the leakage information is then determined using a filter and / or averaging. This allows for a more accurate reading.

[0015] In one embodiment, the pressure profile is recorded at a frequency of at least 1 kHz, preferably at least 5 kHz, and more preferably at least 10 kHz. Such high sampling frequencies allow for particularly accurate readings.

[0016] In one embodiment, the pressure profile in the high-pressure accumulator is recorded at a pressure of at least 1500 bar, preferably at least 2000 bar, and more preferably at least 2300 bar. In particular, it can be provided that the pressure is increased to the maximum possible pressure for the desired measurements. This is precisely where the advantages of overrun operation become apparent, since the pressure can be readily increased accordingly, whereas, for example, increasing the pressure during idling is generally undesirable or even prohibited due to the associated noise. Since the vehicle is operating in overrun mode, and usually at a considerable speed, any noise is hardly, if at all, disruptive.

[0017] In one embodiment, a diagnosis is initiated or performed based on the leakage information. This allows, for example, checking whether the leakage is larger than usual or expected. It is also conceivable that an error message is issued in such cases, for example, if a critical leakage threshold is exceeded. Such an error message could include, for example, a display and / or an audible signal for the vehicle's driver. It could also include an error memory entry that precisely describes, for instance, the magnitude of the pressure drop or leakage and when it occurred. This then facilitates subsequent troubleshooting and repair.

[0018] A computing unit according to the invention, e.g. a control unit, in particular an engine control unit, of a motor vehicle, is, in particular in terms of programming, equipped to carry out a method according to the invention.

[0019] Implementing a method according to the invention in the form of a computer program or computer program product with program code for carrying out all method steps is also advantageous, as this incurs particularly low costs, especially if an executing control unit is already used for other tasks and is therefore already available. Suitable data carriers for providing the computer program are, in particular, magnetic, optical, and electrical storage media, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0020] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0021] The invention is schematically illustrated in the drawing using an exemplary embodiment and is described below with reference to the drawing. Brief description of the drawings Fig. Figure 1 schematically shows a fuel supply system for an internal combustion engine in which the invention can be used. Fig. 2a, Fig. Figure 2b shows a pressure curve in a high-pressure storage tank to illustrate the invention. Fig. Figure 3 shows a process according to the invention in one embodiment. embodiment(s) of the invention

[0022] In Fig. Figure 1 schematically depicts a fuel supply system 100 for a vehicle, comprising an electronic fuel pump 120, a high-pressure pump 122, and an internal combustion engine 140, in which the invention can be used, as will be briefly explained below. In particular, a fuel tank 110 is provided, from which fuel 112 can be drawn by means of the fuel pump 120 (also called a pre-supply pump or low-pressure pump) and supplied to the high-pressure pump 122. The high-pressure pump 122 then delivers the fuel into a high-pressure storage tank 130 (a so-called rail), from where the fuel can be drawn by means of fuel injectors 142 and injected into the combustion chambers of the internal combustion engine 140. For this purpose, a computing unit 170, designed as an engine control unit, is provided and configured to control the fuel injectors 142 as desired.

[0023] The engine control unit 170 is also designed and configured to control the electronic fuel pump 120 and, if applicable, the high-pressure pump 122 or an associated metering unit, so that fuel can be drawn from the fuel tank and, for example, a desired quantity of fuel can be delivered to the high-pressure accumulator 130, or a specific pressure can be regulated there. In addition, a pressure sensor 160 is provided, by means of which the pressure in the high-pressure accumulator 130 can be measured or recorded and which can be read out, for example, by the engine control unit 170.

[0024] Furthermore, an example of a return line 150 (or a return line) from one of the fuel injectors 142 to the fuel tank 110 is shown. A (further) return line can also be provided for each fuel injector as well as for the high-pressure accumulator 130. Any fuel that escapes from the high-pressure accumulator 130 or one of the fuel injectors 142 due to a leak can thus be returned to the fuel tank 110. As already mentioned, the invention now proposes a method for detecting or determining such a leak.

[0025] In Fig. Figure 2a shows a pressure curve 210 in a high-pressure accumulator to illustrate the invention. The pressure 200 is plotted against an angle 202 in six-degree increments (e.g., crankshaft angle). The specific pressure values ​​are not very relevant for the purposes of this explanation, but could, for example, be in the range of 2000 bar. While in Fig. 2a the course over an angle of 720 degrees (120 times six degrees) is shown, is in Fig. 2b the section between 0 and 180 degrees (30 times six degrees) according to Fig. 2a shown.

[0026] The in Fig. The course 210 shown in 2a can be measured, for example, using the pressure sensor 160 according to Fig. 1 will be recorded.

[0027] In Fig. Section 220 is specifically shown in section 2b, in which the vehicle is operating in overrun mode, no fuel is injected into the internal combustion engine, and no fuel is pumped into the high-pressure accumulator. In section 230, however, fuel is pumped into the high-pressure accumulator. As in Fig. As can be seen in 2a, route 210 includes several sections of 220.

[0028] Based on the progression in such sections 220, a pressure drop 240 or a corresponding value can now be determined. In the example in Fig. 2b, the pressure drop value of 240 can be approximately 5 bar, for example. Based on this, information about the leakage can then be determined, as will be explained below.

[0029] In Fig. Figure 3 schematically illustrates the sequence of a method according to the invention in one embodiment, as is the case, for example, in the one described in Fig. The fuel supply system shown in Figure 1 can be used. For this purpose, a pressure profile in the high-pressure accumulator is recorded, e.g., continuously or repeatedly during overrun operation (step 300), as shown in Figure 1. Fig. 2a is shown, this process will then also be provided.

[0030] In step 302, sections are then determined in this process V in which no fuel is injected into the internal combustion engine and no fuel is supplied to the high-pressure accumulator, i.e., sections such as section 220 according to Fig. 2b.

[0031] In step 304, a pressure drop value is then calculated for each of these sections, such as in Fig.As shown in Figure 2b, a reference value 308 can be provided for a leakage in a reference fuel supply system in step 306. For example, this could include a reference value of 4 bar corresponding to a specific leakage quantity.

[0032] In this context, the current (average) pressure for the recorded profile and / or the temperature of the fuel can also be taken into account; accordingly, for example, a reference value corresponding to the (average) pressure and temperature can be taken from a characteristic map for the reference fuel supply system.

[0033] In step 310, information 312 about the leakage is determined and, in particular, made available. Accordingly, with a current value of, for example, 5 bar, it can then be calculated or determined that the current leakage quantity – with a comparable fuel supply system – is approximately 25% higher than in the reference fuel supply system. In step 314, a diagnosis can then be initiated or carried out if necessary.

Claims

[1] Method for determining a fuel leakage (112) in a high-pressure area of ​​a fuel supply system (100) for an internal combustion engine (140) of a vehicle, wherein a profile (210) of a pressure (202) is provided in a high-pressure storage tank (130) of the fuel supply system (100), wherein in one or more sections (220) of the process a value for a pressure drop (240) is determined, wherein in one or in each of the several sections the vehicle is operating in overrun mode, no fuel is injected into the internal combustion engine (140), and no fuel is supplied to the high-pressure accumulator (130), and where, based on one or more values, information (312) about the leakage is determined. [2] Method according to claim 1, wherein the information about the leakage includes information about the level of the leakage. [3] Method according to claim 2, wherein a reference value (308) for a leakage of a reference fuel supply system is further provided, and wherein the level of leakage is determined based on the one or more values ​​and the reference value. [4] Method according to one of the preceding claims, wherein the pressure (p) profile (V) is detected at a frequency of at least 1 kHz, preferably at least 5 kHz, more preferably at least 10 kHz. [5] Method according to one of the preceding claims, wherein the pressure profile (V) of the pressure (p) is recorded in the high-pressure accumulator at a pressure of at least 1500 bar, preferably at least 2000 bar, and more preferably at least 2300 bar. [6] Method according to one of the preceding claims, wherein a value for a pressure drop is determined in several sections of the process, and wherein the information about the leakage is determined based on the several values ​​using a filter and / or an averaging. [7] Method according to any of the preceding claims, wherein a diagnosis is initiated or carried out based on the information about the leakage. [8] Computing unit (170) configured to perform all process steps of a process according to any of the preceding claims. [9] Computer program that causes a computing unit (170) to perform all the process steps of a method according to any one of claims 1 to 7 when executed on the computing unit (170). [10] Machine-readable storage medium with a computer program stored thereon according to claim 9.

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