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

Abstract

The invention relates to a method for determining a fuel leak in a high-pressure region of a fuel supply system for an internal combustion engine of a vehicle, wherein a curve (210) of a pressure (202) in a high-pressure accumulator of the fuel supply system is provided, wherein in one or more sections (220) of the curve, a value for a pressure drop (240) is determined, wherein in the one or in each of the several sections, the vehicle is in overrun mode, no fuel is injected into the internal combustion engine, and no fuel is delivered to the high-pressure accumulator, and wherein information about the leak is determined based on the one or more values.

Description

[0001] The present invention relates to a determination for detecting a leakage of fuel in a high-pressure region 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 out the same. Background of the invention

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

[0003] According to the invention, a method for determining a leak, as well as a computing unit and a computer program for implementing the method, are proposed, having the features of the independent patent claims. Advantageous embodiments are the subject of the subclaims and the following description.

[0004] The invention relates to the operation of a fuel supply system for an internal combustion engine of a vehicle and, in particular, to determining a leak in the high-pressure region. Despite, for example, ever-improving manufacturing processes, leaks in the fuel supply system cannot be avoided; escaping or excess fuel is then generally fed into the fuel tank via return lines. Particularly in the high-pressure region - here, again, primarily at the fuel injectors and the high-pressure accumulator - a leak can not only lead to a loss of fuel, but also to the unnecessary re-supply of fuel, which requires additional energy. Furthermore, certain functions based on the current pressure in the high-pressure region may no longer function properly, particularly if the leak is too large.However, it is not yet possible to determine such a leak, or at least not with sufficient accuracy.

[0005] However, the leakage or its specific value can be relevant for various functions, such as determining the fuel's elastic modulus or detecting coking. This is especially true for diesel fuel.

[0006] 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 this purpose, a pressure sensor, which is usually present, e.g., on the high-pressure accumulator, can be used, which can be read, for example, by an executing engine control unit. For this purpose, the profile is preferably detected or determined via an angle or crankshaft angle of the internal combustion engine (i.e., synchronized with the crank angle), especially since any speed effects then have no impact.

[0007] The pressure curve is typically regulated to a specific value within the framework of a closed-loop control system. While fuel is removed from the high-pressure reservoir by the fuel injectors, which lowers the pressure, the high-pressure pump replenishes fuel into the high-pressure reservoir, causing the pressure to rise.

[0008] It is now proposed that the pressure or pressure curve be considered for one or more specific sections of the curve, namely in which the vehicle is coasting, no fuel is injected into the internal combustion engine, and no fuel is pumped into the high-pressure accumulator. In the case of several such sections, a longer period of coasting can be selected, for example, in which coasting occurs for the entire curve. Sections must then be selected in which no additional fuel is pumped into the high-pressure accumulator. It should also be mentioned at this point that the curve does not necessarily have to be continuous or quasi-continuous; the sections in question are sufficient.Nevertheless, in practice there will be a continuous or quasi-continuous course in which the relevant sections can then be selected or determined accordingly.

[0009] A value for the pressure drop is then determined in each of these sections. For this purpose, for example, a pressure value can be determined at the beginning and end of the section, from which the difference is then calculated. This can also be done using average values. The pressure drop in such sections has been shown to be an indicator of leakage, because other targeted pressure changes are not occurring at that time.

[0010] Based on the one or more values, information about the leak is then determined, wherein the information about the leak preferably comprises information about a level of the leak. In one embodiment, a reference value for a leak of a reference fuel supply system can be provided for this purpose, wherein the level of the leak is then 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 in which comparison values are provided for various conditions such as pressures in the high-pressure accumulator, temperatures and the like. This makes it possible to determine a quotient of the current and nominal leakage.

[0011] It is useful to determine a pressure drop value for each section of the curve, i.e., when multiple measured values are available. The number of sections or values can be, for example, more than ten, more than 20, or even more than 50. Based on the multiple values, the leakage information is then determined using a filter and / or averaging. This allows a more accurate value to be obtained.

[0012] In one embodiment, the pressure profile is recorded at a frequency of at least 1 kHz, preferably at least 5 kHz, more preferably at least 10 kHz. Such high sampling frequencies allow particularly accurate values to be obtained.

[0013] In one embodiment, the pressure profile is recorded at an at least medium pressure of at least 1500 bar, preferably at least 2000 bar, more preferably at least 2300 bar, in the high-pressure accumulator. In particular, it can be provided that the pressure is increased to a maximum possible pressure for the desired measurements. This is precisely where the advantages of overrun mode become apparent, as the pressure can be increased accordingly without further ado, whereas, for example, when idling, an increase in pressure is generally not desired or even permitted due to the associated noise. Since the vehicle is traveling in overrun mode, and generally at a considerable speed, any noise is hardly or not at all disruptive.

[0014] In one embodiment, a diagnosis is initiated or carried out based on the information about the leak. This can also be used to check, for example, whether the leak is larger than usual or expected. It is also conceivable that an error message is issued in such cases, e.g. if a critical threshold for the leak is exceeded. Such an error message can, for example, include a display and / or an acoustic signal for a driver of the vehicle. However, it can also include, for example, an error log entry which then describes exactly how severe the pressure drop or leak was and when it occurred. This then facilitates, for example, later troubleshooting and error correction.

[0015] A computing unit according to the invention, e.g. a control unit, in particular an engine control unit, of a motor vehicle, is set up, in particular in terms of programming, to carry out a method according to the invention.

[0016] Implementing a method according to the invention in the form of a computer program or computer program product with program code for performing all method steps is also advantageous, as this entails particularly low costs, particularly if an executing control unit is also used for other tasks and is therefore already present. Suitable data storage devices for providing the computer program include, in particular, magnetic, optical, and electrical storage devices, such as hard disks, flash memories, EEPROMs, DVDs, and others. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0017] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0018] The invention is illustrated schematically in the drawing using an embodiment and is described below with reference to the drawing. Short description of the drawings Fig. 1 schematically shows a fuel supply system for an internal combustion engine in which the invention can be used. Fig. 2a, Fig. 2b shows a pressure curve in a high-pressure accumulator to explain the invention. Fig. 3 shows a sequence of a method according to the invention in one embodiment. Embodiment(s) of the invention

[0019] In Fig. 1 schematically shows a fuel supply system 100 for a vehicle, with 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 withdrawn by means of the fuel pump 120 (also called a pre-feed pump or low-pressure pump) and fed to the high-pressure pump 122. The high-pressure pump 122 then pumps the fuel into a high-pressure accumulator 130 (a so-called rail), from where the fuel can be withdrawn by means of fuel injectors 142 and introduced 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, which can control the fuel injectors 142 in the desired manner.

[0020] The engine control unit 170 is also provided and configured, for example, 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 withdrawn from the fuel tank and, for example, a desired amount of fuel can be pumped into the high-pressure accumulator 130 or a specific pressure can be regulated there. A pressure sensor 160 is also provided, by means of which a pressure in the high-pressure accumulator 130 can be measured or detected and which can be read, for example, by the engine control unit 170.

[0021] Furthermore, a return line 150 (or a return line) from one of the fuel injectors 142 into the fuel tank 110 is shown as an example. 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 possibility for detecting or determining such a leak.

[0022] In Fig. 2a shows a pressure curve 210 in a high-pressure accumulator to explain the invention. The pressure 200 is plotted against an angle 202 in six-degree increments (e.g., crankshaft angle). The specific pressure values are of little relevance for the purposes of explanation, but can, 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, in Fig. 2b the section between 0 and 180 degrees (30 times six degrees) according to Fig. 2a shown.

[0023] The Fig. The curve 210 shown in Fig. 2a can be measured, for example, by means of the pressure sensor 160 according to Fig. 1 are recorded.

[0024] In Fig. 2b now specifically shows a section 220 in which the vehicle is in overrun mode, no fuel is injected into the internal combustion engine, and no fuel is delivered to the high-pressure accumulator. In section 230, however, fuel is delivered to the high-pressure accumulator. As in Fig. As can be seen in Figure 2a, the course 210 includes several of the sections 220.

[0025] Based on the course in such sections 220, a pressure drop 240 or a value for it can now be determined. In the example in Fig. 2b, the value of the pressure drop 240 can be approximately 5 bar, for example. Based on this, information about the leakage can then be determined, as explained below.

[0026] In Fig. 3 is a schematic representation of a process according to the invention in one embodiment, as is the case, for example, in the Fig. 1. For this purpose, a pressure profile in the high-pressure accumulator is recorded, e.g. continuously or repeatedly during overrun operation, in step 300, as in Fig. 2a, this course is then also provided.

[0027] In a step 302, in this course V, those sections are then determined in which no injection of fuel into the internal combustion engine takes place and no delivery of fuel into the high-pressure accumulator takes place, e.g. sections such as section 220 according to Fig. 2b.

[0028] In a step 304, a value of the pressure drop is then determined for each of these sections, such as in Fig.2b. In step 306, a reference value 308 for a leak of a reference fuel supply system may be provided. For example, this may include a reference value of 4 bar corresponding to a specific leakage amount.

[0029] In particular, the current (average) pressure for the recorded curve and / or the temperature of the fuel can be taken into account; accordingly, a reference value corresponding to the (average) pressure and temperature can be used, for example, from a characteristic map for the reference fuel supply system.

[0030] Then, in step 310, information 312 about the leak is determined and, in particular, also provided. Accordingly, given a current value of, for example, 5 bar, it can be calculated or determined that the current leakage amount—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 performed, if necessary.

Claims

[1] Method for determining a leakage of fuel (112) in a high-pressure region 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 accumulator (130) of the fuel supply system (100), wherein in one or more sections (220) of the curve, a value for a pressure drop (240) is determined, wherein in one or in each of the several sections, the vehicle is in overrun mode, no injection of fuel into the internal combustion engine (140) takes place, and no delivery of fuel into the high-pressure accumulator (130) takes place, and wherein information (312) about the leakage is determined based on the one or more values. [2] The method according to claim 1, wherein the information about the leakage comprises information about a height of the leakage. [3] The method of claim 2, further comprising providing a reference value (308) for a leakage of a reference fuel supply system, and wherein the amount of the 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 curve (V) of the pressure (p) is recorded 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 profile (V) of the pressure (p) is recorded at an at least average pressure of at least 1500 bar, preferably at least 2000 bar, more preferably at least 2300 bar, in the high-pressure accumulator. [6] Method according to one of the preceding claims, wherein in a plurality of sections of the curve a value for a pressure drop is determined in each case, and wherein, based on the plurality of values, the information about the leakage is determined using a filter and / or averaging. [7] Method according to one of the preceding claims, wherein a diagnosis is initiated or carried out based on the information about the leak. [8] Computing unit (170) which is configured to carry out all method steps of a method according to one of the preceding claims. [9] Computer program which causes a computing unit (170) to carry out all method steps of a method according to one of claims 1 to 7 when it is executed on the computing unit (170). [10] A machine-readable storage medium having stored thereon a computer program according to claim 9.

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