DE102015206120A1 - Improved real-time ammonia slip detection - Google Patents

Abstract

Systems and methods for detecting ammonia slip in an exhaust system based on NOx sensor transient response are described. In an example method, an exhaust system allocates the output of an exhaust pipe NOx sensor to NOx and NH3 levels by a segment length method that processes the transient signals based on the total segment length calculated in a window in response to the transient sensors. A ratio of segment lengths relative to a threshold is determined for a measured and expected NOx change rate downstream of an SCR, which SCR is further used to determine NOx and NH3 probabilities based on the measured sensor activities, and a controller is included to set one or more parameters based on the assignment and changes in the output of the sensor.

Description

The present application generally relates to ammonia slip detection in an exhaust treatment system included in an exhaust system of an internal combustion engine.

Diesel vehicles may be equipped with an exhaust treatment system, e.g. For example, a urea based selective catalytic reduction system (SCR system) and one or more exhaust gas sensors, such as. As nitrogen oxide sensors (NO _x sensors), at least one of which may be located downstream of the SCR system can contain. When urea is loaded into the SCR system to a point of saturation that changes with temperature, ammonia slip (NH ₃ slip) may begin in the SCR system. The NH ₃ slip from the SCR system may be detected by the exhaust pipe NO _x sensor as NO _x , resulting in an inaccurate NO _x output that is too high. As such, the efficiency of the SCR system may actually be higher than the efficiency determined based on the inaccurate NOx output.

US 2012/0085083 describes a method of estimating NOx conversion using a polynomial model that also allows the NH ₃ concentration at the downstream exhaust pipe NOx sensor to be estimated. As described herein, the time sensor signatures of a feedgas NOx sensor located upstream of the SCR and an exhaust pipe NOx sensor located downstream of the SCR are determined using a polynomial model that estimates the NH ₃ . Slippage and NOx conversion efficiency, quantified and adjusted. However, because the method uses a segment of each sensor signal for processing, a delay exists between the detection of each output of the NOx sensor and the assignment of an output of the downstream NOx sensor to the NOx and the NH ₃ . If the delay is combined with the described polynomial fitting algorithm, which may be susceptible to localized estimation errors, the realization of a real time NH ₃ slip detection system would be difficult to implement by the described methods.

The inventors have recognized the disadvantages of the above approach, and hereby disclose methods for real time control of ammonia slip in an engine exhaust system. The described methods use the transient response of a NOx sensor to identify the rates of change of a NOx signal. Then, a processor further uses the rates of change of the NOx signals to determine, based on the exhaust flow upstream of the SCR, how to expect the change in the downstream exhaust pipe NOx sensor, assigning the exhaust pipe NOx sensor in the manner described herein allows. The inventors have further recognized that there is a trade-off between sensitivity and accuracy in processing transient signals. Therefore, the disclosed segment length method increases signal sensitivity while maintaining a high degree of accuracy, particularly at low exhaust gas temperatures, allowing for improved signal processing during lightly-powered engine cycles. In addition, the inventors have further recognized that in some cases the envelope technique may have reduced sensitivity over the segment length method, since phase adjustment errors tend to cause the envelopes to be larger due to the phase adjustment. In addition, the envelope method is prone to being deactivated during changes in the direction of the transient signal, which in some cases can lead to reduced accuracy. Therefore, the disclosed segment length method is more robust to noise factors and phase adjustment errors, and thus can have higher sensitivity without there being a significant reduction in accuracy. By way of example only, the inventors have discovered that the sensitivity of the segment-length method for ammonia detection is about 10 ppm, while the sensitivity of the envelope method is about 25-30 ppm. In a specific example, the exhaust system includes two NOx sensors that continuously monitor exhaust flow upstream and downstream of an SCR device. Then, when the entry conditions of the engine system are met, for. For example, if the SCR device is above a temperature threshold, the rate of change of the upstream feed NOx sensor is combined with a current exhaust pipe reading to estimate the expected rate of change of the exhaust NOx sensor based on the rise in the feed gas signal , The expected tailpipe NOx signal is then compared to the actual NOx signal to determine the output of the NOx sensor to the NOx and NH ₃ by the envelope method and / or the segment length method disclosed herein and described in detail below. assign.

In another example, a method is provided that includes assigning an output of a NOx sensor to both the NH ₃ and the NOx based on an upstream NOx change rate and a downstream NOx change rate relative to an SCR emission device, thereby enabling that the amount of the engine exhaust gas supplied Reducing agent is adjusted based on the relative sensor signals. Because the method uses the transient response of the upstream and downstream NOx sensors in addition to the expected NOx signal, therefore, it is possible to achieve a high level of NH ₃ detection. In this way, it is possible to provide an improved allocation of the output of the NOx sensor to determine the relative NOx and NH ₃ levels in the exhaust system.

The present description can provide several advantages. In particular, the segment length approach may allow real-time detection of NH ₃ slip with a high level of detection sensitivity without high feedgas NO x interventions while maintaining detection accuracy. Thus, the NH ₃ slip may be detected while a vehicle is operating, with corrective action taken based on the current state of the exhaust system. In addition, because the detection sensitivity is increased, high levels of NOx are not required to determine the assignment of the output of the exhaust pipe NOx sensor to the NOx and to the NH ₃ .

The above advantages and other advantages and features of the present description will be readily appreciated from the following detailed description when taken alone or in conjunction with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of the concepts that will be further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims which follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that eliminate all disadvantages noted above or in any part of this disclosure.

The advantages described herein will be more fully understood by reading an example of an embodiment, which is referred to herein as the detailed description, when taken alone or with reference to the drawings, in which:

1 shows a schematic diagram of an engine containing an exhaust system with an exhaust treatment system;

2A -D show graphs illustrating an ammonia slip state determined by the envelope method;

3 shows a flowchart illustrating a routine for detecting ammonia slip by the envelope method in an exhaust treatment system;

4 shows a flowchart illustrating a routine for controlling the operating parameters when an output of an exhaust gas sensor is assigned to a nitrogen oxide;

5 shows a flowchart illustrating a routine for controlling the operating parameters when an output of an exhaust gas sensor is assigned to the ammonia;

6A -D and 7A -D show graphs showing NOx and NH ₃ slip states, respectively, determined by the segment length method;

8A -E show an exemplary exhaust gas signal under conditions with high exhaust pipe NH ₃ slip according to the method;

9 shows a flowchart illustrating a routine for detecting ammonia slip in an exhaust treatment system according to the segment length method; and

10 10 is a flowchart illustrating a routine for operating the control system in various processing modes in accordance with the disclosed methods to allocate the exhaust gas sensor NOx and ammonia output.

The following description relates to methods and systems for detecting NH ₃ slip from an SCR system based on the transition NOx signals detected therein. In one example, a method is described that includes using the information from two NOx sensors, a feed gas sensor located upstream of the SCR, and an exhaust pipe sensor located downstream to respond in response to the transitional feedgas NOx Signal to predict the exhaust pipe NOx increase. In one particular example, a segment length method is disclosed, further comprising comparing a predicted (or expected) downstream NOx rate of change with the measured downstream NOx rate of change by a segment length method, and assigning the output of the NOx sensor to each of ammonia and nitrogen oxide in different proportions in response to the detected transient signals. For the sake of simplicity and clarity, the assignment assigns a larger proportion of the NOx sensor output to the NOx than the NH ₃ when a ratio of the measured downstream NOx change rate to an expected downstream one NOx change rate is greater than a threshold. In an alternative embodiment, the method includes generating an envelope around the expected tailpipe NOx signal and assigning the output from the NOx sensor to both the ammonia and the nitrogen oxide in different amounts depending on changes in the sensor output. For example, a transient exhaust pipe sensor output that is outside of an expected envelope may exist. For example, an exhaust system having an NH ₃ slip is further quantified by rising a counter to an upper level indicative of NH ₃ slip. Conversely, a transient tailpipe sensor output that falls within the expected envelope indicates NOx slippage, which is further quantified by the falling of a counter negative to a lower level indicative of NOx slippage. In this way, the exhaust gas sensor may be used to indicate both a reduced efficiency of the exhaust treatment system and a state of NH ₃ slip. The described methods further include adjusting one or more operating parameters based on the determined allocation and the changes in the sensor output.

In 1 FIG. 12 is a schematic diagram illustrating a cylinder of a multi-cylinder engine. FIG 10 shows that z. B. may be included in a drive system of a motor vehicle. The engine 10 can be at least partially controlled by a control system that has a controller 12 contains, and by an input from an operator 132 of the vehicle via an input device 130 to be controlled. In this example, the input device contains 130 an accelerator pedal and a pedal position sensor 134 for generating a proportional pedal position signal PP. A combustion chamber (or a cylinder) 30 the engine 10 can combustion chamber walls 32 contain, in which a piston 36 is positioned. The piston 36 can be connected to a crankshaft 40 be coupled, so that a reciprocating motion of the piston is converted into a rotational movement of the crankshaft. The crankshaft 40 may be coupled via an intermediate gear system to at least one drive wheel of a vehicle. Further, a starter motor via a flywheel to the crankshaft 40 be coupled to a starting operation of the engine 10 to enable.

The combustion chamber 30 can intake air through an inlet channel 42 from an intake manifold 44 receive and can the combustion gases through an exhaust duct 48 Drain. The intake manifold 44 and the outlet channel 48 can optionally have an inlet valve 52 or an outlet valve 54 with the combustion chamber 30 keep in touch. In some embodiments, the combustion chamber 30 include two or more intake valves and / or two or more exhaust valves.

In the in 1 example, the inlet valve 52 and the exhaust valve 54 via respective cam actuation systems 51 and 53 be controlled by cam operation. Each cam actuation system 51 and 53 may include one or more cams, and may include a cam curve switching (CPS) system and / or a variable cam timing (VCT) system and / or a variable valve timing (VVT) system and / or a variable valve lift (FIG. VVL system) used by the controller 12 can be operated to vary the valve operation. The positions of the inlet valve 52 and the exhaust valve 54 can through the position sensors 55 respectively. 57 be determined. In alternative embodiments, the inlet valve 52 and / or the exhaust valve 54 be controlled by electric valve actuation. The cylinder 30 can z. Alternatively, an intake valve controlled via electric valve actuation and an exhaust valve controlled via a cam actuation including CPS and / or VCT systems may be included.

In some embodiments, each cylinder of the engine 10 be configured with one or more fuel injectors to provide fuel. As a non-limiting example, it is shown that the cylinder 30 a fuel injector 66 contains. It is shown that the fuel injector 66 directly to the cylinder 30 is coupled to the fuel proportional to the pulse width of a signal FPW, via an electronic driver 68 from the controller 12 is received, to inject directly. In this way, the fuel injector 66 what is available as direct injection (hereinafter referred to as "DI") of the fuel into the combustion cylinder 30 is known.

It will be appreciated that in an alternative embodiment, the injector 66 may be a port injector located in the inlet port upstream of the cylinder 30 Provides fuel. It is also recognized that the cylinder 30 the fuel from several injectors, such as. B. multiple channel injectors, multiple direct injection nozzles or a combination thereof can receive.

In one example, the engine is 10 a diesel engine that burns air and diesel fuel by compression ignition. In other non-limiting embodiments, the engine may 10 another fuel, including gasoline, biodiesel or an alcohol mixture (eg gasoline and ethanol) or gasoline and methanol) by compression ignition and / or spark ignition.

The inlet channel 42 can a throttle 62 Contain a throttle plate 64 having. In this particular example, the position of the throttle plate 64 via a signal that is an electric motor or an actuator operating in the throttle 62 is provided by the controller 12 be varied, a configuration generally referred to as electronic throttle control (ETC). That way the throttle can work 62 be operated to that of the combustion chamber 30 to vary intake air provided under the other engine cylinders. The position of the throttle plate 64 can by a throttle position signal TP the controller 12 to be provided. The inlet channel 42 can be an air mass flow sensor 120 and a manifold air pressure sensor 122 included to the signals MAF and MAP the controller 12 provide.

Further, in the disclosed embodiments, an exhaust gas recirculation (EGR) system may include a desired portion of the exhaust gas from the exhaust passage 48 via an EGR channel 140 to the inlet duct 42 conduct. The amount of the intake manifold 44 provided EGR can be controlled by a controller 12 via an EGR valve 142 be varied. By introducing exhaust gas into the engine, the amount of available oxygen for combustion is reduced, thereby z. B. the flame temperatures of combustion are reduced and the formation of NO _{x is} reduced. As shown, the EGR system further includes an EGR sensor 144 within the EGR channel 140 can be arranged and which can provide an indication of the pressure and / or the temperature and / or the concentration of the exhaust gas. Under some conditions, the EGR system may be used to control the temperature of the air and fuel mixture within the combustion chamber, and thus provide a method of controlling the timing of the ignition during some combustion modes. Further, during some conditions, a portion of the combustion gases may be controlled by controlling the timing of the exhaust valve, such as exhaust valve timing. By controlling a variable valve timing mechanism in the combustion chamber.

An exhaust system 128 contains an exhaust gas sensor 126 which is upstream of an exhaust treatment system 150 to the outlet channel 48 is coupled. The sensor 128 may be any suitable sensor to provide an indication of the exhaust gas air / fuel ratio, such as: B. a linear oxygen sensor or UEGO (universal or long-range exhaust gas oxygen sensor), a two-state oxygen sensor or EGO, a HEGO (a heated EGO), a NO _x -, HC or CO sensor. It is shown that the exhaust treatment system 150 along the outlet channel 48 downstream of the exhaust gas sensor 126 is arranged.

In the in 1 The example shown is the exhaust gas treatment system 150 a urea-based selective catalytic reduction (SCR) system. The SCR system contains z. B. at least one SCR catalyst 152 , a urea storage container 154 and a urea injector 156 , In other embodiments, the exhaust treatment system 150 additionally or alternatively contain other components, such as. As a particulate filter, a lean NO _x trap, a three-way catalyst, various other emission control devices or combinations thereof. In the example shown, the urea injector 156 Urea from the urea storage tank 154 ready. However, various alternative approaches may be used, such as: For example, solid urea pellets that generate ammonia vapor, which then enter the SCR catalyst 152 injected or dispensed. In yet another example, a lean NO _x trap can upstream of the SCR catalyst 152 be positioned to change the air-fuel ratio NH ₃ for the SCR catalyst, depending on the degree of richness of the lean NO _x trap 152 to create.

The exhaust treatment system 150 also includes an exhaust gas sensor 158 downstream of the SCR catalyst 152 is positioned. In the illustrated embodiment, the exhaust gas sensor 158 z. Example, a NO _x sensor for measuring an amount of post-SCR NO _x . In some examples, an efficiency of the SCR system z. B. based on the exhaust gas sensor 158 and further based on the exhaust gas sensor 126 (if the sensor 126 z. Measuring NO _x ) positioned upstream of the SCR system. In other examples, the exhaust gas sensor 158 be any suitable sensor for determining the concentration of the exhaust components, such. As a UEGO, EGO, HEGO, HC, CO sensor, etc.

The controller 12 is in 1 shown as a microcomputer, which is a microprocessor unit 102 , the input / output ports 104 , an electronic storage medium for executable programs and calibration values, which in this particular example is a read-only memory chip 106 shown is a read-write memory 108 , a hold 110 and a data bus. The controller 12 can go to the engine 10 coupled sensors and therefore in addition to those signals which have been previously discussed, different signals from those to the engine Receive coupled sensors, including the measurement of the inducted mass air flow (MAF) from the mass air flow sensor 120 ; Engine Coolant Temperature (ECT) from one to a cooling sleeve 114 coupled temperature sensor 112 ; a Profile Ignition Pickup (PIP) signal from a Hall effect sensor 118 (or another type) attached to the crankshaft 40 is coupled; a throttle position (TP) from a throttle position sensor; an absolute manifold pressure signal, MAP, from a sensor 122 ; and a concentration of the exhaust gas constituents from the exhaust gas sensors 126 and 158 , An engine speed signal, RPM, can be generated by the controller 12 be generated from the signal PIP.

The read-only memory 106 The storage medium may be programmed with non-transitory computer-readable data by the processor 102 represent executable instructions for performing both the methods described below and other variants that are foreseen but not specifically listed.

In one example, the controller 12 the NH ₃ slip based on the output from the exhaust gas sensor 158 detect as below with reference to 2 will be described in more detail. If as an example the sensor 158 detects a threshold increase in NO _x output, represents the controller 12 the EGR valve 142 a, to reduce a lot of the EGR, so that the NO _x emission from the engine 10 increases. Based on the change in sensor output during the reduced EGR period, the sensor output is assigned to NO _x or NH ₃ . If z. For example, as the sensor output increases, the output is assigned to NO _x because the increased NO _x from the engine is not reduced by the SCR system. On the other hand, if the sensor output does not change by more than a threshold amount, the output is assigned to the NH ₃ and an NH ₃ slip is indicated. Based on the change of output and assignment, the controller can 12 set one or more operating parameters of the engine. As a non-limiting example, the controller 12 adjust the amount of EGR and / or the supply of the reducing agent based on the change of the output and the assignment.

As described above, shows 1 a cylinder of a multi-cylinder engine, wherein each cylinder similarly may include its own set of intake / exhaust valves, a fuel injector, a spark plug, and so on.

In the graphic representations, which in the 2A - D, an exemplary transient NO _x signal representing an ammonia slip condition is provided for the two-sensor system 1 shown. Because the NOx sensors produce output signals that respond to both the NOx and the NH ₃ , a method of detecting NH ₃ slip may be useful to manage the output of the exhaust system and the resources therein. If z. For example, if an urea SCR system is charged to the point of saturation that changes with temperature, it may begin NH ₃ slip. The NH ₃ slip past the SCR may be indicated by the exhaust pipe NOx sensor as NO _x , which confuses the SCR control and monitoring system, suggesting that the system has a lower efficiency than it actually has, because something the signal is actually due to the NH ₃ .

In the 2A -D are four temporal graphs illustrating the method. The four graphs are related and therefore use the same timeline shown for simplicity along the bottom graph. Moreover, although the data is shown schematically as a function of time in seconds, the time unit is not limiting, other time units are possible. From top to bottom, the four graphs represent: the NO _x signals collected by the NO _x sensors in the exhaust system; graphs illustrating the derivatives of the predicted and actual rises of the exhaust pipe NOx sensor in accordance with the method; Fig. 12 is a graph showing the difference between the predicted and the actual rise of the exhaust pipe NOx sensor; and a counter with a threshold to indicate NH ₃ slip.

In 2A is an exemplary feed-gas signal 202 shown in phantom and is an exemplary exhaust pipe signal 204 shown pulled through. If the exhaust system 128 is in a state of NOx slippage, e.g. For example, if the SCR is not saturated and the NH _{3 is} not released into the exhaust system, the exhaust pipe signal may generally be proportional to the feed gas signal. As such, the feedgas NOx signal and tailpipe NOx signal may be in phase and closely follow each other. In addition, when the NOx conversion efficiency is substantially zero, the exhaust pipe signal 204 and the feed-gas signal 202 be essentially the same. Conversely, for higher NOx conversion efficiencies, the shape of the exhaust pipe signal 204 the shape of the feed-gas signal 202 similar, but be a scaled down version of the Speisegassignals. If alternatively the exhaust system 128 is in a state of NH ₃ slip, the Exhaust pipe signal 204 have a slightly flattened appearance or at a lower frequency than the feedgas signal 202 waves. As a result, during NH ₃ hatching, there is normally a period during which the two signals are out of phase. Although the exhaust pipe signal may exceed the feed gas signal, particularly after an increase in temperature, this generally occurs during transient or changing conditions, allowing the NH ₃ slip to be identified from the two signals by the method described herein.

The method relies on a transient response of the NOx sensors to assign the signal to NH ₃ or NOx. Therefore, the rate of change of the NOx signal as a function of time or d (NOx) / dt is a central feature of the method. 2 B FIG. 12 is a graph of the derivative with the rise or rate of change of the exhaust pipe signal. FIG 204 to 2A graphed against time. Transition NH ₃ detection is built around a comparison of the detected actual exhaust pipe NOx surge with the expected predicted tailpipe NOx surge. As such contains 2 B the actual increase 210 , which is the rate of change of the exhaust pipe signal 204 to 2A represents. The actual increase 210 is shown in four parts labeled a-d for reasons which will be described in more detail below. The method further includes predicting an exhaust pipe NOx increase using the rise of the feedgas NOx (from the feedgas signal 202 in 2A ) and the current exhaust pipe NOx signal or an instantaneous reading from the exhaust pipe sensor. The predicted increase 212 for the exhaust pipe NOx sensor, e.g. B. the sensor 158 in 1 , can be generated using a known relationship. Here, the exhaust pipe NOx increase is made using: (dTP _NOx / dt) _exp = (TP / FG) * (dFG _NOx / dt) _act , predicted, where (dTP _NOx / dt) _{exp is} the expected or predicted rate of change of the tailpipe signal, TP is a current exhaust pipe reading, FG is an instantaneous feed gas reading, and (dFG _NOx / dt) _{act is} the actual rate of change of the feed gas signal. Using this method, a comparison of the two slope signals based on the transient response of the NOx sensors allows a high level of NH ₃ detection sensitivity. In some embodiments, the transition detection method may be e.g. B. detect NH ₃ levels as low as 25 ppm.

To measure how close the actual increase 210 during operation at the predicted increase 212 In other words, as the detected change in the NOx signal corresponds to the change expected from the feed gas signals and the system efficiencies, the described ammonia slip detection (ASD) method includes generating an envelope around the predicted rise curve. The envelope defines an area around the predicted rate of change in which the NOx output is likely to fall when the system has NOx slippage. That's why shows 2 B two dash-dotted lines representing a positive offset of the envelope 214 from the predicted increase in the positive direction and a negative offset of the envelope 216 from the predicted increase in the negative direction. When both the positive and negative envelopes are taken together, they define an area around the predicted rate of change curve that enables signal discrimination and assessment of the NOx and NH ₃ levels in the exhaust system.

The actual increase 210 is shown in four parts labeled with a-d. The different regions of the curve mean the time periods when the entry conditions are met, so that a comparison between the two increase curves can be expected to provide accurate determinations of the NOx and NH ₃ levels in the exhaust system. The sensors 126 and 158 inside the exhaust system 128 are z. To the controller 12 coupled, which may contain non-volatile, computer-readable data by the processor 102 represent executable instructions to enable or disable the method based on engine operating conditions. That's why the curves are 210a and 210c shown as non-bold dashed line segments to represent exemplary time periods when the entry conditions are not met and the method is disabled. Conversely, the curves 210b and 210d shown as bold dashed line segments to represent exemplary time periods when the entry conditions are met and the method is enabled. When a controller is turned on, it processes the data by comparing the actual increase 210 with the predicted increase 212 and the surrounding envelope. If the actual increase 210 is basically within the envelope, a window counter will fall negative and will be decremented to zero to indicate that the exhaust system comprises NOx, whereas if the actual increase 210 is outside the envelope, the window counter rises positively and is incremented to an upper level away from zero to indicate the presence of a NH ₃ slip in the exhaust system.

In some embodiments, during the conditions of NH ₃ slip, the Exhaust system include a signal of the exhaust pipe NOx sensor, which includes with respect to the Speisegassignals a content of lower frequency. As a result may indicate the NH ₃ slip is an upper level of the exhaust tube frequency. If the actual increase 210 is greater than a frequency threshold, therefore, the high frequency content that is interpreted as a NOx signal may be indicated. In response, the window counter may be decremented to zero, regardless of whether the slope is within or outside the envelope, to indicate NOx slip. For example, in some embodiments, As a rate of change, (dTP _NOx / dt) _actual (the actual increase 210 in 2 B ), which is greater than a maximum allowable rate, are treated as a NOx reaction by the system.

In 2C is a graphic representation 220 of the difference that shows the relative difference between the actual increase 210 and the predicted increase 212 to 2 B reflects. For clarity, a horizontal line at y = 0 indicating no difference is also shown. Therein, the fluctuations of the actual increase in the predicted increase can be more clearly observed. At early times on the left side z. For example, a negative peak is observed that reflects a lower actual slope than predicted by the method (the actual increase 210 is z. B. less than the predicted increase 212 ). Therefore, the actual slope following the contour of the graphical representation of the difference fluctuates around the predicted slope based on the conditions in the exhaust system. In some embodiments, other horizontal threshold lines may also be included to further indicate the locations where the differences between the two plots are considerably large, although not shown.

In 2D Figure 4 is a graphical representation of the window counter used to indicate NH ₃ slip. As briefly described above, the window counter is incremented to an upper level indicating the NH ₃ slip when the actual increase 210 is outside the envelope, and decrements to a lower level indicative of NOx slip when the actual increase 210 inside the envelope lies when the ASD system is controlled by the controller 12 is released. Therefore it is shown that the window counter 230 increases when the actual increase 210b outside the envelope. In 2D two thresholds are shown. The first threshold 236 indicates the NH ₃ slip in the exhaust system. If the window counter as such is the first threshold 236 An NH ₃ flag is set to indicate the NH ₃ slip from the SCR. For simplicity, in this example method, the NH ₃ flag is a binary flag. If the window counter 230 greater than the first threshold 236 Therefore, an NH ₃ flag is set to 1. Alternatively, if the window counter 230 below the first threshold 236 falls, the NH ₃ flag is reset to 0. In the exemplary signal processing application shown, the detection system is in the two areas designated as 210b and 210d are identified, released. During these periods, the counter is active and the controller uses the state of the system to identify whether NH ₃ slip is occurring or not. In some embodiments, the relative size of the window counter 230 compared to the first threshold 236 used to indicate when a NH ₃ slippage of the exhaust system 128 occurs, while in other embodiments, the current location of the window counter 230 with respect to an upper level (which indicates NH ₃₎ and a lower level (eg., 0, indicating the NOx) can be used to specify a probability or degree of NH ₃ slip in the exhaust system. In still other embodiments, a second threshold 234 be lower than the first threshold 236 is. If the second threshold 234 is present, the NH ₃ flag can be reset to 0 when the window counter 230 instead of below the first threshold 236 below the second threshold 234 falls as described above. The different threshold values allow hysteresis in the system so that the NH ₃ flag is not reset to indicate NOx if the window counter 230 just below the first threshold 236 falls. Instead, the NOx is indicated when the window counter 230 falls below the lower threshold set to indicate a higher level of NOx slippage in the exhaust system.

Because the ammonia slip detection system is under the control of the controller 12 Instructions may be included for disabling the detection system in the programmable software stored by the control system. Although the detection system may be disabled based on many conceivable operating conditions and many combinations of the variables are possible, in one embodiment the programmable instructions may implement the following conditions to disable the detection system: a low SCR temperature, high feedgas NOx levels, indicating a saturated output of the feedgate sensor, high tailpipe NOx levels indicative of a saturated exhaust pipe sensor output, low feedgas or tailpipe NOx levels below a detection threshold, high or low rates of NOx conversion efficiency, low torque output by the engine engine system, low injection pulses of urea from a storage container, a verifiable delay after the feed gas sensor or exhaust pipe sensor becomes active, a high rate of change in space velocity, low exhaust flow, a minimum / maximum actual or predicted increase indicative of a deadband in the detected signal, and a small rate of change of feedgas NOx, which identifies the inflection points of the feed gas. In response to the detection of one or more of these conditions by the controller 12 For example, the ASD method can be disabled, so that no processing of the signal takes place in the manner described here. The actual increase 210c refers to z. B. on a rise signal, which is detected during a period when the detection system is disabled. As another example, the line 232 a binary line indicating the lock state of the system. If the line 232 essentially located on the x-axis, the ASD system is therefore enabled and can be the controller 12 Monitor the exhaust conditions in the manner already described. If, conversely, the line 232 is located above the x-axis, the ASD system may be locked so that no signal processing takes place. As such, the further processing of the exhaust pipe NOx signal is substantially prevented because the information obtained can not reliably express the NOx and NH ₃ levels within the exhaust system. Nevertheless, during the periods when the detection system is disabled, the control system may monitor the conditions within the exhaust system and further have the flexibility to activate the detection system, which in some cases may include the blocking software or the blocking conditions identified therein; override.

For the method for processing the NOx signals by the control system is in 3 a flowchart, which is an example procedure 300 for the detection of ammonia slip in an exhaust treatment system. Therein, the set of programmable decisions that a controller may use when assigning a NOx sensor signal to either the NOx or NH ₃ or a combination thereof is described.

at 302 contains the procedure 300 determining the operating conditions of the engine. The operating conditions may include engine operating conditions (eg, engine speed, engine load, amount of EGR, air-fuel ratio, etc.) as well as the conditions of the exhaust treatment system (eg, exhaust temperature, SCR). Catalyst temperature, the amount of urea injection, etc.).

at 304 contains the procedure 300 determining a predicted rate of change of the exhaust pipe NOx sensor and generating an envelope based on the expected increase. As described above, the rate of change of the exhaust pipe NOx sensor may be predicted using the signal output of the feedgas NOx sensor and an actual measurement of the exhaust pipe NOx sensor signal output. Then, based on the predicted rate of change of the exhaust pipe NOx sensor, the method may further generate an envelope to define an area that can be expected to be in the signal when the exhaust system is operating under conditions of NOx slippage. Although many methods may be designed to produce an envelope, in some embodiments, the envelope is simply a percentage of the predicted increase offset from the predicted increase in the positive and negative directions. A controller, the z. For example, defining a range within 5% of a predicted rise of 10.0 can produce a positive envelope with a value of 10.5 and a negative envelope with a value of 9.5. Alternatively, if the predicted increase is smaller, e.g. 1.0, the positive envelope may have a value of 1.05 and the negative envelope may have a value of 0.95. In this way, the envelope defines an area surrounding the predicted curve, which is within 5% of the curve. In the envelope after 2 B The size of the area defined by the envelope clearly deviates as the magnitude of the slope of the predicted curve fluctuates around zero. at 306 contains the procedure 300 determining the actual rate of change of the exhaust pipe NOx sensor.

Although the procedure 300 The NOx sensors can monitor frequently or even continuously, the controller can 12 besides, the system in the way already concerning 2 B has been described, enable or disable. As such, the process contains 300 at 308 determining if the entry conditions have been met. If the controller 12 determines that the entry conditions allow the detection system to make accurate measurements because e.g. For example, if the temperature of the SCR is above a threshold, then the ASD system can be activated. Therefore contains at 310 the activated system releases the window counter to compare the actual increase with the predicted increase, as in FIG 312 is specified. Alternatively, if the controller 12 determined based on the conditions detected in the engine system that an accurate measurement by the NOx system is not possible, the control system at 314 disable the counter, so that no further signal processing takes place after signal acquisition. In some In embodiments, when the ASD system is disabled, the counter may be reset by negatively falling the counter to indicate NOx trapping by the system. In other embodiments, the counter may not fall in the manner described above, but simply hold a value until the detection system is reactivated.

If at 312 the controller 12 has determined that the entry conditions have been met and the detection system is activated to enable the setting of a counter based on a comparison between the actual and the predicted NOx rate, the controller may, as soon as the comparison has been carried out at 318 programmed to determine if the actual slope is within the envelope. Then, based on a location of the actual slope relative to the envelope, a positive or a negative score may be assigned based on the relative differences. As above regarding 2D has been described in more detail, increases 320 the counter is positive to an upper level indicating the NH ₃ slip when the actual rise is outside the envelope, whereas 316 the counter falls negatively to a lower level (eg, zero) indicating NOx slippage when the measured rate is within the envelope.

After rising or falling of the counter based on the relative location of the actual increase compared to the envelope surrounding the predicted rate of change, compares with 322 the procedure 300 and the counter at a threshold to determine if the exhaust pipe NOx sensor is to be assigned to the NOx or NH ₃ . In one embodiment, the sensor allocation includes assigning a first portion of the NOx sensor output to the NOx and a second, remaining portion of the NOx sensor output to the ammonia. Then, based on the allocation, the reducing agent is supplied to the engine exhaust based on both the first and second portions. The reducing agent may, for. B. can be increased in response to an increased NOx, but reduced in response to an increased NH ₃ . Therefore, the amount of reducing agent injected will generally depend on the relative amounts indicated by the first and second portions.

If the counter is above the first threshold, e.g. The first threshold 236 in 2D , the controller can 12 at 324 at least allocate some of the exhaust pipe output signal to the NH ₃ slip and at 326 set a flag to indicate this. Alternatively, if the controller 12 determines that the counter falls below the first threshold, he can at 328 assign at least some of the exhaust pipe output signal to the NOx slip and at 330 set a flag to indicate this. In some embodiments, the current state of the sensor assignment may correspond to a probability of NH ₃ slip, while in other embodiments, the NH ₃ slip may be indicated by a binary flag. That way, the controller can 12 detect the ammonia slip within the exhaust system and assign the output of the NOx sensor to the NOx and / or NH ₃ while transmitting the current status to a driver and adjusting one or more operating parameters based on the sensor output.

In 4 For example, a routine for adjusting system operation based on the assignment of sensor output to NO _{x is} shown. Specifically, the routine determines an exhaust NO _x concentration downstream of the SCR catalyst, and adjusts one or more operating parameters based on the sensor output.

at 402 the operating conditions are determined. As described above, the operating conditions may include the engine operating conditions (eg, engine speed, engine load, amount of EGR, air-fuel ratio, etc.) and exhaust treatment system conditions (eg, exhaust gas temperature , the SCR catalyst temperature, the amount of urea injection, etc.).

Once the operating conditions have been determined, the routine will increase 404 further, wherein the exhaust gas NOx concentration downstream of the SCR catalyst is determined based on the exhaust gas sensor output.

at 406 one or more operating parameters are adjusted based on the NOx concentration. As non-limiting examples, the operating parameters may include the amount of EGR and the amount of urea injection, or the urea dosing level, wherein the urea dosing level may be adjusted until an actual NOx efficiency corresponds to a predicted NOx efficiency. The amount of EGR may, for. B. increased by an amount corresponding to the change in the amount of NOx over the threshold amount. By increasing the amount of EGR, less NO _x can be emitted by the engine, resulting in a reduced amount of NO _x passing through the SCR catalyst. As another example, the amount of urea injection may be increased by an amount corresponding to the change in NO _x amount over the threshold amount and a temperature of the SCR catalyst. The amount of Urea injection can, for. B. be increased by changing the pulse width or the duration of the urea injection. By increasing the amount of urea injected into the SCR catalyst, a larger amount of NO _x can be reduced by the catalyst, thereby reducing the amount of NO _x passing through the catalyst. In other examples, a combination of an amount of EGR and an amount of urea injection may be adjusted.

In 5 FIG. 12 is a routine for setting the system operation based on the assignment of the sensor output to the NH ₃ . Specifically, the routine determines the exhaust NH ₃ concentration downstream of the SCR catalyst, adjusting one or more operating parameters based on the sensor output.

at 502 the operating conditions are determined. As described above, the operating conditions may include the engine operating conditions (eg, engine speed, engine load, amount of EGR, air-fuel ratio, etc.) and exhaust treatment system conditions (eg, exhaust gas temperature , the SCR catalyst temperature, the amount of urea injection, etc.).

Once the operating parameters have been determined, the routine will begin 504 wherein the exhaust NH ₃ concentration downstream of the SCR catalyst is determined based on the exhaust gas sensor output.

at 506 one or more operating parameters are set based on the NH ₃ concentration. As non-limiting examples, the operating parameters may include the amount of urea injection and the amount of EGR. The amount of urea injection may, for. Example, be reduced so that an amount of NH ₃ -sliping of the excess NH _{3 is} reduced from the SCR catalyst. As described above, the amount of urea injection can be increased by changing the pulse width or the duration of the urea injection. As another example, the amount of EGR may be reduced. By reducing the amount of EGR, z. B. a larger amount of NO _x are emitted from the engine. The increased NO _x can be reduced by the excess NH ₃ in the SCR catalyst, thereby reducing the amount of NO _x passing through the SCR catalyst.

With regard to urea dosing, in one embodiment, the exhaust system may be an adaptive SCR system that achieves an appropriate adaptive value by adjusting the urea dosing level until the actual NOx efficiency is equal to the predicted NOx efficiency. As the exhaust pipe NOx levels increase, the calculated NOx efficiency decreases. If the efficiency falls too low, the adaptive system will respond by increasing the urea dosage to achieve the predicted NOx efficiency. Conversely, as NH ₃ levels increase, the calculated efficiency also decreases because NH ₃ looks to a NOx sensor such as NOx. As such, the adaptive system responds by reducing the urea dosage to achieve the predicted efficiency. Because the adaptive correction for NOx versus NH ₃ slip is different, the control system may depend on the allocation of a NOx sensor output to the NOx or NH ₃ by the methods described herein.

The amount by which the operating parameters are adjusted may also be based on a temperature of the SCR catalyst as the point of urea saturation of the catalyst changes with temperature. When the temperature of the catalyst z. B. is a relatively higher temperature, the amount of EGR can be reduced less and / or the amount of urea injection can be reduced by a smaller amount. Conversely, if the temperature of the catalyst is a relatively lower temperature, the amount of EGR may be increased more and / or the amount of urea injection may be reduced by a larger amount.

In other examples, only the amount of EGR may be reduced or only the amount of urea injected into the SCR catalyst may be increased. In yet other examples, one or more other operating parameters may be additionally or alternatively adjusted. As such, one or more operating parameters may be adjusted to reduce NH ₃ slip.

Referring to a description of the segment length method, FIG 6 - 8th exemplary graphs to illustrate how transient signals may be processed based on the determination of a segment length to determine an assignment of the downstream NOx sensor to NOx and NH ₃ . For example, show 6 and 7 Graphs each representing the segment length method under NOx and NH ₃ -slip states. Then shows 8th an exemplary exhaust timing signal under conditions with a high exhaust pipe NH ₃ slip to demonstrate the method in an exhaust system. 9 FIG. 12 is an exemplary flowchart for a routine for detecting ammonia slip in an exhaust treatment system by the segment length method. FIG.

The segment length method includes detecting a portion of the NOx signal output and further processing the transient signals to determine an allocation to NOx and / or ammonia. As previously described with respect to the envelope method, the segment length method also processes expected and measured downstream NOx signals to determine the allocation. However, rather than creating an envelope around the predicted NOx signal to determine the assignment, the segment length method instead relies on calculating a total segment length for a signal track within a running window that is applied when a predetermined set of conditions is met. For example, if the temperature of the SCR catalyst is higher than a temperature threshold, the controller may 12 determine the exhaust gas allocation based on the detected signals. An advantage of the segment-length method is that the allocation of the output of the NOx sensor can be determined at lower exhaust gas temperatures, for example, during lightly-powered engine cycles where exhaust temperatures (eg, T = 215 ° C) relative to exhaust temperatures of a fully cranked engine ( eg T> 250 ° C) remain cool. Further, as will be described below, the processing includes the iterative movement of the window along each transient signal to process the transient signals as long as the enabling conditions remain satisfied, allowing the output of the sensor to be allocated and therefore real-time operational changes while transient signals are detected to be executed. Thus, the methods enable a highly efficient exhaust gas treatment system with a high sensitivity to NOx and NH ₃ , without resulting in a significant deterioration of the signal accuracy.

6A Figures D-D are graphs showing NOx slip states determined by the segment length method. For simplicity's sake 6A an exemplary feed-gas signal 202 with a dashed line and an exemplary exhaust pipe signal 204 with a solid line. As mentioned previously, the exhaust pipe signal may be proportional to the feed gas signal when the exhaust system 128 is in a NOx slip state, for example because the SCR is not saturated and NH ₃ is not released into the exhaust system. As such, the feed gas NOx signal and the exhaust pipe NOx signal may closely follow each other. Signals that follow each other closely may also have segment lengths that closely follow each other. Therefore, it can be expected that a ratio of the signals or segment lengths has a ratio of 1.0 when the difference between the measured downstream NOx signal and the expected downstream NOx signal is small. Likewise, a lower ratio indicates that the actual amount of downstream measured NOx is smaller than expected based on the upstream NOx signal, which is due to the presence of ammonia in the exhaust system. Because the method relies on the transient response of the NOx sensors to assign the sensor outputs to either NH ₃ or NOx 6B a derivative curve for the actual slope 210 (eg slope 210a -D in 2 B ) or the rate of change of the exhaust pipe signal over time. Transient NH ₃ detection is built upon a comparison of the actual detected exhaust pipe NOx slope with the expected predicted exhaust pipe NOx slope. Therefore shows 6C also the expected or predicted slope 212 representing the expected rate of change of the exhaust pipe signal based on the upstream NOx sensor.

Although controller 12 may be configured to constantly monitor the exhaust system and two NOx sensors to monitor exhaust flow upstream and downstream of the SCR device, these methods generally rely on the allocation of the exhaust gas sensors to NOx and ammonia under a predetermined set of conditions which are also referred to as release conditions. 6B and 6C show schematically the release conditions at a first window 604 and a second window 606 , which represent time periods within which the predetermined set of conditions is fulfilled and therefore the exhaust gas conditions can be reliably determined. For simplicity, two running windows are shown for each detected transient signal (eg, the predicted and actual NOx signals), however, during signal processing aboard an exhaust system, the current window may be iteratively moved along the time indicating x-axis, so that the segment length of the detected signal is constantly calculated within the current window. Alternatively, the release conditions are sometimes met, but not met at other times, as the conditions within the exhaust system often change. Under such dynamic exhaust conditions, the controller can 12 be configured to process the transient signals in a concatenated manner. That is, the controller can process time ranges of the transient signal that are close to each other, but not touching or not related to the previous segment. In this way time ranges that are close to each other but not related to each other can be edited. However, transient signals can be continuously monitored in real time to monitor the conditions within the exhaust system. For the sake of simplicity, the current window 604 in 6B and 6C shown as having a constant size. However, you can the size of the current window can be further adjusted with time constants and time constant modifiers in other examples.

In order to determine the assignment of the sensor output, ie the proportion of the signal due to the presence of NOx and NH ₃ , the segment length method further comprises calculating the total segment length within a detected signal time window. For example, show 6B and 6C segment lengths 612 and 614 that over the actual and predicted tracks within the first running window 604 lie. Then, during a second time period, segment lengths become 622 and 624 shown over the tracks within the second window 606 lie. Therefore show 6B and 6C two exemplary calculations of the segment length method.

On the basis of the signals shown and just described, the segment length method comprises 900 Further, comparing the measured downstream NOx change rate with an expected downstream NOx change rate to determine the allocation, the assignment assigns a greater proportion of the output of the NOx sensor to the NOx than to the NH ₃ when the ratio of the measured downstream NOx change rate is greater than a threshold relative to the expected downstream NOx change rate. Therefore shows 6D a TP ratio for the segment lengths calculated within each current window (eg, the first and second current windows). With respect to the first running window, within its segment length 612 and 614 calculated and compared is in 6D a first relationship 616 shown. Similarly, segment lengths become 622 and 624 calculated and compared, hence the second ratio 626 is created. In this way, segment length ratios are used to compare the actual and predicted signals. For example, the actual amount of NOx within the system is greater than the expected amount of NOx determined based on the upstream NOx sensor when the ratio reaches 1.0 (or greater). As such, the likelihood of NOx within the exhaust system is higher and the assignment of the sensor output reflects this by allocating the sensor output to the NOx. Therefore, according to the described methods, the calculated segment length ratios (eg, the first ratio 616 and the second ratio 626 ) further having a ratio threshold determined by the threshold 630 displayed is compared. As shown, the first ratio 616 and / or the second ratio 626 then greater than the threshold 630 is or is, the controller points 12 the output of the sensor signal to the NOx. Alternatively, the controller points 12 the sensor output to the NH ₃ too if the first ratio 616 and / or the second ratio 626 below the threshold 630 fall, as in the example of 7 shown.

With reference to the assignment of the signal to NOx and ammonia, the controller can 12 and further configured to process the transient signals using the segment length method to assign a first portion of the NOx sensor output to the NOx and a second, remaining portion of the NOx sensor output to the NH ₃ , as described in greater detail above the envelope method has been described. However, for the sake of simplicity, the process assigns the signal to either the NOx or the NH ₃ . Based on the allocation of a first and / or second portion, the supply of the reducing agent may be adjusted based on each of the first and second portions, wherein different settings are made for the first portion compared to the second portion. Therefore, in some examples, a counter may also be included in the segment length method that falls to a lower level indicative of NH ₃ slip (or NOx, depending on how the method is implemented) when the ratio of the transient signal is below the threshold 630 falls and rises to a higher level indicative of NOx slippage when the ratio exceeds the threshold 630 exceeds. In this way, the allocation based on the counter can be made relative to lower and higher levels. As noted previously, one or more operating parameters may be adjusted based on the assignment, and a controller may be programmed with nonvolatile instructions to perform the processing using the disclosed segment length method.

For comparison show 7A -D Graphs showing the NH ₃ slip states determined by the segment length method. For example, shows 7A an exemplary exhaust pipe signal 204 with a solid line and an expected signal 702 based on the upstream NOx sensor with a dashed line. The expected signal 702 is shown as oscillating over time, which z. In response to increasing or decreasing engine torques (or loads) occurs when a vehicle undertakes a commute in dense traffic. The exhaust pipe signal measured by the downstream NOx sensor 204 is shown as undulating less often as it monitors the downstream conditions within the exhaust. Therefore, the two signals shown do not follow closely and are different due to the presence of ammonia in the exhaust gas.

7B shows the actual slope 210 based on the exhaust pipe signal 204 , while 7C the predicted slope 710 shows. Running windows are also shown, in the same way as they were before with reference to 6B and 6C has been described. Therefore, the segment length represents 712 the total length of the exhaust pipe signal 204 within the first running window and the segment length 714 represents the total length of the predicted slope 210 within the current window. Because the feedgate signal and therefore the predicted slope 710 often oscillate within the window, the total segment length of the signal track may be longer than the measured signal track. Therefore, the ratio of the calculated segment lengths provides a measure of the proximity of the actual signal to the expected signal, which provides an indication of the amount of NOx and / or ammonia present in the exhaust system. 7D Figure 4 shows how the ratio of the calculated segment lengths can be used to assign based on the ratio relative to the threshold 630 where the threshold is less than 1.0, but in some cases may be 1.0 or greater. In the example shown, the data points indicate ammonia slip because the first ratio 716 and the second ratio 726 below the threshold 630 fall; this can be conveniently detected while making operational adjustments based on the assignment.

8A -E show an exemplary exhaust signal under high tailpipe NH ₃ slip conditions according to the described methods. For the sake of simplicity, NOx signals in 8th not shown while the predicted slope 802 and the actual slope 810 are shown on different graphs for clarity. Thus shows 8A a time course of the predicted slope 802 , which was determined based on the upstream NOx change rate. Equally shows 8B a time course of an actual slope 810 measured by the downstream NOx sensor. 8C FIG. 12 is a graphical representation of the particular segment lengths for each of the previously noted curves that are within current windows, as previously described with reference to FIG 6 and 7 described. Therefore shows 8C how the segment lengths can be plotted based on the total length computed within a window, while the window iteratively plots along the transient signal lanes used in 8A and B are moved. Curve 820 corresponds to the segment lengths of the predicted slope 802 in 8A were calculated. Equally, curve corresponds 822 the segment lengths taken from the actual slope 804 in 8B were calculated. 8D is a single curve that shows the ratio of segment lengths at each point in time 8C represents. Therefore, the ratio track reflects 832 the ratio of the segment length tracks that are in 8C have been provided, thereby providing a temporal indication of the conditions within the exhaust system as previously described. The threshold 830 in 8D represents the point above which the ratio of calculated segment lengths indicates NOx slip conditions. Conversely, ratios below the threshold show 830 fall, NH ₃ -slip states. 8E shows a binary track 840 indicating NH ₃ and NOx slip states. For simplicity, a signal of zero indicates a high NOx state and a signal of 1.0 indicates a high NH ₃ state. The exemplary exhaust signal shown in the graphs of FIG 8th is shown, places high NH ₃ -Schlupfzustände. Although the processed signals either NOx or NH ₃ are assigned relative to the threshold value on the basis of certain conditions, may in other examples, a portion of the signal x and / or NH ₃ on the basis assigned to the calculated segment length ratios. In other words, a counter falling to a lower level indicative of NH ₃ slip when the ratio of the transient signal falls below the threshold and rising to a higher level indicative of NO x slip may be included the ratio exceeds the threshold, the allocation being performed based on the counter relative to the lower and higher levels.

With respect to the temporal signals shown relative to the x-axis, time passes from left to right. Therefore, the predetermined set of conditions before T1 (ie, from time 0 to T1) has not been met, for example because the vehicle was started after a cold start and therefore the SCR temperature falls below a temperature threshold. Although signals may be monitored during this time period, the controller may 12 do not process the detected signals.

At T1, the ratio of the calculated segment lengths falls through the ratio track 832 is below the threshold 830 , Therefore, the controller rejects 12 the ammonia output signal and indicates this by the binary trace 840 to 1.0, indicating ammonia slip. At T2, the ratio track exceeds 832 short-term the threshold 830 , The binary track 840 is set to zero to indicate NOx slip. Although the method shown represents the binary track 840 in response to the fact that the ratio trace 832 the threshold 830 is changed, the method further includes, in other embodiments, a second threshold or a time threshold to prevent a change in exhaust conditions from being identified based on short or short-term fluctuations in the exhaust system that are not really a change in exhaust conditions. For the sake of simplicity, the transient signals shown contain a threshold value. At T3, the ratio track drops 832 again below the threshold 830 and the binary track 840 is again adjusted so that the detected ammonia slip states are displayed. The time from T4 to T5 represents a state of the exhaust system in which NOx is released in large quantities. In response, the controller picks up 12 provides appropriate settings based on the detected states and displays them by the binary track 840 is updated. In one example, if nox slip conditions are detected, the reductant feed based on the allocation may be adjusted to counteract the high NOx levels. In this way, the system can be used to reduce emissions from the disclosed exhaust system, allowing for increased efficiency. At T5 the ratio track drops 832 below the threshold 830 and the binary track 840 is set so that ammonia slip is displayed. In response, reductant delivery may again be altered to counteract the high detected NH ₃ levels.

Referring to a description of the methods just described 9 a flow chart of a segment length method 900 , which shows a routine for detecting ammonia slip in an exhaust treatment system according to the method described above. Therein, the amount of programmable decisions that a controller may use when assigning a NOx sensor signal of either NOx or NH ₃ or a combination thereof based on a segment length of a detected transient NOx signal is described in more detail.

at 902 includes the method 900 determining engine operating conditions. The operating conditions may include engine operating conditions (eg, engine speed, engine load, amount of EGR, air / fuel ratio, etc.) as well as exhaust treatment system conditions (eg, exhaust gas temperature, SCR catalyst temperature, amount of urea injection, etc.).

at 904 includes the method 900 determining a predicted rate of change of the downstream exhaust pipe NOx sensor based on the upstream NOx change rate. As described above, the rate of change of the exhaust pipe NOx sensor may be predicted by means of the output of the feedgas NOx sensor signal and an actual measure of the exhaust pipe NOx sensor signal output. Then included at 906 the procedure 900 determining the actual rate of change of the exhaust pipe NOx sensor. Therefore, the method further comprises monitoring the measured and predicted NOx signal that is downstream of the SCR catalyst based on the predicted rate of change of the exhaust pipe NOx sensor and the actual rate of change of the downstream NOx sensor. As already stated, the comparison can reliably indicate the allocation of the sensor output to NOx and / or ammonia and therefore serve to determine whether the exhaust system is operating under conditions that create NOx and / or ammonia slip.

Although the procedure 900 The NOx sensors can often or even continuously monitor the controller 12 Also, it may or may not allow the computer system to operate on strung segments that are not continuous but in some cases may be close to each other. As such, the method includes 900 at 910 determining if the entry requirements are met. If the controller 12 determines that the entry requirements allow the detection system to make accurate measurements, for example, because the temperature of the SCR is above a threshold, then the segment length based ASD system may be activated. at 912 Therefore, the activated system includes enabling a window within which the slope is further processed by calculating a total segment length within the window. If the controller 12 alternatively determines that an accurate measurement by the NOx system based on the detected states is not possible, the control system may disable the computer system, so that no further signal processing takes place after the signal detection.

Continuing with a description of the method, the method comprises 900 at 914 calculating the total segment length within the current window for both actual and predicted NOx signal traces. As already noted, the size of the window may be adjusted by adjusting a time constant and / or a time constant modifier included in the processing module of the controller. In addition, the processor may also be configured to automatically calculate the size of the window based on the operating conditions. For example, a smaller or larger window size based on the noise within the detected signal may be used when detecting a signal having a higher noise level, for example, because the temperature within the exhaust system is after a cold start is low. The controller 12 may also be configured to automatically determine the number of data points to be included in the segment length calculation within each window. In this way, the overall segment length of a signal with increased noise can be more accurately determined by increasing the resolution of the analyzer by including a larger number of data points within the calculation. Thus, the signal can be more accurately discretized and therefore more accurately approximated to increase the accuracy of segment length determination within a window based on the detected operating conditions.

at 916 includes the method 900 further comparing the actual and predicted NOx signal traces by calculating a ratio of the segment lengths calculated within the current window. As stated previously, a lower trace ratio indicates a lower NOx level than expected based on the upstream NOx sensor, indicating that there is a reduced amount of NOx in the exhaust system compared to the expected amount. Therefore, the disclosed ratio is an indication of a lower amount of NOx when the measured NOx falls below the NOx expected downstream of the SCR, providing further indication that ammonia is in the exhaust system.

at 920 includes the method 900 determining whether the ratio of the compared signals is above a threshold to further determine whether the exhaust system is operating in the NOx or NH ₃ slip state. If the detected ratio rises above the NOx threshold, the method includes 900 at 922 allocating the output of the downstream sensor to the NOx. Although the assignment is described herein as belonging to either NOx or NH ₃ , in other embodiments, a first portion of the NOx sensor output may be assigned to NOx and a second, remaining portion of the NOx sensor output to NH ₃ . Further, the engine may make one or more adjustments based on the allocation, for example, by adjusting a reductant supply based on each of the first and second portions, wherein different settings are made for the first proportion compared to the second proportion , at 924 can the controller 12 set a flag to indicate the NOx slip conditions in the exhaust system.

Returning to the field 920 , includes the procedure 900 at 930 assigning the output of the downstream sensor to the NH ₃ when the detected ratio instead falls below the NOx threshold. For example, the amount of operating parameters may be adjusted based on a temperature of the SCR catalyst as the point of urea saturation of the catalyst varies with temperature. For example, the amount of EGR may be reduced less and / or the amount of urea injection reduced by a smaller amount if the temperature of the catalyst is a relatively higher temperature. In contrast, the amount of EGR can be increased more and / or the amount of urea injection can be reduced by a greater amount if the temperature of the catalyst is a relatively lower temperature. In other examples, only the amount of EGR may be reduced or only the amount of urea injected into the SCR catalyst may be increased. In still other other examples, one or more other operating parameters may be additionally or alternatively adjusted. As such, one or more operating parameters may be adjusted to reduce NH ₃ slip. at 932 can the controller 12 be programmed to set a flag to indicate the NH ₃ slip states in the exhaust system based on the ratio relative to the threshold. In this way, the described segment length methods allow for increased signal sensitivity with a high degree of accuracy, especially at low exhaust gas temperatures, allowing for improved signal processing during lightly driven cycles.

Although the segment length and envelope methods are described independently herein for the sake of simplicity, in some embodiments, the engine 10 be configured to use both approaches during the engine drive cycle. That's why it shows 10 a flow chart showing the routine 1000 for operating the control system in various processing modes according to the disclosed methods for allocating the output of the exhaust gas sensor to NOx and ammonia. For example, the controller 12 in some circumstances, be programmed to process transient NOx signals using the envelope method while the controller is in operation 12 alternatively, the transient NOx signals may alternatively be processed by the segment length method under other conditions. In one example, the controller 12 Advantageously, the segment length method of 6 - 8th to increase machining sensitivity, and therefore more accurately determine tailpipe exhaust gas composition when the vehicle is operating at cooler exhaust gas temperatures, e.g. B. when the temperature of the SCR catalyst falls below a temperature threshold (T _{exhaust gas} <250 ° C). After the engine has been running for some time, so that the engine heats up and the temperature of the SCR Catalyst has caused to rise above the temperature threshold (T _{exhaust gas} > 250 ° C), the engine can 10 then set the signal processing to use the envelope method as described with reference to FIG 2 is used, which advantageously allows in some cases an increased processing speed. In this way, the segment length method may be used under a first set of operational states while the envelope method is used under a second set of operational states. It is also possible to use both methods simultaneously when processing transient signals during the engine drive cycle.

Operating states are included 1002 certainly. As described above, the operating conditions may include engine operating conditions (eg, engine speed, engine load, amount of EGR, air / fuel ratio, etc.) and exhaust treatment system conditions (eg, exhaust gas temperature, SCR catalyst temperature, amount of urea injection, etc.). Then you can join 1010 the controller 12 and determining whether the engine is operating under a first set of conditions as previously determined. If the controller 12 determines that the engine 10 operated under a first set of conditions, the controller 12 then at 1020 Making changes to operate the control system in a first mode in which the output of the NOx sensor is determined by the segment length method. If the engine alternatively determines that the engine 10 not operated under a first set of conditions, for example, because the engine 10 operated under a second set of conditions, the controller 12 then at 1030 Make changes to operate the control system in a second mode to assign the sensor output using the envelope method described above. In this way, the disclosed engine system may be further configured to use one or more of the previously described methods to more efficiently operate the engine system during operation.

For this reason, in some embodiments, the disclosed system includes an engine with an exhaust system; an exhaust treatment system disposed in the exhaust system and including an SCR emission device, a urea injector disposed upstream of the SCR emission device, and an exhaust gas sensor disposed downstream of the SCR emission device; and a control system in communication with the exhaust gas sensor, the control system including nonvolatile instructions for detecting NH ₃ slip based on a transient NOx signal, wherein the detection of NH ₃ slip includes assigning a sensor output to both the NH ₃ and the NOx and adjusting one or more operating parameters based on an assignment, the assignment further being based on a comparison of an expected rate of change of the NOx and a measured rate of change of the NOx downstream of the SCR emission device and a NOx level upstream of the SCR emission level. Emission system, wherein the control system is further configured to operate in two modes of operation to determine assignment, the two modes including: a first mode operating under a first set of conditions and the transient NOx signals based on a segment length of the transient NOx signal edit and a second mode operating under a second set of conditions and the transient NOx signals based on an allocation of a greater proportion of the output of the NOx sensor to NOx than to ammonia when the measured downstream NOx change rate is the basis of an upstream NOx level within an expected envelope.

It is stated that the example control and estimation methods included herein may be used with various engine and / or vehicle system configurations. The specific routines described herein may include one or more of any number of processing strategies, such as e.g. Event-driven, interrupt-driven, multitasking, multithreading, and the like. As such, the illustrated various acts, operations, or functions may be performed in the illustrated order, performed in parallel, or omitted in some instances. Likewise, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts or functions may be repeatedly performed depending on the particular strategy used. Further, the described acts may graphically represent code to be programmed into the computer readable storage medium in the engine control system.

This concludes the description. Many changes and modifications would become apparent to those skilled in the art upon reading the description without departing from the spirit and scope of the description. The present description could, for. I3, I4, I5, V6, V8, V10 and V12 engines powered by natural gas, Working on gasoline, diesel or alternative fuel configurations, use it favorably.

The following claims set forth particular combinations and sub-combinations that are considered to be novel and not obvious. These claims may refer to "an" element or "first" element or its equivalent. Such claims should be understood to include the inclusion of one or more such elements neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application.

Such claims, whether broader in scope than, more narrowly equal to or less than the scope of the original claims, or other than the scope of the original claims, are also considered to be within the scope of the present disclosure.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2012/0085083 [0003]

Claims (20)

A method comprising: assigning an output of a NOx sensor based on a NOx change rate upstream and a NOx change rate downstream of an SCR emission device to both the NH ₃ and the NOx, wherein the allocation is on a segment length of a particular transient signal based; and adjusting an engine exhaust reducing agent based on the allocation. The method of claim 1, wherein the segment length of the particular transient signal is calculated within a window applied at a predetermined set of conditions, wherein the editing further comprises the iterative movement of the window along the determined transient signal, wherein a window size is determined by a window Time constant and / or a time constant modifier is adjustable. The method of claim 2, wherein calculating the segment length within the window comprises building a signal trace to approximate the determined transient signal, wherein the calculated segment length is based on the signal trace approximating the determined transient signal. The method of claim 3, wherein the allocation assigns a greater proportion of the NOx sensor output to the NOx than the NH ₃ when a ratio of a measured downstream NOx signal trace approximating a measured downstream rate of change is greater than a threshold relative to an expected one downstream NOx signal trace approximating an expected downstream NOx change rate. The method of claim 4, wherein the expected downstream NOx change rate is based on an upstream NOx change rate. The method of claim 5, wherein the upstream NOx change rate is determined by a sensor and / or a model. The method of claim 6, wherein the allocation assigns a greater proportion of the output of the NOx sensor to the NH ₃ than to the NOx when the ratio of the signal traces falls below the threshold, the ratio indicating, if below the threshold, indicating that it is below the threshold There is a high probability that NH _{3 is present} in the engine exhaust. The method of claim 7, wherein the allocation comprises assigning a first portion of the NOx sensor output to the NOx and a second, remaining portion of the NOx sensor output to the NH ₃ , wherein the supply of the reduction agent is on both the first and second The second share is based on different settings for the first share compared to the second share. The method of claim 8, further comprising a counter falling to a lower level indicative of NH ₃ slip when the ratio of the transient signal falls below the threshold, and increasing to a higher level representing the NOx Slip indicates when the ratio exceeds the threshold. The method of claim 9, wherein the assignment is based on the counter with respect to the lower level and the upper level. The method of claim 10, wherein one or more operating parameters are set based on the assignment. The method of claim 11, wherein a controller includes nonvolatile instructions for performing the method. A method, comprising: real-time control of ammonia slip in an engine exhaust system based on assigning the output of a NOx sensor to both the NH ₃ and the NOx based on a rate of change of the NOx upstream of an SCR emission device and a rate of change the NOx downstream of the SCR emission device, wherein the allocation is based on a segment length of the transient NOx signal; and adjusting the supply of a reducing agent to the engine exhaust based on the allocation. The method of claim 13, wherein the allocation is based on a comparison of an expected downstream NOx change rate and a measured downstream NOx change rate, wherein the expected downstream NOx change rate is based on an upstream NOx change rate determined by a sensor and / or a model Further, the comparison is based on a segment length of the transient NOx signal. The method of claim 14, wherein the comparison is further based on a ratio of the segment length determined for the measured downstream NOx change rate to the segment length determined for the expected downstream NOx change rate. The method of claim 15, wherein the allocation of the output of the NOx sensor to both NH ₃ and NOx is based on the ratio of the determined segment lengths for the measured and expected NOx signal. The method of claim 16, wherein at least a portion of the output of the NOx sensor is assigned NH ₃ when the ratio of the determined segment lengths for the measured and expected NOx signal falls below a threshold indicative of the presence of NH ₃ . The method of claim 17, wherein the threshold indicative of the presence of NH ₃ is 1.0. The method of claim 18, wherein one or more operating parameters are set based on the assignment. A system comprising: an engine having an exhaust system; an exhaust treatment system disposed in the exhaust system and including an SCR emission device, a urea injector disposed upstream of the SCR emission device, and an exhaust gas sensor disposed downstream of the SCR emission device; and a control system in communication with the exhaust gas sensor, the control system including nonvolatile instructions for detecting the NH ₃ slip based on a transient NOx signal, wherein the detection of the NH ₃ slip includes assigning a sensor output to both the NH ₃ and NOx and setting one or more operating parameters based on the allocation, the assignment is further based on a comparison of an expected rate of change of the NOx and a measured rate of change of the NOx downstream of the SCR emission device and a NOx level upstream of the SCR Emission apparatus, wherein the control system is further configured to operate in two modes of operation to determine assignment, the two modes including: a first mode operating under a first set of conditions and the transient NOx signals based on a segment length of the transient NOx signal is processed, and e In the second mode operated under a second set of conditions and the transient NOx signals based on an allocation of a greater proportion of the output of the NOx sensor to NOx than to ammonia, when the measured downstream NOx change rate based on a upstream NOx level within an expected envelope.

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