DE102017111232B4 - Method for real-time detection of deposits in combustion engines with AGN systems - Google Patents

Abstract

Device (10) for detecting deposits in an exhaust tract of an internal combustion engine, comprising:
an exhaust pipe (12);
an image recording unit (16) arranged to record a surface (12A, 24A) provided in the exhaust line (12), wherein the image recording unit (16) is designed to capture and output a recording of the surface (12A, 24A); and
an image processing unit (18) which is designed to receive the image output by the image recording unit (16) and to process it for checking for a deposit on the surface (12A; 24A),
wherein the device (10) further comprises a component (24) which is arranged in the exhaust line (12), wherein the image recording unit (16) is arranged to record a surface (24A) of the component (24) and wherein the component (24) is specifically provided as a test body, wherein the test body forms a disturbance element for an exhaust gas flow in the exhaust line (12) and is preferably arranged inclined with respect to a flow direction in the exhaust line (12), in particular at an angle of 90° to the flow direction.

Description

The invention relates to a device for detecting deposits in an exhaust tract of an internal combustion engine, a test bench with a device for detecting deposits, a motor vehicle with a device for detecting deposits and a method for detecting deposits.

To reduce the nitrogen oxides emitted, diesel engines can have a selective catalytic reduction (SCR) system installed in the exhaust system. An SCR system includes a reducing agent injector that injects a reducing agent, such as an aqueous urea solution, into an exhaust line. The reducing agent evaporates in the hot exhaust gas and can reduce the nitrogen oxides with the help of a catalyst.

Under certain conditions, such as low exhaust gas temperatures, it may happen that the reducing agent does not evaporate completely. As a result, reducing agent deposits can form in the exhaust line. Such reducing agent deposits can, for example, adhere to the walls in the exhaust line or to components installed in the exhaust line. This can impair the respective function of the component. In addition, non-evaporated reducing agent is not used to convert nitrogen oxides and thus reduces the efficiency of the system. In addition, the deposits can reach large dimensions, even to the point of clogging the exhaust line.

The EN 10 2008 018 063 A1 discloses a method for improving the performance of an exhaust aftertreatment system of a vehicle. The method includes estimating a urea deposit accumulation in the SCR catalyst to determine timing for regenerating the SCR catalyst to remove the urea deposit accumulation.

WO 2015/150 498 A1 discloses a device for detecting urea deposits in an exhaust pipe of an internal combustion engine. The device comprises at least one radiation receiver which, in use, is arranged within the exhaust line downstream of the reducing agent nozzle. The device further comprises an electronic control unit in communication with the radiation receiver. The radiation receiver communicates radiation data to the control unit which enables the control unit to determine whether deposits have formed within the exhaust line.

The US 8 004 695 B1 discloses systems and methods for measuring the thickness of a film on an interior surface of an exhaust system of a vehicle. The film is typically a layer of a nitrogen oxide reductant. The methods and systems are directed to optical measurements using a laser that directly examine the interior surfaces of the exhaust system to determine the thickness of a urea film built up during operation of the engine and the selective catalytic reduction system.

Other emissions such as unburned hydrocarbons and particles such as soot and ash can lead to clogging of components such as a diesel oxidation catalyst and a diesel particulate filter.

The invention is based on the object of providing a device and a method that enables an alternative and possibly improved detection of deposits. The invention is based in particular on the object of enabling an automated and rapid detection of deposits, preferably reducing agent deposits and combustion product deposits, during ongoing operation of the internal combustion engine.

The object is achieved by a device and a method for detecting deposits in an exhaust tract of an internal combustion engine according to the independent claims. Advantageous further developments are specified in the dependent claims.

The device has an exhaust line and an image recording unit. The image recording unit is arranged to record a surface provided in the exhaust line. The image recording unit is designed to capture and output an image of the surface. The device has an image processing unit. The image processing unit is designed to receive an image output by the image recording unit and to process it to check for a deposit on the surface.

By using an automated evaluation by the image processing unit, a check for deposits, in particular operating fluid deposits, reducing agent deposits and/or combustion product deposits, can be carried out in real time. This also enables deposits to be detected at an early stage so that larger accumulations can be prevented. If deposits are detected, appropriate countermeasures can be initiated, for example.

The image recording unit can in particular have one or more light-sensitive electronic components, e.g. CCD or CMOS sensors.

The image can consist of a plurality of pixels (picture elements).

The device can be used to check for any type of deposits in the exhaust line.

Preferably, the recording has one or a plurality of optical images. With a plurality of optical images, the optical images can show different sections or areas of a surface or different surfaces. Alternatively or additionally, the optical images can be recorded at different times. This allows temporal changes in the surfaces to be analyzed and multiple areas in the exhaust line to be examined.

In one embodiment, the image processing unit is designed to process the image output by the image recording unit to check for a deposit of operating fluid, in particular a deposit of reducing agent, a deposit of a combustion product, in particular soot or ash, and/or a deposit precursor (e.g. operating fluid deposit precursor, reducing agent deposit precursor, combustion product deposit precursor). The deposits can be detected, for example, as a wall film in a liquid or solid state.

In one embodiment, the image processing unit is designed to carry out an image evaluation of the image information of the recording. In particular, an image processing algorithm can be applied to the recording captured by the image recording unit to check for deposits. The use of a specially adapted image processing algorithm increases the detection accuracy and also enables the automation of the evaluation.

The image processing algorithm can, for example, compare the image with a previous image or with a comparison image that does not contain any reduction deposits.

The image analysis can compare two or more images. The image analysis can determine temporal changes in the information in the images.

Additionally or alternatively, the image processing algorithm can apply a filter to the image. For example, several pixels can be combined into one pixel. The color or gray value of the combined pixel can be an average of the combined pixels.

Additionally or alternatively, the image processing algorithm can count the number of pixels where a gray value is above a threshold.

Additionally or alternatively, the image processing algorithm can further divide a range of the gray value above the threshold into classes, count the number of pixels within each of these classes and create a corresponding histogram.

Additionally or alternatively, the image processing algorithm can directly compare the individual pixels between two images and/or use hash functions for evaluation.

In one embodiment, the image processing unit is designed to determine a size of the deposit. Alternatively or additionally, the image processing unit is designed to determine a presence of the deposit. Alternatively or additionally, the image processing unit is designed to determine a change in the deposit over time. The determination of a size of the reducing agent deposit and/or the change in the deposit over time can be used to decide whether a tolerance threshold is exceeded. If the tolerance threshold is exceeded, corresponding measures can be initiated to reduce the reducing agent deposits and/or to prevent further reducing agent deposits. The tolerance threshold can be provided to compensate for detection inaccuracies by the image recording unit.

In one embodiment, the image recording unit is designed as a camera, in particular an endoscope camera. The camera can in particular be designed as a 2D camera, 3D camera, photo camera and/or video camera.

Preferably, the image recording unit is designed to capture an image in the ultraviolet range, in the visible light range and/or in the infrared range.

Advantageously, the image recording unit is arranged at least partially in the exhaust pipe in an environmentally resistant (e.g. acid-resistant, temperature-resistant and/or dust-proof) housing.

In a further embodiment, the device is designed to introduce a fluorescent auxiliary substance into the exhaust line. For example, a separate injector can be provided for introducing the fluorescent auxiliary substance. The fluorescent auxiliary substance can also be introduced together with or separately from an operating medium, for example a reducing agent, by an operating medium injector. The device can have a separate tank for the fluorescent auxiliary substance. The fluorescent auxiliary substance can also be added to or fed to the operating medium in the operating medium tank. The fluorescent auxiliary substance can also be dissolved in the operating medium.

In a further embodiment, the image recording unit is arranged to record an inner wall surface of the exhaust pipe. This enables the inspection for deposits (solid or as a liquid film) on the inner wall surface of the exhaust pipe.

According to the invention, the device further comprises a component. The component is arranged in the exhaust pipe. The image recording unit is arranged to record a surface of the component. This means that components in the exhaust pipe can also be examined for deposits.

According to the invention, the component is specifically designed as a test body that is arranged at critical points in the exhaust line to check for deposits. The test body can be provided in the form of a sheet, for example. The test body can form a disruptive element for the exhaust gas flow in the exhaust line. For this purpose, the sheet can be arranged at an angle with respect to a flow direction in the exhaust line, for example at an angle of 90° to the flow direction.

In a further embodiment, the device further comprises an operating fluid injector which is designed and arranged to introduce an operating fluid (e.g. a reducing agent or a fuel) into the exhaust line. The image recording unit can in particular be arranged downstream or upstream of the operating fluid injector. The image recording unit can thus be arranged flexibly depending on requirements and possibilities. An arrangement upstream of the operating fluid injector can prevent contamination of the image recording unit by the operating fluid.

The reducing agent injector and/or the exhaust line can in particular be part of an SCR system.

The image recording unit is preferably arranged such that an area downstream of the operating fluid injector is in the field of view of the image recording unit. In other words, the surface recorded by the image recording unit is downstream of the operating fluid injector. In this way, the areas susceptible to operating fluid deposits in particular can be recorded by the image recording unit.

In a further embodiment, the device has a control unit. The control unit is in communication with the operating fluid injector. The control unit is designed to control the operating fluid injector based on the check for deposits. For example, a reducing agent dosing rate can be increased to improve nitrogen oxide conversion efficiency if no reducing agent deposits are detected. On the other hand, a reducing agent dosing rate can be reduced to prevent deposits if reducing agent deposits are detected.

The term “control unit” refers to a control electronics unit that, depending on its design, can perform control and/or regulation tasks.

In addition to controlling the operating fluid injector, the control unit can be in communication with the image recording unit. Additionally or alternatively, the control unit can be in communication with a lighting device for controlling the lighting device.

Advantageously, the control unit is designed to control a dosing rate through the operating fluid injector, in particular an opening duration, an opening frequency and/or an opening degree of the operating fluid injector, based on the check for deposits by the image processing unit.

In particular, the control unit is designed to reduce a dosing rate of the operating medium injector if the image processing unit determines the presence of a deposit on the surface, a certain size of the deposit exceeds a predetermined limit value, determines a temporal change in a deposit and/or a temporal change in the deposit exceeds a limit value. Reducing the dosage can prevent the formation of further deposits.

Alternatively or additionally, the control unit can initiate a measure to reduce the deposit. For example, the combustion engine can be controlled to reduce the deposit if the image processing unit determines the presence of a deposit on the surface, the specific size of the reducing agent deposit exceeds a predetermined limit value, determines a temporal change in a deposit and/or a temporal change in the deposit exceeds a limit value. Preferably, for example, an exhaust gas temperature and/or an exhaust gas mass flow can be increased for this purpose.

In a further embodiment, the control unit is designed to determine and/or update a maximum operating fluid dosing rate for one or a plurality of engine operating points of the internal combustion engine, at which no deposit is determined by the image processing unit, a certain size of the deposit does not exceed a predetermined limit value, at which no temporal change in a deposit is determined, and/or a temporal change in the deposit does not exceed a limit value. To do this, the control unit can, for example, increase the operating fluid dosing step by step until a deposit is detected. This enables the automatic creation of characteristic curves in a test bench for later use in practice. An update can be carried out, for example, in an application in the vehicle if a maximum dosing rate determined in the vehicle deviates from one in the laboratory, in field tests or from a previously determined maximum dosing rate.

The control unit can automatically control different engine operating points one after the other and determine a maximum dosing rate for each engine operating point.

The maximum dosing rate can be stored in a memory of the control unit so that too much operating fluid can be prevented from being injected in the future.

In a further embodiment, the device further comprises an illumination device. The illumination device is arranged to illuminate the surface recorded by the image recording unit. Such a configuration has the advantage that the recording quality can be improved.

The lighting device can be used separately from the image recording unit as an additional unit and/or be integrated into the image recording unit.

The lighting device can in particular be designed to emit light with different wavelengths, in particular light in an ultraviolet range, a visible range and/or an infrared range.

It is understood that the term “visible range of light” refers to a range of light visible to the human eye (wavelength between 380 nm and 780 nm).

The lighting device can be designed as a continuous lighting device or a flash device.

In a further embodiment, the illumination device can emit light in the ultraviolet range. This makes it possible, for example, to make fluorescent auxiliary substances in the deposits visible. The illumination can take place before or during the recording by the image recording unit.

The invention further relates to a test bench, in particular an engine test bench, or a motor vehicle, in particular a commercial vehicle, with the device for detecting reducing agent deposits as disclosed herein.

The invention also relates to a method for detecting deposits in an exhaust tract of an internal combustion engine. The deposits are in particular operating fluid deposits, preferably reducing agent deposits, and/or combustion product deposits, preferably soot or ash. The method comprises recording a surface in an exhaust line. The method also comprises applying image processing to the recording to check for deposits on the surface.

As with the device described previously, the use of automated recording and evaluation enables real-time monitoring of deposits. Deposits can be detected at an early stage. If necessary, appropriate countermeasures can be taken to prevent further deposits and/or to reduce or dissolve existing deposits.

The method may use the apparatus as disclosed herein.

In a preferred embodiment, the method further comprises introducing an operating medium, in particular a reducing agent, for example an aqueous urea solution, into the exhaust line. The image processing is based on the recording to check for deposits of the operating fluid on the surface.

The operating agent can be introduced together with a fluorescent auxiliary substance. The method can then further comprise, in particular, irradiating the surface with light that has an excitation wavelength of the fluorescent auxiliary substance. The light can in particular have a component in the ultraviolet range. This has the advantage that fluorescent reducing agent deposits can increase the detection accuracy.

Irradiating the surface with light can occur before the surface is imaged or during the surface is imaged.

• 1 eine schematische Ansicht einer beispielhaften Vorrichtung zur Erfassung von Reduktionsmittelablagerungen;
• 2 eine schematische Ansicht einer weiteren beispielhaften Vorrichtung zur Erfassung von Reduktionsmittelablagerungen;
• 3 ein Flussdiagramm zum Darstellen eines Verfahrens zur Kennfeldermittlung unter Verwendung der Vorrichtung zur Erfassung von Reduktionsmittelablagerungen; und
• 4 ein Flussdiagramm zum Darstellen eines Verfahrens für eine Fahrzeuganwendung unter Verwendung der Vorrichtung zur Erfassung von Reduktionsmittelablagerungen.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. They show:

• 1 a schematic view of an exemplary device for detecting reducing agent deposits;
• 2 a schematic view of another exemplary device for detecting reducing agent deposits;
• 3 a flow chart illustrating a method for determining characteristic maps using the device for detecting reducing agent deposits; and
• 4 a flow chart illustrating a method for a vehicle application using the device for detecting reducing agent deposits.

The embodiments shown in the figures correspond at least partially, so that similar or identical parts are provided with the same reference numerals and for their explanation reference is also made to the description of the other embodiments or figures in order to avoid repetition.

In the following, particular reference is made to a particularly preferred apparatus and method for detecting reducing agent deposits. However, those skilled in the art will readily understand that the apparatus and method are equally applicable to detecting other deposits, e.g. deposits from other operating fluids (e.g. diesel) or combustion products (e.g. soot or ash).

The 1 shows a device 10 for detecting reducing agent deposits. The device 10 has an exhaust line 12, an image recording unit 16 and an image processing unit 18.

The exhaust pipe 12 forms a section of an exhaust tract of an internal combustion engine (not shown in detail). The exhaust pipe 12 can, for example, be arranged downstream of an exhaust manifold of the internal combustion engine for conducting exhaust gas. The arrows A and B show a flow direction through the exhaust pipe 12.

A reducing agent injector 14 extends into the exhaust line 12. The reducing agent injector 14 is designed to inject a reducing agent, for example an aqueous urea solution, into the exhaust line 12. In a known manner, the reducing agent can evaporate in the hot exhaust gas and reduce nitrogen oxides (NO _x ) in the exhaust gas with the help of a catalyst.

In other embodiments, a different operating fluid injector or no injector at all can be provided instead of the reducing agent injector 14. It is understood that the device can be provided in particular without an operating fluid injector (reducing agent injector) if, for example, no SCR system is present and/or (only) combustion product deposits are to be detected.

The reducing agent injector 14 is connected to a reducing agent tank (not shown) via a reducing agent pump (not shown). A control unit 20 can control the reducing agent injector 14 to inject reducing agent.

The image recording unit 16 is arranged such that a surface in the exhaust pipe 12 is in the field of view of the image recording unit 16. In the present embodiment, a portion of an inner wall surface 12A of the exhaust pipe 12 is in the field of view of the image recording unit 16. The image recording unit 16 is designed to record the surface 12A and output the recording, for example in the form of data signals. The image recording unit 16 can be designed, for example, as a 2D or 3D, video or photo camera. The camera can have light-sensitive sensors, for example CMOS or CCD sensors.

The image recording unit 16 is designed to withstand the high temperatures and corrosive conditions in the exhaust system of the internal combustion engine. For example, the image recording unit can be installed in a temperature and acid re-resistant and dust-tight housing. Alternatively or additionally, the image recording unit 16 can be designed as an endoscope camera in which, for example, a fiber optic cable protruding into the exhaust line 12 is connected to one or more light-sensitive components.

In the embodiment shown, the image recording unit 16 is arranged upstream of the reducing agent injector 14. Additionally or alternatively, an image recording unit can also be arranged at a different position in or on the exhaust line 12. The image recording unit can in particular be arranged so that surfaces susceptible to reducing agent deposits are located in a field of view of the image recording unit. This can be the case, for example, in the area of flow resistances, such as curved segments or fittings in the exhaust line 12. In the 1 Two further conceivable arrangements for the image recording unit are indicated by way of example with the reference symbols “X” and “Y”.

The image recording unit 16 is in communication with the image processing unit 18. The image processing unit 18 can receive one or more images from the image recording unit 16. The image processing unit 18 processes the received image in order to detect any reducing agent deposits present on the surface 12A. To do this, the image processing unit 18 can use one or a plurality of predetermined image processing algorithms.

For example, an image processing algorithm can compare the image of the surface 12A with a predefined image of the surface 12A on which no reducing agent deposits are present. Such a comparison can also be made indirectly, for example by storing a data set. The data set has characteristic values to be compared for a situation without reducing agent deposits.

Two images can be compared using various methods, some of which are explained below as examples.

The basic principle for most methods is to take into account the gray and color values of the individual pixels in the image. Before the actual comparison takes place, an image can be pre-filtered. One way of filtering is to combine several pixels into one large pixel, which has the average values of the gray and color values of the combined pixels as its property. In the following, pixel refers to both the pixel and the average of several pixels. When comparing, images that follow one another directly in time or indirectly in time (there are several images between the images to be compared) can be used. Some methods for comparing images are described below as examples.

A limit value is defined for the gray value. For each image, the number of pixels where the gray value is above the limit value is counted. If this number changes between two images, this is proportional to the amount of reducing agent deposits present.

Instead of just counting the number of pixels above the limit, the range of the gray value above the limit can also be divided into classes. The number of pixels within each of these classes is then counted and a histogram is created on this basis. Here, the change in the histogram when comparing two images is proportional to the amount of reducing agent deposits.

The above method using a histogram can also be used without setting a limit value. To do this, the entire range of gray values (0:255) is divided into classes and the number of pixels in an image per class is counted. A histogram is created on the basis of this. In addition to the gray value, a color value analysis (RPG) can also be carried out using this method. That is, classes are introduced for each color value and the number of pixels in each class is determined for each color value. This results in a histogram for each color value. These histograms are used to compare two or more images and a change in the histograms indicates a change in the reducing agent deposits.

Another method involves directly comparing the individual pixels between two images. Since each image has the same total number of pixels, the individual pixels of two or more images can be directly compared. Both gray and color values can be used for comparison. If pixels differ between images, this is a measure of reducing agent deposits.

Hash functions can be used as another comparison method. One such hash function is a cryptological hash function. In this function, all of the color or gray values of an image are recorded in a unique number (for example, MD5 hash; 32-digit hexadecimal number). This number is created for each image and can then be compared with each other. As images differ, this number will vary.

It is understood that the above-mentioned possibilities can be combined with each other and/or other methods of image processing and/or object recognition can be used.

If the image processing unit 18 detects a reducing agent deposit on the surface 12A, the image processing unit 18 may, in some embodiments, determine the size of the reducing agent deposits. The determined size may be compared to a threshold value.

When the presence of a reducing agent deposit is detected by the image processing unit 18, a size of the reducing agent deposit exceeds a limit, a temporal change in a size of a reducing agent deposit is detected, or a temporal change in a size of the reducing agent deposit exceeds a limit, various measures can be taken depending on the requirement and application environment. 3 and 4 different procedures for application on an engine test bench ( 3 ) and in a vehicle ( 4 ) described.

In particular, the control unit 20, which is in communication with the image processing unit 18, can adjust a reductant dosing rate through the reductant injector 14 based on the check for reductant deposition.

Preferably, the control unit 20 can reduce a reducing agent metering rate through the reducing agent injector 14 if a reducing agent deposit has been detected. For this purpose, for example, an opening frequency, an opening degree and/or an opening duration of the reducing agent injector 14 can be reduced.

On the other hand, it is also possible for the control unit 20 to increase a reducing agent metering rate through the reducing agent injector 14 if no reducing agent deposits have been detected. Increasing the reducing agent metering can be particularly useful if a nitrogen oxide sensor (not shown) detects an excessively high nitrogen oxide concentration downstream of the catalyst for selective catalytic reduction. To increase the reducing agent metering, for example, an opening frequency, an opening degree and/or an opening duration of the reducing agent injector 14 can be increased.

The control unit 20 can also be in communication with the image recording unit 16. The control unit 20 can control the image recording unit 16 to take a picture of the surface 12A.

The control unit 20 can be designed as an electronic control unit in a motor vehicle. Alternatively, the control unit 20 can be designed, for example, as a computer system of a test bench, for example an engine test bench.

A lighting device 22 can be provided to illuminate the interior of the exhaust pipe 12 and in particular the surface 12A. The lighting device 22 can be designed as a continuous lighting device or a flash device. The lighting device 22 can be connected to the control unit 20 for switching on and off or triggering.

In some embodiments, the illumination device 22 may be integrated into the image recording unit 16, for example as a light source of an endoscope camera.

In some embodiments, a fluorescent aid may be mixed with the reducing agent. The fluorescent aid may be mixed in during introduction through the reducing agent injector 14 or prior thereto, for example by adding it to the reducing agent tank. The fluorescent aid may facilitate image processing by allowing reducing agent deposits to separate from the surface 12A with greater contrast. To further enhance this, the illumination device 22 may irradiate the surface 12A with light having an excitation wavelength of the fluorescent aid. For example, the illumination device 22 may be designed as a UV (ultraviolet light) illumination device.

The 2 shows a further embodiment of the device for detecting reducing agent deposits, which is provided with the reference number 10`. In comparison with the embodiment of 1 Identical components are provided with the same reference symbols. To avoid repetition, a description of identical components is omitted.

The device 10` additionally has a component 24. The component 24 is arranged in the exhaust line 12. The component 24 can be, for example, a sheet metal, a catalyst, a mixer or a particle filter. The sheet metal can be used, for example, for flow guidance or specifically as a test body for detecting removal of reducing agent deposits.

In addition or as an alternative to recording a section of the inner wall surface 12A, the image recording unit 16 is designed and arranged to take a picture of a surface 24A of the component 24. Consequently, the surface 24A of the component 24 can also be examined for reducing agent deposits. To better illuminate the surface 24A of the component 24, the lighting unit 22 can illuminate the surface 24A.

Even in the embodiment according to 2 it is possible that instead of the reducing agent injector 14 another operating fluid injector or no injector at all is provided.

The device disclosed herein for detecting reducing agent deposits can be used in a variety of ways. The following is a description of the device with reference to 3 an application example in an engine test bench and with reference to 4 An application example in a motor vehicle is described. The processes can be carried out fully automatically or partially automatically.

The 3 shows an exemplary method for determining a map relating a maximum reductant dosing rate to an engine operating point. The engine operating point can be characterized, for example, by a load on the internal combustion engine, a cylinder pressure, a cylinder temperature, an accelerator pedal position, a speed of the internal combustion engine, a torque of the internal combustion engine, an output power of the internal combustion engine, a fuel consumption of the internal combustion engine, an exhaust gas temperature and/or an exhaust gas flow rate of the internal combustion engine.

Below is the exemplary procedure of 3 with reference to the device of 1 described.

In a first step S100, a new engine operating point is set for the internal combustion engine. The internal combustion engine is operated at this new engine operating point. The maximum possible reducing agent dosing rate is then to be determined for this engine operating point.

In step S102, a minimum dosage of the reducing agent is set. The minimum dosage of the reducing agent can be predetermined, for example, by the design and/or controllability of the reducing agent injector 14. The minimum dosage is set in the form of a control command with which the reducing agent injector 14 is controlled.

The control command for controlling the reducing agent injector 14 can relate to an opening duration, an opening frequency and/or an opening degree of the reducing agent injector 14.

In step S104, a reducing agent is introduced into the exhaust line 12 through the reducing agent injector 14. The reducing agent is introduced according to the previously set dosage.

In step S106, the image recording unit 16 takes a picture of the surface 12A. To improve the quality of the picture, the surface 12A is illuminated by the lighting device 22 during the picture. The picture, which can consist of one or more images, is output from the image recording unit 16 to the image processing unit 18.

In step S108, the image of the image recording unit 16 is processed by the image processing unit 18. The image processing unit 18 checks the image for the presence of reducing agent deposits on the surface 12A.

In step S110, it is checked whether the image processing in step S118 has detected a reducing agent deposit. If a reducing agent deposit was detected, the process continues with step S112. If no reducing agent deposit was detected, the process continues with step S116.

In step S112, it is checked whether a detected reducing agent deposit exceeds a limit value. The limit value can be defined in such a way that only small detected reducing agent deposits remain unnoticed, since these can result, for example, from recording inaccuracies, blurring, changed lighting conditions, etc. The limit value can be defined, for example, as the surface size of a reducing agent deposit or indirectly as a comparison characteristic value.

If the limit value has been exceeded, the characteristic map to be created is updated in step S114. In particular, the current reducing agent dosing rate or the previously set reducing agent dosing rate at which the reducing deposits have not yet exceeded a limit value is updated as the maximum possible reducing agent dosing rate for the set engine operating point. The method begins again in step S100 with the setting of a new engine operating point for which a maximum dosing rate is to be determined.

If no limit value has been exceeded (step S112) or no deposit has been detected (step S110), the reducing agent dosing rate is increased in step S116. The method begins again at step S104 with the introduction of the reducing agent.

The 4 shows a method that can be used during operation of a motor vehicle.

The steps S200 to S208 can be carried out essentially like the steps S104 to S112, so that a detailed description is omitted to avoid repetition.

If no deposit is detected in step S206 or no limit value is exceeded in step S208, the method is carried out in a further loop with a restart in step S200.

If a limit value is exceeded in step S208, suitable countermeasures can be initiated in step S210. To remove the reducing agent deposits, an exhaust gas temperature and/or an exhaust gas flow rate can be increased, for example.

In addition, in step S210, a characteristic map stored in the control unit, for example, can be updated with regard to the maximum reducing agent dosing rate.

In step S212, a dosing rate can be adjusted if desired. For example, a dosing rate can be increased if no deposits are detected or no limit value is exceeded. A dosing rate can be reduced, for example, if a limit value for the deposits is exceeded.

The invention is not limited to the preferred embodiments described above. Rather, a large number of variants and modifications are possible which also make use of the inventive concept and therefore fall within the scope of protection.

In particular, the invention also claims protection for the subject matter and features of the subclaims independently of the claims referred to.

List of reference symbols

10

Device for detecting reducing agent deposits (deposits)

12

Exhaust pipe

12A

Inner surface of the exhaust pipe

14

Reducing agent injector (operating fluid injector)

16

Image acquisition unit

18

Image processing unit

20

Control unit

22

Lighting device

24

Component in exhaust pipe

24A

Surface of the component

AWAY

Flow direction

X, Y

Possible positions for image acquisition unit

Claims (14)

Device (10) for detecting deposits in an exhaust tract of an internal combustion engine, comprising: an exhaust line (12); an image recording unit (16) arranged to record a surface (12A, 24A) provided in the exhaust line (12), wherein the image recording unit (16) is designed to record and output a recording of the surface (12A, 24A); and an image processing unit (18) which is designed to receive the image output by the image recording unit (16) and to process it to check for a deposit on the surface (12A; 24A), wherein the device (10) further comprises a component (24) which is arranged in the exhaust line (12), wherein the image recording unit (16) is arranged to record a surface (24A) of the component (24) and wherein the component (24) is specifically provided as a test body, wherein the test body forms a disturbance element for an exhaust gas flow in the exhaust line (12) and is preferably arranged inclined with respect to a flow direction in the exhaust line (12), in particular at an angle of 90° to the flow direction. Device (10) according to Claim 1 , wherein the recording has one or a plurality of optical images, which are in particular recorded at different times and/or show different regions of the surface (12A, 24A). Device according to Claim 1 or Claim 2 , wherein: the image processing unit (18) is designed to use the image output by the image recording unit (16) to check for a deposit of operating fluid, in particular a reduction agent deposit, a deposit of a combustion product, in particular soot or ash, and/or a deposit precursor; and/or the image processing unit (18) is designed to carry out an image evaluation of the image information of the recording, wherein the image processing unit (18) in particular applies an image processing algorithm to the recording captured by the image recording unit (16) to check for a deposit. Device (10) according to one of the preceding claims, wherein the image processing unit (18) is designed to: determine a size of the deposit; and/or determine a presence of the deposit; and/or determine a temporal change in the deposit. Device (10) according to one of the preceding claims, wherein: the image recording unit (16) is designed as a camera, in particular an endoscope camera; and/or the image recording unit (16) is designed to capture an image in the ultraviolet range, in the visible light range and/or in the infrared range; and/or the device (10) is designed to introduce a fluorescent auxiliary substance into the exhaust line (12). Device (10) according to one of the preceding claims, wherein: the image recording unit (16) is arranged to record an inner wall surface (12A) of the exhaust pipe (12). Device (10) according to one of the preceding claims, further comprising an operating medium injector (14) which is designed and arranged to introduce an operating medium, in particular diesel or a reducing agent, into the exhaust line (12), wherein the image recording unit (16) is preferably arranged downstream or upstream of the operating medium injector (14). Device (10) according to Claim 7 , further comprising a control unit (20) which is in communication with the operating medium injector (14) and is designed to control the operating medium injector (14) based on the check for deposits by the image processing unit (18). Device (10) according to Claim 8 , wherein the control unit (20) is designed to: reduce a dosing rate of the operating medium injector (14) if the image processing unit (18) determines the presence of a deposit on the surface (12A; 24A), a certain size of the deposit exceeds a predetermined limit value, determines a temporal change in a deposit and/or a temporal change in the deposit exceeds a limit value; and/or initiate a measure to reduce the deposit, in particular to control the internal combustion engine to increase an exhaust gas temperature and/or an exhaust gas flow rate, if the image processing unit (18) determines the presence of a deposit on the surface (12A; 24A), a certain size of the deposit exceeds a predetermined limit value, determines a temporal change in a deposit and/or a temporal change in the deposit exceeds a limit value. Device (10) according to Claim 8 or Claim 9 , wherein the control unit (20) is designed to determine and/or update a maximum operating medium dosing rate for one or a plurality of engine operating points of the internal combustion engine, at which no deposit is determined by the image processing unit (18), at which a certain size of the deposit does not exceed a predetermined limit value, at which no temporal change in a deposit is determined and/or a temporal change in the deposit does not exceed a limit value. Device (10) according to one of the preceding claims, further comprising an illumination device (22) which is arranged to illuminate the surface (12A, 24A) recorded by the image recording unit (16) and in particular is integrated in the image recording unit (16), wherein the illumination device (22) is preferably designed to emit light in an ultraviolet range, a visible range and/or an infrared range. Test bench, in particular engine test bench, or motor vehicle, in particular commercial vehicle, with the device (10) according to one of the preceding claims. Method for detecting deposits in an exhaust system of an internal combustion engine, in particular operating fluid deposits, preferably reducing agent deposits, and/or combustion product deposits, the method using the device (10) according to one of the Claims 1 until 11 used, the method comprising: recording a surface (12A, 24A) in an exhaust pipe (12); and applying image processing to the recording to check for deposits on the surface (12A, 24A). Procedure according to Claim 13 , further comprising: introducing an operating medium, in particular a reducing agent, for example an aqueous urea solution, into the exhaust line, wherein the image processing is applied to the image to check for a deposit of the operating medium on the surface (12A, 24A) and the reducing agent is introduced in particular together with a fluorescent auxiliary substance and the method further preferably comprises irradiating the surface (12A, 24A) with light which has an excitation wavelength of the fluorescent auxiliary substance.

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