WO2008080725A1

WO2008080725A1 - Device for diagnosing malfunctions in internal combustion engines

Info

Publication number: WO2008080725A1
Application number: PCT/EP2007/063150
Authority: WO
Inventors: Thorsten Sommer; Michael Gebers; Joachim Wagner
Original assignee: Robert Bosch Gmbh
Priority date: 2006-12-28
Filing date: 2007-12-03
Publication date: 2008-07-10
Also published as: DE102006061894A1

Abstract

Proposed is a device (110) for diagnosing malfunctions in the injection system of an internal combustion engine (112). The device (110) comprises at least one control and evaluating unit (114) which is set up to operate the internal combustion engine (112) in at least one diagnostic operating state. Furthermore, the control and evaluating unit (114) is set up to process at least one signal of at least one oxygen sensor (116) which is arranged in the exhaust system (118) of the internal combustion engine (112), and to infer a malfunction of the injection system from the signal taking into consideration the diagnosis operating state.

Description

December 6, 2006

description

title

Device for diagnosing malfunctions in internal combustion engines

State of the art

Due to the increasing complexity of the systems and components used in vehicles, a high level of diagnostics in conjunction with fast and successful troubleshooting in service workshops is required. The focal point 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 described for example in Robert Bosch GmbH: Sensors in the motor vehicle, June 2001, pages 112 to 117. 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.

However, the known sensor systems and diagnostic systems are usually designed only to control or optimize operation of the internal combustion engine. However, objective methods and systems for detecting errors in the engine function, in particular for detecting a faulty or completely missing injection quantity on a cylinder, are not known from the prior art.

Such errors in the injection behavior of the internal combustion engine can result, for example, from wear or drift of injection components. Known injection quantity inspection methods are based only on subjective judgments such as change of combustion noise. Such a sub- However, jive evaluation usually needs to be done by an experienced engineer or mechanic with extensive experience in the field. Furthermore, the operating conditions of the internal combustion engine must be set very carefully in this type of evaluation, since the error to be diagnosed can have different effects under different operating conditions and therefore a misdiagnosis can occur.

Disclosure of the invention

Therefore, a device for diagnosing malfunctions in the injection system of an internal combustion engine is proposed, which avoids the disadvantages of the prior art methods described above and in particular enables an objective diagnosis of malfunctions in the injection system of an internal combustion engine. As a result, system and component functions of the injection system of internal combustion engines can be objectively and reliably investigated. The proposed diagnostic method performed by the device avoids subjective evaluation criteria and thus leads to a high reproducibility of the diagnosis. An expansion of the components to be diagnosed can be avoided in particular. Furthermore, the device is not limited in principle to special types of injection systems.

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

The oxygen sensor may in particular be an oxygen sensor for measuring an oxygen partial pressure, preferably one or more of the lambda probes described above known from the prior art. Various types of lambda probes can be used, in particular, jump probes or preferably broadband probes. Both signals of the lambda probes already installed as standard in vehicles can be used, as well as, alternatively or additionally, lambda probes, which are designed to be mobile and, for example within the framework of a workshop diagnostics, temporarily introduced into the exhaust system of the internal combustion engine or connected thereto can. The latter is particularly useful if a corresponding lambda probe is 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 predetermined malfunctions have been predetermined. 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.

In this case, static signals can be processed, or it can also be a time course of a signal with a desired time waveform to be compared. Thus, for example, the diagnostic operating state may include a chronological sequence of a plurality of operating states, with one or more changes of operating states, wherein the time profile of the oxygen substance signal is recorded and compared with predetermined nominal signal characteristics. By deviating from desired signals or similarity with predetermined specific setpoint signals (for example known error signals), it is possible to deduce, for example, a malfunction in a specific injection system of an internal combustion engine, for example a single fuel injector.

In particular, the control and evaluation unit can be set up to detect periodic modulations in a signal curve of the signal of the oxygen sensor and to correlate with an engine speed. In particular, a speed signal of a speed sensor of the internal combustion engine can be processed. Thus, for example, periodically recurring signal components with an integral multiple or an integral fraction of the rotational speed of the internal combustion engine can be detected selectively in the course of the oxygen sensor, for example automatically, for example using certain filter techniques, such as bandpass filters. If, in addition, the engine phase is preferably taken into account, in this way the signal components can be specifically allocated to specific cylinders of the internal combustion engine. Furthermore, from the described correlation of the periodic modulations with the rotational speed, a plausibility analysis of the error detection can be carried out in order to avoid misinterpretations. -A-

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.

As a result of this targeted influencing of individual cylinders of the internal combustion engine and the observation of the change in the oxygen signal as a result of this targeted influencing, an objective diagnosis can be carried out without having to expand the corresponding components. Thus, in particular, a complete shutdown of the injection of a single or a plurality of injection valves can take place, that is, a control in which the actuation durations are set to zero for all partial injections.

The control and evaluation unit can be designed as a single, central unit or alternatively as a decentralized unit with a plurality of separate components. In particular, the control and evaluation unit may comprise a computer, for example a microcomputer, which is set up in terms of programming in order to carry out the functions described above. In particular, this computer can have one or more volatile or nonvolatile data memories in which, for example, the stated desired signals can be stored. Also, corresponding input and output means, in particular interfaces, graphic output devices or the like can be provided.

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, for example, with a graphical output unit for display of diagnostic results, as well as with an input unit (eg, a keyboard or similar input means known to those skilled in the art), as well as appropriate default means for allowing a user to selectively select diagnostic conditions (eg, within predetermined or user-defined diagnostic programs.

Brief description of the drawings

Exemplary embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

Show it:

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

FIGS. 2a and 2b show signal examples of the device according to FIG. 1 in the case of a normally functioning internal combustion engine (FIG. 2a) or in the case of missing injection on a cylinder of the internal combustion engine (FIG. 2b).

1 shows an embodiment of a device 110 for diagnosing Fehlfunktio- nen in the injection system of an internal combustion engine 112 is shown schematically. In this embodiment, the device 110 comprises a control and evaluation unit 114, which may be part of a diagnostic module, for example, and a lambda sensor 116, which is arranged in the exhaust system 118 of the internal combustion engine 112. For example, the lambda probe 116 may be designed as a broadband lambda probe and may be arranged, for example, in close proximity to a catalytic converter in the exhaust system 118. For the embodiment of the control and evaluation unit 114 reference is made to the above description.

The control and evaluation unit 114 is connected via a signal line 120 with the lambda probe 116, for example via a standard predetermined diagnostic interface of a motor vehicle. In this way, the control and evaluation unit 114 can receive signals from the lambda probe 116. Furthermore, the control and evaluation unit 114 is connected via a control line 122 directly or indirectly to the internal combustion engine 112. For example, this drive line 122 may in turn comprise a factory-set diagnostic interface of a motor vehicle. By "line" is here, as in the case of the signal line 120, to understand any 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 can comprise, for example, a motor control device (not shown in FIG. 1) which can be accessed via the control line 122. In this way, the internal combustion engine 112 can be preset to one of the diagnostic states described above. Also, signal line 120 and drive line 122 need not necessarily be separate lines or interfaces, but it may be, for example, a single interface, which connects the control and evaluation unit 114, for example, with the engine control unit of the internal combustion engine 112.

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

If due to a component error (for example due to drift or wear of a common rail injector), for example in a cylinder of the internal combustion engine 112, no fuel injected, this cylinder provides instead of combustion exhaust ambient air in the exhaust system 118 of the internal combustion engine 112. This increases, periodically with a frequency that correlates to the engine speed of the internal combustion engine 112, the oxygen partial pressure in the exhaust gas 124. This increase can be detected via the lambda probe 116. 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 unit 114) is also a plausibility of the actual useful signal with the signal of the speed sensor of the machine possible to rule out misinterpretations can.

As described above, the control and evaluation unit 114 of the internal combustion engine can specifically specify diagnostic operating states. For example, targeted partial injections (pre-injection, main injection, post-injection) can be carried out on one or more cycles. relieve switched on, changed or turned off (for example, by changing the electrical control of the injection valves by means of the control and evaluation unit 114). The resulting changes in the oxygen partial pressure in the exhaust gas 124 are thereby investigated. From these measurement results, a statement about the system or component behavior can also be made.

As described above, the device 110 may be designed as a device integrated in the motor vehicle or as a separate, for example, workshop-bound device. The device may itself include the lambda probe 116 as a mobile lambda probe, or lambda probes integrated into the motor vehicle as standard may also be used.

FIGS. 2a and 2b show examples of signal curves under different operating conditions. In both cases, the quotient of the oxygen (θ2) partial pressure and the total pressure is plotted dimensionlessly as a function of the time t in seconds.

FIG. 2 a shows a chronological progression of a normal injection on all cylinders of the internal combustion engine 112. At the time 210, a new set of operating conditions for the internal combustion engine 112 is set by the control and evaluation unit 114 via the control line 122. In this case, the new operating conditions are designed so that the speed is to be increased continuously. As can be seen from FIG. 2a, the oxygen partial pressure in the exhaust gas system 118 drops continuously from this point in time 210 due to the setting of the internal combustion engine 112 to the new predetermined operating conditions, in order then to remain at a low level until a renewed switching point.

On the other hand, the waveform is shown in Figure 2b, in an internal combustion engine 112, in which "artificially" the injection on a cylinder of the engine has been switched off, which corresponds, for example, to a malfunction of the injector of this cylinder.

As can be seen from the signal curve in FIG. 2b, the signal between times 210 and 212 initially has a similar course to that in FIG. 2a. However, it should first be noted that the absolute value of the signals (for example an averaged signal curve) is higher by a value ΔC than the signal curve in the case of the normal injection according to FIG. 2a. This is because, as described above, the cylinder in which no injection takes place supplies ambient air into the exhaust system 118 instead of combustion exhaust gases. Furthermore, significant signal oscillations 214 are observed in the waveform between times 210 and 212. 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 plausibility consideration described above can be carried out. 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.

In order to be able to optimally observe the signal oscillations 214, a lambda probe 116 with a fast reaction time is preferably used. The examples shown in FIGS. 2a and 2b were recorded with a broadband probe. However, other types of probes can also be used in principle.

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

Claims

claims

A device (110) for diagnosing malfunctions in the injection system of an internal combustion engine (112), comprising at least one control and evaluation unit (114), wherein the control and evaluation unit (114) is arranged to at least one of the internal combustion engine (112) Operate diagnostic operating state and wherein the control and evaluation unit (114) is further adapted to process at least one signal at least one in the exhaust system (118) of the internal combustion engine (112) arranged oxygen sensor (116) and from the signal taking into account the diagnosis Operating state to close a malfunction of the injection system.

2. Device (110) according to the preceding claim, characterized in that the control and evaluation unit (114) is arranged to compare the signal of the oxygen sensor (116) with a desired signal.

3. Device (110) according to the preceding claim, characterized in that the control and evaluation unit (114) is adapted to compare a time profile of the signal of the oxygen sensor (116) with a desired time signal waveform.

4. Device (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 waveform of the signal of the oxygen sensor (116) to be detected and correlated with an engine speed in particular by incorporating a speed signal of a speed sensor of the internal combustion engine (112).

5. Device (110) according to the preceding claim, characterized in that the control and evaluation unit (114) is further configured to perform from the correlation of the signal oscillations (214) with the rotational speed, a plausibility consideration of the fault detection.

6. Device (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, the internal combustion engine (112) is controlled such that this with from the other injectors deviating operating parameters, in particular deviating Ansteuersignalformen, is acted upon; at least one injection valve, preferably exactly one injection valve, the internal combustion engine (112) is controlled such that this exclusively durchfuhrt a partial injection, in particular a pilot injection, a main injection or a post-injection.

7. Device (110) according to the preceding claim, characterized by a control and evaluation unit (114) comprehensive diagnostic module, preferably a mobile or workshop-bound diagnostic module, wherein the diagnostic module by means of an interface with the internal combustion engine (112) and / or a Motorsteuerungsge- advises the internal combustion engine (112) is connectable.

8. Device (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) is arranged or as a mobile, with the exhaust system (118) connectable lambda probe is designed.

9. Device (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 dynamometer.

10. Device (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.