DE102006061894A1 - Fuel injection system's e.g. fuel injector, malfunctioning diagnosing device for motor vehicle, has controlling and evaluating unit to diagnose malfunctioning of system from sensor signal by considering diagnostic operating condition - Google Patents

Abstract

The device (110) has a controlling and evaluating unit (114) that is arranged to operate an internal-combustion engine (112) of a motor vehicle in a diagnostic operating condition. The controlling and evaluating unit processes a signal of a lambda oxygen sensor (116) that is arranged in an exhaust system (118) of the internal-combustion engine. The controlling and evaluating unit diagnoses the malfunctioning of an injection system of the internal-combustion engine from the signal of the oxygen sensor under considering of the diagnostic operating condition.

Description

State of the art

by virtue of the increasing complexity of vehicles used in vehicles Systems and components have a high diagnostic depth in connection with fast and successful troubleshooting in service workshops required. The focus here is in particular the fuel injection system and increasingly also the air or exhaust system of a vehicle.

Thus, numerous sensor systems for monitoring the functionality of internal combustion engines used in motor vehicles are known from the prior art. As an example, the so-called lambda probes should be mentioned here, which have been used for about 30 years in exhaust systems of internal combustion engines and which have made a decisive contribution to improving the exhaust quality of motor vehicles. Various types of such lambda probes are known and are for example in Robert Bosch GmbH: Sensors in the motor vehicle, June 2001, pages 112 to 117 described. Such sensors are based on an electrochemical measurement of an oxygen concentration and are used, for example, for a control of the internal combustion engine during operation of the motor vehicle.

The However, known sensor systems and diagnostic systems are usually merely configured to operate the internal combustion engine to regulate or optimize. Objective methods and systems for Detection of errors in the engine function, in particular for detection a faulty or missing injection quantity on a cylinder, however, are not known in the art.

such Errors in the injection behavior of the internal combustion engine can For example, by a wear or a drift of injection components. Known method of investigation the injection quantity are based only on subjective assessments, such as changing the combustion noise. However, such subjective evaluation usually has to be done by performed by an experienced engineer or mechanic which has extensive experience on this Area. Furthermore, the operating conditions the engine in this type of evaluation very carefully be set because the error to be diagnosed under different operating conditions can have different effects and it can therefore lead to a misdiagnosis.

Disclosure of the invention

It Therefore, a device for diagnosing malfunctions in the injection system an internal combustion engine proposed which the above-described Disadvantages of the known from the prior art method avoids and in particular an objective diagnosis of malfunctions in the injection system an internal combustion engine allows. This can be done System and component functions of the injection system of internal combustion engines examine objectively and reliably. The proposed, avoids the diagnostic method performed by the device subjective evaluation criteria and thus leads to a high reproducibility of the diagnosis. An expansion of the to be diagnosed Components can be avoided in particular. Furthermore, the Device not limited in principle to special Types of injection systems.

The proposed device comprises at least one control and evaluation unit, which is set to the internal combustion engine in at least to operate a predetermined diagnostic operating condition. there is at least one signal from the control and evaluation at least a arranged in the exhaust system of the internal combustion engine oxygen sensor processed and taking this signal into account the predetermined diagnostic operating condition on a malfunction closed the injection system.

at The oxygen sensor may in particular be an oxygen sensor to measure an oxygen partial pressure, preferably one or more of those described above, from the prior art known lambda probes. Different types of lambda sensors can be used especially jump probes or preferably broadband probes. It can both signals the already standard used in vehicles lambda probes are used as well, alternatively or additionally, of lambda probes which are mobile designed and, for example, as part of a workshop diagnosis, temporarily in the exhaust system of the internal combustion engine can be introduced or connected to this. The latter is particularly suitable if a corresponding lambda probe not provided as standard in the exhaust stream.

In particular, the device is preferably set up to compare signals of the oxygen sensor with comparison data or desired signals. For example, these setpoint signals may be comparison data of engines with known injection behavior or known function, or even comparison data of internal combustion engines, in which specifically certain radio errors specified. Alternatively or in addition to the comparison with setpoint signals, however, other methods for evaluating the signals of the oxygen sensor can also be used. Thus, for example, correlations can be carried out with further signals, or an analytical or semiempirical evaluation can be carried out, such as a Fourier analysis of the signals, for example in order to search specifically for specific frequency components. Other evaluation algorithms can be used and are known in the art.

there static signals can be processed or it can Also, a time course of a signal compared with a desired time waveform become. Thus, for example, the diagnostic operating state a temporal sequence of several operating states include, with one or more changes of operating conditions, wherein the temporal course of the oxygen signal recorded and with predetermined Sollsignalverläufen is compared. By Deviation of nominal signals or similarity with given certain desired signals (for example known error signals) This may, for example, indicate a malfunction in a particular one Injection system of an internal combustion engine, for example a single Fuel injector, to be closed.

Especially the control and evaluation unit can be set up to periodic Modulations in a waveform of the signal of the oxygen sensor to detect and correlate with an engine speed. Especially can be a speed signal of a speed sensor of the internal combustion engine are processed. For example, periodically recurrent signal components with an integer multiple or an integer fraction of the speed of the internal combustion engine be detected selectively in the waveform of the oxygen sensor, For example, automatically, for example, using certain Filtering techniques such as bandpass filters. If preferred in addition the engine phase is considered, In this way, the signal components can be specifically determined Cylinders are assigned to the internal combustion engine. Furthermore, can from the described correlation of the periodic modulations with the speed a plausibility view of the error detection be performed in order to avoid misinterpretations.

• – mindestens ein Einspritzventil, vorzugsweise genau ein Einspritzventil, der Brennkraftmaschine wird derart angesteuert, dass dieses mit von den anderen Einspritzventilen abweichenden Betriebsparametern, insbesondere abweichenden Ansteuersignalformen, beaufschlagt wird;
• – mindestens ein Einspritzventil, vorzugsweise genau ein Einspritzventil, der Brennkraftmaschine wird derart angesteuert, dass dieses ausschließlich eine Teileinspritzung durchführt, insbesondere eine Voreinspritzung und/oder eine Haupteinspritzung und/oder eine Nacheinspritzung.

The diagnostic operating state described above may include a static or a temporally variable operating state of the internal combustion engine. In particular, one or more of the following operating modes may be included:

• - At least one injection valve, preferably exactly one injection valve, the internal combustion engine is controlled such that it is acted upon by deviating from the other injectors operating parameters, in particular deviating Ansteuersignalformen;
• - At least one injection valve, preferably exactly one injection valve, the internal combustion engine is controlled such that this exclusively performs a partial injection, in particular a pilot injection and / or a main injection and / or a post-injection.

By this targeted influencing individual cylinder of the internal combustion engine and the observation of the change in the oxygen signal as a consequence of this purposeful influence an objective diagnosis can be made be carried out without the corresponding components to have to expand. So in particular a complete Shutdown of the injection of a single or multiple injectors take place, so a control in which the drive times for all partial injections are set to zero.

The Control and evaluation unit can be considered a single, central unit or alternatively as a decentralized unit with several separate components be designed. In particular, the control and evaluation unit a computer, for example a microcomputer, which Programmed is set to the functions described above perform. This computer can in particular via one or more volatile or non-volatile Have memory in which, for example, the mentioned Target signals can be stored. Also appropriate Input and output means, in particular interfaces, graphical Output devices or the like may be provided be.

Thus, for example, the control and evaluation unit may be included in a diagnostic module, which may be integrated in the vehicle or may preferably be designed to be mobile or workshop-bound. This diagnostic module can be set up to be connected by means of an interface to the internal combustion engine and / or an engine control unit of the internal combustion engine. The diagnostic module can be designed, for example, with corresponding mechanical and / or electrical interfaces in order to be integrated in a motor vehicle test stand in a motor vehicle workshop. The diagnostic module can be equipped, for example, with a graphical output unit for displaying diagnostic results, as well as with an input unit (for example a keyboard or similar input means known to the person skilled in the art), as well as appropriate default options for enabling a user to selectively diagnose conditions (eg be selected within given or user-defined diagnostic programs.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description explained in more detail.

It demonstrate:

1 a schematic diagram of a device according to the invention for diagnosing malfunctions in the injection system of an internal combustion engine; and

2a and 2 B Signal examples of the device according to 1 in normally functioning internal combustion engine ( 2a ) or in the absence of injection on a cylinder of the internal combustion engine ( 2 B ).

In 1 is an embodiment of a device 110 for diagnosing malfunctions in the injection system of an internal combustion engine 112 shown schematically. The device 110 includes in this embodiment, a control and evaluation 114 which may be part of a diagnostic module, for example, as well as a lambda probe 116 , which in the exhaust system 118 the internal combustion engine 112 is arranged. For example, the lambda probe 116 be configured as a broadband lambda probe and can, for example, in close proximity to a catalyst in the exhaust system 118 be arranged. For the design of the control and evaluation 114 Please refer to the above description.

The control and evaluation unit 114 is via a signal line 120 with the lambda probe 116 connected, for example via a standard predetermined diagnostic interface of a motor vehicle. In this way, the control and evaluation unit 114 Signals of the lambda probe 116 receive.

Furthermore, the control and evaluation unit 114 via a control line 122 directly or indirectly with the internal combustion engine 112 connected. For example, this control line 122 in turn, include a factory default diagnostic interface of a motor vehicle. Under "line" is here, as well as in the case of the signal line 120 to understand each possible embodiment of a device for signal and / or energy transmission, in particular single- or multi-channel wire lines or, alternatively or additionally, also devices for wireless data transmission.

The internal combustion engine 112 For example, a (in 1 not dargstelltes) comprise engine control unit, on which via the Ansteuerleitung 122 can be accessed. In this way, the internal combustion engine 112 one of the diagnostic operating states described above. Also need signal line 120 and control line 122 not necessarily separate lines or interfaces, but it may be, for example, a single interface, which the control and evaluation 114 for example, with the engine control unit of the internal combustion engine 112 combines.

For diagnosis of an injection system of the internal combustion engine 112 is by means of the lambda probe 116 the oxygen partial pressure in an exhaust gas 124 in the exhaust system 118 under different operating conditions of the internal combustion engine 112 measured and in the control and evaluation unit 114 for example, with known values and gradients (here referred to as "setpoint" without restriction of generality).

Is due to a component error (for example, by drift or wear of a common rail injector), for example, in a cylinder of the internal combustion engine 112 no fuel injected, this cylinder delivers ambient air into the exhaust system instead of combustion exhaust gases 118 the internal combustion engine 112 , This increases, periodically with an engine speed of the internal combustion engine 112 correlating frequency, the oxygen partial pressure in the exhaust gas 124 , This increase can be via the lambda probe 116 be detected. By a correlation of this periodic signal with the engine speed (for example by means of one or more electronic or programmatic filter in the control and evaluation 114 ) In addition, a plausibility of the actual useful signal with the signal of the speed sensor of the machine is possible in order to rule out misinterpretations can.

As described above, the control and evaluation unit 114 the engine specifically specify diagnostic operating conditions. For example, this can be specifically switched on certain partial injections (pre-, main, post injection) on one or more cylinders, changed or turned off (for example, by changing the electrical control of the injectors by means of the control and evaluation 114 ). The resulting changes in the oxygen partial pressure in the exhaust gas 124 will be examined. From these measurement results can also be made a statement about the system or component behavior.

As described above, the device 110 be configured as a device integrated in the motor vehicle or as a separate, for example wise workshop-bound device. The device can even use the lambda probe 116 include as a mobile lambda probe, or it can also be used as standard in the vehicle integrated lambda probes.

In the 2a and 2 B Examples of waveforms at various operating conditions are shown. In both cases, the quotient of the oxygen (O ₂ ) partial pressure and the total pressure is dimensionless plotted as a function of the time t in seconds.

2a shows a time course of a normal injection on all cylinders of the internal combustion engine 112 , It is at the time 210 through the control and evaluation unit 114 via the control line 122 a new set of operating conditions for the internal combustion engine 112 specified. In this case, the new operating conditions are designed so that the speed is to be increased continuously. How out 2a shows, sinks from this time 210 due to the setting of the internal combustion engine 112 to the new predetermined operating conditions of the oxygen partial pressure in the exhaust system 118 continuously to then remain at a low level until a new switching point.

In 2 B however, the waveform is shown in an internal combustion engine 112 in which "artificial" injection on a cylinder of the machine was switched off. This corresponds for example to a malfunction of the injector of this cylinder.

As can be seen from the waveform in 2 B results, the signal points between times 210 and 212 initially a similar course as in 2a , In this case, however, it should first be noted that the absolute value of the signals (for example an averaged signal profile) is higher by a value ΔC than the signal curve in the case of the normal injection according to FIG 2a , This is, as described above, due to the fact that the cylinder in which no injection takes place, instead of combustion exhaust gases ambient air in the exhaust system 118 supplies.

Furthermore, in the waveform between the times 210 and 212 significant signal oscillations 214 to observe. These signal oscillations occur in this representation, in which, for example, a six-cylinder four-stroke engine is shown at half the engine speed. At a different number of cycles are correspondingly different multiples of the engine speed, for example, oscillations with the whole engine speed (in a two-stroke engine) to observe. The latter, that is, the correlation with the whole engine speed in two-stroke engines, is particularly relevant in the field of large diesel engines, which is often worked on the two-stroke principle, relevant. From the oscillation and the correlation with the engine speed, for example, the above-described plausibility consideration can be performed. In the simplest case, the oscillations occur with a single frequency, in more complex cases, for example, to perform an analysis of the frequency spectrum of the "oscillation" signal, such as a Fourier analysis.

To the signal oscillations 214 Optimal observation is preferably a lambda probe 116 used with fast reaction time. The in the 2a and 2 B Examples shown were taken with a broadband probe. However, other types of probes can also be used in principle.

Furthermore, as in 2 B to detect a correlation between the amplitude of the signal oscillations 214 and the speed of the internal combustion engine 112 to record. In this case, in which a continuous increase in speed between the times 210 and 212 is shown, take the amplitudes of the signal oscillations 214 with increasing speed. This decrease can also be used, for example, for a plausibility check or for further evaluations.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• - Robert Bosch GmbH: Sensors in the motor vehicle, June 2001, pages 112 to 117 [0002]

Claims (10)

Contraption ( 110 ) for diagnosing malfunctions in the injection system of an internal combustion engine ( 112 ) comprising at least one control and evaluation unit ( 114 ), whereby the control and evaluation unit ( 114 ) is arranged to the internal combustion engine ( 112 ) operate in at least one diagnostic operating state and wherein the control and evaluation unit ( 114 ) is further arranged to at least one signal at least one in the exhaust system ( 118 ) of the internal combustion engine ( 112 ) arranged oxygen sensor ( 116 ) and to conclude from the signal taking into account the diagnostic operating state on a malfunction of the injection system. Contraption ( 110 ) according to the preceding claim, characterized in that the control and evaluation unit ( 114 ) is adapted to the signal of the oxygen sensor ( 116 ) to compare with a desired signal. Contraption ( 110 ) according to the preceding claim, characterized in that the control and evaluation unit ( 114 ) is adapted to a temporal course of the signal of the oxygen sensor ( 116 ) to compare with a desired time waveform. Contraption ( 110 ) according to one of the preceding claims, characterized in that the control and evaluation unit ( 114 ) is adapted to signal oscillations ( 214 ) in a signal waveform of the oxygen sensor signal ( 116 ) and to correlate with an engine speed, in particular with the involvement of a speed signal of a speed sensor of the internal combustion engine ( 112 ). Contraption ( 110 ) according to the preceding claim, characterized in that the control and evaluation unit ( 114 ) is further configured to determine from the correlation of the signal oscillations ( 214 ) with the speed to perform a plausibility consideration of the fault detection. Contraption ( 110 ) according to the preceding claim, characterized in that the diagnostic operating state comprises at least one of the following operating modes: - at least one injection valve, preferably exactly one injection valve, of the internal combustion engine ( 112 ) is controlled such that this is applied with different from the other injection valves operating parameters, in particular deviating Ansteuersignalformen; At least one injection valve, preferably exactly one injection valve, of the internal combustion engine ( 112 ) is controlled in such a way that it exclusively carries out a partial injection, in particular a pre-injection, a main injection or a post-injection. Contraption ( 110 ) according to the preceding claim, characterized by a control and evaluation unit ( 114 ) comprehensive diagnostic module, preferably a mobile or workshop-based diagnostic module, wherein the diagnostic module by means of an interface with the internal combustion engine ( 112 ) and / or an engine control unit of the internal combustion engine ( 112 ) is connectable. Contraption ( 110 ) according to the preceding claim, further comprising at least one lambda probe as an oxygen sensor ( 116 ), wherein the lambda probe in the exhaust system ( 118 ) of the internal combustion engine ( 112 ) or as mobile, with the exhaust system ( 118 ) connectable lambda probe is designed. Contraption ( 110 ) according to one of the two preceding claims, characterized in that the device ( 110 ) is equipped with mechanical and / or electrical interfaces for implementation in a motor vehicle test bench. Contraption ( 110 ) according to one of the three preceding claims, characterized in that the diagnostic module is equipped with at least one input unit for specifying diagnostic conditions by a user and at least one graphical output unit for displaying diagnostic results.