DE102012011484A1 - Method for monitoring injection operation for internal combustion engine mounted in vehicle, involves determining injection start timing and injection end timing in accordance with the detected time pressure pattern - Google Patents

Abstract

The method involves detecting time pressure pattern in a spacer (14) by which fuel is fed to an injection valves (6-9) of the internal combustion engine (1). The injection start timing and injection end timing are determined in accordance with the detected time pressure pattern. The start time of pressure drop in the spacer is determined in response to the time pressure pattern. The pressure difference of the spacer between the injection start timing and injection end timing is determined. Independent claims are included for the following: (1) device for monitoring injection operation for internal combustion engine; and (2) vehicle.

Description

The present invention relates to a method and apparatus for monitoring an injection event in an internal combustion engine. More particularly, the present invention relates to monitoring an injection event in an internal combustion engine having a common pressure pipe which directs fuel to injectors of a plurality of cylinders of the internal combustion engine. Injection systems with such a pressure pipe are also referred to as common rail injection systems.

In a multi-cylinder engine, each cylinder usually contributes a share to the overall engine output. Therefore, it is desirable that each cylinder contribute an equal share to the overall performance of the engine. As a result, for example, emissions, in particular a particle emission and a CO ₂ emission, can be reduced, consumption can be reduced and smoother running can be achieved. To achieve this goal, it is necessary that each cylinder is supplied with an equal amount of fuel and that the timing of the fuel injection is the same for each cylinder. This is particularly desirable in multiple injection internal combustion engines, where fuel is injected into each cylinder for a combustion cycle several times in succession. In common rail injection internal combustion engines, the metering of fuel from the common pressure tube may be accomplished, for example, by means of electromagnetically or piezoelectrically actuated injectors. For this purpose, the injection valve is controlled at a certain time or at several specific times by a control unit output stage such that the opening cross-section of the valve is released and a certain amount of fuel is conveyed into the combustion chamber. For the combustion process to be operated at an optimum operating point in terms of consumption and emissions, it is necessary to set the fuel quantity and the injection times as precisely as possible. Due to wear on the injection valves, poor fuel quality or the like, it may happen that there is coking on the injection valves. Therefore, a check or diagnosis of the actual injection events is desirable.

In this context is from the JP 62186034 A an internal combustion engine is known in which fuel injected into corresponding cylinder amounts of fuel are balanced in order to avoid torque fluctuations. At this time, an actual fuel injection amount is calculated from a change of a fuel pressure in a fuel path before and after an injection to correct the basic injection amount according to the result of the calculation. The internal combustion engine has a fuel output port of a fuel pump which is connected to a fuel injection valve via the fuel path, which preferably has a fuel pressure collecting pipe which is arranged in common for each cylinder and on the way therebetween. A fuel pressure sensor for detecting a fuel pressure in the fuel path is provided in the fuel pressure collecting pipe. Based on the output of the fuel pressure sensor, a change in pressure before and after injection is determined to calculate the actual injection amount and to correct the basic injection amount.

The object of the present invention is therefore to provide a comparison with the prior art improved diagnosis of the actual injection operations.

This object is achieved according to the present invention by a method for monitoring an injection process for an internal combustion engine according to claim 1, an apparatus for monitoring an injection process in an internal combustion engine according to claim 8 and a vehicle according to claim 10. The dependent claims define preferred and advantageous embodiments of the invention.

In accordance with the present invention, a method of monitoring an injection event for an internal combustion engine is provided. In the method, a time pressure curve in a line through which fuel is supplied to an injection valve of the internal combustion engine, detected and determines an injection start time or an injection end time in dependence on the temporal pressure curve. As a result, the actual injection process can be analyzed in a simple manner. For example, the injection start timing may be related to a drive start of the injector, and the injection end timing may be related to a corresponding end of the injection valve drive. As a result, for example, a proper reaction of the injection valve to a control can be checked.

Determining the start of injection timing may include determining a time start of a pressure drop in the line in response to the pressure history over time. Furthermore, determining the injection end timing may include determining a time end of the pressure drop in the line in response to the pressure history over time. The pressure curve in the pipe can be detected, for example, by means of a pressure sensor. A signal from the pressure sensor can, for example, by means of an engine electronics are processed, which samples the signal supplied by the pressure sensor. A sampling rate can be set such that a start and an end of an edge in the temporal pressure curve can be determined with high temporal resolution. Thereby, the injection start time and the injection end time can be determined correspondingly accurately.

Further, according to an embodiment, a pressure difference in the line between the start of injection and the end of injection is determined for a pair of injection start timing and injection end timing. From the pressure difference, an injection quantity can be determined or a quantitative ratio between different injections can be determined. As a result, injection quantities of different cylinders can be compared with one another or injection quantities into a cylinder can be compared with one another in, for example, a multiple injection.

According to a further embodiment, the internal combustion engine comprises a plurality of cylinders, each with a multiple injection. In the multiple injection, fuel is sequentially injected into each cylinder for one combustion cycle from the multi-cylinder common line. The common line may for example comprise a common pressure tube through which fuel is supplied to the injection valves of the plurality of cylinders of the internal combustion engine. Such an injection system is also referred to as a common-rail injection system. In the pipe, a pressure difference between an injection start timing and an injection end timing is determined for a pair of injection start timing and injection end timing. The pair of injection start timing and injection end timing is assigned to injection into one of the plurality of cylinders depending on the injection start timing and the injection end timing and the associated pressure difference. In particular, in multiple injections in multi-cylinder internal combustion engines, injections from two cylinders may overlap or injection into one cylinder may occur between two injections of a multiple injection of another cylinder. By taking into account not only the start of injection and the end of injection but also the pressure difference between the start of injection and the end of injection, such superimposed injections can be identified and assigned to the different cylinders. Furthermore, in multiple injections, the pressure differences associated with the pairs of injection start timing and injection end timing may be used to determine a quantity ratio of the plurality of injections into a cylinder.

Further, according to an embodiment, erroneous injection may be diagnosed depending on the pressure difference or depending on the injection start timing and the injection end timing. For example, it can be determined whether an injection has actually taken place at the requested time of an injection.

According to the present invention, there is further provided an apparatus for monitoring an injection event in an internal combustion engine. The internal combustion engine has a line for supplying fuel to an injection valve of the internal combustion engine. The apparatus includes a pressure sensor disposed in the conduit for detecting pressure values in the conduit. The apparatus further comprises a processing unit, which is coupled to the pressure sensor and configured to determine a temporal pressure curve in the line and to determine an injection start time and / or an injection end time of an injection by the injection valve as a function of the time pressure curve. The device may also be designed to carry out the method described above and therefore also includes the advantages described in connection with the method. The internal combustion engine may include a plurality of cylinders, which are supplied via a common line with fuel. Such injection systems are also referred to as common rail systems. In this case, a pressure sensor in the common line detects pressure values in the line from which the processing unit can determine injection start times and injection end times for injections into the plurality of cylinders.

Finally, according to the present invention, there is provided a vehicle including an internal combustion engine and the above-described apparatus.

The present invention will be described below in detail with reference to the drawings.

1 shows an internal combustion engine with a device according to an embodiment of the present invention.

2 shows a temporal pressure curve in a line through which fuel is supplied to an injection valve of an internal combustion engine.

3 shows a temporal pressure curve in a line which supplies fuel to a plurality of cylinders of an internal combustion engine.

4 shows a further temporal pressure curve in a line which supplies fuel to a plurality of cylinders of an internal combustion engine at respective multiple injections.

5 shows a vehicle according to an embodiment of the present invention.

1 schematically shows an internal combustion engine 1 with four cylinders 2 - 5 , which in each case an injection valve 6 - 9 assigned. The injectors 6 - 9 For example, are electrically controlled injectors, which release or lock a fuel flow through the respective valve due to an electrical control. On the input side are the injectors 6 - 9 in each case via assigned lines 10 - 13 with a common pressure pipe 14 connected. On the output side are the injectors 6 - 9 with the interiors of each associated cylinder 2 - 5 in connection. Using a fuel pump 15 gets fuel from a fuel tank via a pipe 16 in the pressure tube 14 pumped. The fuel pump 15 builds a pressure in the pressure tube 14 on. With injection valve open 6 - 9 the pressurized fuel from the pressure tube 14 into the combustion chamber of the corresponding cylinder 2 - 5 , In the pressure tube 14 is a pressure sensor 17 arranged, which depends on the in the pressure tube 14 prevailing pressure provides a corresponding analog electrical signal. This electrical signal is via an electrical line 18 to a processing unit 19 guided. In the processing unit 19 may be the fuel pressure corresponding electrical signal of the pressure sensor 17 digitized and further processed using, for example, a digital controller or a microprocessor. In the 1 illustrated arrangement with the for the cylinder 2 - 5 common pressure tube 14 is also referred to as common rail injection system. The internal combustion engine 1 For example, it may include a diesel engine with common rail injection.

The metering of the fuel from the common pressure pipe 14 done using the valves 6 - 9 which can be actuated electromagnetically or piezoelectrically, for example. The respective injection valve 6 - 9 For this purpose, it is activated by a control unit output stage at a certain point in time, so that the opening cross-section of the valve is released and a predetermined amount of fuel is introduced into the combustion chamber of the corresponding cylinder 2 - 5 is encouraged. Thus the combustion process of the internal combustion engine 1 can be operated at an optimal operating point in terms of consumption and emissions, in addition to the most accurate adjustment of the amount of fuel and an accurate timing of the injection is required. To further improve consumption, emissions and smoothness of the engine, the predetermined amount of fuel for a combustion cycle may be injected in succession in a plurality of small sub-quantities. Such an operation is also referred to as multiple injection. In particular, in the multiple injection precise timing of the individual injection operations is required to the desired effects in terms of consumption, emissions and smoothness of the engine 1 to achieve.

Using the pressure measurement in the common pressure tube 14 , which also serves as a fuel manifold 14 is called and with which the fuel through the injectors 6 - 9 into the combustion chamber of the respective cylinder 2 - 5 is promoted, a diagnosis of the delivered injections can be performed. At the same time, the pressure difference in the fuel manifold becomes 14 evaluated, which results between a measurement before and after the injection. By evaluating an edge of the pressure signal, a time of an injection start and a time of an injection end can be determined. By a correspondingly high sampling of the signal from the pressure sensor 17 For example, the injection start timing and the injection end timing can be determined with high accuracy. 2 shows one with the pressure sensor 17 recorded pressure curve in the fuel rail 14 for two single injections into two different cylinders of the internal combustion engine 1 , By detecting a respective edge start and end, the times for the start of injection and the end of injection can be determined.

About the pressure difference between the pressure in the manifold 14 Before the injection and after the injection, a diagnosis can be made with regard to the delivered injection quantity. In particular, it can be checked whether an injection has taken place at the requested time. 3 shows single injections in a four-cylinder engine with injections into the cylinders 1 - 3 take place and in the cylinder 4 there is an injection misfire. As from the pressure course of 3 it is apparent that the cylinder is missing 4 with the injection misfire the characteristic pressure drop, which characterizes the injection process. To detect injection misfires, the resulting pressure difference in the injection is monitored using appropriate thresholds. The threshold value can be determined, for example, as a function of an injection quantity currently to be output.

For multiple injections, in addition to the times for the start of injection and the end of injection, as related to 2 also described a ratio take place between the individual injections via an evaluation of the pressure differences of the pressure edges of the individual injections. 4 shows a multiple injection, in which two injections take place in each cylinder. In a first injection (1.ES), a first partial fuel quantity is injected into the respective cylinder, and in a second injection (2.ES), a second partial quantity of the total fuel quantity provided for the combustion cycle is injected in each case. About the pressure difference, which respectively before and after the individual injections in the fuel manifold 14 prevails, a ratio of the injection quantities can be determined.

wobei m_k die abgegebene Einspritzmasse, V_Rail das Volumen in der Kraftstoffsammelleitung 14, p₂ der Druck nach der Einspritzung, p₁ der Druck vor der Einspritzung, K ein Kompressionsmodul des Kraftstoffs, β ein Volumenausdehnungskoeffizient des Kraftstoffs, T_ist die Isttemperatur des Kraftstoffs, T_ref eine Referenztemperatur und ρ_ref eine Referenzdichte des Kraftstoffs ist. Wie zuvor beschrieben, können aus dem Druckabfall in dem Kraftstoffsammelrohr 14 die Kraftstoffteilmengen oder ein Verhältnis der Kraftstoffteilmengen, so genannte Splitfaktoren, bestimmt werden. Darüber hinaus können bei Mehrfacheinspritzungen auch überlappende Einspritzungen detektiert und ausgewertet werden, welche insbesondere bei Mehrfacheinspritzungen auftreten können, wenn beispielsweise eine letzte Teileinspritzung in einen ersten Zylinder gleichzeitig mit einer ersten Teileinspritzung in einen zweiten Zylinder stattfindet, so dass ein überlagerter Druckabfall dieser beiden Teileinspritzungen in dem Drucksignal auftritt.A more accurate diagnosis of the injected injection amount in both single and multiple injection may be determined by the magnitude of the pressure drop according to the following equation:

where m _{k is} the delivered injection mass, V _{rail is} the volume in the fuel _rail 14 p _{2 is} the pressure after injection, p _{1 is} the pressure before injection, K is a compression modulus of the fuel, β is a volume expansion coefficient of the fuel, T _is the actual temperature of the fuel, T _{ref is} a reference temperature and ρ _{ref is} a reference density of the fuel. As described above, the pressure drop in the fuel manifold can be reduced 14 the fuel subset or a ratio of the fuel subset, so-called split factors determined. Moreover, in the case of multiple injections, overlapping injections can also be detected and evaluated, which can occur, in particular, in the case of multiple injections, if, for example, a last partial injection into a first cylinder takes place simultaneously with a first partial injection into a second cylinder, so that a superimposed pressure drop of these two partial injections in the second partial injection takes place Pressure signal occurs.

5 finally shows a vehicle 60 with the internal combustion engine 1 and a device 61 for monitoring an injection process in the internal combustion engine 1 , The device 61 includes, for example, the components 17 - 19 of the 1 , The device 61 can continue a motor control for the internal combustion engine 1 and on the basis of the monitoring of the injection process, efficiency and emission-influencing errors in the injection output of the internal combustion engine 1 detect and the injection quantities or injection times of the individual cylinders 2 - 5 accordingly, try to readjust to compensate for the error. In addition, such errors in a fault memory of the device 61 be filed, queried via an on-board diagnosis or to a driver of the vehicle 60 be issued.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 62186034 A [0003]

Claims (10)

Method for monitoring an injection process for an internal combustion engine, comprising: detecting a time pressure curve in a line ( 14 ), through which fuel to an injection valve ( 6 - 9 ) of the internal combustion engine ( 1 ), and - determining an injection start time and / or an injection end time depending on the time pressure curve. The method of claim 1, wherein determining the start of injection timing comprises determining a time start of a pressure drop in the line. 14 ) and / or wherein the determination of the injection end time point comprises determining a time end of the pressure drop in the line (FIG. 14 ) as a function of the temporal pressure curve. The method of claim 1 or 2, further comprising: - determining a pressure difference in the conduit ( 14 ) between injection start timing and injection end timing for a pair of injection start timing and injection end timing. Method according to one of the preceding claims, wherein the internal combustion engine ( 1 ) several cylinders ( 2 - 5 ) with multiple injection, in which in each cylinder ( 2 - 5 ) for a combustion cycle several times in succession fuel from the for the multiple cylinders ( 2 - 5 ) common line ( 14 ), the method further comprising: determining a pressure difference in the line ( 14 ) between injection start time and injection end time for a pair of injection start timing and injection end time, and - associating the pair of injection start timing and injection end timing with injection into one of the plurality of cylinders ( 2 - 5 ) depending on the injection start time, the injection end time and the associated pressure difference. The method of claim 4, further comprising: determining a mass ratio between a plurality of injections into one of the plurality of cylinders ( 2 - 5 ) as a function of the pressure differences associated with the multiple injections. The method of any of claims 3-5, further comprising - Diagnosing a faulty injection in dependence on the pressure difference and / or in dependence on the injection start time and the injection end time. Method according to one of the preceding claims, wherein the line ( 14 ) comprises a pressure tube through which fuel to injectors ( 6 - 9 ) of several cylinders ( 2 - 5 ) of the internal combustion engine ( 1 ) is supplied. Device for monitoring an injection process in an internal combustion engine, wherein the internal combustion engine ( 1 ) a line for supplying fuel to an injection valve ( 6 - 9 ) of the internal combustion engine ( 1 ), the device ( 61 ) comprises: a pressure sensor ( 17 ), which in the line ( 14 ) for detecting pressure values in the line ( 14 ), and - a processing unit ( 19 ) connected to the pressure sensor ( 17 ) and is configured, a temporal pressure curve in the line ( 14 ) and, depending on the chronological pressure curve, an injection start time and / or an injection end time of an injection by the injection valve (FIG. 6 - 9 ). Apparatus according to claim 8, wherein the device ( 61 ) is configured for carrying out the method according to any one of claims 1-7. Vehicle comprising: - an internal combustion engine ( 1 ), and - a device ( 61 ) according to claim 8 or 9.

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