WO2011117108A1

WO2011117108A1 - Method for testing the functionality of an exhaust gas recirculation valve of an internal combustion engine

Info

Publication number: WO2011117108A1
Application number: PCT/EP2011/053871
Authority: WO
Inventors: Thomas Breitbach; Jens Pawlak
Original assignee: Robert Bosch Gmbh
Priority date: 2010-03-24
Filing date: 2011-03-15
Publication date: 2011-09-29
Also published as: RU2560091C2; BR112012024042B1; RU2012145008A; DE102010003203A1; CN102791995B; BR112012024042A2; CN102791995A

Abstract

The invention relates to a method for testing the functionality of an exhaust gas recirculation valve (13) of an internal combustion engine (1). The position of an actuator (13a) of the exhaust gas recirculation valve (13) is periodically changed, and a system variable (LM, LD) that is influenced by the movement of the actuator (13a) is measured. The measured signal is analyzed in order to test the functionality of the exhaust gas recirculation valve (13).

Description

Description title

Method for testing the functionality of an exhaust gas recirculation valve of an internal combustion engine

The present invention relates to a method for testing the functionality of an exhaust gas recirculation valve of an internal combustion engine.

State of the art

Exhaust gas recirculation (EGR) valves are used in internal combustion engines to produce a mixture of fresh air and recirculated exhaust gas in the intake manifold and so to improve the combustion behavior, in particular with regard to a consumption and emission minimization. For example, the exhaust gas recirculation reduces the NOx emission. For the exhaust gas recirculation from the exhaust pipe to the intake manifold, a continuously adjustable exhaust gas recirculation valve is used and its open position regulated. During operation, however, due to contamination, sooting, aging, etc., it may lead to a malfunction of the functionality, in particular by a deviation of the actual position from the desired position. This has a negative effect on the combustion.

It is therefore desirable to be able to easily and reliably check the functionality of an exhaust gas recirculation valve.

Disclosure of the invention

According to the invention, a method with the features of claim 1 is proposed. Advantageous embodiments are the subject of the dependent claims and the following description. Advantages of the invention

Essentially, the invention is based on the measure of applying a periodically modulated signal to the actuator of an EGR valve and influencing a system output influenced by it, e.g. the signal of the boost pressure

Sensor or the signal of the air mass sensor to analyze in the frequency domain. The method is applicable in wide operating ranges of the engine, in particular both stationary and dynamic, and can thus meet the requirement of a continuous diagnosis. The proposed concept can get along with already existing sensors and actuators, which are installed as standard in the vehicle, so that no additional costs for other sensors or actuators or ECU hardware arise. In a continuous implementation of the method, the functionality of the exhaust gas recirculation valve can be checked at any time. With a small modulation of the control signal, the soot / NOx ratio can be considered approximately as linear, so that the method has no influence on the total emission. Although the method thus basically intervenes in the EGR control, there is nevertheless no appreciable influence on the emission, which makes the invention particularly well applicable in practice. The invention is suitable for internal combustion engines with self-ignition or spark ignition.

As a periodic control signal, a sinusoidal signal or a rectangular signal can be used. A square wave signal is better reproducible at a lower sampling rate than a sine wave signal of the same frequency. In principle, however, any periodic signal is suitable for modulation.

It makes sense to calculate a moving average (low-pass filtering) of the measuring signal and to subtract this mean from the measuring signal in order to increase the robustness of the diagnosis.

To evaluate the measurement signal, a Fourier analysis or a lock-in method can be used. The additional advantage of a phase-sensitive method, in particular a lock-in method, is that it directly measures the characteristic of the controlled system as a function of the position of the actuator can be. In order to assess the functionality, it is then only necessary to monitor a characteristic gradient with regard to predetermined threshold values. This can be in addition to a stiffness of the EGR valve and any change in the control path characteristic, for example, by aging of return springs, sooting of the valve, manipulation u.ä. recognize reliably.

An arithmetic unit according to the invention, e.g. a control device of a motor vehicle is, in particular programmatically, configured to perform a method according to the invention.

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

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

FIG. 1 shows a schematic representation of an internal combustion engine with a control unit.

FIG. 2 schematically shows a flowchart of different alternatives of a preferred embodiment of a method according to the invention.

Embodiment (s) of the invention FIG. 1 shows an internal combustion engine 1 in which a piston 2 can be moved up and down in a cylinder 3. The cylinder 3 is provided with a combustion chamber 4, to which via valves 5, an intake pipe 6 and an exhaust pipe 7 are connected. The intake pipe 6 is connected to the exhaust pipe 7 via an exhaust gas recirculation valve 13 with a valve flap 13a as an actuator for external exhaust gas recirculation. The valve flap 13a can be controlled by a signal (EGR) from a control unit (ECU) 16. Furthermore, an injection valve 8 that can be controlled with a signal T 1 and a spark plug 9 that can be activated with a signal ZW are connected to the combustion chamber 4. The internal combustion engine 1 according to FIG. 1 is based on the spark ignition method. It should be understood, however, that the invention He does not depend on the ignition of the engine and is well suited for internal combustion engines with auto-ignition.

In the intake manifold 6, a boost pressure sensor 18, which outputs a signal LD indicating the boost pressure in the intake manifold, and a throttle valve 12 whose rotational position is adjustable by means of a signal DK housed. Between the air mass sensor 10 and the throttle valve 12, the turbocharger compressor would be arranged in turbocharged engines.

The intake pipe 6 is further provided with an air mass sensor 10 and the exhaust pipe 7 with a lambda sensor 1 1. The air mass sensor 10 measures the air mass of the fresh air supplied to the intake pipe 6 and generates a signal LM in response thereto. The lambda sensor 1 1 measures the oxygen content of the exhaust gas in the exhaust pipe 7 and generates a signal lambda (λ) in dependence thereon. The lambda probe 11 is an exhaust system (not shown) including a catalytic converter, for example a 3-way catalytic converter, followed by. In the case of turbocharged engines, the turbine of a turbocharger would be installed after the lambda probe.

In operation, a crankshaft 14 is rotated by the driven piston, which ultimately drives the wheels of the motor vehicle. It is understood that an internal combustion engine with external or self-ignition may have more than one cylinder, which are assigned to the same crankshaft and the same exhaust pipe and form an exhaust bank. In a preferred embodiment of the invention, the valve flap 13a are controlled modulated by the control unit 16 and, for example, the charge pressure LD and / or the air mass LM evaluated. For this purpose, the control unit 16 is provided with a microprocessor which has stored in a storage medium, in particular in a read only memory (ROM), a program which is adapted to perform the entire control and / or regulation of the internal combustion engine 1. The control unit 16 is set up to carry out a method according to the invention.

The control unit 16 is acted upon by input signals representing operating variables of the internal combustion engine measured by means of sensors. For example, the control unit 16 with the air mass sensor 10, the lambda sensor 1 1 and the boost pressure sensor 18 is connected. Furthermore, the control unit 16 is connected to an accelerator pedal sensor 17, which generates a signal FP, which indicates the position of a driver-actuated accelerator pedal and thus the torque requested by the driver. The control unit 16 generates output signals with which the behavior of the internal combustion engine 1 can be influenced in accordance with the desired control and / or regulation via actuators. For example, the control unit 16 is connected to the EGR valve 13, the injection valve 8, the spark plug 9 and the throttle valve 12 and generates the signals required for their control EGR, Tl, ZW and DK.

The course of several preferred alternatives of a method according to the invention will be explained below with reference to FIG. These embodiments may be based on an internal combustion engine according to FIG. The illustrated steps do not necessarily take place one after the other, but can also take place parallel in time. The method begins in an optional step 101, in which the presence of corresponding release conditions is checked and the functionality check or diagnosis method is started if necessary. In a step 102, the actuator 13a of the EGR valve 13 is excited with a periodic signal having a predetermined amplitude and frequency, ie, a modulation signal is superimposed on the normal actuating signal. The modulation signal may preferably be sinusoidal in accordance with 103a or rectangular in accordance with 103b. It should be understood, however, that in principle any periodic signal may be used for modulation.

In an essentially simultaneous step 104, a system variable influenced by the setting movement or position of the actuator or actuator 13a is measured, wherein it is expedient according to 105a to the measurement signal LM of an air mass meter 10, for example a hot-film air mass meter, or according to 105b the measurement signal LD of a boost pressure sensor 18 can act. It should also be clarified here that in principle any system size can be measured, which is influenced by the adjusting movement of the actuator 13a.

In a subsequent, optional step 106, a moving average value of the measurement signal is calculated by means of low-pass filtering and this is subtracted from the original measurement signal in a step 107 in order to increase the robustness of the diagnosis.

Subsequently, the subtraction result is evaluated as a new measurement signal, whereby according to 108a a Fourier analysis or according to 108b a phase-sensitive lock-in method is offered. In the Fourier analysis according to 108a, the Fourier spectrum is examined for the occurrence of the excitation frequency with a significantly higher amplitude than adjacent amplitudes. This can be done using a threshold comparison. In the lock-in method according to FIG. 108b, the measured characteristic gradient is compared with a predetermined characteristic gradient. This can also be done using a threshold comparison. In this case, the modulation frequency is expediently detected selectively in the measurement signal. Due to the fixed phase relationship between modulation and measuring signal, this can be a very good

Achieve noise suppression. In addition, there is the possibility to check the characteristic steepness of the actuator, since the output signal of a lock-in amplifier is proportional to the characteristic gradient. In the case of a controller with a non-linear characteristic, it is thus possible to check whether the desired position of the actuator has actually been reached within predefined limits.

In a step 109, a symptom formation is performed on the basis of the respective comparison result (for example the integration of relevant frequencies over specific time intervals or other types of symptom formation) and finally in a step 1 10 a symptom evaluation or error detection is performed. This evaluation is made e.g. by a comparison (larger / smaller / the same) with an application-specific threshold value or a difference formation (sign of the result), in order to conclude the intact or error case. As a result, a faulty or intact exhaust gas recirculation valve can be detected.

Claims

claims

1 . Method for testing the functionality of an exhaust gas recirculation valve (13) of an internal combustion engine (1)

wherein the position of an actuator (13a) of the exhaust gas recirculation valve (13) is changed periodically (103a, 103b),

a system quantity (LM, LD) influenced by the movement of the actuator (13a) is measured (105a, 105b) and

the measurement signal for checking the functionality of the exhaust gas recirculation valve (13) is evaluated (106-1 10).

2. The method of claim 1, wherein as a system size, a boost pressure (LD) o- an air mass (LM) in a suction pipe (6) is measured.

3. The method of claim 1 or 2, wherein a Fourier transform is used to evaluate the measurement signal (108a).

4. The method according to any one of the preceding claims, wherein for evaluating the measurement signal, a phase-sensitive method, in particular a lock-in method, is used (108b).

5. The method according to any one of the preceding claims, wherein the measurement signal is filtered before the evaluation (106), in particular by means of a low-pass filter.

6. The method of claim 5, wherein in the filtering a moving average of the measurement signal is formed (106) and before the evaluation of the moving average value is subtracted from the original measurement signal (107) and the subtraction result is evaluated as a new measurement signal.

7. The method according to any one of the preceding claims, wherein a periodic actuating signal, a sinusoidal signal or a rectangular signal is used (103a, 103b).

8. arithmetic unit which is adapted to perform a method according to any one of the preceding claims.