Method for determining leaks in high-pressure zone of 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, a curve (210) of a pressure (202) in a high-pressure accumulator of the fuel supply system being provided, a value of a pressure drop (240) being determined in each case in one or more sections (220) of the curve, in the one section or in each of the plurality of sections the vehicle is in coasting operation, no fuel is injected into the internal combustion engine and no fuel is supplied to the high-pressure accumulator, and wherein information regarding leaks is determined on the basis of the one value or the plurality of values.

Description

Technical Field

[0001] The present 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, and a computing unit and a computer program product for performing the method. Background Art

[0002] In modern internal combustion engines, fuel is supplied by fuel injectors which obtain fuel from a high-pressure accumulator (also referred to as a rail or common rail). To transport fuel from the fuel tank into the high-pressure accumulator, a high-pressure pump is used, and the fuel is supplied to the high-pressure accumulator by means of a low-pressure pump. Summary of the Invention

[0003] According to the present invention, there is provided a method for determining a leak and a computing unit and a computer program product for performing the method, having the features of the independent claims. Advantageous designs are the subject matter of the dependent claims and the following description.

[0004] The present invention relates to the operation of a fuel supply system for an internal combustion engine of a vehicle, in particular to the determination of a leak in a high-pressure region.

[0005] Although, for example, manufacturing processes are constantly improving, leaks in the fuel supply system still inevitably occur; the leaked or excessive fuel is then usually introduced into the fuel tank through a return pipe. Especially in the high-pressure region, particularly in the fuel injectors and the high-pressure accumulator, leaks not only result in fuel loss but also cause unnecessary fuel replenishment. This thus requires additional energy. In addition, certain functions based on the pressure in the current high pressure may no longer work properly, especially in the case of a large leak. However, at present, such a leak cannot be determined, at least not accurately enough.

[0006] However, the leak or its specific value may be related to various functions, such as determining the elastic modulus of the fuel or coking identification. This is especially applicable to diesel fuel.

[0007] In this context, it is proposed to provide a pressure curve in the high-pressure accumulator of the internal combustion engine; for this purpose, the pressure can be detected or determined by means of a suitable sensor. For this purpose, for example, a commonly existing pressure sensor can be used, such as a pressure sensor on the high-pressure accumulator, which can be read out, for example, by an implemented motor control device. For this purpose, the curve is preferably detected or determined by means of the angle of the internal combustion engine or the crankshaft angle (i.e., synchronously with the crankshaft angle), and in particular any rotational speed effect has no influence.

[0008] In the regulation, the pressure curve is usually regulated to a determined value. By injecting fuel through the fuel injector, fuel is withdrawn from the high-pressure accumulator, thereby reducing the pressure, while at the same time fuel is replenished to the high-pressure accumulator by the high-pressure pump, thereby causing the pressure to rise.

[0009] It is now proposed to consider one or more specific curve sections of the pressure or the pressure curve, i.e., sections in which the vehicle is in coasting operation (Schubbetrieb), no fuel is injected into the internal combustion engine and no fuel is supplied to the high-pressure accumulator. If there are multiple such sections, a longer coasting operation time can be selected during which the vehicle is in coasting operation throughout the curve. In this case, the corresponding section without refueling the high-pressure accumulator should be selected. It should also be mentioned at this point that the curve does not necessarily have to be a continuous or quasi-continuous curve, and the relevant section is sufficient. However, in practice, continuous or quasi-continuous curves will occur, and the relevant sections can be selected or determined accordingly.

[0010] Then, the pressure drop values are determined separately in these sections; for example, the pressure values at the start and end of the section can be determined, and then the difference can be determined from them. This can also be done using the average value. As mentioned above, since no other targeted pressure changes occur, the pressure drop in these sections is an indicator of leakage.

[0011] Then, information about leakage is determined based on one or more values, where the information about leakage preferably includes information about the leakage amount or leakage height. In one embodiment, a leakage reference value of a reference fuel supply system can be provided for this purpose, and then the leakage amount is determined based on the one or more values and the reference value. The reference value can be obtained, for example, from the corresponding characteristic field, which provides comparison values under various conditions, such as the pressure, temperature, etc. in the high-pressure accumulator. In this way, the quotient of the actual leakage and the nominal leakage can be determined.

[0012] Preferably, the pressure drop values are determined separately in multiple sections of the curve, i.e., there are multiple measurement values. For example, the number of sections or the number of values can exceed 10 or exceed 20, or even exceed 50. Then, based on the multiple values, information about leakage is determined using a filter and / or an averaging method. In this way, more accurate values can be obtained.

[0013] In one embodiment, the pressure curve is detected using a frequency of at least 1 kHz, preferably at least 5 kHz, and more preferably at least 10 kHz. Particularly accurate values can be obtained through this high sampling frequency.

[0014] In one embodiment, the pressure curve is detected at an average pressure of at least 1500 bar, preferably at least 2000 bar, and more preferably at least 2300 bar in the high-pressure accumulator. In particular, the pressure can be increased to the maximum possible pressure required for measurement. This is exactly the advantage of coasting operation, because the pressure can be increased accordingly without doing anything else, while increasing the pressure in the case of, for example, idling is usually not advisable or not permitted due to the associated noise. Since the vehicle is traveling during coasting operation, usually at a non-low speed, any noise will hardly or not cause interference at all.

[0015] In one embodiment, the diagnosis is initiated or carried out based on information about leakage. For example, this can also be used to check whether the leakage is greater than the usual or expected value. It is also conceivable to issue an error report in these cases, for example, if a critical threshold of leakage is exceeded. The error report can include, for example, a display and / or a sound signal provided for the vehicle driver. But it can also include a fault memory entry, for example, describing the exact degree and the occurrence time of the pressure drop or leakage. This will help with subsequent fault troubleshooting and fault elimination, etc.

[0016] The computing unit according to the invention, such as the control device of a motor vehicle, in particular the motor control device, is in particular programmed to carry out the method according to the invention.

[0017] It is also advantageous to implement the method according to the invention in the form of a computer program or a computer program product, which computer program or computer program product has program code for carrying out all method steps, because the cost is particularly low, especially if the implemented control device is still used for other tasks and is therefore present anyway. Suitable data carriers for providing the computer program are in particular magnetic, optical and electronic memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. The program can also be downloaded via a computer network (Internet, intranet, etc.).

[0018] Further advantages and design options of the invention are described in the description and the drawings.

[0019] The invention is schematically illustrated by way of embodiments in the drawings and is described below with reference to the drawings. Description of the Drawings

[0020] Figure 1 A fuel supply system for an internal combustion engine is schematically shown, in which the invention can be used.

[0021] Figure 2a 、 2b The pressure curve in the high-pressure accumulator is shown to illustrate the invention.

[0022] Figure 3Shows the flow of the method according to the present invention in one embodiment. Detailed Embodiment

[0023] Figure 1 Schematically shows a fuel supply system 100 for a vehicle, which fuel supply system has an electric fuel pump 120, a high-pressure pump 122 and an internal combustion engine 140, and the present invention can be used in this fuel supply system, and the present invention will be briefly described below. In particular, a fuel tank 110 is provided here, and the fuel 112 can be pumped out of the fuel tank by the fuel pump 120 (also called a pre-delivery pump or a low-pressure pump) and supplied to the high-pressure pump 122. Then, the fuel is delivered into a high-pressure accumulator 130 (i.e., a so-called rail) by the high-pressure pump 122, and the fuel is then pumped out of the high-pressure accumulator by a fuel injector 142 and introduced into the combustion chamber of the internal combustion engine 140. For this purpose, a computing unit 170 configured as a motor control device is provided and arranged, which can control the fuel injector 142 in a desired manner.

[0024] In addition, the motor control device 170 is also provided and arranged, for example, for controlling the electric fuel pump 120, and if necessary, can also control the high-pressure pump 122 or a related metering unit, in order to pump fuel out of the fuel tank, for example, to deliver a required fuel quantity into the high-pressure accumulator 130, or to adjust a determined pressure there. In addition, a pressure sensor 160 is provided, and the pressure in the high-pressure accumulator 130 can be measured or detected by the pressure sensor and can be read out, for example, by the motor control device 170.

[0025] In addition, a return flow 150 (or a return pipeline) from one of the fuel injectors 142 to the fuel tank 110 is shown exemplarily. (Other) return pipelines can also be provided for each fuel injector and for the high-pressure accumulator 130. In this way, any fuel leaking from the high-pressure accumulator 130 or one of the fuel injectors 142 due to a leak can return to the fuel tank 110. As described above, the present invention now proposes a method for identifying or determining such a leak.

[0026] For this purpose Figure 2a a curve 210 of the pressure in the high-pressure accumulator is plotted to illustrate the present invention. Here, the pressure 200 is plotted on the angle 202 (for example, the crankshaft angle) in six-degree increments. The specific value of the pressure is not of great relevance to the purpose of this description, but can be in the range of, for example, 2000 bar. Figure 2a The curve shown is for an angle of 720 degrees (120 multiplied by 6 degrees), Figure 2b The curve shown is according to Figure 2a a section between 0 and 180 degrees (30 multiplied by 6 degrees).

[0027] Figure 2a The curve 210 shown can be, for example, by according toFigure 1 is detected by the pressure sensor 160.

[0028] Figure 2b Now, a section 220 in which the vehicle is in coasting operation is specifically shown. In this section, no fuel is injected into the internal combustion engine and no fuel is supplied to the high-pressure accumulator. In contrast, in section 230, fuel is supplied to the high-pressure accumulator, for example. As can be seen from Figure 2a the curve 210 includes a plurality of sections 220.

[0029] Based on the curve in these sections 220, the pressure drop 240 or the value of the pressure drop can now be determined. In the Figure 2b example in, the value of the pressure drop 240 is, for example, approximately 5 bar. Based on this, information about the leak can be determined, which will be described below.

[0030] Figure 3 Schematically shows the flow of the method according to the invention in one embodiment, which can be used, for example, for Figure 1 the fuel supply system shown. For this purpose, for example, in step 300, the pressure curve in the high-pressure accumulator is continuously or repeatedly detected during coasting operation, for example as Figure 2a shown, and then this curve is provided.

[0031] In step 302, in this curve V, sections in which no fuel is injected into the internal combustion engine and no fuel is supplied to the high-pressure accumulator are then determined, for example according to Figure 2b the section 220 shown.

[0032] In step 304, the pressure drop value for each section is then determined, for example as Figure 2b shown. In step 306, a leak reference value 308 of a reference fuel supply system can be provided. For example, this can include: a reference value of 4 bar corresponds to a determined amount of leak.

[0033] In particular, the current (average) pressure of the detected curve and / or the temperature of the fuel can also be taken into account here; thus, for example, a reference value corresponding to the (average) pressure and temperature can be extracted from the characteristic field of the reference fuel supply system.

[0034] Then, in step 310, information 312 about the leak is determined and in particular also provided. Thus, in the case where the current value is, for example, 5 bar, the current amount of leak can be calculated or determined - in a comparable fuel supply system - to be approximately 25% more than that of the reference fuel supply system. In step 314, if necessary, for example, a diagnosis can also be started or executed.

Claims

1. A method for determining a fuel (112) leak in a high-pressure region of a fuel supply system (100) for an internal combustion engine (140) of a vehicle, Among them, providing a curve (210) of a pressure (202) in a high-pressure accumulator (130) of the fuel supply system (100), wherein a value of a pressure drop (240) is respectively determined in one or more sections (220) of the curve, wherein the vehicle is in coasting operation in the one section or in each of the multiple sections, no fuel is injected into the internal combustion engine (140), and no fuel is supplied to the high-pressure accumulator (130), and wherein information (312) about the leak is determined based on the one value or the multiple values.

2. The method according to claim 1, wherein The information about the leak includes information about the amount of the leak.

3. The method according to claim 2, wherein, A reference value (308) for the leak of a reference fuel supply system is further provided, and wherein the amount of the leak is determined based on the one value or the multiple values and the reference value.

4. The method according to any one of the preceding claims, wherein, The curve (V) of the pressure (p) is detected at a frequency of at least 1 kHz, preferably at least 5 kHz, more preferably at least 10 kHz.

5. The method according to any one of the preceding claims, wherein, The curve (V) of the pressure (p) is detected 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. The method according to any one of the preceding claims, wherein, Values of pressure drops are respectively determined in multiple sections of the curve, and wherein the information about the leak is determined based on the multiple values using a filter and / or an averaging method.

7. The method according to any one of the preceding claims, wherein, Based on the information about the leak, a diagnosis is initiated or executed.

8. A computing unit (170) configured to perform all method steps of the method according to any one of the preceding claims.

9. A computer program product which, when implemented on a computing unit (170), causes the computing unit (170) to perform all method steps of the method according to any one of claims 1 to 7.

10. A machine-readable storage medium having stored thereon the computer program product according to claim 9.

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