DE102008051711A1 - Internal combustion engine i.e. diesel engine, operating method for motor vehicle, involves detecting measured variable, and determining difference between upstream pressure and downstream pressure of cooling device and flow rate - Google Patents

Abstract

The method involves detecting measured variable for examining functional efficiency of a cooling device, where the cooling device is provided in an exhaust gas return line in an internal combustion engine. A difference (deltap) between upstream pressure and downstream pressure of the cooling device and flow rate (12) via the exhaust gas return line are determined during detection of measured variable. A throttle device arranged in an exhaust strand of the engine is maximally closed for throttling exhaust gas stream acting on a turbine of an exhaust-turbocharger. An independent claim is also included for an internal combustion engine comprising a cooling device.

Description

The Invention relates to a method for operating an internal combustion engine, in which one in an exhaust gas recirculation line arranged cooling device is exposed to exhaust gas, and in which to check a functionality of the Cooling device at least one measured variable is detected. Furthermore, the invention relates to an internal combustion engine.

application Specific loses one in an exhaust gas recirculation line arranged cooling device when operating on cooling capacity a, as the cooling device increasingly clogged. As a result such, also called sooting or pollution, Adding the cooling device can lead to an increase emissions, in particular nitrogen oxide emissions, of the internal combustion engine come. This is particularly important when doing this with transgressions emissions limits are to be expected. Of Further, it may be due to the clogging of the cooling device to errors in controlling the operation of the internal combustion engine come, which can even lead to a business failure.

The DE 10 2004 041 767 A1 describes a method for checking a functionality of arranged in an exhaust gas recirculation line of an internal combustion engine cooling device. In this case, the cooling device is acted upon by recirculated exhaust gas and detected as a measured variable, a temperature downstream of the cooling device. If, when the cooling device is exposed to exhaust gas, a temperature is detected which deviates by more than a threshold value from a value of the temperature predetermined for an intact cooling device, it is concluded that the cooling device has an error.

When disadvantageous in such a method is the circumstance that a temperature sensor naturally comparatively sluggish on a change in the temperature of the the measuring medium responds and thus the detection of the measured variable a comparatively long period of time must be in order to ensure proper functioning to check the cooling device.

task The present invention is therefore a method of operation an internal combustion engine and an internal combustion engine to provide which or which an improved review the functionality of the cooling device allows.

These The object is achieved by a method with the features of claim 1, and by an internal combustion engine solved with the features of claim 9. advantageous Embodiments with expedient developments The invention are in the respective dependent claims specified.

at the method of operation according to the invention an internal combustion engine, wherein one in an exhaust gas recirculation line arranged cooling device is exposed to exhaust gas, and in which to check a functionality the cooling device detects at least one measured variable becomes, are at the detection of the at least one measured variable a difference between a pressure upstream and a pressure downstream of the cooling device and a throughput determined by the exhaust gas recirculation line.

Of the Invention is based on the finding that with increasing life the cooling device as a result of Versottung the pressure loss the cooling device rises. At the same time, the throughput decreases through the exhaust gas recirculation line with increasing Sooting of the cooling device from. These two, especially simple, safe and quickly measurable quantities allow in their synopsis thus a particularly reliable Recognizing the degree of clogging of the cooling device.

By the improved checking of the functionality the cooling device is an early recognition the pollution of the cooling device allows and a failure of the exhaust gas recirculation with the possible consequences of increased emissions and / or a breakdown the internal combustion engine can, for example, by exchange and / or Maintenance of the cooling device to be prevented.

In an advantageous embodiment of the invention, the at least one measured variable is used to calculate a parameter K, based on which reference is made to a clogging degree of the cooling device with reference to a reference parameter for an intact cooling device. Since the difference between the pressure upstream and the pressure downstream of the cooling device increases quadratically with the flow rate through the exhaust gas recirculation line, the characteristic K can be calculated according to: K = Δp / throughput 2 ,

Here, Δp is a difference between the pressure upstream and the pressure downstream of the cooling device. As throughput either an exhaust gas recirculation rate, ie a proportion of exhaust gas at a medium supplied to the internal combustion engine, or a mass flow of the exhaust gas through the exhaust gas recirculation line can be determined. The Ab Gas recirculation rate can be expressed as a percentage.

Especially, if these measures in the context of a diagnosis the functionality of the internal combustion engine recorded anyway and stored, for example in an endurance run script be, allows easy calculation of the characteristic K a recognizable with very little effort recognition of pollution the cooling device.

In A further advantageous embodiment of the invention is based on the parameter K with reference to the difference characteristic for the intact cooling device to a limited Functioning of at least one component of a Intake tract and / or limited functionality an exhaust gas turbocharger closed. Thus, that allows Calculate a single characteristic to extra simple way of distinguishing different error cases.

The At least one measured variable can be found in particular a presence of a predetermined speed of the internal combustion engine on a test bench or during a push operation the internal combustion engine, ie during a driving operation a motor vehicle having the internal combustion engine, be recorded. Because of the particularly quickly measurable parameters a recognition of the sooting of the cooling device in overrun mode the internal combustion engine is enabled, is the implementation the procedure particularly comfortable.

According to one Another aspect of the invention, the above object is achieved by an internal combustion engine having one in an exhaust gas recirculation line arranged cooling device, which with recirculated Exhaust gas is acted upon, and with at least one measuring device for detecting a measured variable, based on which a Functioning of the cooling device verifiable is, wherein means of the at least one measuring device a difference between a pressure upstream and a pressure downstream the cooling device and a flow rate through the exhaust gas recirculation line are detectable. The for the inventive method described preferred embodiments and advantages also apply to the invention Internal combustion engine.

Further Advantages, features and details of the invention will become apparent the following description of a preferred embodiment as well as the drawing.

These shows a diagram with curves showing a relationship between a difference between a pressure upstream and a pressure downstream of a in an exhaust gas recirculation line arranged cooling device and a throughput the exhaust gas recirculation line for an intact Cooling device and for a dirty cooling device describe.

In a diagram shown in the figure 10 is on an ordinate a throughput 12 plotted by an exhaust gas recirculation line, which in the present case is detected as the exhaust gas recirculation rate in percent, that is, as a proportion of exhaust gas on a medium supplied to an internal combustion engine. On an abscissa is in the diagram 10 a difference .DELTA.p is plotted as a difference between a pressure upstream of a cooling device disposed in the exhaust gas recirculation passage and a pressure downstream of the cooling device. The pressures and the throughput 12 are determined by means of measuring equipment.

present becomes for recognizing a sooting of the cooling device the, for example, self-igniting, diesel-operated, Internal combustion engine subjected to compressed supply air. in this connection is the supply air by means of a compressor of an exhaust gas turbocharger compacted. Downstream of a compressor wheel of the exhaust gas turbocharger is a charge air cooler and downstream of the intercooler arranged a throttle. Downstream of the throttle the exhaust gas recirculation line discharges into the intake tract the internal combustion engine, over which cylinders one Engine block the compressed supply air, which recycled Exhaust gas is mixed, is supplied.

In the diagram 10 is a first turn 14 which shows a relationship between the difference Δp and the throughput 12 characterized by the exhaust gas recirculation line for an intact cooling device. A second turn 16 , which are below the first curve 14 has a lower slope than the first curve 14 on. This second curve 16 indicates this relationship between difference Δp and throughput 12 for a scuttled, comparatively strongly added cooling device.

The internal combustion engine will now be used to determine a characteristic K which is on the curve 16 is idle at a speed of 1500 revolutions per minute. This can be done both on a test bench and during a driving operation of a combustion engine having the motor vehicle, namely during a coasting operation of the internal combustion engine.

From the cylinder having the engine block of the internal combustion engine exhaust gas released via an exhaust line of a turbine supplied to the exhaust gas turbocharger to drive a turbine wheel. Upstream of the turbine of the exhaust gas turbocharger, the exhaust gas recirculation line branches off from the exhaust gas line of the internal combustion engine. A valve controlling an inflow into the exhaust gas recirculation line is during the detection of the measured quantities, namely the throughput 12 and the difference Δp, maximum open. Furthermore, a throttle valve arranged in the intake tract of the internal combustion engine, by means of which the pressure in the intake tract downstream of the cooling device is adjustable, is likewise maximally opened.

The respective cylinder of the engine block of the internal combustion engine in the present case have two parallel supply air paths with supply air acted upon. A first supply air path of the intake is hereby provided for supplying the main mass flow of the supply air. A second Supply air path is mainly for generating a swirl flow designed the supply air, resulting in a particularly advantageous combustion in the cylinders. In this second Zuluftpfad is in this case arranged a further throttle, which also as Inlet channel shutdown (EKAS) is called. This throttle is for calculating the measured quantities the characteristic K is also open at most.

A arranged in the exhaust system of the internal combustion engine throttle device for throttling a turbine of the exhaust gas turbocharger acting Exhaust gas flow, however, is maximally closed. Is it correct? the turbine of the turbocharger to a turbine with variable turbine geometry (VTG), so here are the distances between the individual Guide vanes of the turbine guide grid maximum narrowed. Rejects that Internal combustion engine in the exhaust system, a bypass line for bypassing the turbine of the exhaust gas turbocharger, so is an in the bypass line arranged shut-off device, for example a flap also called wastegate, closed.

additionally In the present case, engine electronics sizes, such as a Mass flow of the exhaust gas through the exhaust gas recirculation line, an exhaust back pressure in the exhaust system, a boost pressure in the intake the internal combustion engine, a temperature of the exhaust gas downstream the cooling device and an opening width of the controlling the influx into the exhaust gas recirculation line Valves recorded continuously and stored in an endurance run script.

From the measured variables difference Δp and throughput 12 the parameter K is determined according to: K = Δp / [(throughput 12 ) ² ].

This characteristic K becomes with a reference characteristic 18 which is indicative of the intact cooling device. Accordingly, the reference characteristic is 18 on the first corner 14 in the diagram 10 the Figure.

As shown in the example of the figure, the characteristic K with respect to the reference characteristic 18 both in the direction of a larger difference Δp to the right and in the direction of a reduced throughput 12 offset down, so essentially the course of an arrow 20 following in the diagram 10 shifted, it can be concluded on the basis of the characteristic K on a lack of proper functioning of the cooling device.

On the other hand, the characteristic is along a horizontal arrow 22 shifted, so when determining the measured variables, an increase in the difference .DELTA.p in the exhaust gas recirculation line with respect to the reference characteristic 18 detected while the throughput 12 is largely constant, it can be concluded that a limited functionality of the exhaust gas turbocharger. A poor pressure ratio of the pressure upstream of the cooling device relative to the pressure downstream of the cooling device thus suggests that the exhaust gas turbocharger does not cause a desired compression of the supply air.

In another scenario, however, determining the metrics will decrease the throughput 12 through the exhaust gas recirculation line at, based on the reference characteristic 18 , largely constant difference Δp detected. Accordingly, the characteristic is in the direction of a substantially vertical arrow 24 in the diagram 10 shifted compared to the intact cooling device. On the basis of the parameter determined in this case, a limited functionality of at least one component of the intake tract can be concluded. For example, a charge air hose may be defective, or an air mass meter may be compromised in its functionality and provide incorrect values.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - DE 102004041767 A1 [0003]

Claims (10)

Method for operating an internal combustion engine, wherein exhaust gas is applied to a cooling device arranged in an exhaust gas return line, and in which at least one measured variable (Δp, 12 ), characterized in that, upon detecting the at least one measured variable, a difference (Δp) between a pressure upstream and a pressure downstream of the cooling device and a throughput ( 12 ) are determined by the exhaust gas recirculation line. Method according to Claim 1, characterized in that the at least one measured variable (Δp, 12 ) is used to calculate a parameter (K) based on which, with reference to a reference parameter (K), 18 ) is closed for an intact cooling device to a clogging degree of the cooling device. A method according to claim 2, characterized in that based on the parameter (K) with reference to the reference parameter ( 18 ) is concluded for the intact cooling device to a limited functionality of at least one component of an intake tract and / or on a limited functionality of an exhaust gas turbocharger. Method according to one of claims 1 to 3, characterized in that the at least measured variable (Δp, 12 ) is detected at a presence of a predetermined speed of the internal combustion engine at a test stand or during a coasting operation of the internal combustion engine. Method according to one of Claims 1 to 4, characterized in that a valve regulating an inflow into the exhaust gas recirculation line and / or at least one throttle valve arranged in an intake section of the internal combustion engine are detected during the detection of the at least one measured variable (Δp, 12 ) maximum open. Method according to one of claims 1 to 5, characterized in that one in an exhaust line of the internal combustion engine arranged throttle device for throttling a turbine of a Exhaust gas turbocharger acting exhaust gas flow maximum closed becomes. Method according to one of claims 1 to 6, characterized in that a in a bypass line to Bypassing a turbine of an exhaust gas turbocharger arranged shut-off device is closed. Method according to one of claims 1 to 7, characterized in that a proportion of exhaust gas at one of Internal combustion engine supplied medium and / or a Mass flow of the exhaust gas through the exhaust gas recirculation line and / or an exhaust backpressure in the exhaust system and / or a boost pressure in an intake tract of the internal combustion engine and / or a Temperature of the exhaust gas downstream of the cooling device and / or an opening of an influx into the Exhaust gas recirculation line regulating valve detected become. Internal combustion engine with a cooling device arranged in an exhaust gas recirculation line, which can be acted upon by recirculated exhaust gas, and with at least one measuring device for detecting a measured variable (Δp, 12 ), by means of which a functional capability of the cooling device can be checked, characterized in that by means of the at least one measuring device a difference (Δp) between a pressure upstream and a pressure downstream of the cooling device and a throughput ( 12 ) are detectable by the exhaust gas recirculation line. Internal combustion engine according to claim 9, characterized characterized in that the internal combustion engine for performing A method according to any one of claims 1 to 8 is.