• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
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    • 专利摘要:

    公开号:SE1150789A1
    申请号:SE1150789
    申请日:2011-08-31
    公开日:2013-03-01
    发明作者:Anders Simon
    申请人:Scania Cv Ab；
    IPC主号:
    专利说明:

    10for small or no dosage amounts, the system also consists of a return hosewhich is arranged from a pressure side of the system back to the container.
    The SCR catalyst in the vehicle's exhaust duct includes oneevaporation module and a part with an SCR substrate. Said evaporator part isarranged to vaporize metered reducing agent to provide a bettermixture between the exhaust gases and said dosed reducing agent.
    In cases where not all dosed reducing agent is evaporated, precipitates thereof may occurformed. These precipitates normally consist of crystals attached to a veinseveral pieces of the evaporator module of the SCR catalyst. At continueddosing of reducing agents, these crystals can build up further,whereby undesirable consequences are likely to follow. The problem withconstruction of reducing agent crystals in SCR systems of motor vehiclesis well known.
    One reason for said undesirable buildup of reducing agent crystals maybe that the evaporation capacity of the evaporation module in certain operating casesovertaxed. Said reducing agent crystals may also be termed urea-stones.
    There are a number of problems associated with the buildup of urea stones inthe evaporation module of the SCR catalyst.
    First, an exhaust back pressure can increase in the engine exhaust system. Thiscauses the engine to sense a larger load and will be forced towork unnecessarily hard, with unwanted high loads.
    Second, a degree of conversion of the SCR catalyst may be impaired.which leads to an increase in unwanted emissions from the vehicle.
    Third, in a case where the buildup of urea stones is not prevented, canfinally the exhaust system is completely blocked, whereby the passage of an exhaust streamcompletely blocked.
    US 2008/0271440finishing device connecteddescribes a method of operating onedownstream of an internal combustion engine.
    The aftertreatment device comprises an SCR catalyst. The procedureincludes the steps of establishing a threshold value for accumulated urea depositionfor regeneration of the SCR catalyst, determine that the threshold value has been metand in response, regenerating the SCR catalyst by maintainingThe SCR catalyst at a predetermined regeneration temperature during onepredetermined time interval.
    US2010 / 0122525 describes an exhaust gas purification system in which it is determined whetheran accumulated deposit quantity of an inner wall of an exhaust passageis equal to or greater than a predetermined value. If so, it is reducedsupply of urea solution into the system by means of a valve. Then raisedthe temperature of the exhaust gases quickly then a torque of a diesel engineincreases. In this case, the accumulation that has accumulated on the inner wall andis added to the SCR catalyst as ammonia.
    SUMMARY OF THE INVENTIONAn object of the present invention is to provide a novel andadvantageous procedure for improving the performance of an SCR system.
    Another object of the invention is to provide a new and advantageousSCR system and a new and advantageous computer program to improveperformance of an SCR system.
    An object of the present invention is to provide a novel andadvantageous method for reliably detecting the presence ofundesired reducing agent crystals in the SCR catalyst of the SCR system.
    Another object of the invention is to provide an alternativeprocedure for an SCR system and an alternative computer program for an SCRsystem and an alternative SCR system, where reliable detection ofpresence of undesirable reducing agent crystals in the SCR catalyst ofThe SCR system is provided.
    These objects are achieved by a method in an SCR system therereducing agent is fed to an exhaust gas stream upstream of an SCR catalyst and therethe content of NOX in the exhaust gases is measured upstream and downstream of the SCR catalystreducing agent crystals in the SCR catalystdetected, according to claim 1.and where the presence ofAccording to one aspect of the invention, there is provided a method of an SCRsystems where reducing agents are supplied with an exhaust gas flow upstream of an SCRcatalyst and where the NOX content of the exhaust gases is measured upstream anddownstream of the SCR catalyst and there the presence of reducing agent crystallizationThe SCR catalyst is detected. The innovative process involves the steps of:- at a first time, turn off the supply of reducing agent to the exhaust gas flow,so that the SCR catalyst is substantially emptied of vaporized reducing agent;at a second, later time, corresponding to a first temperature of the SCRthe catalyst, wherein said first temperature corresponds to a temperature atwhich reducing agent crystals evaporate, measure NOX content upstream anddownstream SCR catalyst;- compare measured NOX content upstream of the SCR catalyst with measured NOX contentdownstream of the SCR catalyst, whereby the difference between the measured NOX contentupstream of the SCR catalyst and measured NOX content downstream of the SCR catalystexceeds a certain value, this is taken as an indication of the possible presence ofreducing agent crystals in the SCR catalyst;at a third time corresponding to a second temperature of the SCRthe catalyst, wherein said second temperature corresponds to a temperature atwhich reducing agent crystals do not evaporate,measuring NOX content upstream of the SCR catalyst and downstream of the SCRthe catalyst;- compare measured NOX content upstream of the SCR catalyst with measured NOX contentdownstream of the SCR catalyst, whereby the difference between the measured NOX contentNOX content downstream of the SCRthe catalyst is below a certain value it is determined that the NOX levels are correctupstream of the SCR catalyst with measuredsaturated; andprovided that the NOX levels are correctly measured and that the presence ofreducing agent crystals in the SCR catalyst have been indicated, determinepresence of reducing agent crystals.
    By emptying the SCR catalyst of stored dosed urea and later,at a temperature where reducing agent crystals can evaporate, measure NOX contentupstream and downstream of the SCR catalyst, it can be determined whether adifference between measured level NOX exists. If the difference exceeds a certainlevel, it can be assumed thata) At least one of the two NOx sensors provided isassociated with an error, and / orb) At least one reducing agent crystal is present in the SCR catalyst,which crystal in this case has at least partially evaporated and affected measuredNOX content downstream of the SCR catalyst.
    This means that the NOX levels are correctly measured if the NOX sensors operate onintended manner and thus measures said NOX levels in a correct manner, ie withoutwrong.
    To exclude that any of the NOX sensors is associated with an error, according to a)above, such as e.g. a so-called Gain error, a second measurement of NOX content is performedupstream and downstream of the SCR catalyst, at a temperature therereducing agent crystals cannot be evaporated. There may be a possible differencebetween NOX content upstream and downstream the SCR catalyst is determined. Ifthe difference is below a certain level, it can be determined that the sensors worknormal and that there is at least one reducing agent crystal in the SCRthe catalyst. In this case, the two sensors must measure essentially the same NOx contentat their respective positions upstream and downstream of the SCR catalyst.
    Detection of the presence of reducing agent crystals in the evaporator moduleof the SCR catalyst can be performed while propelling the vehicle on the road. Theis thus a user-friendly method provided according to one aspectof the invention because the vehicle does not need to be taken out of service to performthe detection procedure of a workshop or service hall.
    Detection of the presence of reducing agent crystals in the evaporator moduleof the SCR catalyst can alternatively be carried out in a particular workshop orservice hall. This may be suitable for e.g. a planned maintenance event.
    In this case, an elevated temperature of the SCR catalyst, which temperatureallowing evaporation of reducing agent crystals, is accomplished bydrive the vehicle's engine at an increased speed and apply appropriatelyexhaust back pressure by means of an exhaust brake of the vehicle. Furthermore, a lowertemperature of the SCR catalyst, which temperature does not allow evaporationof reducing agent crystals, is achieved by driving the engine of the vehicleat idle speed for a certain time. By performing measurements of NOxcontent upstream and downstream of the SCR catalyst, at these two differenttemperatures, of which measurement at the higher temperature is preceded bythe step of emptying the SCR catalyst of stored dosed reducing agentaccording to the invention, it can be determined in a workshop or in a service hallwhether reducing agent crystals are present in the SCR catalyst.
    Said third time may be a further later time, ie saidthird time can occur after both the first time and the secondthe time.
    Said third time may be a time which is before said firsttime and said other time. This achieves a more versatilemethod according to one aspect of the present invention.
    By providing an opportunity to perform one set ofof NOX contentessentially at any time when appropriate, ie the set of measurementsmeasurements upstream and downstream of the SCR catalystcarried out at a temperature where reducing agent crystals do not evaporate,provides a more flexible method according to the present invention.
    Said first temperature may be a temperature exceeding 300 degreesCelsius. Said first temperature may be a temperature exceeding onepredetermined value. In this case, a suitable temperature that allowsevaporation the intended reducing agent in the SCR system is used. Thisprovides a more versatile solution according to one aspect of the invention.
    Said second temperature may be a temperature below 200 degreesCelsius. Said second temperature may be a temperature below onepredetermined value. In this case, a suitable temperature that does not allowevaporation the intended reducing agent in the SCR system is used. Thisprovides a more versatile solution according to one aspect of the invention.
    Said reducing agent may be a urea-based reducing agent, such asfor example AdBlue.
    The process may further comprise the step of adding reducing agents tothe exhaust gas flow after the second time. The procedure may include the stepto add reducing agent to the exhaust stream after the second time butbefore the third time, in which case the third time is after itat the SCR systemachieved while waiting for an operating case where a lower temperature of the SCRsecond time. In this case, lower emissions canthe system is obtained, at which lower temperature measurement of NOX content upstreamand the downstream SCR catalyst is carried out, the reducing agent crystals notcan evaporate.
    The procedure is easy to implement in existing motor vehicles. Software atan SCR system where reducing agent is supplied to an exhaust fume upstream of oneSCR catalyst and where the NOX content in the exhaust gases is measured upstream anddownstream of the SCR catalyst and where the presence of reducing agent crystals inThe SCR catalyst detected according to the invention can be installed in acontrol unit of the vehicle in the manufacture of the same. A buyer of the vehiclemay thus be able to choose the function of the procedure as an option.
    Alternatively, software including program code can perform the innovativethe process in an SCR system where reducing agent is supplied to an exhaust gas flowupstream of an SCR catalyst and where the NOX content in the exhaust gases is measuredupstream and downstream of the SCR catalyst and the presence ofreducing agent crystals in the SCR catalyst are detected installed in acontrol unit of the vehicle when upgrading at a service station. In this case, canthe software is loaded into a memory in the controller. Implementation of itThe innovative procedure is thus cost-effective, especially since noneadditional sensors or components need to be installed in the vehicle.
    The required hardware is already present in the vehicle today.
    The invention thus provides a cost-effective solution to the abovespecified problems.
    Software that includes program code for an SCR system therereducing agent is fed to an exhaust gas stream upstream of an SCR catalyst and therethe content of NOX in the exhaust gases is measured upstream and downstream of the SCR catalystand where the presence of reducing agent crystals in the SCR catalyst is detectedcan be easily updated or replaced. Furthermore, different parts of the software such asincludes program code in an SCR system where reducing agent is supplied to oneexhaust gas flow upstream of an SCR catalyst and where the content of NOX in the exhaust gasesmeasured upstream and downstream of the SCR catalyst and the presence ofReducing agent crystals in the SCR catalyst are detected and replaced independentlyof each other. This modular configuration is advantageous from onemaintenance perspective.
    According to one aspect of the invention there is provided an SCR system comprisingmeans arranged to supply reducing agent to an exhaust gas stream upstream of aSCR catalyst and means for measuring the NOX content inthe exhaust gases upstream and downstream of the SCR catalyst and the presence ofreducing agent crystals in the SCR catalyst are detected. The SCR systemincludes:means for, at a first time, shutting off the supply of reducing agents toexhaust gas, so that the SCR catalyst is substantially emptied of evaporatedreducing agents;means for at a second, later date, corresponding to a firsttemperature of the SCR catalyst, where said first temperature correspondsa temperature at which reducing agent crystals evaporate, measuring NOX contentupstream and downstream of the SCR catalyst;means for comparing measured NOX content upstream of the SCR catalyst with measuredNOX content downstream of the SCR catalyst, whereby the difference between measuredNOX content upstream of the SCR catalyst and measured NOX content downstream of the SCR catalystthe catalyst exceeds a certain value, this is taken as an indication of anypresence of reducing agent crystals in the SCR catalyst;means for at a third time corresponding to a second temperature ofThe SCR catalyst, wherein said second temperature corresponds to a temperaturein which reducing agent crystals are not elongated,measuring NOX content upstream of the SCR catalyst and downstream of the SCRthe catalyst;means for comparing measured NOX content upstream of the SCR catalyst with measuredNOX content downstream of the SCR catalyst, whereby the difference between measuredNOX content upstream of the SCR catalyst with measured NOX content downstream of the SCRthe catalyst is below a certain value it is determined that the NOX levels are correctsaturate; andmeans for, provided that the NOX levels are correctly measured and that the presence ofreducing agent crystals in the SCR catalyst (260) have been indicated, determinepresence of reducing agent crystals.
    Advantageous embodiments appear with reference to the dependent onesclaims 9-13.
    The above objects are also achieved with a motor vehicle comprising the SCRthe system. The motor vehicle can be a truck, bus or car.
    According to one aspect of the invention, a computer program is provided in an SCRsystems where reducing agents are supplied with an exhaust gas flow upstream of an SCRcatalyst and where the NOX content of the exhaust gases is measured upstream anddownstream of the SCR catalyst and there the presence of reducing agent crystallizationThe SCR catalyst is detected, where said computer program includesprogram code stored on a computer-readable medium to cause oneelectronic control unit or another computer connected to the electronicthe control unit to perform the steps according to any one of claims 1-7.
    According to one aspect of the invention, a computer program is provided in an SCRsystems where reducing agents are supplied with an exhaust gas flow upstream of an SCRcatalyst and where the NOX content of the exhaust gases is measured upstream anddownstream of the SCR catalyst and there the presence of reducing agent crystallizationThe SCR catalystprogram code to cause an electronic controller or another computerdetected, wherein said computer program includesconnected to the electronic control unit to perform the steps according to any ofclaims 1-7.
    According to one aspect of the invention, there is provided a computer software productcomprising a program code stored on a computer readable medium forperforming the method steps according to any one of claims 1-7, when said11computer programs run on an electronic controller or other computer connectedto the electronic control unit.benefitsthe invention will be apparent to those skilled in the art from the following details, as wellAdditional objects, and novel features of the present inventionvia the practice of the invention. While the invention is described below,it will be apparent that the invention is not limited to those specifically describedthe details. Those who have access to the teachings herein will recognizeand incorporations into othersadditional applications, modificationsareas which are within the scope of the invention.SUMMARY DESCRIPTION OF THE DRAWINGSFor a more complete understanding of the present invention and furtherpurposes and benefits thereof, reference is now made to the following detaileddescription to be read together with the accompanying figures there equallyreference numerals refer to equal parts in the various figures, and in which:Figure 1 schematically illustrates a vehicle, according to an embodiment ofthe invention;Figure 2a schematically illustrates a subsystem of the vehicle shown in Figure 1, according toan embodiment of the invention;Figure 2b schematically illustrates a subsystem of the vehicle shown in Figure 1, according toan embodiment of the invention;Figure 3 schematically illustrates a number of different graphs, according to an aspect ofthe invention;Figure 4a schematically illustrates a flow chart of a method, according to aembodiment of the invention;Figure 4b schematically illustrates in further detail a flow chart over onemethod, according to an embodiment of the invention; andillustrates a computer,Figure 5 schematically according to an embodiment ofthe invention.12DETAILED DESCRIPTION OF THE FIGURESReferring to Figure 1, a side view of a vehicle 100 is shownThe exemplary vehicle 100 consists of a tractor 110 and a trailer 112.
    The vehicle can be a heavy vehicle, such as a truck or a bus. The vehiclecan alternatively be a car.
    It should be noted that the invention is suitable for application in aarbitrary SCR system and is not sold limited to SCR system atmotor vehicle. The innovative procedure and the innovative SCR systemaccording to one aspect of the invention is well suited for other platforms such asincludes an SCR system other than motor vehicles, such as e.g. watercraft.
    The watercraft can be of any kind, such as e.g. motorboats,ships, ferries or ships.
    The innovative procedure and the innovative SCR system according to one aspectof the invention is also well suited for e.g. systems includingindustrial engines and / or motorized industrial robots.
    The innovative procedure and the innovative SCR system according to one aspectof the invention is also well suited for different types of power plants, such as e.g.an electric power plant comprising a diesel generator.
    The innovative procedure and the innovative SCR system are well suitedfor any motor system including an engine and an SCR system,such as e.g. at a locomotive or other platform.
    The innovative procedure and the innovative SCR system are well suitedfor an arbitrary system that includes a NOX generator and an SCRsystem.13Here, the term "link" refers to a communication link that may be onephysical wire, such as an opto-electronic communications wire, or anon-physical wiring, such as a wireless connection, such as a radio ormicrowave link.
    Here, the term "lead" refers to a passage for holding and transportinga fluid, such as e.g. a reducing agent in liquid form. The management can bea tube of any dimension. The management can consist of an arbitrary,suitable material, such as e.g. plastic, rubber or metal.
    Herein, the term "reducing agent" refers to an agent used toreact with certain emissions in an SCR system. These emissions can e.g.be NOx gas. Another term for said reducing agent is "reductant".
    The terms "reductant" and "reducing agent" are used synonymously herein.
    Said reducing agent is according to an embodiment so-called AdBlue. Of course canother types of reducing agents are used. Here, AdBlue is listed as oneexample of a reducing agent but a professional realizes that it is innovativethe procedure and the innovative SCR system can be realized for other typesof reducing agents.
    Referring to Figure 2a, a subsystem 299 of the vehicle 100 is shown.
    The subsystem 299 is arranged in the tractor 110. The subsystem 299 may constitute apart of an SCR system. According to this example, the subsystem 299 consists of acontainer 205 which is arranged to hold a reducing agent in liquid form.
    The container 205 is arranged to contain a suitable amount of reducing agentand is further arranged to be able to be refilled if necessary. The container can holdfor example 75 or 50 liters of reducing agent.
    A first line 271 is arranged to lead the reducing agent to a pump 230from the container 205. The pump 230 may be any suitable pump.
    The pump 230 may be a diaphragm pump comprising at least one filter.
    The pump 230 may be arranged to be operated by means of an electric motor. The pump is14230 arranged to pump up the reducing agent from the container 205 via itfirst line 271 and via a second line 272 supply saidreducing agent to a dosing unit 250. Dosing unit 250includes an electrically controlled metering valve, by means of which a flow of tothe exhaust system added reducing agent can be controlled. The pump 230 is arrangedpressurizing the reducing agent in the second line 272. Dosing unit250 is provided with a throttling unit, against which said pressure ofthe reducing agent is built up in the subsystem 299.
    The dosing unit 250 is arranged to supply said reducing agent to aexhaust system of the vehicle 100. The exhaust system is shown in further detail withreference to Figure 2b below. More specifically, the dosage unit is 250arranged to supply in a controlled manner an appropriate amount of reducing agent to aexhaust system of the vehicle 100. According to this embodiment, an SCR catalyst(see Figure 2b) arranged downstream of a position of the exhaust system where the supply ofreducing agents are provided.
    The dosing unit 250 is arranged at e.g. an exhaust pipe arranged tolead exhaust gases from an internal combustion engine (see Figure 2b) of vehicle 100 toThe SCR catalyst.
    A third conduit 273 is provided between the metering unit 250and the container 205. The third conduit 273 is arranged to return onecertain amount of the reductant fed to the metering valve 250 tocontainer 205. With this configuration, advantageous cooling is providedof the dosing unit 250.
    A first control unit 200 is arranged for communication with a pressure sensor220 via a link 293. The pressure sensor 220 is arranged to detect a prevailingpressure at the reductant where the sensor is mounted. According to this embodiment isthe pressure sensor 220 arranged at the second line 272 to measure oneoperating pressure of the reductant downstream of the pump 230. The pressure sensor 220 isarranged to continuously send signals to the first control unit 200including information on a prevailing pressure of the reductant.
    The first control unit 200 is arranged for communication with the pump 230via a link 292. The first control unit 200 is arranged to control the operation ofthe pump 230 to e.g. regulate flows of the reductant within the subsystem 299.
    The first control unit 200 is arranged to control an operating power of the pump230 by regulating the electric motor thereby.
    The first control unit 200 is arranged for communication withthe dosing unit 250 via a link 291. The first control unit 200 isarranged to control operation of the dosing unit 250 to e.g. regulate supplyof the reductant to the exhaust system of the vehicle 100. The first control unit200 is arranged to control operation of the dosing unit 250 to e.g. regulaterefilling the reductant to the container 205.
    A second control unit 210 is provided for communication with the firstthe control unit 200 via a link 290. The second control unit 210 may bedetachably connected to the first control unit 200. The second control unit210 may be an external control unit for the vehicle 100. The second control unit210 may be arranged to perform the innovative process steps according tothe invention. The second control unit 210 can be used to overloadsoftware for the first control unit 200, in particular software for performingthe innovative procedure. The second control unit 210 may alternatively bearranged for communication with the first control unit 200 via an internalnetwork in the vehicle. The second control unit 210 may be arranged to performsubstantially the same functions as the first control unit 200, such as e.g.to compare measured NOX content upstream of the SCR catalyst with measured NOX contentdownstream of the SCR catalyst at different temperatures to determine indicationon the possible presence of reducing agent crystals in the SCR catalyst anddetermine that the presence of reducing agent crystals in the SCR catalyst hasdetected. The innovative procedure can be performed by the first control unit16200 or the second control unit 210, or by both the first control unit200 and the second control unit 210, where the first control unit 200 canperform certain parts of the innovative procedure and the other control unit210 can perform certain other parts.
    Referring to Figure 2b, a subsystem 298 of the vehicle 100 is shown.
    The subsystem 298 is arranged in the tractor 110. The subsystem 298 may be apart of an SCR system. According to this example, the subsystem 298 consists of ainternal combustion engine 240 and a first exhaust passage 241 arranged to guide oneexhaust gas generated by the internal combustion engine 240 to an SCR catalyst 260.
    The SCR catalyst is included in a muffler of the vehicle 110 in a known manner.
    Furthermore, a second exhaust passage 251 is arranged to direct the exhaust stream toan environment of the vehicle 110.
    A first NOX sensor 245 is provided at the firstthe exhaust passage 241. The first NOX sensor 245 is arranged to measure oneprevailing NOX content in the first exhaust passage 241. The first NOX sensor245 is arranged to measure a prevailing NOX content in the first exhaust passage241 upstream of the SCR catalyst 260. The first NOX sensor 245 isarranged for communication with the first control unit 200 via a link246. The first NOX sensor 245 is arranged to send signals continuouslyincluding information on a prevailing NOX content of the exhaust gas stream to itfirst control unit 200. The first control unit 200 is arranged to receivecomprising a prevailing NOX content insaid signals exhaust gas flowupstream of the SCR catalyst 260.
    A second NOX sensor 255 is provided at the otherthe exhaust passage 251. The second NOX sensor 255 is arranged to measure oneprevailing NOX content in the second exhaust passage 251. The second NOX sensor255 is arranged to measure a prevailing NOX content in the second exhaust passage251 downstream of the SCR catalyst 260. The second NOX sensor 255 isarranged for communication with the first control unit 200 via a link17256. The second NOX sensor 255 is arranged to send signals continuouslyincluding information on a prevailing NOX content of the exhaust gas stream to itfirst control unit 200. The first control unit 200 is arranged to receiveprevailing NOX content insaid signals including adownstream of the SCR catalyst 260.exhaust gas butA temperature sensor 265 is provided at the SCR catalyst 260.
    The temperature sensor 265 is arranged to measure a representation of currenttemperature of the SCR catalyst 260. The temperature sensor 265 may bearranged to measure a prevailing temperature of the exhaust stream in the SCRthe catalyst 260. Alternatively, the temperature sensor 265 may be arranged tomeasuring a temperature of an evaporation module of the SCR catalyst 260.
    The temperature sensor 265 is arranged for communication with the firstthe control unit 200 via a link 266. The temperature sensor 265 is arranged tocontinuously send signals including information about a prevailingtemperature at its sensing range to the first control unit 200. Itfirst control unit 200 is arranged to receive said signals comprisinga prevailing temperature in the sensing range at the SCR catalyst 260.
    The first control unit 200 is arranged for communication with the secondthe control unit 210, as also shown in Figure 2a above.
    The first control unit 200 is arranged to continuously receive signalsincluding information on the prevailing temperature of the SCR catalyst andNOX content upstream and downstream of the SCR catalyst. On the basis of thesesignals, the first control unit can switch off the supply at a suitable timeof reducing agent to the exhaust gas flow, so that the SCR catalyst is substantially emptiedon vaporized reducing agent. The first control unit 200 is further arrangedthat, where applicable, i.e. at a temperature of the SCR catalyst 260 therereducing agent crystals evaporate, measuring NOX content upstream and downstreamThe SCR catalyst and compare the measured NOX content upstream of the SCR catalystwith measured NOX content downstream of the SCR catalyst, whereby if the difference between18measured NOX content upstream of the SCR catalyst and measured NOX content downstreamThe SCR catalyst exceeds a certain value, this is taken as an indication ofpossible presence of reducing agent crystals in the SCR catalyst.
    The first control unit 200 is further arranged to measure NOX content upstreamThe SCR catalyst and downstream the SCR catalyst at a temperature therereducing agent crystals do not evaporate, and compare measured NOX content upstreamThe SCR catalyst with measured NOX content downstream of the SCR catalyst, whereinabout the difference between measured NOX content upstream of the SCR catalyst with measuredNOX content downstream of the SCR catalyst below a certain value is determinedthat the NOX levels are correctly measured; and provided that the NOX levels are correctsaturated and that the presence of reducing agent crystals in the SCR catalyst hasindicated, determine the presence of reducing agent crystals.
    Figure 3 schematically illustrates how three different parameters depend on the time according to oneembodiments illustrating an aspect of the present invention.
    The first parameter refers to the NOX content in the exhaust stream from the engine 240 asfunction of time. The solid graph a refers to the measured NOX content upstreamSCR Catalyst 260. NOX content upstream of SCR Catalyst 260 is measuredcontinuous of the first NOX sensor 245. The broken graph b refers to measuredNOX content downstream of the SCR catalyst 260. NOX content downstream of the SCR catalystCatalyst 260 is continuously measured by the second NOX sensor 255.
    The second parameter refers to a prevailing temperature T of the SCR catalyst260. The temperature T is continuously measured by the temperature sensor 265.
    The third parameter refers to the dosed amount of reducing agent (includingurea) to the exhaust stream. Dosed amount of reducing agent is calculatedcontinuous of the first control unit 200, inter alia on the basis of aprevailing pressure of the reducing agent (measured by the pressure sensor 220) andopening hours of the dosing unit 250.19It can be seen from Figure 3 that urea dosing is switched off at a first time t1,after which the SCR catalyst is emptied of stored (evaporated) reducing agent. Onefirst measurement of NOX content upstream of the SCR catalyst 260 and downstreamThe SCR catalyst is performed and compared at a second time t2, thenthe temperature of the SCR catalyst exceeds 300 degrees Celsius. According tothis example differs the measured values sufficiently for itshould be taken as an indication that there may be reducing agent crystals inSCR.catalyst 260.
    At a time z1, drive of the vehicle 100 is changed in such a way that aat the SCR catalyst drops tobelow a temperature of 200 degrees Celsius. At time z2 isprevailing temperature a level thatthe temperature of the SCR catalyst is 200 degrees Celsius.
    At a third time t3, a second measurement of NOX content is performed and comparedupstream of the SCR catalyst 260 and downstream of the SCR catalyst. According tothis example, the measured values at this time are sufficiently equal forthat it can be determined that there are reducing agent crystals in the SCRthe catalyst 260.
    According to one example, a running average value can be calculated for measured NOXcontent upstream and downstream of the SCR catalyst 260 over a time intervaldefined by the third time and a time 23. If theycalculated moving averages during this interval are sufficiently equal canit is determined that the SCR catalyst 260detected.reducing agent crystals inAccording to one example, reducing agent dosing may be performed between the othertime t2 and time z2. At time z2, the first control unit can200 actively turn off reducing agent dosing as it is not appropriateto dose reducing agents at temperatures below 200 degreesCelsius.
    Figure 4a schematically illustrates a flow chart of a process at oneSCR system where reducing agent is supplied to an exhaust gas upp upstream of an SCRcatalyst and where the NOX content of the exhaust gases is measured upstream anddownstream of the SCR catalyst and where the presence of reducing agent crystals inThe SCR catalyst is detected, according to an embodiment of the invention.
    The method comprises a first method step s401. Includes s401 includedthe steps to:- at a first time, turn off the supply of reducing agent to the exhaust gas flow,so that the SCR catalyst is substantially emptied of narrowed reducing agent;at a second, later time, corresponding to a first temperature of the SCRthe catalyst, wherein said first temperature corresponds to a temperature atwhich reducing agent crystals evaporate, measure NOX content upstream anddownstream SCR catalyst;- compare measured NOX content upstream of the SCR catalyst with measured NOX contentdownstream of the SCR catalyst, whereby the difference between the measured NOX contentupstream of the SCR catalyst and measured NOX content downstream of the SCR catalystexceeds a certain value, this is taken as an indication of the possible presence ofreducing agent crystals in the SCR catalyst;at a third time corresponding to a second temperature of the SCRthe catalyst, wherein said second temperature corresponds to a temperature atwhich reducing agent crystals do not evaporate,measuring NOX content upstream of the SCR catalyst and downstream of the SCRthe catalyst;- compare measured NOX content upstream of the SCR catalyst with measured NOX contentdownstream of the SCR catalyst, whereby the difference between the measured NOX contentNOX content downstream of the SCRthe catalyst is below a certain value it is determined that the NOX levels are correctupstream of the SCR catalyst with measuredsaturate; and21provided that the NOX levels are correctly measured and that the presence ofreducing agent crystals in the SCR catalyst have been indicated, determinepresence of reducing agent crystals.
    After step s401, the process is terminated.
    Figure 4b schematically illustrates a flow chart of a process at oneSCR system where reducing agent is supplied with an exhaust gas flow upstream of an SCRcatalyst and where the NOX content of the exhaust gases is measured upstream anddownstream of the SCR catalyst and there the presence of reducing agent crystallizationThe SCR catalyst 260 is detected, according to an embodiment of the invention.
    The method includes a first method step s410. Procedure step s410involves the step of, at a first time t1, turning off the supply ofreducing agent to the exhaust stream, so that the SCR catalyst 260 substantiallyemptied of evaporated (stored) reducing agent. This procedure step is performed atan appropriate time. By this time, the SCR catalyst 260 may have been reacheda temperature that exceeds e.g. 300 degrees Celsius, which is equivalent to onetemperature at which reducing agent crystals in the SCR catalyst can be evaporated.
    After the process step s410, a subsequent process step s420 is performed.
    Method step s420 includes the step of at a second, later time t2,corresponding to a first temperature of the SCR catalyst, where said firsttemperature T1 corresponds to a temperature at which reducing agent crystalscan be evaporated, measuring NOX content upstream and downstream of the SCR catalyst.
    Said first temperature T1 exceeds 300 degrees Celsius according to an example.
    Said measurement is performed by the first NOx sensor 245 and the second, respectivelyThe NOX sensor 255. According to an alternative, a running average value is taken from measuredNOX content upstream and downstream of the SCR catalyst during a predeterminedtime intervals, such as e.g. 10 seconds. Said time interval is at onetime when the SCR catalyst 260 is considered to be evaporated22reducing agents, e.g. at the second time t2. After the procedure steps42O a subsequent procedure step s430 is performed.
    The process step s430 includes the step of comparing measured NOX content upstreamThe SCR catalyst with measured NOX content downstream of the SCR catalyst, whereinabout the difference between measured NOX content upstream of the SCR catalyst and measuredNOX content downstream of the SCR catalyst exceeds a certain value, this is taken into accountas an indication of the possible presence of reducing agent crystals in the SCRthe catalyst.
    According to one embodiment, it is taken as an indication of the possible presence ofreducing agent crystals in the SCR catalyst about the difference between the measured NOXcontent upstream of the SCR catalyst and measured NOX content downstream of the SCRthe catalyst exceeds a relative difference of 35%.
    After the process step s430, a subsequent process step s440 is performed.
    The process step s440 includes the step of at a third time t3corresponding to a second temperature T2 of the SCR catalyst 260, wheretimereducing agent crystals do not evaporate, measure NOX content upstream of the SCRsaid third t3 corresponds to a temperature at whichthe catalyst and the downstream SCR catalyst.
    Said measurement is performed by the first NOX sensor 245 and the second, respectivelyThe NOX sensor 255. According to an alternative, a running average value is taken from measuredNOX content upstream and downstream of the SCR catalyst during a predeterminedtime intervals, such as e.g. 10 seconds. Said time interval is at oneappropriate time, either before or after the above measurement at itsecond time.23Said second temperature T2 falls below, according to an example, 200 degreesCelsius. After the process step s440, a subsequent process step is performeds450.
    The process step s450 includes the step of comparing measured NOX content upstreamThe SCR catalyst with measured NOX content downstream of the SCR catalyst, whereinabout the difference between measured NOX content upstream of the SCR catalyst with measuredNOX content downstream of the SCR catalyst below a certain value is determinedthat the NOX levels are correctly measured; andprovided that the NOX levels are correctly measured and that the presence ofreducing agent crystals in indicated, determinepresence of reducing agent crystals.
    The SCR catalyst hasAccording to one embodiment, it is determined that the presence of reducing agent crystals inThe SCR catalyst has been detected on the difference between measured NOX contentupstream of the SCR catalyst and measured NOX content downstream of the SCR catalystless than a relative difference of 10%.
    After the procedure step s350, the procedure is terminated.
    Referring to Figure 5, a diagram of an embodiment of one is showndevice 500. The control units 200 and 210 described with reference toFigure 2 may in one embodiment comprise the device 500. The device 500includes a non-volatile memory 520, a data processing unit 510, and aread / write memory 550. The non-volatile memory 520 has a first memory portion 530wherein a computer program, such as an operating system, is stored for controlthe function of the device 500. Furthermore, the device 500 comprises a buscontroller, a serial communication port, an I / O device, an A / D converter, atime and date input and transfer unit, an event counter andan interrupt controller (not shown). The non-volatile memory 520 also hasa second memory part 540.24A computer program P is provided which includes routines for at afirst time, turn off the supply of reducing agent to the exhaust gas flow, so thatThe SCR catalyst is substantially emptied of vaporized reducing agent.
    The program P includes routines for at a second, later time,corresponding to a first temperature of the SCR catalyst, where said firsttemperature corresponds to a temperature at which reducing agent crystalsevaporate, measure NOX levels upstream and downstream of the SCR catalyst.
    The program P includes routines for comparing measured NOX content upstreamThe SCR catalyst with measured NOX content downstream of the SCR catalyst, whereinabout the difference between measured NOX content upstream of the SCR catalyst and measuredNOX content downstream of the SCR catalyst exceeds a certain value, this is taken into accountas an indication of the possible presence of reducing agent crystals in the SCRthe catalyst.
    The program P includes routines for at a third time corresponding to onesecond temperature of the SCR catalyst, where said second temperaturecorresponds to a temperature at which reducing agent crystals do not evaporate,NOX content SCR catalyst SCRthe catalyst.measure upstream and downstreamThe program P includes routines for comparing measured NOX content upstreamThe SCR catalyst with measured NOX content downstream of the SCR catalyst, whereinabout the difference between measured NOX content upstream of the SCR catalyst with measuredNOX content downstream of the SCR catalyst below a certain value is determinedthat the NOX levels are correctly measured; andprovided that the NOX levels are correctly measured and that the presence ofreducing agent crystals in the SCR catalyst (260) have been indicated, determinepresence of reducing agent crystals.
    The program P can be stored in an executable way or in a compressed wayin a memory 560 and / or in a read / write memory 550.
    When it is described that the data processing unit 510 performs a certain functionit should be understood that the data processing unit 510 performs a certain part ofthe program which is stored in the memory 560, or a certain part of the program whichis stored in the Read / Write memory 550.
    The data processing device 510 can communicate with a data port 599 viaa data bus 515. The non-volatile memory 520 is for communicationwith the data processing unit 510 via a data bus 512. The separate memory560 is intended to communicate with the data processing unit 510 via adata bus 511.the data processing unit 510 via a data bus 514. To the data port 599 canfor example links 246, 256, 266, 290, 291, 292 and 293 are connected (see Figure 2a,2b).
    The read / write memory 550 is arranged to communicate withWhen data is received on data port 599, it is temporarily stored in the other540. Whenthe data processing unit 510 is prepared to perform code execution onthe memory part received input data has been temporarily stored, isa manner described above. According to one embodiment, signals include receivedon the data port 599 information about a prevailing temperature at the SCRthe catalyst 260.
    According to one embodiment, signals received at the data port 499 includeinformation on a prevailing NOx content upstream of the SCR catalyst 260.
    According to one embodiment, signals received at the data port 499 includeinformation on a prevailing NOx content downstream of the SCR catalyst 260.26The received signals on the data port 599 can be used by the devicereducing agent crystals in SCRcatalyst 260 according to the innovative process.500 to detect the presence ofParts of the methods described herein may be performed by the device 500 by means ofof the data processing unit 510 running the program stored in the memory 560or read / write memory 550. When the device 500 is running the program, it is executedprocedures described herein.
    The foregoing description of the preferred embodiments ofthe present invention has been provided for the purpose of illustrating and describingthe invention. It is not intended to be exhaustive or restrictivethe invention to the described variants. Obviously many will comemodifications and variations to be apparent to those skilled in the art. The embodimentswas selected and described to best explain the principles of the invention andits practical applications, thus enabling those skilled in the art to understandthe invention for different embodiments and with the different modifications asare suitable for the intended use.
    权利要求:
    Claims (18)
    [1]
    A process in an SCR system in which reducing agent is fed to an exhaust gas fl desolate upstream of an SCR catalyst (260) and in which the NOX content of the exhaust gases is measured upstream and downstream of the SCR catalyst (260) and in which the presence of reducing agent crystals in the SCR catalyst is detected, characterized by the steps of - at a first time (t1), switching off (s410) supply of reducing agent to the exhaust gas,, so that the SCR catalyst (260) is substantially emptied of the reduced reducing agent; at a second (t2), later time, corresponding to a first temperature (T1) of the SCR catalyst (260), said first temperature corresponding to a temperature at which reducing agent crystals evaporate, measuring (s420) NOX content upstream and downstream of the SCR the catalyst (260); -compare (s430) measured NOX content upstream of the SCR catalyst (260) with measured NOX content downstream of the SCR catalyst (260), wherein if the difference between measured NOX content upstream of the SCR catalyst (260) and measured NOX content downstream The SCR catalyst (260) exceeds a certain value, this is taken as an indication of the possible presence of reducing agent crystals in the SCR catalyst (260); at a third time point (t3) corresponding to a second temperature (T2) of the SCR catalyst (260), said second temperature corresponding to a temperature at which reducing agent crystals do not evaporate, - measuring (s440) NOX content upstream of the SCR catalyst (260) ) and downstream of the SCR catalyst (260); -compare (s450) measured NOX content upstream of the SCR catalyst (260) with measured NOX content downstream of the SCR catalyst (260), wherein if the difference between measured NOX content upstream of the SCR catalyst (260) with measured NOX content downstream The SCR catalyst (260) is below a certain value, it is determined that the NOX levels are correctly measured; and - provided that the NOX levels are correctly measured and that the presence of reducing agent crystals in the SCR catalyst (260) has been indicated, determine the presence of reducing agent crystals.
    [2]
    The method of claim 1, wherein said third time (t3) is a further later time.
    [3]
    The method of claim 1, wherein said third time (t3) is a time prior to said first time (t1) and said second time (t2).
    [4]
    A method according to any one of the preceding claims, wherein said first temperature (T1) is a temperature exceeding 300 degrees Celsius.
    [5]
    A method according to any one of the preceding claims, wherein said second temperature (T2) is a temperature below 200 degrees Celsius.
    [6]
    A method according to any one of the preceding claims, wherein said reducing agent is a urea-based reducing agent, such as e.g. AdBlue.
    [7]
    A method according to any one of the preceding claims, further comprising the step of: - adding reducing agent to the exhaust gas stream after the second time (t2).
    [8]
    An SCR system comprising means arranged to supply reducing agent to an exhaust gas stream upstream of an SCR catalyst (260) and means (245, 255) arranged to measure the content of NOX in the exhaust gases upstream and downstream of the SCR catalyst (260) and where of reducing agent crystals in the SCR catalyst (260) is detected, characterized by - means (200; 210; 500) for at a first time (t1), shutting off the supply of reducing agent to the exhaust gas flow, so that the SCR catalyst (260) is substantially emptied on vaporized reducing agent; Means (245, 255) for at a second, later time (t2), corresponding to a first temperature (T1) of the SCR catalyst (260), said first temperature corresponding to a temperature at which reducing agent crystals evaporate, measure NOX content upstream and downstream of the SCR catalyst (260); means (200; 210; 500) for comparing measured NOX content upstream of the SCR catalyst (260) with measured NOX content downstream of the SCR catalyst (260), whereby if the difference between measured NOX content upstream of the SCR catalyst (260) ) and measured NOX content downstream of the SCR catalyst (260) exceeds a certain amount of any reducing agent crystals in the SCR catalyst (260); means (245, 255) for at a third time point (t3) corresponding to a second value indicating the presence of temperature (T2) of the SCR catalyst (260), said second temperature corresponding to a temperature at which reducing agent crystals are not elongated, measuring NOX content upstream of the SCR catalyst (260) and downstream of the SCR catalyst (260); means (200; 210; 500) for comparing measured NOX content upstream of the SCR catalyst (260) with measured NOX content downstream of the SCR catalyst (260), whereby if the difference between measured NOX content upstream of the SCR catalyst (260) ) with measured NOX content downstream of the SCR catalyst (260) below a certain value it is determined that the NOX levels are correctly measured; and - means for determining, provided that the NOX levels are correctly measured and that the presence of reducing agent crystals in the SCR catalyst (260) has been indicated, the presence of reducing agent crystals.
    [9]
    The SCR system of claim 8, wherein said third time (t3) is a further later time.
    [10]
    The SCR system of claim 8, wherein said third time (t3) is a time prior to said first time (t1) and said second time (t2).
    [11]
    An SCR system according to any one of claims 8-10, wherein said first temperature (T1) is a temperature exceeding 300 degrees Celsius. 10 15 20 25 30 30
    [12]
    An SCR system according to any one of claims 8-11, wherein said second temperature (T2) is a temperature below 200 degrees Celsius.
    [13]
    An SCR system according to any one of claims 8-12, wherein said reducing agent is a urea-based reducing agent, such as e.g. AdBlue.
    [14]
    An SCR system according to any one of claims 8-13, further comprising: - means (250, 200, 210, 500) for supplying reducing agent to the exhaust gas stream after the second time point (t2).
    [15]
    A motor vehicle (100; 110) comprising an SCR system according to any one of claims 8-14.
    [16]
    A motor vehicle (100; 110) according to claim 15, wherein the motor vehicle is something of a truck, bus or passenger car.
    [17]
    Computer program (P) in an SCR system where reducing agent is supplied to an exhaust gas stream upstream of an SCR catalyst (260) and where the NOX content in the exhaust gases is measured upstream and downstream of the SCR catalyst (260) and where the presence of reducing agent crystals in the SCR catalyst (260) is detected, wherein said computer program (P) comprises program code for causing an electronic control unit (200; 400) or another computer (210; 400) connected to the electronic control unit (200; 400) to perform the steps according to any one of the claims 1-7.
    [18]
    A computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-7, when said computer program is run on an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500).
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    同族专利:
    公开号 | 公开日
    SE536083C2|2013-04-30|
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    EP2751406B1|2016-07-27|
    WO2013032390A1|2013-03-07|
    BR112014003538A2|2017-03-14|
    EP2751406A1|2014-07-09|
    RU2563595C1|2015-09-20|
    BR112014003538B1|2021-07-20|
    KR101591034B1|2016-02-03|
    KR20140063755A|2014-05-27|
    JP2014527599A|2014-10-16|
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    法律状态:
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    SE1150789A|SE536083C2|2011-08-31|2011-08-31|A method of detecting reducing agent crystals in an SCR system and corresponding SCR system|SE1150789A| SE536083C2|2011-08-31|2011-08-31|A method of detecting reducing agent crystals in an SCR system and corresponding SCR system|
    JP2014528326A| JP2014527599A|2011-08-31|2012-08-28|Method and system for detecting reductant crystals in an SCR exhaust aftertreatment system|
    PCT/SE2012/050909| WO2013032390A1|2011-08-31|2012-08-28|Method and system for detecting reducing agent crystals in an scr exhaust after treatment system|
    RU2014112224/06A| RU2563595C1|2011-08-31|2012-08-28|Method and system for detecting of crystals of reducing agent in scr system of subsequent treatment of exhaust gases|
    KR1020147008586A| KR101591034B1|2011-08-31|2012-08-28|Method and system for detecting reducing agent crystals in an scr exhaust after treatment system|
    BR112014003538-5A| BR112014003538B1|2011-08-31|2012-08-28|METHOD AND SYSTEM FOR DETECTING REDUCING AGENT CRYSTALS IN AN SCR DISCHARGE POST-TREATMENT SYSTEM AND MOTOR VEHICLE|
    EP12827511.2A| EP2751406B1|2011-08-31|2012-08-28|Method and system for detecting reducing agent crystals in an scr exhaust after treatment system|
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