SE1151192A1 - Method of reducing agent dosing in an SCR system with pressure control based on a temperature at exhaust pipes - Google Patents

Abstract

The invention relates to a method in the SCR system of a motor vehicle (100; 110), comprising a feeding device (230) for feeding from container (205) reducing agent to a dosing unit (250) pre-supplying said reducing agent to an exhaust duct of the vehicle (100). ; 110) .dosing by means of a pressure (Pr) below which reducing agent is reduced. The method comprises the step of controlling the dosing unit (250). The invention also relates to a computer program product comprising program code (P) for a computer (200; 210) for implementing a method according to the invention. The invention also relates to SCR systems and a motor vehicle (100) equipped with the SCR system. Figure 2 for publication

Description

10 15 20 25 30 There are various ways to reduce emissions from motor vehicles. One way is to different ways to regulate a prevailing temperature of the exhaust stream to optimize a degree of conversion of an SCR catalyst in the vehicle.

SUMMARY OF THE INVENTION There is a constant need to improve the current SCR system to reduce the amount of unwanted emissions from an internal combustion engine.

An object of the present invention is to provide a novel and advantageous procedure for improving the performance of an SCR system.

Another object of the invention is to provide a new and advantageous SCR system and a new and advantageous computer program to improve performance of an SCR system.

An object of the present invention is to provide a novel and advantageous procedure to reduce the amount of unwanted emissions from an internal combustion engine.

Another object of the invention is to provide an alternative procedure for an SCR system and an alternative computer program for an SCR system and an alternative SCR system.

These objects are achieved by a method in SCR systems of a motor vehicle according to claim 1.

According to one aspect of the invention, there is provided a method of SCR systems of a motor vehicle, comprising a feeding device for from a container feed reducing agent to a dosage unit for delivery of said reducing agent to an exhaust duct of the vehicle. The procedure 10 15 20 25 30 comprises the step of controlling the dosing of the dosing unit by means of a pressure below which reducing agent is dosed.

This enables an exemplary dosing of the reduction medium of an SCR system. A relatively high working pressure of said reduction medium generally produces smaller droplets that can be more easily captured in one exhaust flow from the vehicle's engine. A relatively low working pressure of the said reduction media can generally produce larger droplets as with a higher kinetic energy is not affected by the exhaust flow in the same way as less drops. In some operating cases it is advantageous with smaller drops, e.g. at low exhaust gas temperature where a small drop can be evaporated relatively quickly in the exhaust gas flow. In another operating case, where a high thermal energy is stored in the exhaust system, it is advantageous to have larger droplets which can then be directed towards for example a surface of the exhaust system. In this case, an improvement is achieved performance of the SCR system.

By varying according to the invention the working pressure Pr in a suitable manner, depending on e.g. inherent characteristics of the dosage unit, one can cone angle of the dosed reductant is advantageously changed in the desired manner. l analogy to the above, this can be used to optimize the hit image and / or mixture of reducing medium and exhaust gases. By changing a working pressure with the SCR system can speed affected. This entails substantially identical benefits as described above. also of the reducing agent droplets By controlling the dosage of the dosing unit by the pressure below which thereto droplet size distribution is affected. This can have a big impact depending on reduction medium can be dosed thus an associated type of dosing equipment used.

The method may include the step of controlling the pressure below which reduction medium dosed by controlling a speed of said feeding device.

In this case, an accurate procedure is provided in an SCR system according to a 10 15 20 25 30 aspect of the invention. Said pump speed can be controlled with very high accuracy and thus a working pressure of the SCR system can also be controlled with a high accuracy. In this case, a robust procedure can be achieved a reliable way.

The method may include the step of controlling the pressure by changing one throttling in a reducing line return line from the dosing unit to said container. In this case, a careful procedure is achieved at one SCR system according to an aspect of the invention. Said throttling can be changed with very high accuracy and thus a working pressure of the SCR the system is also controlled with a high accuracy. In this case, a robust procedure is accomplished in a reliable manner.

The method may include the step of controlling the pressure by changing dosage unit configuration. In this case, a careful is achieved method in an SCR system according to an aspect of the invention. Mentioned configuration can be changed with very high accuracy and thus one can working pressure of the SCR system is also controlled with a high accuracy. Hereby a robust process can be achieved in a reliable manner.

The method may include the step of controlling the dosage of the dosage unit by means of the pressure on the basis of a prevailing temperature of an exhaust gas flow from an engine and / or a prevailing mass flow of exhaust gases from an engine. Hereby an improved performance of the SCR system can be achieved. Hereby a versatile procedure is also provided in an SCR system, since alternative designs are possible. A prevailing mass flow of the exhaust gases can is calculated by a control unit of the vehicle, or alternatively measured by a mass flow sensor. Because temperature sensors are relatively inexpensive a cost-effective procedure is also provided according to an aspect of the invention. 10 15 20 25 30 The method may include the step of controlling the dosage of the dosage unit by means of the pressure on the basis of a prevailing temperature of a surface in an exhaust pipe at the vehicle. In this case, the intended temperature sensor must therefore be installed at the vehicle in an appropriate manner if one is not already installed.

The method may include the step of controlling the dosage of the dosage unit by means of the pressure on the basis of a prevailing temperature of an ambient air at the vehicle. In this case, the intended temperature sensor must therefore be installed at the vehicle in an appropriate manner if one is not already installed.

The method may include the step of controlling the dosage of the dosage unit by means of the pressure on the basis of previous operating cases of the vehicle. Here is one control unit of the vehicle arranged to by means of calculations according to a stored model control the dosing unit dosing by means of the pressure in an appropriate manner.

The method may include the step of controlling the dosage of the dosage unit by the pressure and a cycle frequency of the dosage. This is achieved a procedure in an SCR system with improved performance. By combine control of the dosage unit dosage by the pressure of the reductant during dosing and by means of changes of a prevailing cycle frequency of the SCR system can provide an optimized spray image of the said dosed reducing agents are provided. In this case, the amount may be undesirable emissions from the vehicle's engine are advantageously reduced.

The process may include the step of varying the pressure of the reductant within one range of [5, 15] bar. According to one embodiment, the method may comprise the step to vary the pressure of the reductant within a range of [7, 13] bar. According to one execution, the method may include the step of varying the pressure of the reductant within a range of [10, 50] bar. According to one embodiment, the procedure may including the step of varying the pressure of the reductant within a range of [100, 300] bar. According to one embodiment, the method may include the step of varying the pressure of the reductant within any suitable range. Hereby 10 15 20 25 30 a robust procedure is achieved where a work interval is defined in advance thus eliminating the risk of unwanted spray image caused by too low or high working pressure. This ensures a reliable and dependable procedure in an SCR system according to an aspect of the present invention.

The process may include the step of varying the pressure of the reductant steplessly in said control of the dosage of the dosing unit. This is achieved a method in which a desired spray image of said reductant can be set a well-defined way. In this case, a method of one is advantageously provided SCR system where a desired mixture of exhaust gases and reducing agents can set with a very high accuracy.

The method may further comprise the step of varying the pressure of the reductant in discrete steps in said control of the dosage unit dosage. Hereby provides a method of an SCR system where relatively simple programming routines are required. By providing control of dosing of the dosing unit where discrete adjustable steps of the working pressure are existing, a speed of the feeding device can be controlled against predetermined setpoints, which has the advantage of being less computationally difficult data processing is required.

The method may include the step of changing a cycle frequency of the dosage steplessly. In this case, a method is provided in which a desired spray image of Hereby advantageously, a method of an SCR system where a desired one is provided said reductant can be set in a well-defined manner. mixture of exhaust gases and reducing agents can be set with a very high accuracy.

The method may comprise the step of changing a cycle frequency of the dosage in discrete steps in said control of the dosage unit dosage. Through to provide control of the dosage unit dosage there discrete adjustable steps of the cycle frequency are present can a speed of 10 15 20 25 30 the feeding device is controlled against predetermined setpoints, which entails the advantage that less computationally heavy data processing is required.

The method may include the step of controlling the dosage of the dosage unit by the pressure of the reductant and a cycle frequency of the dosing on basis of a prevailing exhaust gas temperature and / or a prevailing exhaust gas mass flow of exhaust gases from an engine of the motor vehicle.

It should be noted that the procedure may include any of the above said feature inappropriate combination.

The procedure is easy to implement in existing motor vehicles. Software at an SCR system according to the invention can be installed in a control unit of the vehicle in the manufacture of the same. A buyer of the vehicle can thus get possibility to select the function of the procedure as an option. Alternatively can software including program code to perform the innovative procedure at an SCR system. In this case, the software can be loaded into a memory in the control unit.

Implementation of the innovative procedure is thus cost-effective, in especially since no additional sensors or components are needed installed in the vehicle. Required hardware is already available in the vehicle. The invention thus provides a cost-effective solution to the the above problems.

Software comprising program code for an SCR system according to the invention can be easily updated or replaced. Furthermore, different parts of the software such as includes the program code exchanged independently. This modular configuration is advantageous from a maintenance perspective.

According to one aspect of the invention, an SCR system is provided in one motor vehicle, comprising a feeding device for moving from a container feeding reducing agent to a dosage unit for supplying said reducing agent to an exhaust duct of the vehicle. The SCR system includes 10 15 20 25 30 means for controlling the dosing of the dosing unit by means of a pressure below which reducing agents are dosed.

The SCR system may further comprise means for controlling the pressure by control of a speed of said feeding device.

The SCR system may include means for controlling the pressure by changing one throttling in a reducing agent return line from the dosing unit to said container.

The SCR system may include means for controlling the pressure by changing dosage unit configuration.

The SCR system may include means for controlling the dosage of the dosage unit by means of the pressure on the basis of a prevailing temperature of an exhaust gas flow from an engine and / or a prevailing mass flow of exhaust gases from an engine.

The SCR system may further comprise means for controlling the dosing unit dosing by means of the pressure and a cycle frequency of the dosing.

The SCR system may further include means for varying the pressure of the reductant within a range of [5, 15] bar.

The SCR system may include means for varying the pressure of the reductant steplessly in said control of the dosage of the dosing unit.

The SCR system may include means for varying the pressure of the reductant in discrete steps in said control of the dosage unit dosage.

The SCR system may include means for changing a cycle frequency of the dosing steplessly or in discrete steps in said control of dosing unit dosage. 10 15 20 25 30 The SCR system may include means for controlling the dosage of the dosage unit by the pressure of the reductant and a cycle frequency of the dosing on basis of a prevailing exhaust gas temperature and / or a prevailing exhaust mass flow rate of exhaust gases from an engine of the motor vehicle.

The above objects are also achieved with a motor vehicle comprising the SCR the system. The motor vehicle can be a truck, bus or car.

According to one aspect of the invention, there is provided a computer program for an SCR system, wherein said computer program comprises program code stored on one, by one computer readable, medium for causing an electronic controller or another computer connected to the electronic control unit to perform the steps according to something of claims 1-11.

According to one aspect of the invention, there is provided a computer program for an SCR system, wherein said computer program includes program code stored on a medium to cause an electronic controller or another computer connected to the electronic control unit to perform the steps according to any of claims 1-11.

According to one aspect of the invention, there is provided a computer software product comprising a program code stored on a computer readable medium for performing the method steps according to any one of claims 1-11, when said computer programs run on an electronic controller or other computer connected to the electronic control unit.

Additional objects, advantages and novel features of the present invention the invention will be apparent to those skilled in the art from the following details, as well via the practice of the invention. While the invention is described below, it will be apparent that the invention is not limited to those specifically described the details. Those who have access to the teachings herein will recognize 10 15 20 25 30 10 additional applications, modifications and incorporations within others areas which are within the scope of the invention. SUMMARY DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and further purposes and benefits thereof, reference is now made to the following detailed description to be read together with the accompanying drawings there equally reference numerals refer to equal parts in the various figures, and in which: Figure 1 schematically illustrates a vehicle, according to an embodiment of the invention; Figure 2 schematically illustrates a subsystem of the vehicle shown in Figure 1, according to an embodiment of the invention; Figure 3a schematically illustrates a flow chart of a method, according to a embodiment of the invention; Figure 3b schematically illustrates in further detail a flow chart over one method, according to an embodiment of the invention; and illustrates a computer, Figure 4 schematically according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE FIGURES Referring to Figure 1, a side view of a vehicle 100 is shown The 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 vehicle can alternatively be a car.

It should be noted that the invention is suitable for application in a arbitrary SCR system and is not sold limited to SCR system at motor vehicle. The innovative procedure and the innovative SCR system according to one aspect of the invention is well suited for other platforms such as 10 15 20 25 30 11 includes 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 aspect of the invention is also well suited for e.g. systems including industrial engines and / or motorized industrial robots.

The innovative procedure and the innovative SCR system according to one aspect of 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 suited for 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 suited for an arbitrary system that includes a NOX generator and an SCR system.

Here, the term "link" refers to a communication link that may be one physical wire, such as an opto-electronic communications wire, or a non-physical wiring, such as a wireless connection, such as a radio or microwave link.

Here, the term "lead" refers to a passage for holding and transporting a fluid, such as e.g. a reductant in liquid form. The wire can be a tube of arbitrary dimension. The management can consist of an arbitrary, appropriate materials, such as e.g. plastic, rubber or metal.

Here, the terms "reductant" or "reducing agent" refer to an agent which is used to react with certain emissions in an SCR system. These 10 15 20 25 30 12 "Reductant" "Reducing agent" is used synonymously herein. Said reductant is according to one emissions can e.g. be NOX gas. The terms and execution so-called AdB | ue. Of course, other types of reductants can be used.

Here, AdB | ue is given as an example of a reductant but one skilled in the art will recognize that the innovative procedure and the innovative device can be realized for other types of reductants, with the necessary appropriate adjustments in control algorithms in accordance with the innovative procedure.

Here, the term cycle frequency refers to a frequency defined by the number of dosing intervals, also called dosing cycles, per second. The should be noted, however, that at least one active dosage of reducing agent of the dosing unit can be performed during a dosing cycle.

Here, the term pressure of the reductant refers to a pressure below which said reductant is metered from a dosing unit of the innovative SCR system.

The pressure below which said reductant is dosed and the working pressure Pr are used here synonymous.

Referring to Figure 2, a subsystem 299 of the vehicle 100 is shown.

The subsystem 299 is arranged in the tractor 110. The subsystem 299 may constitute a part of an SCR system. According to this example, the subsystem 299 consists of a container 205 arranged to hold a reductant. The container 205 is arranged to contain a suitable amount of reductant and is further arranged to be able to top up when needed.

A first line 271 is arranged to lead the reductant to a pump 230 from 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 driven by means of an electric motor (not shown). The pump is 230 arranged to inflate the reductant from the container 205 via the first line 271 and via a second line 272 supply said reductant to a dosing unit 250. Dosing unit 250 includes an electrically controlled 10 15 20 25 30 13 dosing device, by means of which a flow of to the exhaust system is added reductant can be controlled. The dosing unit 250 may include an electrically controlled dosing valve, by means of which a flow of reductant added to the exhaust system can be controlled. The pump 230 is arranged to pressurize the reductant in the other the line 272. The dosing unit 250 is provided with a throttling unit, which can also be called throttle valve, against which said pressure of the reductant can be built up in subsystem 299. This pressure is referred to herein as the working pressure Pr of the SCR system.

The dosing unit 250 is arranged to supply said reductant to a 100. the dosing unit 250 arranged to supply a suitable amount in a controlled manner exhaust system (not shown) of the vehicle More specifically reductant to an exhaust system of the vehicle 100. According to this embodiment, a SCR catalyst (not shown) arranged downstream of a position of the exhaust system where supply of the reductant is effected. The amount of reductant added in the exhaust system is intended to be used in the SCR catalyst to reduce the amount of unwanted emissions.

The dosing unit 250 may be arranged at an exhaust pipe (not shown) which is arranged to conduct exhaust gases from an internal combustion engine (not shown) of the vehicle 100 to the SCR catalyst and further to an environment of the vehicle.

A third conduit 273 is provided between the metering unit 250 and the container 205. The third conduit 273 is arranged to return one certain amount of the reductant fed to the metering valve 250 to container 205. With this configuration, advantageous cooling is provided of the dosing unit 250. In this way, the dosing unit 250 is cooled by a flow of the reductant as it is pumped through the dosing unit 250 from the pump 230 to the container 205.

A first control unit 200 is arranged for communication with a pressure sensor 220 via a link 221. The pressure sensor 220 is arranged to detect a prevailing one 10 15 20 25 30 14 press Pr at the reductant where the sensor is mounted. According to this embodiment is the pressure sensor 220 provided at the second line 272 for measuring the working pressure Pr of the reductant downstream of the pump 230. According to another In this embodiment, the pressure sensor 220 is arranged in the dosing unit 250 for measuring the working pressure Pr of the reductant downstream of the pump 230. The pressure sensor 220 is arranged to continuously send signals to the first via the link 221 the control unit 200 including information about a prevailing pressure Pr at the reductant.

The first control unit 200 is arranged for communication with the pump 230 via a link 231. The first control unit 200 is arranged to control the operation of the pump 230. According to one example, the first control unit 200 is arranged to control the pump 230 by means of an electric motor. The first control unit 200 is arranged to influence the working pressure Pr in the second line 272. This can take place in various appropriate ways.

According to one example, the first control unit 200 is arranged to change one current speed RPM of the pump 230. In this case, the pressure Pr can be changed desirable way. By increasing the RPM speed of the pump 230 can the working pressure Pr is increased. By lowering the RPM speed of the pump 230 can working pressure Pr is lowered.

According to another example, the first control unit 200 may be arranged to affect the pressure Pr by controlling a change of a stroke of a piston or a diaphragm of the pump 230. By actuating an internal configuration or internal geometry of the pump 230, the pressure Pr can be varied even while maintaining a substantially constant RPM speed of the pump 230. In this case, the influence of the pressure Pr can be effected by for example change the stroke of pistons or diaphragms of pump 230.

The first control unit 200 is arranged for communication with one temperature sensor 240 via a link 241. The temperature sensor 240 is arranged 10 15 20 25 30 15 to detect a prevailing temperature T of an exhaust stream from the vehicle engine. According to one example, the temperature sensor 240 is arranged directly downstream of the vehicle engine and upstream of a dosing unit 250.

The temperature sensor 240 is arranged to continuously detect a current temperature T of the exhaust stream and send signals including information about said prevailing temperature T via the link 241 to the first the control unit 200.

The first control unit 200 is arranged for communication with the dosing unit 250 via a link 251. The first control unit 200 is arranged to control operation of the dosing unit 250 to e.g. regulate supply of the reductant to the exhaust system of the vehicle 100.

The dosing unit 250 may include a nozzle for dosing the reductant for mixing with exhaust gases in an exhaust system of the vehicle 100. According to a embodiment, a geometry of said nozzle may be variable, wherein a control of the pressure Pr of the reductant can be achieved. The first the control unit 200 is arranged to influence said variable configuration of the dosing unit so as to control the pressure Pr of the reductant.

According to one embodiment, the first control unit 200 is arranged to on the basis of the signals received from the pressure sensor 220 including information about a prevailing pressure of the reductant drive said pump 230 in a manner such as 1 in accordance with one aspect of the innovative process. This is achieved a feedback control of the working pressure Pr.

The first control unit 200 is arranged to calculate an exhaust mass flow MF in the exhaust gases from the vehicle's engine. The first control unit 200 is arranged to continuously determine an exhaust mass flow MF of the exhaust gases from the engine of the vehicle. This can be done in any suitable way. 10 15 20 25 30 16 According to one embodiment, the subsystem comprises a mass fl fate sensor (not shown) which is arranged to continuously measure a prevailing exhaust gas mass flow from the engine of the vehicle 100. Said mass flow sensor is arranged to continuously send signals including information about a prevailing exhaust mass flow to the first control unit via a link.

The first control unit 200 is arranged to control the dosing unit 250 dosing by means of a pressure Pr below which the reducing medium is dosed. The the first control unit 200 may be arranged to control the pressure Pr by control of RPM speed of pump 230. The first control unit 200 may be arranged to control the pressure Pr by changing a throttle in the line 273 for reducing medium from the dosing unit 250 to the container 205. According to a alternatively, the first control unit 200 is arranged to control the pressure Pr through to change a throttle of reducing agent fl fate in the dosing unit 250, which reducing agent flow is intended to lead to the container 205. The first the control unit 200 may be arranged to control the pressure Pr by changing The first the control unit 200 may be arranged to control the dosing unit 250 configuration of the dosing unit 250 dosing device. dosing by means of the pressure Pr on the basis of a prevailing temperature T of a exhaust gas flow from an engine and / or a prevailing mass flow MF of exhaust gases from an engine. The first control unit 200 may be arranged to control dosing of the dosing unit 250 by means of the pressure Pr of the reductant and a cycle frequency CF at the dosage. The first control unit 200 may be arranged to vary the pressure Pr of the reductant within a range of [5, 15] bar. The first control unit 200 may be arranged to vary the pressure Pr at the reductant steplessly in said control of the dosing unit 250 dosage. The first control unit 200 may be arranged to vary the pressure Pr of the reductant in discrete steps in said control of the dosing unit 250 dosage. The first control unit 200 may be arranged to change one cycle frequency CF of the dosage steplessly or in discrete steps at said control of the dosage unit 250 dosage. The first control unit 200 can be arranged to control the dosage of the dosing unit 250 by means of the pressure Pr 10 15 20 25 30 17 of the reductant and a cycle frequency CF of the dosage on the basis of a prevailing exhaust gas temperature T and / or a prevailing exhaust gas mass flow MF of exhaust gases from an engine of the motor vehicle.

A second control unit 210 is provided for communication with the first the control unit 200 via a link 201. The second control unit 210 may be detachably connected to the first control unit 200. The second control unit 210 may be an external control unit for the vehicle 100. The second control unit 210 may be arranged to perform the innovative process steps according to the invention. The second control unit 210 can be used to overload software for the first control unit 200, in particular software for performing the innovative procedure. The second control unit 210 may alternatively be arranged for communication with the first control unit 200 via an internal network in the vehicle. The second control unit 210 may be arranged to perform substantially the same functions as the first control unit 200, such as e.g. to control the dosing of the dosing unit 250 by means of a pressure Pr below which reducing agents are dosed. The innovative procedure can be performed by it first control unit 200 or the second control unit 210, or both the first control unit 200 and the second control unit 210.

Below are some examples of how the working pressure Pr can be controlled by the first the control unit 200 for a few different operating cases of the motor vehicle 100.

Example 1. In this case, a change from a reference state to one is determined conditions with higher exhaust temperature T and higher exhaust mass flow MF (e.g.

T> 400 degrees C and MF> 1000 kg / h.) The working pressure Pr is thereby lowered (from e.g. 9 bar to 5 bar) to produce larger dosed reducing agent droplets which can be better controlled in the high exhaust flow and hit the desired hot surface in the exhaust system of the vehicle. In this case, one is advantageously obtained controlled wall hit. 10 15 20 25 30 18 Example 2. In this case, a change from a reference state to one is determined conditions with higher exhaust gas temperature T and lower mass flow (eg T> 40O degrees C and MF <1000 kg / h). The working pressure Pr is thereby increased (from eg 9 bar to 15 bar) to produce smaller reducing agent droplets which can evaporates directly into the exhaust stream before it hits a surface of the exhaust system of the vehicle. This advantageously provides improved evaporation of reducing agent before wall hit.

Example 3. In this case, a change from a reference state to one is determined conditions with lower exhaust temperature T and higher exhaust mass flow MF, (e.g.

T <250 degrees C and MF> 1000kg / h). The working pressure Pr can be maintained in this case at a reference level (eg 9 bar) to provide one droplet size distribution that contains both large and small droplets of the reducing agent. This means that some drops can be drawn into the exhaust gas while other droplets can be controlled by the flow. In this case, a large meeting surface in the exhaust system of the vehicle to make the best use of it available heat energy and avoid local cooling.

Example 4. In this case, a change from a reference state to one is determined conditions with lower exhaust gas temperature T and lower exhaust gas mass flow MF, (e.g.

T <250 degrees C and MF <1000kg / h). The working pressure Pr can be increased to produce droplets that can evaporate more quickly on the surfaces in the exhaust system that is hit or may have time to evaporate in the exhaust flow.

This results in a rapid evaporation in the exhaust gas and / or on surfaces in the exhaust system as this operating case has the lowest heat energy available for evaporation of said reducing agent.

In a case of transient operation, the procedure can be supplemented so that control based on a previous operating case. According to one example, the exhaust system can of the vehicle after a long period of operation with relatively high exhaust gas temperature T and a relatively high exhaust flow will still be hot despite a prevailing exhaust mass flow and a prevailing exhaust temperature are currently low. 10 15 20 25 30 19 In this case, a corresponding previously prevailing working pressure can advantageously continue be used for an appropriate period of time.

According to one aspect of the invention, the working pressure Pr can be controlled on the basis of a change of a detected exhaust back pressure in the vehicle. At an increase one exhaust back pressure of the vehicle, the working pressure can advantageously be increased appropriately method of maintaining a desired spray image for metered reducing agent.

According to one aspect of the invention, the working pressure Pr can be controlled on the basis of a prevailing ambient air temperature of the vehicle.

In a condition where the ambient air temperature is lower than 0 degrees C the working pressure can be increased in an appropriate manner, e.g. with 2 bar, to change the droplet size distribution towards smaller droplets which can facilitate one evaporation of dosed reducing agent.

According to one aspect of the invention, the working pressure Pr can be controlled on the basis of a prevailing temperature of the reducing agent of the SCR system of the vehicle.

In a condition where the prevailing temperature of the reducing agent is higher than e.g. 50 degrees C, the working pressure can be lowered in a suitable way, e.g. with 2 bar, to compensate for a faster evaporation rate than the hot one the reducing agent entails.

Figure 3a schematically illustrates a flow chart of a method of SCR system of a motor vehicle, comprising a feed device for a container feeding reducing agent to a dosage unit for delivery of said reducing agent to an exhaust duct of the vehicle, according to a embodiment of the invention. The method comprises a first process step s301. Step s301 includes the step of controlling the dosage of the dosing unit 10 15 20 25 30 20 by means of a pressure below which reducing agent is metered. After the step s301 the procedure is terminated.

Figure 3b schematically illustrates a flow chart of a method of SCR system of a motor vehicle, comprising a feed device for a container feeding reducing agent to a dosage unit for delivery of reducing agent to embodiment of the invention. said an exhaust duct of the vehicle, according to a The method includes a first method step s310. Procedure step s310 involves the step of determining a prevailing temperature T of exhaust gases from the vehicle's 100 engine. This can be done by means of the temperature sensor 240. After the process step s310 performs a subsequent process step s320. establish a prevailing exhaust gas mass flow MF of said exhaust gases. The exhaust mass flow MF can according to The process step s320 includes the step of an example is calculated with the first controller 200. Alternatively, the exhaust gas flow MF is detected by means of a suitable sensor or equipment. After the process step s320 performs a subsequent process step s330.

Method step s330 includes the step of controlling the dosage unit 250 dosing by means of a pressure Pr under which reducing agent is dosed. The pressure Pr can be changed by affecting a speed of the pump 230. The pressure Pr can alternatively or in combination is changed by affecting a throttle in line 273. The pressure Pr can alternatively or in combination be changed by to change the configuration of the dosing unit 250 dosing device.

According to a preferred embodiment, the dosage of the dosing unit 250 is controlled by means of the pressure Pr on the basis of said determined prevailing temperature T at the exhaust gas flow and / or on the basis of said established prevailing exhaust mass flow MF. 10 15 20 25 30 21 After the process step s330, a subsequent process step s340 is performed.

Method step s340 includes the step of controlling the dosage unit 250 dosing by a cycle frequency of the SCR system. According to one embodiment said control of the dosing unit 250 dosing is performed by the pressure Pr during which reducing agent is dosed at the same time as said control of dosing unit 250 dosage by a cycle frequency of the SCR the system is executed.

According to one embodiment, the dosage of the dosing unit 250 is controlled by the pressure Pr at the reductant and by means of a cycle frequency CF of the dosing simultaneously on the basis of said determined prevailing exhaust gas temperature T and / or said determined prevailing exhaust gas mass flow MF.

After the procedure step s340, the procedure is terminated.

Referring to Figure 4, a diagram of an embodiment of one is shown device 400. The control units 200 and 210 described with reference to Figure 2 may in one embodiment comprise the device 400. The device 400 includes a non-volatile memory 420, a data processing unit 410, and a read / write memory 450. The non-volatile memory 420 has a first memory portion 430 wherein a computer program, such as an operating system, is stored for control the function of the device 400. Furthermore, the device 400 comprises a bus controller, a serial communication port, an I / O device, an A / D converter, a time and date input and transfer unit, an event counter and an interrupt controller (not shown). The non-volatile memory 420 also has a second memory part 440.

A computer program P is provided which includes control routines dosing of the dosing unit 250 by means of a pressure Pr below which reducing agents are dosed. Program P includes routines for controlling the pressure Per by controlling the RPM speed of the pump 230. The program P 10 15 20 25 30 22 includes routines for controlling the pressure Pr by changing a throttle in the reduction medium line 273 from the metering unit 250 to the container 205. According to an alternative, the program P includes routines for controlling the pressure Pr by changing a restriction flow restrictor flow in the dosing unit 250, which reducing agent flow is intended to lead to the container 205.

The program P includes routines for controlling the pressure Pr by changing configuration of the dosing unit 250 dosing device. The program P includes routines for controlling the dosage of the dosage unit 250 by means of the pressure Pr on the basis of a prevailing temperature T of an exhaust gas flow from a engine and / or a prevailing mass flow MF of exhaust gases from an engine.

Program P includes routines for controlling the dosage unit 250 dosage by the pressure Pr of the reductant and a cycle frequency CF of the dosage.

The program P includes routines for varying the pressure Pr of the reductant within a range of [5, 15] Bar. Program P includes routines for varying stepless at dosage unit 250 dosage. Program P includes routines for the pressure Pr of the reductant said control of varying the pressure Pr of the reductant in discrete steps in said control of dosage unit 250 dosage. Program P includes routines for change a cycle frequency CF of the dosage steplessly or in discrete steps at said control of the dosing unit 250 dosage. The program P includes routines for controlling the dosage of the dosage unit 250 by means of the pressure Pr of the reductant and a cycle frequency CF of the dosing on a basis of a prevailing exhaust gas temperature T and / or a prevailing exhaust gas mass flow MF of exhaust gases from an engine of the motor vehicle.

The program P can be stored in an executable way or in a compressed way in a memory 460 and / or in a read / write memory 450.

When it is described that the data processing unit 410 performs a certain function it should be understood that the data processing unit 410 performs a certain part of the program which is stored in the memory 460, or a certain part of the program which is stored in the read / write memory 450. 10 15 20 25 30 23 The data processing device 410 can communicate with a data port 499 via a data bus 415. The non-volatile memory 420 is for communication with the data processing unit 410 via a data bus 412. The separate memory 460 is intended to communicate with the data processing unit 410 via a data bus 411. the data processing unit 410 via a data bus 414. To the data port 499 can for example links 201, 221, 231, 241 and 251 are connected (see Figure 2).

The read / write memory 450 is arranged to communicate with When data is received on data port 499, it is temporarily stored in the other memory day 440. When received input is temporarily stored, is the data processing unit 410 prepared to perform code execution on a manner described above. According to one embodiment, signals include received on the data port 499 information about a prevailing working pressure Pr at the reductant in the SCR system. According to one embodiment, signals received on include data port 499 information on a prevailing temperature T of the exhaust gases in a exhaust system of the vehicle. According to one embodiment, signals include received on the data port 499 information about a prevailing exhaust mass flow MF at the exhaust gases in an exhaust system of the vehicle.

The received signals on the data port 499 can be used by the device 400 to perform the innovative procedure herein.

Parts of the methods described herein can be performed by the device 400 by means of of the data processing unit 410 running the program stored in the memory 460 or read / write memory 450. When the device 400 runs the program, it is executed procedures described herein.

The foregoing description of the preferred embodiments of the present invention has been provided for the purpose of illustrating and describing the invention. It is not intended to be exhaustive or restrictive the invention to the described variants. Obviously many will come 24 modifications and variations to be apparent to those skilled in the art. The embodiments was selected and described to best explain the principles of the invention and its practical applications, thus enabling professionals to understand the invention for different embodiments and with the different modifications as are suitable for the intended use.

Claims (26)

10 15 20 25 30 25 PATENT REQUIREMENTS A method of SCR system of a motor vehicle (100: 110), comprising (230) for feeding from a container (205) reducing agent to a metering unit (250) for supplying said feeding device to reducing agent to an exhaust duct of the vehicle (100). ; 110), characterized by the step of: - controlling the dosing of the dosing unit (250) by means of a pressure (Pr) under which reducing agent is dosed. The method of claim 1, further comprising the step of: - controlling the pressure (Pr) by controlling a speed (RPM) of said feeding device (230). The method of claim 1 or 2, further comprising the step of: - controlling the pressure (Pr) by changing a throttle in a reducing agent return line (273) from the metering unit (250) to said container (205). A method according to any one of the preceding claims, further comprising the step of: - controlling the pressure (Pr) by changing the configuration of the dosing unit (250). A method according to any one of the preceding claims, further comprising the step of: - controlling the dosing of the dosing unit (250) by means of the pressure (Pr) on the basis of a prevailing temperature (T) of an exhaust gas fate from an engine and / or a prevailing mass flow (MF) in exhaust gases from an engine. A method according to any one of the preceding claims, further comprising the step of: - controlling the dosing of the dosing unit (250) by means of the pressure (Pr) and a cycle frequency (CF) of the dosing. A method according to any one of the preceding claims, further comprising the step of: - varying the pressure (Pr) of the reductant within a range of [5, 15] Bar. 10 15 20 25 30 26 A method according to any one of the preceding claims, further comprising the step of: - varying the pressure (Pr) of the reductant steplessly in said control of the dosage of the dosing unit (250). A method according to any one of claims 1-7, further comprising the step of: - varying the pressure (Pr) of the reductant in discrete steps in said control of the dosage of the dosing unit (250). A method according to any one of claims 6-9, further comprising the step of: - changing a cycle frequency (CF) of the dosage steplessly or in discrete steps in said control of the dosage of the dosing unit (250). A method according to any one of the preceding claims, further comprising the step of: - controlling the dosing of the dosing unit (250) by means of the pressure (Pr) and a cycle frequency (CF) of the dosing on the basis of a prevailing exhaust gas temperature (T) and / or a prevailing exhaust mass flow ( MF) of exhaust gases from an engine of the motor vehicle (100; 110). An SCR system of a motor vehicle (100; 110), comprising a (230) for reserving (205) reducing agent to a metering unit (250) for supplying said feeding device from a feeding reducing agent to an exhaust duct of the vehicle (100; 110). ), characterized by: - means (200; 210; 400) for controlling the dosing of the dosing unit (250) by means of a pressure (Pr) under which reducing agent is dosed. The SCR system of claim 12, further comprising: - means (200; 210; 400) for controlling the pressure (Pr) by controlling a speed (RPM) of said feeding device (230). 10 15 20 25 30 27 The SCR system of claim 12 or 13, further comprising: - means (200; 210; 400) for controlling the pressure (Pr) by changing a throttle in a reducing agent return line (273) from the dosing unit (250) to said container (205). An SCR system according to any one of claims 12 to 14, further comprising: - means (200; 210; 400) for controlling the pressure (Pr) by changing the configuration of the dosing unit (250). An SCR system according to any one of claims 12 to 15, further comprising: - means (200; 210; 400) for controlling the dosing of the dosing unit (250) by means of the pressure (Pr) on the basis of a prevailing temperature (T) of an exhaust gas flow from an engine and / or a prevailing mass flow (MF) of exhaust gases from an engine. An SCR system according to any one of claims 12-16, further comprising: - means (200; 210; 400) for controlling the dosing of the dosing unit (250) by means of the pressure (Pr) and a cycle frequency (CF) of the dosing. An SCR system according to any one of claims 12 to 17, further comprising: - means (200; 210; 400) for varying the pressure (Pr) of the reductant within a range of [5, 15] Bar. An SCR system according to any one of claims 12 to 18, further comprising: - means (200; 210; 400) for varying the pressure (Pr) of the reductant steplessly in said control of the dosage of the dosing unit (250). The SCR system according to any one of claims 12 to 18, further comprising: - means (200; 210; 400) for varying the pressure (Pr) of the reductant in discrete steps in said control of the dosage of the dosing unit (250). An SCR system according to any one of claims 17 to 20, further comprising: means (200; 210; 400) for changing a cycle frequency (CF) of the dosage steplessly or in discrete steps in said control of dosage unit (250) dose fi ng. An SCR system according to any one of claims 12-21, further comprising: - means (200; 210; 400) for controlling the dosing of the dosing unit (250) by the pressure (Pr) and a cycle frequency (CF) of the dosing on the basis of a prevailing exhaust gas temperature (T) and / or a prevailing exhaust mass flow (MF) of exhaust gases from an engine of the motor vehicle (100; 110). A motor vehicle (100; 110) comprising an SCR system according to any one of claims 12-22. A motor vehicle (100; 110) according to claim 23, wherein the motor vehicle is something of a truck, bus or passenger car. A computer program (P) comprising one (230) for (205) reducing means to a metering unit (250) for supplying said SCR system, feeding device from a container feeding reducing agent to an exhaust duct of the vehicle (100; 110), wherein said computer program (P) comprises program code stored on a medium 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 claims 1 -11. A computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-11, when said computer program is run on an electronic control unit (200; 400) or another computer (210; 400) connected to the electronic control unit (200; 400).