WO2015088428A1

WO2015088428A1 - Method and device for thawing frozen reducing agent in an scr system

Info

Publication number: WO2015088428A1
Application number: PCT/SE2014/051469
Authority: WO
Inventors: Per Bremberg; David VESTGÖTE
Original assignee: Scania Cv Ab
Priority date: 2013-12-09
Filing date: 2014-12-09
Publication date: 2015-06-18
Also published as: SE1351463A1; SE537851C2; DE112014005200T5

Abstract

The invention relates to a method and device for thawing frozen reducing agent in an SCR system. The reducing agent is heated with a heating medium circulating (281) through the container (205) when a need of heating is determined. The temperature (Tred) and the level (L) of the reducing agent in the container (205) are determined and the accumulated amount (V) of thawed reducing agent is continuously determined. Start up of circulation of the reducing agent is suitable when the temperature (Tred) exceeds a predetermined first temperature value (Th1), and/or when the determined accumulated amount (V) of thawed reducing agent exceeds a predetermined first quantity value (VTh1). The dosage of the reducing agent is suitable when the determined temperature (Tred) exceeds a predetermined second temperature value (Th2), and/or when the determined accumulated amount (V) of thawed reducing agent exceeds a predetermined second quantity value (VTh2). The first temperature value (Th1), the second temperature value (Th2), the first quantity value (VTh1), and the second quantity value (VTh2) are determined based on said determined level (L) of the reducing agent in the container.

Description

METHOD AND DEVICE FOR THAWING FROZEN REDUCING AGENT IN AN

SCR SYSTEM

TECHNICAL FIELD

The present invention relates to a method at an SCR system. The invention also relates to a computer program product, comprising program code for a computer, to implement a method according to the invention. The invention also relates to an SCR system and a motor vehicle equipped with such an SCR system.

BACKGROUND

In vehicles today e.g. urea is used as a reducing agent in SCR systems comprising an SCR catalyst, in which catalyst said reducing agent and NO_x gas may react and transform into nitrogen and water. Different types of reducing agents may be used in SCR systems. Such reducing agents have different freezing points. A commonly occurring reducing agent is e.g. AdBlue.

In one type of SCR system a container holding a reducing agent is included. The SCR system also has a pump, which is arranged to pump said reducing agent from the container via a suction hose, and add it to a dosage device, which is arranged in an exhaust system of the vehicle, via a pressurised hose. The dosage device is arranged to inject a required amount of reducing agent into an exhaust system upstream of the SCR catalyst, according to operational procedures stored in a control device of the vehicle.

Said reducing agent may have a freezing point within the range of -10 to -15 degrees Celsius. Different reducing agents have unique freezing points depending on e.g. their substance composition. AdBlue, for example, has a freezing point at around -1 1 degrees Celsius. Accordingly, said reducing agent will freeze in the container and in other parts of the SCR system, if an ambient temperature is below said freezing point for a certain time.

According to applicable provisions relating to emissions, certain vehicles equipped with an SCR system must be operated in a normal way after a certain predetermined time following start up of the vehicle. Said predetermined time may, according to one example, be 70 minutes. Accordingly, frozen reducing agent must at least partly be thawed in order to be circulated within the SCR system, before the dosage is started within said time period.

According to a prior art manner of assessing whether start up of the pump and reducing agent dosage is suitable, a temperature sensor arranged in the container to measure a prevailing temperature of said reducing agent is used. Accordingly, it may be determined with a certain degree of probability whether said reducing agent in the container is thawed. One disadvantage of said method is that temperature measurements as a basis do not always provide a correct assessment, depending on e.g. where the sensor is fitted, the configuration of e.g. the suction hose and the container's configuration and size. The temperature sensor itself is also afflicted by a certain measurement uncertainty. Therefore, rather large safety margins are required to avoid starting a pump in the SCR system too soon. If the pump is started too soon, when an insufficient amount of reducing agent has thawed, there is a risk that the pump may "suck dry", which may lead to a number of unwanted effects. One example of such an unwanted effect is when air enters the SCR system, which may markedly impair the performance of the system. Furthermore, the efficient continued thawing of frozen reducing agent is prevented. In cases where a circulating reducing agent is used to cool a dosage unit for reducing agent, the latter may overheat when circulation is disrupted or absent.

In some cases, where frozen reducing agent in the tank is thawed e.g. with a circulating heating medium, and where the pump sucks dry, a situation may arise, where further thawing of the frozen reducing agent in the container with said circulating heating medium may not be possible. This may have very serious consequences, where applicable statutory requirements relating to emissions of the vehicle may not be met within the required time. Furthermore, the pump may risk incurring permanent damage or be afflicted by high wear if it is started up too early.

WO 20121 13669 describes a method to melt urea solution in an SCR system, wherein the temperature of said urea solution is taken into consideration, and the amount of urea solution in a container for said urea solution. SUMMARY OF THE INVENTION

There is thus a need of assessing in a reliable manner whether a pump in the SCR system, where the reducing agent has frozen, may be started without using excessively large safety margins, to avoid unwanted effects when the pump is forced to suck dry.

One objective of the present invention is to provide a novel and advantageous method for an SCR system.

Another objective of the invention is to provide a novel and advantageous SCR system, and a novel and advantageous computer program for an SCR system.

Another objective of the invention is to provide an alternative method for an SCR system, an alternative SCR system, and an alternative computer program for an SCR system in a motor vehicle, where a reducing agent for exhaust purification is at least partly frozen.

Another objective of the invention is to provide a method for an SCR system, an SCR system, and a computer program to achieve a reliable start-up of an SCR system in a motor vehicle.

Another objective of the invention is to provide a method for an SCR system, an SCR system, and a computer program to achieve improved performance in a motor vehicle.

Some of said objectives are achieved with a method for an SCR system according to claim 1 . Other objectives are achieved with an SCR system according to claim 7. The preferred embodiments are specified in the dependent claims.

According to one aspect of the invention, a method for an SCR system, comprising a pump and a dosage unit, is provided, comprising the steps to:

- determine a need to heat a reducing agent for exhaust purification arranged in a container; - when a need of heating is determined, continuously heat said reducing agent with a heating medium circulating through said container;

- continuously determine a temperature of said reducing agent in said container;

- determine a level of said reducing agent in said container;

- continuously determine an accumulated amount of thawed reducing agent;

- determine that start up of circulation of said reducing agent is suitable, when said determined temperature of said reducing agent in said container exceeds a predetermined first temperature value, and/or when the determined accumulated amount of thawed reducing agent exceeds a predetermined first quantity value;

and/or

- determine that start up of dosage of said reducing agent is suitable, when said determined temperature of said reducing agent in said container exceeds a predetermined second temperature value, and/or when the determined accumulated amount of thawed reducing agent exceeds a predetermined second quantity value; wherein said level of said reducing agent in said container is included at the determination of the start up suitability relating to said circulation and/or said dosage.

Advantageously, according to one aspect of the invention, it may be determined when dosage or consumption of reducing agent may be started.

According to one aspect of the invention, a method for an SCR system is provided, comprising a pump and a dosage unit, comprising the steps to:

- determine a need to heat a reducing agent for exhaust purification arranged in a container;

- when a need of heating is determined, continuously heat said reducing agent with a heating medium circulating through said container;

- determine a level of said reducing agent in said container;

- continuously determine an accumulated amount of thawed reducing agent;

- when determining the start up suitability relating to said circulation, include said level of said reducing agent in said container;

- where suitable, start said circulation of said reducing agent.

- determine a level of said reducing agent in said container;

- continuously determine an accumulated amount of thawed reducing agent;

- determine that start up of dosage of said reducing agent is suitable, when said determined temperature of said reducing agent in said container exceeds a

predetermined second temperature value, and/or when the determined accumulated amount of thawed reducing agent exceeds a predetermined second quantity value;

- when determining the start up suitability relating to said dosage, include said level of said reducing agent in said container, and

- where suitable, activate said dosage of said reducing agent.

At a reduced level of reducing agent in said container in relation to a maximum possible level, the reducing agent will, in some heating configurations, be exposed to the existing heating configuration for heating of said reducing agent in said container to a lower degree. Hereat, a prevailing level of said reducing agent in said container may be taken into consideration, when calculating a prevailing thawed amount of reducing agent in said container. This may advantageously be carried out with a factor, whereby a reduced level of reducing agent in said container entails that an amount of thawed reducing agent, required to allow a start up of said circulation of reducing agent and/or dosage of reducing agent, is increased. Said multiplier may e.g. be 25% when the container is half full. Said multiplier may e.g. be 50% when the container is a quarter full. Said multiplier may be provided in fixed discrete steps or continuously.

By taking into consideration said level of reducing agent in said container, start up of circulation of reducing agent, and/or start up of dosage of reducing agent, may occur under substantially optimal conditions, within the time set and with a sufficient amount of thawed reducing agent to ensure a safe and reliable operation of said SCR system.

The method may comprise the step to:

- determine said first temperature value, second temperature value, first quantity value and second quantity value based on said determined level.

Thus, a safe, robust and reliable operation of said SCR system is achieved.

The method may also comprise the step to:

- add extra heating time after the start up suitability has been reached, in order to compensate for a reduced level in relation to a possible highest level of reducing agent in said container. Thus, a safe, robust and reliable operation of said SCR system is achieved.

The method may also comprise the step to:

- increase said first temperature value, second temperature value, first quantity value and second quantity value, in order to compensate for a reduced level in relation to a possible highest level of reducing agent in said container. Accordingly, a simple and automated method is achieved to achieve a reliable operation of said SCR system. Accordingly, a cost effective method is provided, which achieves at least some of said objectives.

The method may also comprise the step to:

- increase said first temperature value, second temperature value, first quantity value and second quantity value, based on said determined level of said reducing agent. This is carried out to compensate for a reduced level in relation to a possible highest level of reducing agent in said container. The method may also comprise the step to:

- include said level of said reducing agent in said container at the determination of the start up suitability, relating only to said dosage.

The method may also comprise the step to:

- compensate for a reduced level in relation to a possible highest level, so that the more reduced the level, the longer the heating time before each start up.

Accordingly, both the circulation start and the dosage start may be delayed in a suitable manner compared to prior art technology, to achieve a reliable method for an SCR system, wherein at least part of said reducing agent in said container is in solid (frozen) form.

The method may also comprise the step to:

- activate start up of said circulation and said dosage, when start up is determined to be suitable.

Advantageously, partially filled containers for reducing agent will not contain too small an amount of thawed reducing agent at the start of circulation of reducing agent, and/or at the start of dosage of reducing agent.

According to one aspect of the present invention, an SCR system is provided, comprising a pump and a dosage unit, comprising:

- elements adapted to determine a need to heat a reducing agent for exhaust purification arranged in a container;

- elements adapted to, when a need of heating is determined, continuously heat said reducing agent with a heating medium circulating through said container;

- elements adapted to continuously determine a temperature of said reducing agent in said container; - elements adapted to determine a level of said reducing agent in said container;

- elements adapted to continuously determine an accumulated amount of thawed reducing agent;

- elements adapted to determine that start up of circulation of said reducing agent is suitable when said determined temperature of said reducing agent in said container exceeds a predetermined first temperature value, and/or when the determined accumulated amount of thawed reducing agent exceeds a predetermined first quantity value; and/or

- elements adapted to determine that start up of dosage of said reducing agent is suitable when said determined temperature of said reducing agent in said container exceeds a predetermined second temperature value, and/or when the determined accumulated amount of thawed reducing agent exceeds a predetermined second quantity value; and

- elements adapted, when determining the start up suitability relating to said circulation and/or said dosage, to include said level of said reducing agent in said container;

The SCR system may comprise:

- elements adapted to determine said first temperature value, second temperature value, first quantity value and second quantity value, based on said determined level.

The SCR system may comprise:

- elements adapted to add extra heating time after suitability for start up has been reached, in order to compensate for a reduced level in relation to a possible highest level of reducing agent in said container.

The SCR system may comprise:

- elements adapted to increase said first temperature value, second temperature value, first quantity value and second quantity value, in order to compensate for a reduced level in relation to a possible highest level of reducing agent in said container.

The SCR system may comprise: - elements adapted to include said level of said reducing agent in said container at the determination of the start up suitability, relating only to said dosage.

The SCR system may comprise:

- elements adapted to compensate for a reduced level in relation to a possible highest level, so that the more reduced the level, the longer the heating time before each start up.

The SCR system may comprise:

- elements adapted to activate start up of said circulation and said dosage, when start up is determined to be suitable.

According to one aspect of the present invention, a motor vehicle is provided comprising an SCR system according to any of the claims 7-12.

Said motor vehicle may be a truck, a bus or a car.

According to one aspect of the present invention, a computer program is provided for an SCR system, where said computer program comprises program code to cause an electronic control device, or a computer connected to the electronic control device, to perform the steps according to any of claims 1 -6.

According to one aspect of the present invention, a computer program is provided for an SCR system, where said computer program comprises program code to cause an electronic control device, or another computer connected to the electronic control device, to perform the steps according to any of claims 1 -6, when said program code is executed in said electronic control device or said other computer.

According to one aspect of the present invention, a computer program is provided in an SCR system, wherein said computer program comprises program code stored in a computer-readable medium in order to cause an electronic control device, or another computer connected to the electronic control device, to perform the steps according to any of the claims 1 -6. According to one aspect of the present invention, a computer program product, comprising program code stored in a computer-readable medium, is provided to perform the method steps according to any of the claims 1 -6, when said program code is executed in an electronic control device or in another computer connected to the electronic control device.

According to one aspect of the present invention, a computer program product, comprising program code stored in a non-volatile way in a computer-readable medium, is provided to perform the method steps according to any of the claims 1 -6, when said program code is executed in an electronic control device or in another computer connected to the electronic control device.

Additional objectives, advantages and novel features of the present invention will be apparent to one skilled in the art from the following details, and through exercising the invention. While the invention is described below, it should be apparent that the invention is not limited to the specifically described details. One skilled in the art, having access to the teachings herein, will recognise additional applications, modifications and incorporations in other areas, which are within the scope of the invention.

GENERAL DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the additional objects and advantages thereof, reference is now made to the following detailed description, which is to be read together with the accompanying drawings, in which the same reference designations pertain to identical parts in the various figures, and in which:

Figure 1 schematically illustrates a vehicle, according to one embodiment of the invention;

Figure 2 schematically illustrates a sub-system of the vehicle displayed in Figure 1 , according to one embodiment of the invention;

Figure 3 schematically illustrates a sub-system of the vehicle displayed in Figure 1 , according to one embodiment of the invention; Figure 4a schematically illustrates a flow chart of a method, according to one embodiment of the invention;

Figure 4b schematically illustrates in more detail a flow chart of a method, according to one embodiment of the invention;

Figure 5 schematically illustrates a computer, according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE FIGURES

A side view of a vehicle 100 is shown with reference to Figure 1 . The exemplary vehicle 100 consists of a tractor 1 10 and a trailer 1 12. The vehicle may be a heavy goods vehicle, such as a truck or a bus. The vehicle may, alternatively, be a car.

The term "link" herein refers to a communications link, which may be a physical line, such as an opto-electronic communication line, or a non-physical line, such as a wireless connection, e.g. a radio or microwave link.

The term "reducing agent", as used herein, means a substance used to react with certain emissions in an SCR system. These emissions may be e.g. NO_x gas. The said reductant is, according to one embodiment, also known as AdBlue. Obviously other types of reductants may be used. Herein, AdBlue is provided as an example of a reducing agent, but a person skilled in the art will realise that the innovative method and the SCR system according to the invention may be realised for other types of reducing agent, with the required adaptations, such as adaptations to an adequate freezing point for selected reducing agents, and in control algorithms in order to execute program code in accordance with the innovative method.

The term "heating element", as used herein, refers to a device, which is arranged to heat an adjacent component, such as a conduit, a pump or dosage unit containing said reducing agent. The heating elements specified herein are thus arranged to heat the reducing agent at different positions in the vehicle 100. A heating element may be an electrical heating element which is powered with e.g. one or several batteries (not displayed). Alternatively, a heating element may be a coolant-based heating element, which uses coolant from an engine in the vehicle to heat said reducing agent in a container for reducing agent in the SCR system.

It should be pointed out that the invention is suitable for application in a suitable SCR system, and is therefore not limited to SCR systems in motor vehicles. According to one aspect of the invention, the innovative method and the innovative SCR system are well suited to platforms other than motor vehicles, comprising an SCR system, e.g. watercraft. The watercraft may be of any suitable type, such as motor boats, ships, ferries or vessels.

According to one aspect of the invention, the innovative method and the innovative SCR system are also well suited for e.g. systems comprising tractors, dump trucks, machinery, industrial engines and/or engine-powered industrial robots.

According to one aspect of the invention, the innovative method and the innovative SCR system are also well suited for different types of power plants, e.g. electricity power plants comprising a diesel generator.

The innovative method and the innovative SCR system are also well suited for any suitable engine system, comprising an engine and an SCR system, e.g. in a locomotive or another platform.

The innovative method and the innovative SCR system are well suited for a system comprising an NO_x generator, e.g. a diesel engine whose exhausts must be purified.

The term "conduit" herein means a passage to hold and transport a fluid, such as a reducing agent in liquid form. The conduit may be a conduit of any dimension. The conduit may consist of any suitable material, such as plastic, rubber or metal. Figure 2 shows a sub-system 299 in the vehicle 100. The sub-system 299 may be arranged in the tractor 1 10. The sub-system 299 may form part of an SCR system. According to this example, the sub-system 299 comprises a container 205, which is arranged to hold a reducing agent. The container 205 is arranged to comprise a suitable amount of reducing agent and is also arranged to be filled as needed.

A first pipe 271 is arranged to lead the reducing agent to a pump 230 from the container 205. Said pump 230 is arranged to pump the reducing agent from the container 205, via the first conduit 271 and via a second conduit 272, to add said reducing agent to a dosage device 250. The pump 230 is arranged to pressurise the reducing agent in the second pipe 272.

The dosage device 250 is arranged to add said reducing agent to an exhaust system (not displayed) in the vehicle 100. More precisely, the dosage device 250 is arranged to, in a controlled manner, add a suitable amount of reducing agent to an exhaust system in the vehicle 100. According to this embodiment, an SCR catalyst (not displayed) is arranged downstream of a position where the reducing agent is added. The amount of reducing agent which is added in the exhaust system is intended to be used in the SCR catalyst in order to reduce the amount of undesired emissions.

A third conduit 273 is arranged between the dosage device 250 and the container 205. The third conduit 273 is arranged to lead back to the container 205 a certain amount of the reducing agent, which has been fed to the dosage device 250.

A first fluid conduit 281 is arranged to hold and transport a fluid. Said fluid is a heating medium. Said fluid may be a coolant for an engine (not displayed) in the vehicle 100. The first fluid conduit 281 is partly arranged in the container 205 to heat the reducing agent contained therein. The first fluid conduit 281 is partly arranged in the container 205 in order to, where applicable, thaw frozen reducing agent contained therein through energy transfer. According to this example, the first fluid conduit 281 is arranged to lead coolant that has been heated by the vehicle's engine back to the engine of the vehicle 100, in a closed loop through the container 205 and a second fluid conduit 282. According to one example embodiment, a pump (not displayed) is arranged to feed said fluid through said first fluid conduit 281 and said second fluid conduit 282, to achieve heating of said reducing agent in said container 205. In case where said fluid comprises coolant for said engine in the vehicle, said pump may consist of a normal coolant pump.

According to another example embodiment, said fluid may be fed through said first fluid conduit 281 and said second fluid conduit 282, to achieve heating of said reducing agent in said container 205 via said pump 230. Hereat, said pump 230 is arranged to feed said reducing agent as well as said fluid. It should be pointed out that said reducing agent and said fluid are not mixed in this context, but fed through separate loops.

Said pump 230 may also be referred to as a feeding element or a circulation pump. Said pump 230 may be of any suitable type. Said pump 230 may be a membrane pump. Said pump 230 may, according to one embodiment, be heated with a circulating heating medium. According to one example, e.g. the first conduit 271 may be arranged to heat the pump 230 downstream of said container 205. According to one alternative, the pump may be heated with a circulating medium, which is supplied by equipment intended for this purpose.

According to one embodiment, the first fluid conduit 281 is partly configured as a spiral, which is arranged around said first conduit 271 and said third conduit 273 located in the container 205, as schematically illustrated by Figure 2. This achieves an efficient heating or thawing of reducing agent in the container 205. The first fluid conduit 281 may also have another suitable shape, e.g. a U shape.

A first heating element 261 is arranged at the second conduit 272, in order to heat the reducing agent therein when needed. A second heating element 262 is arranged at the dosage valve 250, in order to heat both the dosage valve 250 and the reducing agent therein when needed. A third heating element 263 is arranged at the third conduit 273, in order to heat the reducing agent therein when needed. Said first heating element 261 , second heating element 262 and third heating element 263 may be electrical heating elements. According to one example embodiment, the conduits 271 , 272 and 273 may be arranged to be heated with coolant for cooling the vehicle's engine. Hereat, so-called two-channel conduits may be provided, wherein two separate passages for reducing agent and coolant are arranged in close proximity to each other for efficient heat transfer.

It should be pointed out that according to the invention it is possible to place a heating element in any suitable place of the sub-system 299, e.g. inside the container 205. Different configurations of said heating element are possible to realise. According to one example, the heating element may be placed in said container 205 to heat reducing agent therein. Said heating element may be an electrical heating element. Sad heating element may comprise a suitable number of separate heating elements. Said electrical heating element may be a spiral-shaped electrical loop, which loop, according to one example, may be arranged around the conduits 271 and 273 inside the container 205.

A first control device 200 is arranged to control the operation of said first heating element 261 , said second heating element 262 and said third heating element 263 in a suitable manner. Said first control device 200 may be arranged to control the operation of said first heating element 261 , said second heating element 262 and said third heating element 263 independently of each other. According to one embodiment, the first control device is arranged to activate and operate said heating element, when circulation of said reducing agent in the SCR system is deemed suitable.

Said first control device 200 is arranged for communication with a first temperature sensor 221 via a link L221 . Said first temperature sensor 221 is arranged to detect a prevailing temperature Tred of the reducing agent in the place where the sensor is fitted. According to one embodiment, the first temperature sensor 221 is arranged in immediate proximity to the first conduit 271 and/or the third conduit 273 in the container 205. According to one embodiment, the first temperature sensor 221 is arranged in immediate proximity to the first conduit 271 and/or the third conduit 273 at the bottom of the container 205. According to one embodiment, the first temperature sensor 221 is arranged in a lower part of the container 205. The temperature sensor 221 is arranged to continuously send signals, comprising information about said prevailing temperature Tred of the reducing agent, to the first control device 200 via the link L221 .

The first control device 200 is arranged for communication with the pump 230 via a link L230. The first control device 200 is arranged to control the operation of the pump 230, in order to e.g. control the flow of the reducing agent within the subsystem 299. The first control device 200 is arranged to activate circulation of said reducing agent when deemed suitable, according to one embodiment of the present invention.

The first control device 200 is arranged for communication with the dosage device 250 via a link L250. The first control device 200 is arranged to control the operation of the dosage device 250 in order to e.g. control the supply of reducing agent to the exhaust system of the vehicle 100. The first control device 200 is arranged to activate circulation of said reducing agent via said pump 230 when deemed suitable, according to one embodiment of the present invention. The first control device 200 is arranged to activate dosage of said reducing agent when deemed suitable, according to one embodiment of the present invention.

A second control device 210 is arranged for communication with the first control unit 200 via a link L210. The second control device 210 may be detachably connected to the first control device 200. The second control device 210 may be a control unit external to the vehicle 100. The second control device 210 may be arranged to carry out the method steps according to the invention. The second control device 210 may be used to transfer program code to the first control device 200, in particular program code to perform the method according to the invention. Alternatively, the second control device 210 may be arranged for communication with the first control device 200 via an internal network in the vehicle. The second control device 210 may be arranged to carry out substantially similar functions as the first control device 200.

According to the embodiment, which is schematically illustrated with reference to Figure 2, the first control device 200 is arranged to control the pump 230 in such a way that, where applicable, at least a part of said thawed reducing agent is extracted from the container 205, in order to enable heating of the same with at least one of the heating elements 261 , 262 and 263 outside the container 205. The first control device 200 is also arranged to control the pump 230, in such a way that the thawed part of said reducing agent is recycled to the container 205, before dosage of the same via the dosage unit 250 is initiated in the SCR system.

Figure 3 schematically illustrates a part of the sub-system 299, as described with reference to Figure 2. Figure 3 omits a part of the components described with reference to Figure 2.

Said first control device 200 is arranged for communication with a second temperature sensor 222, via a link L222. Said second temperature sensor 222 is arranged to continuously measure a prevailing temperature T2 of said fluid upstream of said container 205. Said second temperature sensor 222 is arranged to continuously send signals comprising information about a prevailing temperature T2 of said fluid to the first control device 200, via said link L222. Said second temperature sensor 222 may be arranged in immediate proximity to the container 205 at an upstream side thereof, or at the vehicle's engine, or at a suitable place between said engine and said container 205.

Said first control device 200 is arranged for communication with a third temperature sensor 223, via a link L223. Said third temperature sensor 223 is arranged to continuously measure a prevailing temperature T3 of said fluid downstream of said container 205. Said third temperature sensor 223 is arranged to continuously send signals comprising information about a prevailing temperature T3 of said fluid to the first control device 200, via said link L223. Said third temperature sensor 223 may be arranged in immediate proximity to the container 205 at a downstream side thereof, or at the vehicle's engine, or at a suitable place between said engine and said container 205. According to one example, said third temperature sensor 223 may be arranged at the pump 230.

According to one embodiment, said first control device 200 is arranged to communicate with said first temperature sensor 221 , second temperature sensor 222 and said third temperature sensor 223, via said second control device 210, which may be signal-connected to said first temperature sensor 221 , second temperature sensor 222 and said third temperature sensor 223.

Said first conduit 281 is arranged to lead a heating fluid to achieve thawing of frozen reducing agent in the container 205. According to one example, said first conduit is arranged for cooling of an engine in the vehicle. At said cooling of the engine, thermal energy is transferred from said engine to said fluid. According to one example, said fluid is a coolant in an engine cooling system. According to one example, said pump 230 is arranged to circulate said fluid in a closed loop from the engine to the container 205, and back to the engine, via the conduit 282. It should be pointed out that said reducing agent and said heating fluid never mix, but are physically separated by said conduits.

According to an alternative embodiment, a heating medium external to the vehicle may be used. According to this embodiment, a separate container with a heating medium may be used, whereat the container may be connected to a circulation conduit in the vehicle. Hereat, either a feed device external to the vehicle, or a feed device in the vehicle intended for this purpose, may be used for circulation of said heating fluid.

According to one embodiment, the first control device 200 is arranged to, based on the received signals comprising a prevailing temperature Tred of the reducing agent at the placement of the temperature sensor 221 and a prevailing temperature T2 of the fluid upstream of said container 205, control the operation of the pump 230 and the dosage unit 250.

According to one embodiment, the first control device 200 is arranged to, based on the received signals comprising a prevailing temperature Tred of the reducing agent at the placement of the temperature sensor 221 and a prevailing temperature T2 of the fluid upstream of said container 205, determine a temperature difference therebetween.

According to one embodiment, the first control device 200 is arranged to, based on the received signals comprising a prevailing temperature T3 of the fluid downstream of said container 205 and a prevailing temperature T2 of the fluid upstream of said container 205, to determine a temperature difference therebetween, in accordance with one aspect of the innovative method.

The first control device 200 may be arranged to continuously determine an

accumulated amount V of thawed reducing agent in the container, based on said determined temperature difference T3-T2 of said reducing agent, and the time elapsed for the heat transfer.

The first control device 200 may be arranged to continuously determine an

accumulated amount V of thawed reducing agent in the container, based on said determined temperature difference T2-Tred of said reducing agent, and the time elapsed for the heat transfer.

Said accumulated amount of thawed reducing agent V in the container 205 may hereat be modelled/calculated/estimated in a suitable manner.

A level sensor 245 is arranged in said container 205. Said level sensor 245 is arranged for communication with the first control device 200, via a link L245. Said level sensor 245 is arranged to continuously or intermittently determine a prevailing level L of said reducing agent in said container 205. Said level sensor is arranged to continuously or intermittently send signals comprising information about said determined prevailing level L of said reducing agent to the first control device 200, via said link L245. Said level sensor 245 may be a float sensor. Said level sensor 245 may comprise a suitable electronic, opto-electronic or electromechanical sensor. Said level sensor 245 may e.g. comprise a laser sensor or a UV sensor.

The first control device 200 is arranged to determine a need to heat a reducing agent arranged in said container 205, for exhaust purification via a heating medium circulating through said container. The first control device 200 is arranged to initiate operation of the SCR system according to the present invention, when it has been determined that there is a need to heat (thaw) said reducing agent in said container. The first control device 200 is arranged to continuously determine a temperature Tred of said reducing agent in said container 205. This may be carried out by means of said first temperature sensor 221 . The first control device 200 is arranged to determine a level L of said reducing agent in said container 205. This may be achieved via said level sensor 245. The first control device 200 is arranged to continuously determine/calculate/model/estimate an accumulated amount V of thawed reducing agent in said container 205.

The first control device 200 is arranged to determine that start up of circulation of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined first temperature value Th1 , and/or when the determined accumulated amount V of thawed reducing agent exceeds a predetermined first quantity value VTh1 .

The first control device 200 is arranged to determine that start up of dosage of said reducing agent is suitable, when said determined temperature Tred of said thawed reducing agent in said container 205 exceeds a predetermined second temperature value Th2, and/or when the determined accumulated amount V of thawed reducing agent exceeds a predetermined second quantity value VTh2.

The first control device 200 is arranged to include said level L of said reducing agent in said container at the determination of the start up suitability, relating to said circulation and said dosage.

The first control device 200 may be arranged to determine said first temperature value Th1 , second temperature value Th2, first quantity value VTh1 and second quantity value VTh2 based on said determined level L. This may comprise increasing said first predetermined temperature value Th1 . According to one example, said first predetermined temperature value may be increased by 3 or 7 degrees Celsius, such as from -5 degrees Celsius to -2 or 2 degrees Celsius. This may comprise increasing said second predetermined temperature value Th2. According to one example, said second predetermined temperature value Th2 may be increased by 1 or 5 degrees Celsius, such as from -1 degrees Celsius to 0 or 4 degrees Celsius. Similarly, said first quantity value VTh1 and said second quantity value VTh2 may be increased to suitable quantity values, respectively.

The first control device 200 may be arranged to add extra heating time after the start up suitability has been reached, to compensate for a reduced level L in relation to a possible highest level of reducing agent in said container. Hereat, said first predetermined temperature value Th1 and said second predetermined temperature value Th2 are not adjusted. Instead, initiating circulation of reducing agent and/or initiating dosage of reducing agent is controlled, in such a way that the respective initiation is delayed by a suitable time period after said first predetermined

temperature value Th1 and said second predetermined temperature value Th2 have been reached by said thawed reducing agent in said container 205.

Hereat, said first predetermined quantity value VTh1 and said second predetermined quantity value VTh2 are not adjusted. Instead, initiating circulation of reducing agent and/or initiating dosage of reducing agent is controlled, in such a way that the respective initiation is delayed by a suitable time period after said first predetermined quantity value VTh1 and said second predetermined quantity value Th2 have been reached, by said thawed reducing agent in said container 205.

Said respective time periods are suitable time periods. Said respective time periods may be 2, 5 or 10 minutes. Said time periods may be mutually different. According to one embodiment, a delay with respect to initiation of dosage of reducing agent is substantially longer than said delay relating to said initiation of circulation of reducing agent. According to one embodiment, said delay with respect to initiation of dosage of reducing agent is 5 minutes and said delay relating to said initiation of circulation of reducing agent is zero (0) minutes. According to one embodiment, said delay with respect to said initiation of dosage of reducing agent is 10 minutes and said delay relating to said initiation of circulation of reducing agent is 2 minutes.

The first control device 200 may be arranged to increase said first temperature value Th1 , second temperature value Th2, first quantity value VTh1 and second quantity value Vth2 in order to compensate for a reduced level L in relation to a possible highest level of reducing agent in said container 205. The first control device 200 may be arranged to comprise said level L of said reducing agent in said container 205 at the determination of start up suitability, with respect to only said dosage. Accordingly, no delay in initiating circulation of reducing agent takes place based on said level L.

The first control device 200 is arranged to compensate for a reduced level L in relation to a possible highest level, so that the more reduced the level, the longer the heating time before each start up. This may also entail that changes of said first temperature value Th1 , second temperature value Th2, first quantity value Vth1 and second quantity value Vth2 are greater, the more reduced the level L is in relation to a possible highest level.

The first control device 200 is arranged to activate start up of said circulation and said dosage respectively, when start up is determined to be suitable. Activation of start up of said circulation and said dosage may be deemed suitable, when at least one of said first temperature value Th1 , second temperature value Th2, first quantity value Vth1 and second quantity value Vth2 is reached. Said at least one value and/or measurement has been corrected hereat, based on said reduced level L in relation to a possible highest level.

Figure 4a schematically illustrates a flow chart of a method for an SCR system comprising a pump 230 and a dosage unit 250. The method comprises an initial method step of the procedure s401 . Step s401 comprises the steps of:

- determine a need to heat a reducing agent for exhaust purification, arranged in a container 205;

- when a need of heating is determined, continuously heat said reducing agent with a heating medium circulating through said container 205;

- continuously determine a temperature Tred of said reducing agent in said container 205;

- determine a level L of said reducing agent in said container 205;

- continuously determine an accumulated amount V of thawed reducing agent; - determine that start up of circulation of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined first temperature value Th1 , and/or when the determined accumulated amount V of thawed reducing agent exceeds a predetermined first quantity value VTh1 ; and/or

- determine that start up of dosage of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined second temperature value Th2, and/or when the determined accumulated amount V of thawed reducing agent exceeds a predetermined second quantity value VTh2; wherein said level L of said reducing agent in said container 205 is included in s440 at the determination of the start up suitability relating to said circulation and/or said dosage.

Following the method step s401 the method is completed.

Figure 4b schematically illustrates a flow chart of a method for an SCR system comprising a pump 230 and a dosage unit 250. The method may be activated when it is deemed that there is a need to heat a reducing agent arranged in a container 250, for exhaust purification via a heating medium circulating through said container 205. This may occur at start up of the vehicle 100. A need to heat said reducing agent may be determined if said reducing agent is at least partly frozen in said container 205. This may be determined based on information about the prevailing temperature of the ambient air, the prevailing temperature of the reducing agent, the exposure time with regard to the temperature of the ambient air, the type of reducing agent (freezing point, etc.)

The method comprises an initial method step of the procedure s410. The method step s410 may comprise the step to continuously determine a temperature Tred of said reducing agent in said container 205. This may be carried out through said first temperature sensor 221 . Alternatively, said temperature Tred may be

estimated/calculated/modelled via the first control device 200, according to

procedures stored therein. Following the method step s410, a subsequent method step s420 is completed. The method step s420 may comprise the step of determining a level L of said reducing agent in said container 205. This may be achieved via said level sensor 245. Alternatively, said level L may be estimated/calculated/modelled via the first control device 200, according to procedures stored therein. Following the method step s420, a subsequent method step s430 is completed.

The method step s430 may comprise the step of continuously determining an accumulated amount of thawed reducing agent V in the container 205. This may occur via the first control device 200, based on information about e.g. the first temperature T2 of said reducing agent upstream of said container, and the second temperature T3 of said reducing agent downstream of said container 205. This may occur via the first control device 200, based on information about a difference between the first temperature T2 of said reducing agent upstream of said container 205, and the second temperature T3 of said reducing agent downstream of said container 205. According to one embodiment, the accumulated amount of thawed reducing agent V in the container 205 may be modelled/calculated/estimated via the first control device 200, according to procedures stored therein. Following the method step s430, a subsequent method step s440 is completed.

The method step s440 may comprise the step of determining that start up of circulation of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined first

temperature value Th1 , and/or when the determined accumulated amount V of thawed reducing agent exceeds a predetermined first quantity value VTh1 .

The method step s440 may comprise the step of determining that start up of dosage of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined second temperature value Th2, and/or when the determined accumulated amount V of thawed reducing agent exceeds a predetermined second quantity value VTh2;

The method step s440 may comprise that said level L of said reducing agent in said container 205 is included at the determination of the start up suitability, relating to said circulation and/or said dosage. Following the method step s440, a subsequent method step s450 is completed.

The method step s450 may comprise the step of, where applicable, starting

circulation of reducing agent in said SCR system. Hereat, said reducing agent may advantageously be heated. Heating may be effected via at least one of the heating elements 261 , 262, and 263. Heating may also, or as a complement, be effected via said fluid in the conduit 281 .

The timing for starting said circulation is determined herein according to the

innovative method based on said determined level L of said reducing agent in said container 205. Following the method step s450, a subsequent method step s460 is completed.

The method step s460 may comprise the step of, where applicable, starting said dosage of said reducing agent via said dosage unit 250. Here it should be

understood that actual dosage may not be necessary. Actual dosage is carried out according to procedures stored in said first control device 200. Here it should be pointed out that actual dosage after start of dosage only occurs when it is suitable, depending on different factors, such as the prevailing load and/or exhaust

temperature of the vehicle's engine.

The timing for starting said dosage is determined hereat according to the innovative method, based on said determined level L of said reducing agent in said container 205.

Following the method step s460, the method is completed.

With reference to Figure 5, a diagram of an embodiment of a system 500 is shown. The control units 200 and 210, which are described with reference to Figure 2, may in one embodiment comprise the system 500. The unit 500 includes a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The nonvolatile memory 520 has a first memory part 530, wherein a computer program, such as an operating system, is stored to control the function of the unit 500. Further, the unit 500 includes a bus controller, a serial communications port, an I/O device, an A/D converter, a date-time input and transmission unit, an event counter and an interrupt controller (not shown). The non-volatile memory 520 also has a second memory part 540.

A computer program P is provided, comprising procedures to, for an SCR system comprising a pump 230 and a dosage unit 250:

- determine a need to heat a reducing agent for exhaust purification arranged in a container 205;

- continuously determine a temperature Tred of said reducing agent in said container 205; and

- determine a level L of said reducing agent in said container 205.

The computer program P may comprise procedures to continuously determine an accumulated amount of thawed reducing agent. The computer program P may comprise procedures to determine that start up of circulation of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined first temperature value Th1 , and/or when the determined accumulated amount V of thawed reducing agent exceeds a

predetermined first quantity value VTh1 . The computer program P may comprise procedures to determine that start up of dosage of said reducing agent is suitable, when said determined temperature Tred of said reducing agent in said container 205 exceeds a predetermined second temperature value Th2, and/or when the

determined accumulated amount V of thawed reducing agent exceeds a

predetermined second quantity value, VTh2. The computer program P may comprise procedures to include said level L of said reducing agent in said container 205 at the determination of the start up suitability, relating to said circulation and/or said dosage.

The computer program P may comprise procedures to determine said first

temperature value Th1 , second temperature value Th2, first quantity value VTh1 and second quantity value VTh2, based on said determined level L. The computer program P may comprise procedures to add extra heating time after the start up suitability has been reached, in order to compensate for a reduced level L in relation to a possible highest level of reducing agent in said container 205.

The computer program P may comprise procedures to increase said first temperature value Th1 , second temperature value Th2, first quantity value VTh1 and second quantity value Vth2, in order to compensate for a reduced level L in relation to a possible highest level of reducing agent in said container 205.

The computer program P may comprise procedures to include said level of said reducing agent in said container 205 at the determination of the start up suitability, relating to only said dosage.

The computer program P may comprise procedures to compensate for a reduced level L in relation to a possible highest level, so that the more reduced the level, the longer the heating time before each start up.

The computer program P may comprise procedures to activate start up of said circulation and said dosage when start up is determined to be suitable.

The program P may be stored in an executable manner, or in a compressed manner, in a memory 560 and/or a read/write memory 550.

A statement that the data processing unit 510 performs a certain function means that the data processing unit 510 performs a certain part of the program stored in the memory 560, or a certain part of the program stored in the read/write memory 550.

The data processing unit 510 may communicate with a data port 599 via a data bus 515. The non-volatile memory 520 is intended for communication with the data processing unit 510 via a data bus 512. The separate memory 560 is intended for communication with the data processing unit 510 via a data bus 51 1 . The read/write memory 550 is arranged for communication with the data processing unit 510 via a data bus 514. The links L210, L221 , L222, L223, L230, L245 may e.g. be connected to the data port 599 (see Figure 2 and Figure 3).

When data is received in the data port 599, it is temporarily stored in the second memory part 540. When input data received is temporarily stored, the data processing unit 510 is ready to carry out execution of code in the manner described above. According to one embodiment, signals received in the data port 599 comprise information about the prevailing temperature Tred of said reducing agent in the container 205. According to one embodiment, signals received in the data port 599 comprise information about the prevailing temperature T2 of the said heating medium upstream of the container 205. According to one embodiment, signals received in the data port 599 comprise information about a prevailing temperature T3 of the said heating medium downstream of the container 205.

Parts of the methods described herein may be carried out by the unit 500 with the help of the data processing unit 510, which runs the program stored in the memory 560 or the read/write memory 550. When the unit 500 runs the program, the procedures described herein are executed.

The foregoing description of the preferred embodiments of the present invention has been furnished for illustrative and descriptive purposes. It is not intended to be exhaustive, or to limit the invention to the variants described. Many modifications and variations will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order to best explicate the principles of the invention and its practical applications, and to thereby enable one skilled in the art to understand the invention in terms of its various embodiments and with the various modifications that are applicable to its intended use.

Claims

1 . Method for an SCR system comprising a pump (230) and a dosage unit (250), comprising the steps to:

- determine (s410) a need to heat a reducing agent for exhaust purification arranged in a container (205);

- when a need of heating is determined, continuously heat said reducing agent with a heating medium circulating through said container (205);

- continuously determine (s420) a temperature (Tred) of said reducing agent in said container (205);

- determine a level (L) of said reducing agent in said container (205),

characterised by the steps of:

- to continuously determine (s430) an accumulated amount (V) of thawed reducing agent;

- to determine (s440) that start up of circulation of said reducing agent is suitable, when said determined temperature (Tred) of said reducing agent in said container (205) exceeds a predetermined first temperature value (Th1 ), and/or when the determined accumulated amount (V) of thawed reducing agent exceeds a

predetermined first quantity value (VTh1 ); and/or

- determine (s440) that start up of dosage of said reducing agent is suitable, when said determined temperature (Tred) of said reducing agent in said container exceeds a predetermined second temperature value (Th2), and/or when the determined accumulated amount (V) of thawed reducing agent exceeds a predetermined second quantity value (VTh2);

wherein said determined level (L) of said reducing agent in said container (205) is included (s440) at the determination of the start up suitability of said circulation, and/or of said dosage, and wherein said first temperature value (Th1 ), second temperature value (Th2), first quantity value (VTh1 ) and second quantity value (VTh2) are determined based on said determined level (L).

2. Method according to claim 1 , also comprising the step to:

- add extra heating time after the start up suitability has been reached, in order to compensate for a reduced level (L) in relation to a possible highest level of reducing agent in said container (205).

3. Method according to any of claims 1 or 2, further comprising the step to:

- increase said first temperature value (T1 ), second temperature value (T2), first quantity value (V1 ) and second quantity value (V2) in order to compensate for a reduced level (L), in relation to a possible highest level of reducing agent in said container (205).

4. Method according to any of claims 1 -3, further comprising the step to:

- include said level (L) of said reducing agent in said container (205) at the

determination of the start up suitability, relating only to said dosage.

5. Method according to any of claims 1 -4, further comprising the step to:

- compensate for a reduced level (L) in relation to a possible highest level, so that the more reduced the level, the longer the heating time before each start up.

6. Method according to any of claims 1 -5, further comprising the step to:

- activate start up of said circulation and said dosage when start up is determined to be suitable.

7. SCR system comprising a pump (230) and a dosage unit (250), comprising:

- elements (200; 210; 500) adapted to determine the need to heat a reducing agent for exhaust purification arranged in a container (205);

- elements (200; 210; 500; 230; 281 ) adapted to, when a need of heating is determined, continuously heat said reducing agent with a heating medium circulating through said container (205);

- elements (200; 210; 500; 221 ) adapted to continuously determine a temperature (Tred) of said reducing agent in said container (205);

- elements (200; 210; 500; 245) adapted to determine a level (L) of said reducing agent in said container (205);

characterised by:

- elements (200; 210; 500) adapted to continuously determine an accumulated amount (V) of thawed reducing agent;

- elements (200; 210; 500) adapted to determine that start up of circulation of said reducing agent is suitable when said determined temperature (Tred) of said reducing agent in said container (205) exceeds a predeternnined first temperature value (Th1 ), and/or when the determined accumulated amount (V) of thawed reducing agent exceeds a predetermined first quantity value (VTh1 ); and/or

- elements (200; 210; 500) adapted to determine that start up of dosage of said reducing agent is suitable when said determined temperature (Tred) of said reducing agent in said container (205) exceeds a predetermined second temperature value (Th2), and/or when the determined accumulated amount (V) of thawed reducing agent exceeds a predetermined second quantity value (VTh2); and

- elements (200; 210; 500) adapted to include said determined level (L) of said reducing agent in said container (205) at the determination of the start up suitability of said circulation and/or said dosage, wherein said elements (200, 210, 500) are adapted to determine said first temperature value (Th1 ), second temperature value (Th2), first quantity value (VTh1 ) and second quantity value (VTh2) based on said determined level (L).

8. SCR system according to claim 7, comprising:

- elements (200; 210; 500) adapted to add extra heating time after the reached start up suitability, in order to compensate for a reduced level (L) in relation to a possible highest level of reducing agent in said container (205).

9. SCR system according to any of claims 7 or 8, comprising:

- elements (200; 210; 500) adapted to increase said first temperature value (T1 ), second temperature value (Th2), first quantity value (VTh1 ) and second quantity value (VTh2), in order to compensate for a reduced level (L) in relation to a possible highest level of reducing agent in said container (205).

10. SCR system according to any of claims 7-9, comprising:

- elements (200; 210; 500) adapted to include said level (L) of said reducing agent in said container (205) at the determination of the start up suitability, relating only to said dosage.

1 1 . SCR system according to any of claims 7-10, comprising: - elements (200; 210; 500) adapted to compensate for a reduced level (L) in relation to a possible highest level, so that the more reduced the level (L), the longer the heating time before each start up

12. SCR system according to any of claims 7-1 1 , comprising:

- elements (200; 210; 500) adapted to activate start up of said circulation and said dosage when start up is determined to be suitable.

13. Motor vehicle (100; 1 10), comprising an SCR system according to any of claims 7-12.

14. Motor vehicle (100; 1 10) according to claim 13, wherein the motor vehicle is a truck, a bus or a car.

15. Computer program (P) in an SCR system, wherein said computer program (P) comprises program code to cause an electronic control device (200; 500), or another computer (210; 500) connected to the electronic control device (200; 500), to perform the steps according to any of claims 1 -6.

16. Computer program product, comprising a program code stored in a computer- readable medium, in order to perform the method steps according to any of claims 1 - 6, wherein said program code is executed in an electronic control device (200; 500), or in a computer (210; 500) connected to said electronic control device (200; 500).