DE102017203878A1 - A method of purging a dosing module for injecting a liquid into an exhaust stream of an internal combustion engine of a road vehicle - Google Patents

Abstract

Disclosed is a method for purging a for injection of a liquid in an exhaust system (13) of an internal combustion engine (10) projecting dosing (40), wherein an elapsed since a last rinse operation period of the internal combustion engine (10) is detected and wherein initiating a purging presupposes in that the operating time which has elapsed since the last rinse exceeds a predetermined threshold. The method is characterized in that a current value of at least one exhaust parameter is detected, a future development of the value of the predicted, and a triggering of a purge depending on the current value of the exhaust gas parameter and the predicted future development of the exhaust gas parameter. Further independent claims are directed to a controller, a computer program product and a computer readable medium.

Description

State of the art

The present invention relates to a method for purging a metering module mounted for injecting a liquid into an exhaust system of an internal combustion engine of a motor vehicle in a wall of the exhaust system and projecting into the exhaust system according to the preamble of claim 1 and to a control device configured to control the sequence of the method Generic term of the independent device claim.

Thereafter, with regard to the method aspects, it is provided that an operating time of the internal combustion engine which has elapsed since a last purge is detected and that triggering of a purge presupposes as necessary condition that the operating time which has elapsed since the last purge exceeds a predetermined first threshold value.

According to the device aspects, it is provided that the control unit is set up to detect an operating time of the internal combustion engine that has elapsed since a last rinse and to trigger a rinse only if the operating time that has elapsed since the last rinse exceeds a predetermined minimum duration.

In diesel internal combustion engines, injection systems are used for exhaust aftertreatment, which inject fuel into the exhaust gas stream immediately before the oxidation catalyst. With the aid of this fuel injection high exhaust gas temperatures can be generated, which lead to the regeneration of a downstream of the oxidation catalyst arranged in the exhaust gas flow particle filter. The dosing module used for the injection is mounted in a wall of the exhaust system and protrudes into the exhaust gas flow. It is therefore thermally coupled to the hot wall and the hot exhaust gas.

Injection of fuel, which takes place, for example, for the regeneration of the particulate filter, is usually only necessary at longer intervals in exhaust aftertreatment systems. Regeneration takes place, for example, only every 2,000 km, which at an average speed of 50 km / h results in a time interval between two regenerations of approximately 40 operating hours.

The trapped fuel in the dosing module can therefore be exposed to high temperatures for many hours of operation, resulting in undesirable aging of the fuel. In order to limit the unwanted aging, the dosing module is also rinsed between regeneration processes from time to time by brief opening. The term "short-term" means that the valve opening time during short-term rinsing is smaller than during regeneration processes. A typical time span between two such brief rinses is 6 to 8 hours. After each regeneration or after each rinse, a timer is started. Once the time elapsed since the last time the dosing module was opened exceeds a predetermined time threshold (e.g., 6 hours), a new flush is requested.

For the flushing process, a separate engine operating mode is requested in the prior art. This is necessary, among other things, so that the temperatures in the exhaust gas are not too high, which could otherwise happen as an undesirable side effect. If the exhaust gas temperature is undesirably high, a spontaneous and undesired regeneration of the particulate filter could take place. It would be advantageous if this direct intervention in the engine management can be avoided or mitigated. Currently, the rinse time is not optimized. Periodically, a purge is requested and the engine operating point is changed during purging

From the DE10 2004 005 072 It is already known to use track data of a road vehicle, which are available from GPS signals, a navigation system of the motor vehicle, traffic telematics services, etc., to engine control and in particular exhaust aftertreatment or exhaust gas sensor functions with the aim of optimizing their Pollutant mitigation, achieving or maintaining their operational readiness and / or accuracy and / or diagnostic capability with the lowest possible fuel and additive consumption and / or the greatest possible component protection (life) and / or the greatest possible engine power or greatest possible comfort to influence.

As an example of such engine control and exhaust aftertreatment or exhaust gas sensor functions, the regeneration control of a particulate filter or a NO _x storage catalytic converter may be explicitly mentioned here. The polluting effect of these exhaust aftertreatment components must be restored from time to time by a specific operation of the engine. For this purpose, the engine must be operated so that suitable conditions with respect to exhaust gas temperature, exhaust gas mass flow and mixture state (O ₂ - content, regenerant concentration such as CO or HC, etc.) in the exhaust system for a certain duration regardless of the driver's accelerator pedal request and regardless of requirements of ancillary units according to engine power, speed and torque.

This task of regeneration control can be optimized by using the information about the expected driving distance of the vehicle, in that these regenerations are preferably started when the engine operating point required by the preceding route is favorable for the necessary exhaust gas state of this regeneration and is expected to last long enough. To DE10 2007 027 182 In addition, it is known that, for this purpose, it is also advantageously possible to include driving and route data from other, eg, preceding vehicles. Thereby, the accuracy or the probability of the occurrence of the prediction of engine operating points can be increased. An improvement in the prediction is after DE10 2008 008 566 In addition, it is possible to additionally identify and assign driver-specific routes and driving modes in such a way that they can be taken into account in the prediction of the engine operation during the current journey. In DE10 2008 041 617 is suggested as how this driver-specific data can be assigned and implemented in a feedback to the driver.

Disclosure of the invention

Compared to the aforementioned prior art, the present invention is characterized with respect to their method aspects in that it is checked whether the elapsed since the last purging operating time is greater than a second threshold, which is greater than the first threshold, and that Purging is triggered when the operating time elapsed since the last purge is greater than the second threshold, and if the elapsed time since the last purge is greater than the first threshold and less than the second threshold, a current value of at least one Exhaust gas parameter is detected, it is checked whether the current value of the at least one exhaust gas parameter is in a predetermined range, a future development of the value of the at least one exhaust gas parameter is predicted, and a triggering of a purge additionally from the current value of the exhaust gas parameter and the v predicted future development of the exhaust gas parameter is dependent.

With regard to its aspects relating to the control device, the present invention is characterized by the characterizing features of the independent control device claim.

With the state prediction in the exhaust aftertreatment can be estimated, how the exhaust gas parameters tend to develop in the near future (minutes to hours). Thus, the timing of purging of an injection system can be optimized. The invention, in this context, contemplates purging the system when purging conditions will deteriorate and retarding purging of the system as purging conditions improve.

By preference, interventions in the engine operating mode are reduced without appreciably affecting the quality of the rinsing process.

If a state prediction is available, the evolution of the conditions for a purge can be checked before the expiration of this time (e.g., 5.5 hours). This would look like the example temperature:

The exhaust gas temperatures are low and will increase according to state prediction, since, for example, a highway journey is pending. This means that the purge conditions are just cheap and likely to worsen. In this case, the rinse is triggered immediately.

In another example, the exhaust gas temperatures are currently high and will decrease according to state prediction, since, for example, a city route is pending. This means that the rinse conditions are just unfavorable and are likely to improve. In this case, initially a release of a rinse does not initially. The rinse process is then started at a later time.

Thus, a rinsing process is preferably carried out under good rinsing conditions. An intervention in the engine operating mode is not necessary or only for a shorter time.

If the exhaust gas temperatures do not behave as expected and even permanently worsen, this is unfavorable but not critical. The flushing process is then carried out at a later time and takes longer. On average, however, the conditions of rinsing will improve with the prediction.

The quality of the rinsing process is not significantly affected. Small time delays are not detrimental, as the state of aging of the fuel changes only slightly when rinsing occurs up to half an hour earlier or later. Due to the change in the purging interval, the fuel consumption for rinsing operations can change minimally, the change being dependent on the driving profile. Since the volume per flush is only about 10 ml, this is not critical.

Further advantages will be apparent from the dependent claims, the description and the attached figures.

It is understood that the abovementioned and those still to be explained below Characteristics can be used not only in the specified combination, but also in other combinations or in isolation, without departing from the scope of the present invention.

• 1 das technische Umfeld der Erfindung; und
• 2 ein Flussdiagramm als Ausführungsbeispiel eines erfindungsgemäßen Verfahrens.

Embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. In this case, the same reference numerals in different figures denote the same or at least functionally comparable elements. In each case, in schematic form:

• 1 the technical environment of the invention; and
• 2 a flowchart as an embodiment of a method according to the invention.

In detail, the shows 1 an internal combustion engine 10 with an air supply system 12 , an exhaust system 13 , various actuators 14 , a sensor 16 , a control unit 18 and a regenerant dosing system 20 ,

The air supply system 12 has an air mass meter 24 on top of the mass in the combustion chambers of the internal combustion engine 10 inflowing air and its readings to the control unit 18 passes. The control unit 18 additionally receives measured values of further sensors of the internal combustion engine 10 whose totality in the 1 the sensors 16 forms.

The exhaust system 13 has exhaust aftertreatment components. In the example shown, these are an oxidation catalyst 26 and a downstream of the oxidation catalyst 26 arranged particle filter 28 ,

In addition, the exhaust system points 13 various sensors that measure exhaust gas parameters and their readings to the controller 18 to hand over. In the example shown, these sensors are the differential pressure across the particulate filter 28 measuring differential pressure sensor 30 and one between the oxidation catalyst 26 and the particulate filter 28 projecting into the exhaust gas and the exhaust temperature detected temperature sensor 32 and an exhaust gas sensor projecting into the exhaust gas flow and detecting a concentration of an exhaust gas constituent such as oxygen 33 , The exhaust system 13 can also have other sensors, in particular lambda probes and other temperature sensors.

The regenerant dosing system 20 has a regenerant reservoir 34 , one from the reservoir 34 fed and an injection pressure generating regenerant pump 36 , a metering unit 38 and a dosing module 40 on. The metering unit 38 is in the example shown by the controller 18 controlled, including the other actuators of the internal combustion engine 10 controls. For injecting regenerant into the exhaust stream upstream of the oxidation catalyst 26 controls the controller 18 the metering unit 38 at. The metering unit 38 is from the regenerant pump 36 supplied with pressurized regeneration agent and leaves regeneration agent on the preferred pressure-controlled dosing 40 flow into the exhaust gas. For example, the regeneration agent is fuel that is just upstream of the oxidation catalyst 26 is injected into the exhaust stream. In conjunction with existing in the exhaust gas and the catalytic effect of the oxidation catalyst 26 the exhaust gas is heated up so much that in the particulate filter 28 stored soot ignites and is burned. The dosing module 40 is in an opening of a wall 42 the exhaust system 13 attached and thus is in thermal contact with the possibly hot wall 42 the exhaust system 13 and possibly also hot exhaust gas. It has, for example, a nozzle needle, which lifts under pressure control from a sealing seat and thus opens an injection cross-section to the exhaust gas when the metering unit 38 the injection pressure of the reducing agent pump 36 on the dosing module 40 turns on. When also by driving the metering unit 38 If the injection pressure is switched off, the dosing module closes again. This leaves a small amount of fuel after closing the dosing 40 in the dosing module 40 , It is this small amount that passes through from time to time also between two regeneration processes involving the dosing module 40 is opened to regenerate the particulate filter is renewed. As a result, for example, deposits of solid by aging or tough becoming regenerant can be avoided.

Incidentally, the controller controls 18 the actuators 14 of the internal combustion engine 10 depending on the signals of the sensors 16 of the internal combustion engine 10 and the different ones in the exhaust system 13 arranged and exhaust gas parameters measuring sensors 30 . 32 and 33 as well as possibly existing further sensors. In the control of the metering unit 38 , or in the control of the regeneration agent supply in the exhaust stream, ie in the exhaust system 13 In order to predict the development of the purge conditions, data of a navigation and / or mobile radio communication system are also preferred 43 from the controller 44 processed.

In addition, the control unit 18 set up, in particular programmed to control the flow of a method according to the invention. For this purpose, the controller 18 among other things, a computer program product that includes instructions that cause the controller to perform the method steps of process according to the invention performs. The computer program product is on a computer readable medium 44 , For example, a memory of the controller 18 , saved.

2 shows a flowchart as an embodiment of a method according to the invention, wherein the dashed program path 105 belongs to the prior art and in which in the 2 illustrated embodiment by the steps 114 to 120 is replaced. In the following, a method part is first explained, which could also be carried out in the prior art.

A main program 100 runs in the control unit to control the internal combustion engine 10 from. For this main program 100 out, a step is repeated in a predetermined manner 102 achieved in which one since a last opening of the dosing 40 elapsed operating time t of the internal combustion engine is detected. The operating time t is continuously during operation of the internal combustion engine by a in the control unit 18 updated timer. In one step 104 that after the step 102 is reached, there is a comparison of the detected operating time t with a predetermined first threshold value SW1. For example, the first threshold is six hours and corresponds, for example, to the dosing module purge control threshold used in the prior art 40 ,

When the operating time in the prior art is not greater than the first threshold value SW1, the prior art returns to the main program, which is described in US Pat 2 through the dashed program path 105 is represented.

If the operating time is greater than the first threshold value SW1, after step 104 a step 106 reached, in which an exhaust gas parameter is detected, indicating whether the current operating conditions for flushing the dosing 40 are favorable. The exhaust parameter is, for example, an exhaust gas temperature T derived from the exhaust temperature sensor 32 measured and sent to the control unit 18 is passed, or by the control unit 18 with a calculation model from the signals of the sensors 16 of the internal combustion engine 10 and possibly also signals from in the exhaust system 13 arranged sensors 33 is calculated.

For a purge favorable operating conditions, which are also referred to below as purge conditions, are, for example, when the exhaust gas temperatures T are high enough to flush the dosing 40 metered regeneration agent in the oxidation catalyst 26 completely exothermic react with exhaust gas oxygen, and at the same time are so low that such a reaction does not lead to an unwanted ignition in the particulate filter 28 stored soot leads. If such favorable purge conditions are present, after step 108 a step 112 carried out in which the dosing module 40 is flushed by injecting a small amount of regenerant. The amount of regenerant injected per flush is low (for example, about 10 ml). The regeneration means is preferably fuel of the same kind, with which also the internal combustion engine 10 is operated.

Will in step 108 on the other hand, it has been determined that the flushing conditions currently being present are unfavorable to flushing, then after step 108, a step will be taken 110 reached before the step 112 to be performed rinse takes place. The step 110 serves to set flushing conditions that are favorable for flushing. As described above, this step should be avoided in the invention as far as possible. After the step 112 flushing process returns to the main program 100 back. Before that gets in step 113 nor the timer for the elapsed since the last opening of the metering module 40 time reset to zero.

This sequence of steps 100 to 112 Although forms part of a method according to the invention, but is also already carried out in the known method.

A difference of the prior art method according to the invention results following a negation of the query in the step 104 , in which it checks whether the since the last opening of the dosing 40 elapsed time t is greater than a first threshold SW1. If this time is not greater than the first threshold value SW1, in the prior art the program returns via the dashed path 105 directly back to the main program 100.

In the in the 2 illustrated embodiment of the invention leads to the negative of the step 104 on the other hand, it does not return to the main program, but first to a step 114 , In the step 114 is checked if the since a last opening of the dosing 40 the elapsed service life of the internal combustion engine is greater than a second threshold value SW2, which is smaller than the first threshold value SW1. For example, when the first threshold SW1 is 6 hours, the second threshold SW2 may be 5.5 hours.

If this query is answered in the affirmative, which means that since the last time the dosing module was opened 40 elapsed time t between the (smaller) second threshold SW2 and the (larger) first threshold value SW1, becomes after step 114 the step 116 reached. The step 116 corresponds for example to the step 106 , In step 116 Thus, an exhaust gas parameter is detected, which indicates whether the currently existing operating conditions for a rinsing of the dosing 40 are favorable. The exhaust parameter is, for example, an exhaust gas temperature T derived from an exhaust gas temperature sensor 32 measured and sent to the control unit 18 is passed, or by the control unit 18 with a calculation model from the signals of the sensors 16 of the internal combustion engine 10 and possibly also signals from in the exhaust system 13 arranged sensors 33 is calculated.

After the step 116 becomes a step 118 reached, in which a future development of the exhaust gas parameter is predicted. The forecast horizon is preferably a few minutes to hours. The prediction takes place, for example, on the basis of an anticipated driving route, which results, for example, from the current position of the vehicle and a travel route calculated by the navigation device and / or mobile radio communication system of the motor vehicle for the next few minutes. A prediction of a development of the exhaust gas parameter is also referred to as state prediction.

For example, if an exhaust gas temperature T is used as the exhaust gas parameter, the state prediction will predict an increase in the exhaust gas temperature if the current exhaust gas temperature is low and highway travel is imminent. This can be considered as an example of a development of an exhaust gas parameter at which the current purge conditions are likely to deteriorate. In this case, it is advantageous to start the flushing process immediately.

On the other hand, if the current exhaust temperatures are high and it is probable that the exhaust temperature values will decrease as the probable route descends or passes through a city after state prediction, the current purge conditions are rather poor and likely to improve. In this case, it is advantageous not to start the flushing process immediately but to wait for the improvement.

In step 120 It is checked whether there are currently good rinsing conditions and whether a deterioration of the rinsing conditions is likely. Good rinsing conditions are present, for example, when the exhaust gas temperature is neither so high that an unwanted soot ignition threatens, nor is so low that an incomplete conversion threatens. In case of imminent deterioration, the purging process is triggered by the step 120 who in this alternative after the step 120 is reached. As a result, the purging is carried out before the time t = SW1 compared to the prior art without the step 110 an intrinsically undesirable intervention in the control of the internal combustion engine must take place. In all other cases, the program returns from the step 120 into the main program 100 back.

The steps 102 to 120 preferably follow one another in the order described. In this case, however, between each two steps, other steps can be performed, which are in the main program 100 be performed to control other functions such as interventions in the air supply and fuel supply to the internal combustion engine. It is then possible to temporarily return to the main program between each particular step of the method described here, so that priority parts of the main program are processed there. The main program then branches again into the method described here, this method then being continued with the procedure following the particular step. To clarify this, one can choose between any two steps or groups of steps 102 to 120 a block 100 think, for the sake of clarity in the 2 but not shown.

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

• DE 102004005072 [0008]
• DE 102007027182 [0010]
• DE 102008008566 [0010]
• DE 102008041617 [0010]

Claims (11)

Method for purging a dosing module (40) mounted for injecting a liquid into an exhaust system (13) of an internal combustion engine (10) of a motor vehicle in a wall (42) of the exhaust system (13) and projecting into the exhaust system (13), one since one last purging elapsed operating life of the internal combustion engine (10) is detected and wherein a triggering of a purging presumes that the elapsed since the last purging operating time exceeds a predetermined threshold, characterized in that it is checked whether the elapsed since the last purging operating time greater than a is the first threshold and that purging is triggered when the operating time elapsed since the last purging is greater than the first threshold, and when the operating time elapsed since the last purging is less than the first threshold and greater than a second threshold, - a current value of we at least one exhaust gas parameter is detected, a future development of the value of the at least one exhaust gas parameter is predicted, and a triggering of a purge additionally depends on the current value of the exhaust gas parameter and on the predicted future development of the exhaust gas parameter. Method according to Claim 1 , characterized in that a probable future driving distance of the motor vehicle is determined from the current time and that the future development of the at least one exhaust gas parameter is predicted in dependence on the determined probable future driving distance of the motor vehicle. Method according to Claim 2 , Characterized in that a flush is triggered when since the last flushing elapsed operation time is less than the first threshold and greater than the second threshold value, the current value of the at least one exhaust parameter is in a predetermined range of values and the predicted future development of the exhaust parameter expect that the value of the at least one exhaust gas parameter will run out of the predetermined range. Method according to Claim 2 characterized in that flushing is not initially initiated when the operating time elapsed since the last purge is greater than the second threshold but not greater than the first threshold and the current value of the exhaust parameter is not within the allowed range or predicted Future development of the at least one exhaust gas parameter can expect that the value of the at least one exhaust gas parameter runs into the predetermined range. Method according to one of the preceding claims, characterized in that the at least one exhaust gas parameter is an exhaust gas temperature. Method according to Claim 5 , characterized in that the exhaust gas temperature is detected by an exhaust gas temperature sensor. Method according to one of the preceding claims, characterized in that the liquid to be injected is diesel fuel. Control unit (18), which is set up, a method for purging a for injection of a liquid in an exhaust system (13) of an internal combustion engine (10) of a motor vehicle in a wall (42) of the exhaust system (13) and mounted in the exhaust system (13 ), wherein the control unit (18) is adapted to detect an elapsed since a last opening of the metering module (40) operating time of the internal combustion engine (10) and trigger a purging only if that since the last Purging elapsed operating time exceeds a predetermined threshold, characterized in that - the controller (18) is adapted to check whether the elapsed since the last rinse operation period is greater than a first threshold and trigger a purging, if since the last rinse elapsed operating time is greater than the first threshold, and then if that since the last Purging elapsed operating time is less than the first threshold and greater than a second threshold is to - capture a current value of at least one exhaust parameter, - predict a future development of the value of the at least one exhaust parameter, - and a purging in addition depending on the current value the exhaust gas parameter and the predicted future development of the exhaust gas parameter. Control unit (18) after Claim 8 , characterized in that it is adapted to a sequence of a method according to one of Claims 2 to 7 to control. Computer program comprising commands for causing the control unit (18) of the Claim 8 the process steps of Claim 1 performs. Computer readable medium (44) on which the computer program is based Claim 10 is stored.

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