SE536241C2 - 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

15 20 25 30 535 241 i. Ambient pressure. A specific pressure is set, depending on the ambient pressure and the dosing of reducing agent is controlled by setting the time when the dosing valve is open.

US2011232267 describes a method and apparatus for dosing reducing agents in an exhaust system. The reducing agent must be added to the exhaust system evenly distributed. A desired droplet size is determined based on at least one exhaust parameter and then a pressure is set as a function of the desired droplet size. The exhaust gas parameters on which the desired droplet size is based are at least one of the following: the volume flow, the flow rate, the mass flow, the gas temperature, the gas pressure.

WO2006050318 describes a method and apparatus for dosing reducing agents in an exhaust system. To adjust the dosage of the reducing agent for all operating conditions, you can also add evaporated reducing agent to the engine. The amount of reducing agent dosed is based on a predetermined optimized amount of reducing agent, the temperature of the exhaust gases and how the engine operates.

US2005235632 discloses an apparatus and method for injecting a reducing agent into an exhaust stream to reduce emissions from an engine.

To get as small drops as possible, a vortex plate [0O13] is used. To inject a certain amount of reducing agent, where the amount depends on the engine speed, the temperature of the exhaust gases, exhaust gas fl fate, exhaust pressure, when the engine fuel supply takes place and desired NOx reduction, the dosage 'is controlled by adjusting the injection time, ie the valve (22 ) in the dosing unit 16 is open, under a predetermined predetermined pressure on the reducing agent.

EP1291498 describes a device for controlling emissions from an engine by injecting a fuel into an exhaust system. The fuel is injected in the form of drops of a controlled size. The diameter of the droplets is determined depending on the temperature of the exhaust gases or depending on the temperature in the middle of the catalyst. To control the dosage, an electronic control unit (ECU) controls the amount of fuel to be supplied.

US2009301067 discloses a device for dosing reducing agent into an exhaust stream in an internal combustion engine. The dosing takes place according to two different schedules depending on the operating condition of the engine.

There is a constant need to reduce the amount of emissions from the engines of motor vehicles. This applies not least to heavy motor vehicles such as e.g. trucks and buses as legal requirements for ever smaller emissions are continuously tightened.

There are different ways to reduce emissions from motor vehicles. One way is to regulate in a different way a prevailing temperature of the exhaust gas stream in order 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 new and advantageous method 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 for improving the performance of an SCR system.

An object of the present invention is to provide a new and advantageous method for reducing the amount of unwanted emissions from an internal combustion engine. A further object of the invention is to provide an alternative method of an SCR system and an alternative computer program of an SCR system and an alternative SCR system.

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

According to one aspect of the invention, there is provided a method of SCR system of a motor vehicle, comprising a feeding device for feeding from a container reducing agent to a dosing unit for supplying said reducing agent to an exhaust duct of the vehicle. The method comprises the step of controlling the dosing of the dosing unit by means of a pressure under which reducing agent is dosed.

This enables a flexible dosing of reducing agents in an SCR system. A relatively high generally produces smaller droplets that can be more easily captured in an exhaust stream from the vehicle's engine. A relatively low working pressure of said reducing agent can generally produce larger droplets which with a working pressure of said reducing agent higher kinetic energy are not affected by the exhaust gas flow in the same way as smaller droplets. In some operating cases it is advantageous with smaller drops, e.g. at low exhaust temperature where a small drop can be evaporated relatively quickly in the exhaust flow. In another operating case, where a high thermal energy is stored in the exhaust system, it is advantageous with larger droplets which can then be directed towards e.g. a surface of the exhaust system. This results in an improved performance of the SCR system.

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

In this case, a careful procedure is achieved in an SCR system according to an 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 method can be achieved in a reliable manner.

The method may include the step of controlling the pressure by changing a throttle in a reducing agent return line from the dosing unit to said container. In this case, an accurate method is provided in an 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 system can also be controlled with a high accuracy. In this case, a robust method can be achieved in a reliable manner.

The method may include the step of controlling the pressure by changing the configuration of the dosage unit. In this case, an accurate method is provided in an SCR system according to an aspect of the invention. Said configuration can be changed 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 method can be achieved in a reliable manner. The method may comprise the step of controlling the dosing of the dosing 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. In this case, an improved performance of the SCR system can be achieved. In this case, a versatile method is also provided in an SCR system, since alternative embodiments are possible. A prevailing mass flow of the exhaust gases can be calculated by a control unit of the vehicle, or alternatively measured by means of a mass flow sensor. Since temperature sensors are relatively inexpensive, a cost-effective method according to one aspect of the invention is also provided.

The method may comprise the step of controlling the dosing of the dosing unit by means of the pressure on the basis of a prevailing temperature of a surface in an exhaust pipe of the vehicle. Therefore, the intended temperature sensor must be installed in the vehicle in a suitable manner if one is not already installed.

The method may comprise the step of controlling the dosing of the dosing unit by means of the pressure on the basis of a prevailing temperature of an ambient air of the vehicle. Therefore, the intended temperature sensor must be installed in the vehicle in a suitable manner if one is not already installed.

The method may comprise the step of controlling the dosing of the dosing unit by means of the pressure on the basis of previous operating cases of the vehicle. In this case, a control unit of the vehicle is arranged to control the dosage of the dosing unit by means of the pressure in a suitable manner by means of calculations according to a stored model.

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

The process may comprise the step of varying the pressure of the reductant within a range of [5, 15] bar. According to one embodiment, the method may comprise the step of varying the pressure of the reductant within a range of [7, 13] bar. According to one embodiment, the method may comprise the step of varying the pressure of the reductant within a range of [10, 50] bar. According to one embodiment, the method may comprise the step of varying the pressure of the reductant within a range of [100, 300] bar. According to one embodiment, the method may comprise the step of varying the pressure of the reductant within any suitable range. In this case, a robust method is achieved where a working interval is defined in advance and thus eliminates the risk of unwanted spray image caused by too low or high working pressure. In this case, a reliable and reliable method is provided in an SCR system according to an aspect of the present invention.

The method may comprise the step of varying the pressure of the reductant steplessly in said control of the dosage of the dosing unit. Hereby a method is provided where a desired spray image of said reductant can be set in a controlled manner. In this case, a method of an SCR system is advantageously provided where a desired mixture of exhaust gases and reducing agents can be 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 of the dosing unit. This provides a method of an SCR system where relatively simple programming routines are required. By providing control of the dosing unit dosing where discrete adjustable steps of the working pressure are present, a speed of the feeding device can be controlled towards predetermined setpoints, which has the advantage that less computationally heavy data processing is required. The method may comprise the step of changing a cycle frequency of the dosage steplessly. Hereby a method is provided where a desired spray image of said reductant can be set in a well-defined manner. In this case, a method of an SCR system is advantageously provided where a desired 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. By providing control of the dosing unit dosing where discrete adjustable steps of the cycle frequency are present, a speed of the feeding device can be controlled towards predetermined setpoints, which has the advantage that less computationally heavy data processing is required.

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

It should be noted that the method may include one or more of the above features in an appropriate combination.

The procedure is easy to implement in existing motor vehicles. Software in an SCR system according to the invention can be installed in a control unit of the vehicle in the manufacture thereof. A buyer of the vehicle can thus have the opportunity to choose the function of the procedure as an option. Alternatively, software including program code may be used to perform the innovative procedure of 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, especially since no additional sensors or components need to be installed in the vehicle. The required hardware is already present in 10 15 20 25 30 533 241 “in the vehicle. The invention thus provides a cost-effective solution to the above problems.

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

According to one aspect of the invention, there is provided an SCR system of a motor vehicle, comprising a feeding device for feeding from a container reducing agent to a dosing unit for supplying said reducing agent to an exhaust duct of the vehicle. The SCR system includes means for controlling the dosing of the dosing unit by means of a pressure below which reducing agent is dosed.

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

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

The SCR system may include means for controlling the metering of the metering unit by the pressure based on 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 include means for controlling the dosage of the dosage unit by the pressure and a cycle frequency of the dosage. The SCR system may further comprise 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 during said control of the dosing unit dosage.

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

The SCR system may comprise means for changing a cycle frequency of the dosing steplessly or in discrete steps in said control of the dosing unit dosage.

The SCR system may include means for controlling the metering of the metering unit by means of the pressure of the reductant and a cycle frequency of the metering based on a prevailing exhaust gas temperature and / or a prevailing exhaust mass fl the fate of exhaust gases from an engine of the motor vehicle.

The above objects are also achieved with a motor vehicle that includes the SCR 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, said computer program comprising program code stored on a computer readable medium for causing an electronic control unit or another computer connected to the electronic control unit to perform the steps of any of the claims 1-10.

According to one aspect of the invention, there is provided a computer program for an SCR system, said computer program comprising program code stored on a medium for causing an electronic control unit or another computer connected to the electronic control unit to perform the steps according to any one of claims 1-10. According to one aspect of the invention, there is provided a computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-10, when said computer program is run on an electronic control unit or a computer. another computer connected to the electronic control unit.

Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following details, as well as through the practice of the invention. While the invention is described below, it should be understood that the invention is not limited to the specific details described. Those skilled in the art having access to the teachings herein will recognize additional applications, areas, which are within the scope of the invention. modifications and incorporations within other SUMMARY DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and further objects and advantages thereof, reference is now made to the following detailed description taken in conjunction with the accompanying drawings in which like reference numerals refer to like parts throughout the 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 an embodiment of the invention; Figure 3b schematically illustrates in further detail a flow chart of a method, according to an embodiment of the invention; and Figure 4 schematically illustrates a computer, 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 to any SCR system and is not limited to SCR systems of motor vehicles. The innovative method and the innovative SCR system according to an aspect of the invention are well suited for platforms which include 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 method and the innovative SCR system according to an aspect of the invention are also well suited for e.g. systems including industrial engines and / or powered industrial robots.

The innovative method and the innovative SCR system according to an aspect of the invention are 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 an arbitrary engine system that includes 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 which may be a physical line, such as an optoelectronic communication line, or a non-physical line, such as a wireless connection, for example a radio or microwave link.

Herein, the term "conduit" refers to a passageway for holding and transporting a fluid, such as e.g. a reductant in liquid form. The pipe can be a pipe of any dimension. The conduit may consist of any suitable material, such as e.g. plastic, rubber or metal.

Here, the terms "reductant" or "reducing agent" refer to an agent used to react with certain emissions in an SCR system. These emissions, "reductant" "reducing agent" can be used synonymously herein. Said reductant is according to an e.g. be NOx gas. The terms and execution so-called AdBlue. Of course, other types of reductants can be used.

Here, AdBlue is cited as an example of a reductant, but one skilled in the art will recognize that the innovative procedure and 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 that is denoted by the number of dosing intervals, also called dosing cycles, per second. It should be noted, however, that at least one active dosing of reducing agent in 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 synonymously herein.

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 form part of a SCR system. According to this example, the subsystem 299 consists of a container 205 which is 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 be refilled if necessary.

A first conduit 271 is provided to direct 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 operated by means of an electric motor (not shown). The pump is arranged to pump 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. The dosing unit 250 comprises an electrically controlled dosing device, by means of which a flow of reductant added to the exhaust system can be controlled. The dosing unit 250 may comprise an electrically controlled dosing valve, by means of which a fate of the reductant added to the exhaust system can be controlled. The pump 230 is arranged to pressurize the reductant in the second line 272. The dosing unit 250 is arranged with a throttling unit, which can also be called throttling valve, against which said pressure of the reductant can be built up in the subsystem 299. This pressure is referred to herein as the operating pressure Pr of the SCR. the system.

The dosing unit 250 is arranged to supply said reductant to a 100. The dosing unit 250 is arranged to supply in a controlled manner a suitable amount of reductant to an exhaust system of the vehicle 100. According to this embodiment, an SCR catalyst (not shown) is arranged downstream of a position of the exhaust system. where supply of the reductant is effected. The amount of reductant added to the exhaust system is intended to be used in the SCR catalyst to reduce the amount of unwanted emissions. Exhaust system (not shown) of the vehicle More specifically, 10 15 20 25 30 538 241 FS The dosing unit 250 may be arranged at an exhaust pipe (not shown) which is arranged to direct exhaust gases from an internal combustion engine (not shown) of the vehicle 100 to the SCR catalyst. and on 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 a certain amount of the reductant fed to the metering valve 250 to the container 205. This configuration advantageously provides cooling of the metering unit 250. In this way the metering unit 250 is cooled by a flow of the reductant as it is pumped through the metering 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 pressure Pr of the reductant where the sensor is mounted. According to this embodiment, the pressure sensor 220 is arranged at the second line 272 to measure the working pressure Pr of the reductant downstream of the pump 230. According to another embodiment, the pressure sensor 220 is arranged in the dosing unit 250 to measure the working pressure Pr of the reductant downstream of the pump 230. The pressure sensor 220 is arranged to signals sent continuously via the link 221 to the first control unit 200 including information about a prevailing pressure Pr of 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 operation of the pump 230. According to an 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 be done in various suitable ways.

According to one example, the first control unit 200 is arranged to change a prevailing speed RPM of the pump 230. In this case, the pressure Pr can be changed in a desired manner. By increasing the RPM speed of the pump 230, the working pressure Pr can be increased. By lowering the RPM speed of the pump 230, the working pressure Pr can be reduced.

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

The first control unit 200 is arranged for communication with a temperature sensor 240 via a link 241. The temperature sensor 240 is arranged 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 engine of the vehicle and upstream of a dosing unit 250.

The temperature sensor 240 is arranged to continuously detect a prevailing temperature T of the exhaust gas stream and send signals including information about said prevailing temperature T via the link 241 to the first 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 in order to e.g. regulate the supply of the reductant to the exhaust system of the vehicle 100.

The dosing unit 250 may comprise a nozzle for dosing the reductant for mixing with exhaust gases in an exhaust system of the vehicle 100. According to one embodiment, a geometry of said nozzle may be variable, whereby a control of the pressure Pr of the reductant can be achieved. The first 10 15 20 25 30 536 241 l? 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.

The first control unit 200 is according to an embodiment arranged to operate on the basis of the signals received from the pressure sensor 220 comprising information about a prevailing pressure of the reductant said pump 230 in a manner which according to an aspect of the innovative method. In this case, a feedback control of the working pressure Pr.

The first control unit 200 is arranged to calculate an exhaust mass flow MF of the exhaust gases from the vehicle engine. The first control unit 200 is arranged to continuously determine an exhaust gas mass flow MF of the exhaust gases from the vehicle engine. This can be done in any suitable way.

According to one embodiment, the subsystem comprises a mass flow sensor (not shown) which is arranged to continuously measure a prevailing exhaust 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.

The first control unit 200 is arranged to control the dosing of the dosing unit 250 by means of a pressure Pr under which reducing agent is dosed. The first control unit 200 may be arranged to control the pressure Pr by controlling the RPM speed of the pump 230. The first control unit 200 may be arranged to control the pressure Pr by changing a restriction in the line 273 for reducing agent 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 by changing a throttle of reducing agent fl in the dosing unit 250, which reducing agent flow is intended to lead to the container 205. The first control unit 200 may be arranged to control the pressure Pr by changing the dosing device 250 of the dosing unit 250. configuration. The first control unit 200 may be arranged to control the dosing unit 250 1 15 20 25 30 535 241 1% dosing 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. The first control unit 200 may be arranged to control the dosing of the dosing unit 250 by means of the pressure Pr of the reductant and a cycle frequency CF of the dosing. 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 of the reductant steplessly in said control of the dosage of the dosing unit 250. The first control unit 200 may be arranged to vary the pressure Pr of the reductant in discrete steps in said control of the dosage of the dosing unit 250. The first control unit 200 may be arranged to change a cycle frequency CF of the dosing steplessly or in discrete steps in said control of the dosing unit 250 dosing. The first control unit 200 may be arranged to control the dosing of the dosing unit 250 by the pressure Pr of the reductant 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.

A second control unit 210 is arranged for communication with the first 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 a control unit external to the vehicle 100. The second control unit 210 may be arranged to perform the innovative method steps according to the invention. The second control unit 210 can be used to upload software to the first control unit 200, in particular software for performing the innovative method. 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 similar functions as the first control unit 200, such as e.g. to control the dosage of the dosing unit 250 by means of a pressure Pr under which reducing agent is dosed. The innovative method can be performed by the first control unit 200 or the second control unit 210, or by 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 control unit 200 for a few different operating cases of the motor vehicle 100.

Example gel 1. This determines a change from a reference state to a state with higher exhaust gas temperature T and higher exhaust mass fl desolate MF (e.g.

T> 400 degrees C and MF> 1000 kg / h.) The working pressure Pr is thereby lowered (from eg 9 bar to 5 bar) in order to achieve larger dosed reducing agent droplets which can be better controlled in the high exhaust gas flow and hit the desired winning surface in the exhaust system of the vehicle. In this case, a controlled wall hit is advantageously achieved.

Example 2. This determines a change from a reference state to a state with higher exhaust gas temperature T and lower mass flow (eg T> 400 degrees C and MF <1000 kg / h). The working pressure Pr is thereby raised (from, for example, 9 bar to 15 bar) in order to produce smaller reducing agent droplets which can be evaporated directly in the exhaust gas before it hits a surface in the exhaust system of the vehicle. In this case, advantageously improved evaporation of reducing agent before wall impact is achieved.

Example gel 3. This determines a change from a reference state to a state with lower exhaust gas temperature T and higher exhaust gas mass flow MF, (e.g.

T <250 degrees C and MF> 1000kg / h). The working pressure Pr can in this case be maintained at a reference level (eg 9 bar) in order to achieve a droplet size distribution which contains both large and small droplets of the reducing agent. This means that some droplets can be drawn into the exhaust gas flow while other droplets can be controlled through the flow. In this case, a large impact surface is provided in the exhaust system of the vehicle in order to make the best use of the heat energy available therein and to avoid local cooling. Example 4. Hereby a change from a reference state to a state 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 then be raised to produce small droplets which can be evaporated more quickly on the surfaces in the exhaust system which are hit or may possibly have time to evaporate in the exhaust gas flow.

In this case, a rapid evaporation is achieved 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 is based on a previous operating case. According to one example, the exhaust system of the vehicle after a long period of operation with relatively high exhaust temperature T and a relatively high exhaust fate can still be hot even though a prevailing exhaust mass flow and a prevailing exhaust temperature are currently low.

In this case, a corresponding previously prevailing working pressure can advantageously continue to be used for a suitable 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 of the vehicle. In the event of an increase in the exhaust back pressure of the vehicle, the working pressure can advantageously be increased in a suitable manner in order to maintain a desired spray image with respect to the metered reducing agent.

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

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

Figure 3a schematically illustrates a flow chart of a method of SCR system of a motor vehicle, comprising a feeding device for feeding from a container reducing agent to a dosing unit for supplying said reducing agent to an exhaust duct of the vehicle, according to an embodiment of the invention. The method comprises a first method step s301. Step s301 includes the step of controlling the dosing of the dosing unit by means of a pressure below which reducing agent is dosed. After step s301, the process is terminated.

Figure 3b schematically illustrates a flow chart of a method in the SCR system of a motor vehicle, comprising a feeding device for feeding from a container reducing agent to a dosing unit for supplying said reducing agent to an exhaust duct of the vehicle, according to an embodiment of the invention.

The method includes a first method step s310. Process step s310 includes the step of determining a prevailing temperature T of exhaust gases from the vehicle 100 engine. This can be done by means of the temperature sensor 240. After the process step s310, a subsequent process step s320 is performed.

The process step s320 comprises the step of determining a prevailing exhaust gas mass MF of said exhaust gases. The exhaust mass flow MF can according to an example be calculated with the first control unit 200. Alternatively, the exhaust mass flow MF can be detected by means of a suitable sensor or equipment. After the process step s320, a subsequent process step s330 is performed. The process step s330 comprises the step of controlling the dosing of the dosing unit 250 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 be changed by influencing a throttle in the line 273. The pressure Pr can alternatively or in combination be changed by changing the configuration of the dosing unit 250 dosing device.

According to a preferred embodiment, the dosing of the dosing unit 250 is controlled by the pressure Pr on the basis of said determined prevailing temperature T of the exhaust gas flow by said determined prevailing and / or on the basis of exhaust gas mass flow MF.

After the process step s330, a subsequent process step s340 is performed.

The method step s34O includes the step of controlling the dosing of the dosing unit 250 by means of a cycle frequency of the SCR system. According to one embodiment, said control of the dosing of the dosing unit 250 is performed by means of the pressure Pr under which reducing agent is dosed at the same time as said control of the dosing of the dosing unit 250 is performed by means of a cycle frequency of the SCR system.

According to one embodiment, the dosing of the dosing unit 250 is controlled by the pressure Pr of the reductant and by 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 mass flow MF.

After process step s34O, the process is terminated.

Referring to Figure 4, there is shown a diagram of an embodiment of a device 400. The control units 200 and 210 described with reference to Figure 2 may in one embodiment include the device 400. The device 400 comprises a non The memory memory 420 has a first memory portion 430 in which a computer program, such as an operating system, is stored to control the operation of the device 400. Further, the device 400 includes a bus controller, a serial communication port, I / O means, 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 portion 440.

A computer program P is provided which includes routines for controlling the dosing of the dosing unit 250 by means of a pressure Pr under which reducing agent is dosed. The program P includes routines for controlling the pressure Pr by controlling the RPM speed of the pump 230. The program P includes routines for controlling the pressure Pr by changing a restriction in the line 273 for reducing agent from the dosing unit 250 to the container 205. According to an alternative, the program P routines for controlling the pressure Pr by changing a throttling of reducing agent fl 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 the configuration of the dosing unit 250 dosing device. The program P comprises routines 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.

The program P includes routines for controlling the dosing of the dosing unit 250 by means of the pressure Pr of the reductant and a cycle frequency CF of the dosing.

The program P includes routines for varying the pressure Pr of the reductant within a range of [5, 15] Bar. The program P includes routines for varying the pressure Pr steplessly at the dosing unit 250 dosing. The program P comprises routines for varying the pressure Pr of the reductant in discrete steps in said control of the dosing unit 250 dosage. The program P comprises routines for changing a cycle frequency CF of the dosing steplessly or in discrete steps at the control of the reductant said control of said dosing of the dosing unit 250 dosing. The program P comprises routines for controlling the dosing of the dosing unit 250 by means of the pressure Pr of the reductant 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.

The program P can be stored in an executable manner or in a compressed manner 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 is to 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.

The data processing device 410 can communicate with a data port 499 via a data bus 415. The non-volatile memory 420 is intended 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. Read / write memory 450 is arranged to communicate with the data processing unit 410 via a data bus 414. To the data port 499, e.g. links 201, 221, 231, 241 and 251 are connected (see Figure 2).

When data is received on the data port 499, it is temporarily stored in the second memory part 440. Once the received input data has been temporarily stored, the data processing unit 410 is arranged to perform code execution in a manner described above. According to one embodiment, signals received at the data port 499 include information about a prevailing operating pressure Pr of the reductant in the SCR system. According to one embodiment, signals received at the data port 499 include information about a prevailing temperature T of the exhaust gases in an exhaust system of the vehicle. According to one embodiment, signals received at the data port 499 include information about a prevailing exhaust mass flow MF of the exhaust gases in an exhaust system of the vehicle. 10 15 535 241 _23.

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

Parts of the methods described herein may be performed by the device 400 using the data processing unit 410 running the program stored in the memory 460 or the read / write memory 450. When the device 400 runs the program, the methods described herein are executed.

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 to limit the invention to the variations described. Obviously, many modifications and variations will be apparent to those skilled in the art. The embodiments were selected and described to best explain the principles of the invention and its practical applications, thereby enabling those skilled in the art to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims (24)

10 15 20 25 30 535 241 26 PATENT REQUIREMENTS A method of SCR system of a motor vehicle (100; 110), comprising a feeding device (230) for feeding from a container (205) a reducing agent to a dosing unit (250) for supplying said 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 pressure (Pr) being controlled by controlling a speed (RPM) of said feeding device (230) and wherein the dosing unit dosing is controlled with said pressure (Pr) on the basis of a prevailing temperature of a surface in an exhaust pipe of the vehicle. The method of claim 1, further comprising: - controlling the pressure (Pr) also by changing a choke 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: - controlling the pressure (Pr) also 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) also on the basis of a prevailing temperature (T) of an exhaust gas fl fate from an engine and / or a prevailing mass flow (MF) ) of 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. 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 1-6, 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 5-8, 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 dosage 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 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) container (205) feeding reducing agent to a dosing unit (250) for supplying said reducing agent to an exhaust duct of the vehicle (100; 110), characterized by : feeding device that from a - a temperature sensor for sensing a prevailing temperature of a surface in the exhaust pipe; means (200; 210; 400) for controlling the dosing of the dosing unit (250) by means of a pressure (Pr) below which reducing agent is dosed, on the basis of said prevailing temperature; Means (200; 210; 400) for controlling the pressure (Pr) by controlling a speed (RPM) of said feeding device (230). The SCR system of claim 11, further comprising: - means (200; 210; 400) for also controlling the pressure (Pr) by changing a throttle in a return line (273) for the dosing unit (250) to said container (205). ). reducing agents from An SCR system according to any one of claims 11 or 12, further comprising: - means (200; 210; 400) for also controlling the pressure (Pr) by changing the configuration of the dosing unit (250). An SCR system according to any one of claims 11-13, further comprising: - means (200; 210; 400) for controlling the dosing of the dosing unit (250) by means of the pressure (Pr) also on the basis of a prevailing temperature (T) of a exhaust flow from an engine and / or a prevailing mass (MF) of exhaust from an engine. An SCR system according to any one of claims 11-14, 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 11-15, 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 11-16, further comprising: - means (200; 210; 400) for varying the pressure (Pr) of the reductant steplessly during said control of the dosage of the dosing unit (250). An SCR system according to any one of claims 11-16, further comprising: means (200; 210; 400) for varying the pressure (Pr) of the reductant in discrete steps in said control of the dosing unit. (250) dosage. An SCR system according to any one of claims 15-18, further comprising: - means (200; 210; 400) for changing a cycle frequency (CF) of the dosage steplessly or in discrete steps in said control of the dosage of the dosage unit (250). An SCR system according to any one of claims 11-19, 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 11-20. A motor vehicle (100; 110) according to claim 21, wherein the motor vehicle is something of a truck, bus or passenger car. A computer program (P) in an SCR system, comprising a (230) container (205) feeding reducing agent to a metering unit (250) for supplying said 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 1-10. feeding device that from a A computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-10, 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).