DE102008054764A1 - Method for diagnosing ambient air-pulsed valve of charging device of internal combustion engine, involves determining information about operability of valve based on switching condition determined by modeling - Google Patents

Abstract

The method involves detecting a pressure difference in an air supply channel. Two switching conditions of an ambient air-pulsed valve (13) are determined based on the detected pressure difference. A physical parameter and/or temporal characteristic of the physical parameter is detected, where the parameter characterizes the air supply in the air supply channel. Information about the operability of the valve is determined based on the switching condition determined by modeling and based on the detected physical parameter and/or the detected temporal characteristic of physical parameter. Independent claims are also included for the following: (1) a device for diagnosing an ambient air-pulsed valve of a loading device of an internal combustion engine (2) a computer program comprising a set of instructions for performing a method for diagnosing an ambient air-pulsed valve of a charging device of an internal combustion engine.

Description

Technical area

The The invention relates to supercharged internal combustion engines, in which a Compressor pumps by means of a pneumatic diverter valve is prevented.

State of the art

modern Engine systems have internal combustion engines with superchargers on. In such a charging device is using a turbine in the exhaust line a compressor driven, the air in an air supply system promotes. Such an engine system is common a so-called diverter valve on which the compressor in an air supply system arranged the internal combustion engine short-circuiting diverter is. The diverter valve is used for load changes of the internal combustion engine to prevent compressor pumping of the charging device.

Out cost reasons is currently common used a so-called pneumatic diverter valve, the is not driven electrically, d. H. it does not find activation For example, by an engine control unit instead. A pneumatic Recirculation valve opens dependent from a pressure difference between a suction pipe section of the air supply system and Z. B. the ambient pressure or the pressure before compressor. Thereby the return air duct is opened, allowing air from one downstream the compressor lying section of the air supply system, eg. B. air from a volume between the compressor and a throttle, in the environment or discharged before the compressor.

On This way, a high pressure difference across the compressor of the charging device reduced.

The Diverter valve is to do this with a suction tube, which is between a Throttle valve and the internal combustion engine is arranged, via an air line connected. A valve diaphragm of the diverter valve is in a closed position by a counterforce, z. B. held by a spring. The diverter valve opens, when due to the differential pressure between the pressure of the environment (or the pressure in front of the compressor) and the pressure in the suction pipe a sufficiently large Force is applied to the valve membrane, which overcomes the drag. In combustion engines there is an opening of the diverter valve when the requested torque drops and the throttle reduces the air supply throttled into the internal combustion engine. This reduces the intake manifold pressure and the pressure difference between the environment and before the compressor and the suction tube increases accordingly.

In an error case in which z. B. the diverter valve does not open d. H. stuck in a closed position, It can be at these operating conditions come to a so-called compressor pumps. The compressor pumps Occurs when there is a periodic backflow through the compressor. hereby can the blades the compressor wheel of the compressor are excited to vibrate. This can be for the charging device be harmful and significantly reduce the life of the compressor. moreover is the compressor pumps associated with an additional disturbing noise.

It So far, no methods are known, the operation of a pneumatic Check diverter valve.

It is therefore an object of the present invention, a method and a device for diagnosing a function of a pneumatic Provide diverter valve.

Disclosure of the invention

These Task is performed by the method of diagnosis of a pneumatic Diverter valve according to claim 1 and by the device according to the independent claim solved.

advantageous Embodiments are in the dependent claims specified.

• – Erfassen der Druckdifferenz in dem Luftzufuhrkanal;
• – Bestimmen des ersten oder des zweiten Schaltzustandes des Schubumluftventils abhängig von der Druckdifferenz durch Modellierung;
• – Erfassen einer die Luftzufuhr im Luftzufuhrkanal charakterisierenden physikalischen Größe und/oder eines zeitlichen Verlaufs der physikalischen Größe;
• – Ermitteln einer Angabe über eine Funktionsfähigkeit des Schubumluftventils abhängig von dem durch Modellierung bestimmten Schaltzustand und abhängig von der erfassten physikalischen Größe und/oder dem erfassten zeitlichen Verlauf der physikalischen Größe.

According to a first aspect, there is provided a method of diagnosing a pneumatic diverter valve of a supercharger of an internal combustion engine having a compressor in an air supply passage for supplying air to the engine. The recirculating air valve is disposed in a recirculation bypass duct surrounding the compressor, the recirculation valve being switched between a first switching state in which the recirculation air valve is opened and a second switching state in which the recirculation air valve is closed depending on a pressure difference in the air supply channel; with the following steps:

• - detecting the pressure difference in the air supply channel;
• - Determining the first or the second switching state of the diverter valve depending on the pressure difference by modeling;
• Detecting a physical quantity characterizing the air supply in the air supply duct and / or a time course of the physical variable;
• - Determining an indication of a Funktionsfä ability of the diverter valve depending on the determined by modeling switching state and depending on the detected physical quantity and / or the detected time course of the physical quantity.

A Idea of the above method is the current state the diverter valve from known system variables, such as the pressure difference in the air supply system, to model and verify whether the system behavior the modeled state of the diverter valve equivalent.

Farther may be determining the indication about the functionality the diverter valve performed is checked by whether a temporal oscillation of the physical quantity occurs when the switching state of the diverter valve determined by modeling indicates the first switching state.

Checking the operability the diverter valve is thus carried out by a modeled Switching state, which is an open valve indicating is being checked whether there is a compressor pumps. If a compressor pump is detected, it can an error in the form of a diverting in the closed state diverter valve be recognized.

According to one embodiment can be exceeded several times a first threshold value and / or when falling below several times a second threshold by the detected physical quantity the presence the temporal oscillation can be determined.

According to one another embodiment an error of the diverter valve is detected when passing through Modeling certain switching state of the diverter valve the indicates second switching state and a modeled, through the compressor flowing Air mass flow of a measured air mass flow supplied to the compressor as the physical air characterizing the air supply in the air supply channel Size deviates.

The physical size can a boost pressure at an outlet of the compressor or one in the Air supply channel flowing Correspond to air mass flow.

It can be provided that the pressure difference as a difference between a pressure in a downstream a throttle arranged volume in the air supply passage of the internal combustion engine and a pressure upstream of the compressor in the Air supply channel is determined.

Farther can as the switching state of the diverter valve, the first switching state be determined when the pressure difference as the difference of pressure in the downstream the throttle valve arranged volume minus a pressure upstream of the Compressor falls below a predetermined threshold, and / or wherein as the switching state of the diverter valve, the second switching state is determined when the pressure difference exceeds the predetermined threshold. In particular, a change of the switching state after expiry of a Duration after the detection of an exceeding or falling below the predetermined threshold to be dynamic Behavior of the diverter valve to be considered.

• – eine Einrichtung zum Erfassen der Druckdifferenz in dem Luftzufuhrkanal;
• – eine Einrichtung zum Bestimmen des ersten oder des zweiten Schaltzustandes des Schubumluftventils abhängig von der Druckdifferenz durch Modellierung;
• – eine Einrichtung zum Erfassen einer die Luftzufuhr im Luftzufuhrkanal charakterisierenden physikalischen Größe und/oder eines zeitlichen Verlaufs der physikalischen Größe; und
• – eine Einrichtung zum Ermitteln einer Angabe über eine Funktionsfähigkeit des Schubumluftventils abhängig von dem durch Modellierung bestimmten Schaltzustand und abhängig von der erfassten physikalischen Größe und/oder dem erfassten zeitlichen Verlauf der physikalischen Größe.

In another aspect, an apparatus for diagnosing a pneumatic diverter valve of a supercharger of an internal combustion engine ( 2 ) with a compressor in an air supply duct for supplying air to the internal combustion engine, the diverter valve being disposed in a diverting piston bypassing a compressor of the charging apparatus, the diverter valve being dependent on a pressure difference in the air supply duct between a first switching state in which the diverter valve is opened, and a second switching state in which the diverter valve is closed, switches; full:

• - means for detecting the pressure difference in the air supply duct;
• - Means for determining the first or the second switching state of the diverter valve depending on the pressure difference by modeling;
• A device for detecting a physical variable characterizing the air supply in the air supply duct and / or a time course of the physical variable; and
• - A device for determining an indication of a functionality of the diverter valve depending on the determined by modeling switching state and depending on the detected physical quantity and / or the detected time course of the physical quantity.

According to one Another aspect is a computer program is provided, the program code contains which, when executed on a data processing unit, performs the above method.

Brief description of the drawings

1 shows an engine system with a charging device in which a compressor is short-circuited by a thrust reverser, in which a pneumatic diverter valve is arranged;

2 a schematic cross-sectional view of a pneumatic diverter valve; and

3 a signal diagram illustrating the timing of a boost pressure, an air mass flow, a Saugrohrdrucks and a throttle position.

Description of embodiments

1 shows an engine system 1 with an internal combustion engine 2 , the air through an air supply duct of an air supply system 3 is supplied from the combustion exhaust gas via a Abgasabführungsabschnitt 4 is dissipated. In the air supply duct is a throttle 5 arranged to be in the cylinder of the internal combustion engine 2 adjust introduced amount of air. On the input side is at the air supply duct, an air mass sensor 6 arranged in the form of a hot air mass sensor and measures the amount of air flowing into the air supply channel and provides a corresponding sensor signal as air mass flow indication.

The engine system 1 has a charging device, which is an exhaust gas turbine 8th in the exhaust discharge section 4 and a compressor 9 in the air supply duct in front of a suction pipe 14 includes. The exhaust gas turbine 8th drives the compressor 9 via a shaft, not shown. The coupling between the exhaust gas turbine 8th and the compressor 9 is shown in dashed lines.

Input side and output side of the exhaust gas turbine 8th are via a bypass line 10 interconnected, in which a controllable bypass valve 11 is arranged.

The compressor 9 in the air supply system 3 is with a diverting air duct 12 provided on the output side (outlet) of the compressor 9 with the input side (inlet) connects. In the diverting air duct 12 is a diverter valve 13 provided, which is pneumatically operated to air between the compressor 9 and the throttle 5 dissipate.

For controlling the bypass valve 11 and the throttle 5 is an engine control unit 15 provided that performs a control in accordance with the engine operation to be set. This control is carried out in accordance with one or more default variables VG, which may include, for example, a driver's desired torque, and depending on further measured variables, such as one via a speed sensor 7 detected speed of the internal combustion engine 2 and an indication of one in the air supply system 3 amount of air flowing in from the air mass sensor 6 provided.

2 shows a schematic representation of the pneumatic diverter valve 13 , The diverter valve 13 has a first connection 21 to connect to the outlet of the compressor 9 or with the between the outlet of the compressor 9 and the throttle 5 defined volume and a second connection 22 for connection to the ambient air or to the inlet side of the compressor 9 or a volume located there. The diverter valve 13 also has a membrane 23 on, which is shown both in a closed position (solid line) and in an open position (dashed). Furthermore, the diverter valve has 13 a third connection 24 as a control port on, with a suction pipe 14 designated portion of the air supply system 3 is connected, ie with the section of the air supply system 3 between the throttle 5 and the input of the internal combustion engine 2 ,

In the normal state is the diverter valve 13 in a closed state. Depending on the pressure difference between the intake manifold 14 and the external environment, that is, the pressure difference between a pressure applied to the second port 22 is applied, and a pressure at the third port 23 the diverter valve 13 is applied, the membrane 23 moved from the closed position and the diverter valve 13 will be opened.

The membrane 23 is in the closed position by a counter force by means of a spring 25 held. Exceeds the pressure difference between the pressure in the environment and the pressure in the suction pipe 14 one by the spring 25 predetermined limit, then the membrane 23 moved into the open position shown by the dashed line. This will create a flow channel between the first port 21 and the second port 22 open, allowing air from the outlet side of the compressor 9 can drain into the environment.

Such a pneumatic diverter valve 13 is used to prevent unfavorable operating conditions of the compressor 9 to avoid, in particular to avoid a so-called compressor pumps. In compressor pumping pulsations in the air supply system 3 caused when there is periodic backflow of air through the compressor 9 due to stalling on paddle wheels of the compressor 9 comes. This compressor pumping increases the wear of the components of the compressor 9 and thereby reduces the life of the compressor 9 ,

The critical operating conditions of the compressor ters 9 occur especially when a fast load change of the engine 2 is, that is, switched from a high load operating point to a low load operating point, wherein the throttle 5 completely or partially closed. The compressor 9 but still promotes a large amount of air, leading to a rapid increase in boost pressure (pressure in front of the throttle 5 ) on the outlet side of the compressor 9 leads. This results in a decreasing air mass flow through the compressor 9 , The low air mass flow in connection with the high pressure difference across the compressor 9 causes stalls on the compressor blades of the compressor 9 that express themselves in the compressor pumps.

Because such a pneumatic diverter valve 13 not with the engine control unit 15 may be a diagnosis of a failure of the diverter valve 13 only indirectly. Possible errors that can occur are that the diverter valve 13 stuck in a closed state or in an open state. In particular, the clamping in a closed state has the disadvantage that in the above-mentioned operating conditions, a compressor pumps can occur.

To diagnose the diverter valve 13 To be able to perform the current valve state in the event that the diverter valve 13 works properly, be known. Since the diverter valve 13 neither for a status query nor for a control has an electrical connection, the current state must be modeled, ie it must be estimated at what time the diverter valve 13 is open or closed. This is done by determining the differential pressure between the ambient pressure and the intake pipe pressure p_suction pipe and comparing the pressure difference with an opening pressure resulting from the characteristics of the overall system taking into account the spring force acting on the valve diaphragm 23 acts, results. If the differential pressure exceeds the opening pressure, proper functioning is assumed, the diverter valve 13 open. In this case, a compressor pumps can be avoided in the above-mentioned operating conditions.

A compressor pumps z. B. by checking the signal of the air mass sensor 6 or the charge pressure on the outlet side of the compressor 9 (measured by a corresponding pressure sensor) are detected. This is done by checking if oscillations occur in any of the signals. As a compressor pumps only with a closed diverter valve 13 can occur, a fault of the diverter valve 13 then be detected when the modeled state of the diverter valve 13 indicates an open position and at the same time a compressor pumps occurs.

In 3 are the time profiles of the air mass flow mHFM through the air mass sensor 6 , the throttle position DKW, the boost pressure p_Lade and the intake manifold pressure p_suction pipe in the event of a sudden load drop and in the event of a faulty, ie in the closed position, jamming diverting valve 13 shown. It can be seen that in the case of the load drop (sharp drop in the value for the throttle position DKW), an oscillation can be detected both on the basis of the profile of the air mass flow mHFM and on the course of the charge pressure p_Lade, which indicates a compressor pumping.

Especially the boost pressure is suitable for successive control value comparisons good to detect an oscillating signal. This will depend on an average of the boost pressure, an upper threshold and a lower Threshold defined and it is further checked whether the thresholds in Consecutive or consecutive or fall below.

To an inertia of the diverter valve 13 sufficiently considered, the modeled open state of the diverter valve 13 are adopted after a certain period of time after the determination of the exceeding of the opening pressure by the pressure difference, so that the inertia of the spring 25 and the valve membrane 23 be sufficiently taken into account. On the one hand, the specific time period should be chosen large enough to ensure that with a proper diverter valve 13 the open position and also the closed position can be achieved after a corresponding change in the pressure difference. On the other hand, the certain period of time is sufficiently small to choose that the effects of switching or failing to switch over the diverter valve to the air system can be reliably detected.

An in-position clamped diverter valve 13 is detected when the switching state of the diverter valve determined by modeling 13 indicates the second switching state and a modeled, by the compressor 9 flowing air mass flow from a measured the compressor 9 deviates supplied air mass flow. The modeled air mass flow can, with the help of a given compressor map depending on operating point data such. B. the speed of a compressor wheel of the compressor 9 and a pressure difference across the compressor 9 , be determined. The compressor 9 supplied air mass flow can with the help of the air mass sensor 6 measured who the.

Claims (11)

Method for diagnosing a pneumatic diverter valve ( 13 ) a charging device of an internal combustion engine ( 2 ) with a compressor ( 9 ) in an air supply duct for supplying air to the internal combustion engine ( 2 ), whereby the diverter valve ( 13 ) in a compressor ( 9 ) bypass diverter pipe ( 12 ), wherein the diverter valve ( 13 ) depending on a pressure difference in the air supply channel between a first switching state in which the diverter valve ( 13 ) is open, and a second switching state in which the diverter valve ( 13 ) is closed, switches; comprising the steps of: - detecting the pressure difference in the air supply duct; Determining the first or the second switching state of the diverter valve ( 13 ) depending on the pressure difference through modeling; Detecting a physical quantity characterizing the air supply in the air supply duct and / or a time course of the physical variable; - Determining an indication of a functionality of the diverter valve ( 13 ) depending on the switching state determined by modeling and depending on the detected physical quantity and / or the detected time course of the physical quantity. The method of claim 1, wherein determining the indication of the operability of the diverter valve ( 13 ) is performed by checking whether a temporal oscillation of the physical quantity occurs when the switching state of the diverter valve ( 13 ) indicates the first switching state. Method according to claim 2, wherein an error of the diverter valve ( 13 ) is determined when the switching state of the diverter valve ( 13 ) indicates the first switching state and a temporal oscillation of the detected physical quantity occurs. The method of claim 3, wherein when exceeded several times a first threshold value and / or when falling below several times a second threshold by the detected physical quantity the presence the temporal oscillation is detected. Method according to one of claims 1 to 4, wherein an error of the diverter valve ( 13 ) is determined when the switching state of the diverter valve ( 13 ) indicates the second switching state and a modeled, through the compressor ( 9 ) mass flow of air flows from a measured air mass flow supplied to the compressor as the physical quantity characterizing the air supply in the air supply duct deviates. Method according to one of claims 1 to 5, wherein the physical quantity of a boost pressure at an outlet of the compressor ( 9 ) or an air mass flow (mHFM) flowing into the air supply duct. Method according to one of claims 1 to 6, wherein the pressure difference as the difference between a pressure in a downstream of a throttle valve arranged volume in the air supply passage of the internal combustion engine ( 2 ) and a pressure upstream of the compressor ( 9 ) is detected in the air supply channel. Method according to claim 7, wherein as the switching state of the diverter valve ( 13 ) the first switching state is determined when the pressure difference as the difference of the pressure in the downstream of the throttle valve arranged volume minus a pressure upstream of the compressor ( 9 ) falls below a predetermined threshold, and / or wherein as switching state of the diverter valve ( 13 ) the second switching state is determined when the pressure difference exceeds the predetermined threshold. A method according to claim 8, wherein a change of the switching state after expiry of a predetermined period of time after the determination of an exceeding or falling below the predetermined threshold value is determined to a dynamic behavior of the diverter valve ( 13 ). Device for diagnosing a pneumatic diverter valve ( 13 ) a charging device of an internal combustion engine ( 2 ) with a compressor ( 9 ) in an air supply duct for supplying air to the internal combustion engine ( 2 ), whereby the diverter valve ( 13 ) in a compressor ( 9 ) of the charging device bypassing the return air circulation line ( 12 ), wherein the diverter valve ( 13 ) depending on a pressure difference in the air supply channel between a first switching state in which the diverter valve ( 13 ) is open, and a second switching state in which the diverter valve ( 13 ) is closed, switches; comprising: means for detecting the pressure difference in the air supply duct; A device for determining the first or the second switching state of the diverter valve ( 13 ) depending on the pressure difference through modeling; - A device for detecting an air supply in the air supply channel characterizing physical quantity and / or a time course of the physical quantity; and - means for determining an indication of the operability of the diverter valve ( 13 ) depending on the switching state determined by modeling and depending on the detected physical quantity and / or the detected time course of the physical quantity. Computer program containing a program code which, when running on a computing device, a method according to a the claims 1 to 9 executes.