TECHNICAL FIELD

The present invention relates to a method for determining safe start-up of a reducing agent provision configuration comprising a reducing agent tank, a pump unit, at least one dosing unit for providing said reducing agent to an engine emission control system of a combustion engine. In particular the present invention relates to a method for determining safe start-up of a reducing agent provision configuration during relatively cold conditions. The invention relates also to a computer program product comprising program code for a computer for implementing a method according to the invention. It relates also to a system for determining safe start-up of a reducing agent provision configuration and a motor vehicle equipped with the system.

BACKGROUND ART

Vehicle combustion engine emission control systems are today arranged with catalytic configurations e.g. for conversion of NO _x gas. The emission control systems may comprise a DOC-unit (Diesel Oxidation Catalyst), DPF-unit (Diesel Particulate Filter), SCR-unit (Selective Catalytic Reduction) and an ammonia slip catalyst. In such a system a reducing agent is provided for reducing a prevailing NO _x -content of an exhaust gas of said engine. The reducing agent is held in a tank and a pump is arranged to via lines provide pressurized fluid reducing agent to a dosing unit. Usually such a system is provided with a line for achieving a return flow of excessive reducing agent to the tank from said dosing unit. Further, the reducing agent provision configuration is arranged with heating devices for heating frozen reducing agent within the configuration. One such heating device is a line comprising flowing heated engine coolant, which line is arranged within the tank. If ambient air has a temperature below a freezing point of said reducing agent at least a portion of said reducing agent may be in a solid state (frozen).

Vehicles of today, such as heavy vehicles, are subjected to laws and regulations concerning maximum allowed exhaust gas emission regarding e.g. NO _x -content and maximum allowed start-up time of the reducing agent provision configuration when being deep frozen, i.e. when all reducing agent in the configuration is frozen. If at least a portion of the reducing agent is in a solid state there is a need to determine if and when the reducing agent provision configuration is operable regarding reducing agent provision (circulation within the system) to said dosing unit and potentially dosing of reducing agent. Various methods for deciding if dosing of the reducing agent should be initiated are known today. One such method involves the step of determining a prevailing temperature of the reducing agent provided in said tank. If said temperature exceeds a predetermined temperature value it is determined that a safe start-up of the reducing agent provision configuration is possible. Another such method involves the steps of measuring the prevailing temperature in various parts of the reducing agent provision configuration and estimating a mass of molten reducing agent within the configuration by means of a heat transfer model relating to heat transferred to the reducing agent by means of heating elements.

Accurate temperature measurements of frozen or partly frozen reducing agent being held by a tank are difficult, in particular in tanks having heating elements being arranged close to each other and/or wherein baffles may isolate temperature sensors being arranged within the reducing agent tank from a reducing agent bulk portion in said tank. Estimation of the mass of molten reducing agent by using a heat transfer model is only working properly if a relatively large portion of the reducing agent is initially frozen in the tank. If a relatively small portion, or no portion at all, of the reducing agent is frozen it is very difficult to initiate the heat transfer model to a state reflecting the actual portion of fluid reducing agent. It is further difficult to estimate a change rate of melting the frozen reducing agent because it depends on that heat transfer from heating elements to the reducing agent is correctly estimated. This is in particularly difficult if an engine coolant is used as heat transfer medium.

DE102008031645 relates to a method for measuring temperature of a reducing agent tank. By measuring a temperature change rate of the reducing agent when heating elements have been deactivated, and combining this with heating properties, information regarding a physical state and how much of the reducing agent being in liquid form is achieved. SUMMARY OF THE INVENTION

There is a need of providing a robust method for deciding when a sufficient amount of the reducing agent has been molten during cold conditions for activating circulation and/or dosing while meeting requirements of laws and regulations and minimizing the risk of consuming molten reducing agent faster than more reducing agent is melting.

An object of the present invention is to propose a novel and advantageous method for determining safe start-up of a reducing agent provision configuration. Another object of the invention is to propose a novel and advantageous system and a novel and advantageous computer program for determining safe start-up of a reducing agent provision configuration.

Another object of the present invention is to propose a novel and advantageous method providing a cost effective and reliable start-up of a reducing agent provision configuration.

Another object of the invention is to propose a novel and advantageous system and a novel and advantageous computer program providing a cost effective and reliable start-up of a reducing agent provision configuration.

Yet another object of the invention is to propose a method, a system and a computer program achieving an automated and safe start-up of a reducing agent provision configuration of a combustion engine in a relatively cold environment. Yet another object of the invention is to propose an alternative method, an alternative system and an alternative computer program for determining safe start-up of a reducing agent provision configuration.

Some of these objects are achieved with a method according to claim 1. Other objects are achieved with a system in accordance with what is depicted herein. Advantageous embodiments are depicted in the dependent claims. Substantially the same advantages of method steps of the innovative method hold true for corresponding means of the innovative system.

According to an aspect of the invention there is provided a method for determining safe start-up of a reducing agent provision configuration comprising a reducing agent tank, a pump unit, at least one dosing unit for providing said reducing agent to an engine emission control system of a combustion engine, comprising the steps of:

- activating heating of a reducing agent held in said tank to at least a level above a freezing temperature of said reducing agent; - de-activating heating of said reducing agent;

- determining a temperature change rate of a determined reducing agent temperature after de-activating heating of said reducing agent;

- determining a level of said reducing agent in said tank;

- determining a heat transfer coefficient relating to heat transfer between frozen reducing agent and fluid reducing agent;

- determining a geometric configuration of fluid reducing agent in said tank;

- determining a size of the outer surface of said geometric configuration of fluid reducing agent in said tank on the basis of said determined temperature change rate, said determined level of said reducing agent in said tank, said determined heat transfer coefficient and said determined geometric configuration of fluid reducing agent in said tank;

- determining a volume of fluid reducing agent in said tank on the basis of said determined size of the outer surface of said geometric configuration of fluid reducing agent in said tank and said geometric configuration of fluid reducing agent in said tank; and

- if the thus determined volume exceeds a predetermined value, allowing operation of said reducing agent provision configuration. Hereby a reliable and accurate method for determining safe start-up of a reducing agent provision configuration is provided. The inventive method is particularly adapted to determine safe start-up of the configuration when at least a portion of the reducing agent in said tank is frozen. Advantageously this method is applicable for reducing agent tanks of various geometries.

The step of activating heating of a reducing agent held in said tank to at least a level above a freezing temperature of said reducing agent comprises the step of heating, by means of e.g. an engine coolant line configuration provided within said tank, reducing agent to said temperature level above said freezing temperature of said reducing agent. This will typically form a characteristic geometry of molten reducing agent, which geometry is depending upon the actual arrangement of the heating member being used. Typical geometries of molten reducing agent may be e.g. a cylinder, cone or sphere. The geometry is also referred to as configuration of fluid reducing agent in said tank. Thus, by configuration of fluid reducing agent in said tank means henceforth the geometric configuration of fluid reducing agent in said tank. The geometry may be a predetermined configuration. After the heating has been turned off a temperature change rate is measured. Hereby frozen reducing agent will affect the temperature of molten reducing agent. These measurements provide information about a heat transfer process involving heat transfer from a melted portion of reducing agent to surrounding frozen reducing agent in said tank. By determining the surface area of the geometry of molten reducing agent among other parameters a volume of the geometry may be determined/estimated/calculated/modelled. By comparing the

determined volume with a predetermined threshold value it may be determined if the reducing agent provision system can be started, whereby reducing agent may be provided ( by means of a pump) to a dosing unit and, if required, dosed to exhaust gases of an engine for emission control.

Advantageously difficulties associated with complex heat transfer modelling according to prior art are eliminated by the inventive method. The inventive method is further not dependent on that the reducing agent is completely frozen in the reducing agent tank for working accurately. If the reducing agent is not frozen in said tank there will not be any frozen reducing agent cooling the molten reducing agent in said tank why the proposed solution correctly will estimate that a large portion reducing agent in said tank is melted. The method may comprise the step of determining if a temperature of characteristic parts of said reducing agent provision configuration and/or a prevailing ambient temperature are below a predetermined level. Said characteristic parts may be any of e.g. the reducing agent at a close proximity of an engine coolant line provided in said tank, a dosing unit for reducing agent and a portion of a reducing agent line outside said tank. Said predetermined level may correspond to the freezing temperature of said reducing agent.

Hereby it may be determined if it is likely that at least a portion of the reducing agent in said tank is in a solid state (frozen). Hereby it may be determined if all reducing agent provided in said tank is frozen.

The method may comprise the steps of:

- if the thus determined volume does not exceed said predetermined value, estimating a need of additional energy supply for obtaining a fluid volume exceeding said predetermined value; and

- re-activating heating of said reducing agent held in said tank.

Hereby an estimate of required heating for allowing start-up of the reducing agent provision configuration may be determined. Hereby additional heating may be controlled

automatically so as to allow start-up of the reducing agent provision configuration without unnecessary time delays, while ensuring proper operation.

According to one embodiment there is provided a system for determining safe start-up of a reducing agent provision configuration comprising a reducing agent tank, a pump unit, at least one dosing unit for providing said reducing agent to an engine emission control system of a combustion engine, comprising: - means arranged for activating heating of a reducing agent held in said tank to at least a level above a freezing temperature of said reducing agent;

- means arranged for de-activating heating of said reducing agent; - means arranged for determining a temperature change rate of a determined reducing agent temperature after de-activating heating of said reducing agent;

- means arranged for determining a level of said reducing agent in said tank;

- means arranged for determining a heat transfer coefficient relating to heat transfer between frozen reducing agent and fluid reducing agent;

- means arranged for determining a geometric configuration of fluid reducing agent in said tank;

- means arranged for determining a size of the outer surface of said geometric configuration of fluid reducing agent in said tank on the basis of said determined temperature change rate, said determined level of said reducing agent in said tank, said determined heat transfer coefficient and said determined geometric configuration of fluid reducing agent in said tank;

- means arranged for determining a volume of fluid reducing agent in said tank on the basis of said determined size of the outer surface of said geometric configuration of fluid reducing agent in said tank and said geometric configuration of fluid reducing agent in said tank; and - means arranged for, if the thus determined volume exceeds a predetermined value, allowing operation of said reducing agent provision configuration.

The system may comprise:

- means arranged for determining if a temperature of characteristic parts of said reducing agent provision configuration and/or a prevailing ambient temperature is below a predetermined level. Said predetermined level may correspond to the freezing temperature of said reducing agent.

The system may comprise: - means arranged for, if the thus determined volume does not exceed said predetermined value, estimating a need of additional energy supply for obtaining a fluid volume exceeding said predetermined value; and

- means arranged for re-activating heating of said reducing agent held in said tank.

According to an aspect of the invention there is provided a vehicle comprising a system according to what is presented herein. Said vehicle may be any from among a truck, bus or passenger car. According to an embodiment the system is provided for a marine application or industrial application. According to an aspect of the invention there is provided a computer program for determining safe start-up of a reducing agent provision configuration, wherein said computer program comprises program code for causing an electronic control unit or a computer connected to the electronic control unit to perform anyone of the method steps depicted herein, when run on said electronic control unit or said computer.

According to an aspect of the invention there is provided a computer program for determining safe start-up of a reducing agent provision configuration, wherein said computer program comprises program code stored on a computer-readable medium for causing an electronic control unit or a computer connected to the electronic control unit to perform anyone of the method steps depicted herein.

According to an aspect of the invention there is provided a computer program for determining safe start-up of a reducing agent provision configuration, wherein said computer program comprises program code stored on a computer-readable medium for causing an electronic control unit or a computer connected to the electronic control unit to perform anyone of the method steps depicted herein, when run on said electronic control unit or said computer.

According to an aspect of the invention there is provided a computer program product containing a program code stored on a computer-readable medium for performing anyo of the method steps depicted herein, when said computer program is run on an electronic control unit or a computer connected to the electronic control unit.

According to an aspect of the invention there is provided a computer program product containing a program code stored non-volatile on a computer-readable medium for performing anyone of the method steps depicted herein, when said computer program is run on an electronic control unit or a computer connected to the electronic control unit.

Further objects, advantages and novel features of the present invention will become apparent to one skilled in the art from the following details, and also by putting the invention into practice. Whereas the invention is described below, it should be noted that it is not confined to the specific details described. One skilled in the art having access to the teachings herein will recognise further applications, modifications and incorporations in other fields, which are within the scope of the invention.

BRI EF DESCRI PTION OF THE DRAWI NGS

For fuller understanding of the present invention and its further objects and adva ntages, the detailed description set out below should be read in conjunction with the accompanying drawings, in which the same reference notations denote similar items in the various diagrams, and in which:

Figure 1 schematically illustrates a vehicle according to an embodiment of the invention; Figure 2a schematically illustrates a system according to an embodiment of the invention; Figure 2b schematically illustrates a system according to an embodiment of the invention; Figure 2c schematically illustrates a portion of the reducing agent provision configuration according to an embodiment of the invention;

Figure 3 schematically illustrates a diagram according to an aspect of the invention;

Figure 4a is a schematic flowchart of a method according to an embodiment of the invention; Figure 4b is a schematic function diagram of a method according to an embodiment of the invention; and

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

DETAILED DESCRIPTION

Figure 1 depicts a side view of a vehicle 100. The exemplified vehicle 100 comprises a tractor unit 110 and a trailer 112. The vehicle 100 may be a heavy vehicle, e.g. a truck or a bus. It may alternatively be a car. It should be noted that the inventive system is applicable to various vehicles, such as e.g. a mining machine, tractor, dumper, wheel-loader, platform comprising an industrial robot, forest machine, earth mover, road construction vehicle, road planner, emergency vehicle or a tracked vehicle.

It should be noted that the invention is suitable for application in various systems comprising a combustion engine and an associated emission control system having a tank for holding a reductant. The invention is suitable for application in various systems comprising a combustion engine and a catalytic configuration. Said catalytic configuration may comprise at least one SCR-unit. Said catalytic configuration may comprise one or more DOC-units, DPF-units (Diesel Particulate Filter) and SCR-units. It should be noted that the invention is applicable to various catalytic configurations and is therefore not confined to catalytic configurations for motor vehicles. The innovative method and the innovative system according to one aspect of the invention are well suited to other platforms which comprise a combustion engine and a catalytic configuration than motor vehicles, e.g. watercraft. The watercraft may be of any kind, e.g. motorboats, steamers, ferries or ships.

The innovative method and the innovative system according to one aspect of the invention are also well suited to, for example, systems which comprise industrial combustion engines and/or combustion engine-powered industrial robots and an associated emission control system comprising a catalytic configuration having a tank for holding a reductant. The innovative method and the innovative system according to one aspect of the invention are also well suited to various kinds of power plants, e.g. an electric power plant which comprises a combustion engine-powered generator and an associated emission control system comprising a catalytic configuration having a tank for holding a reductant.

The innovative method and the innovative system are also well suited to various combustion engine systems comprising an associated emission control system having a tank for holding a reductant. The innovative method and the innovative system are well suited to any engine system which comprises an engine, e.g. on a locomotive or some other platform, and an associated emission control system having a tank for holding a reductant.

The innovative method and the innovative system are well suited to any system which comprises a NO _x -generator an associated emission control system having a tank for holding a reductant.

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

The term "line" refers herein to a passage for holding and conveying a fluid, e.g. a reducing agent in liquid form. The line may be a pipe of any size and be made of any suitable material, e.g. plastic, rubber or metal.

The term "reductant" or "reducing agent" refers herein to an agent used for reacting with certain emissions in an SCR system. These emissions may for example be NO _x -gas. The terms "reductant" and "reducing agent" are herein used synonymously. In one version, said reductant is so-called AdBlue. Other kinds of reductants may of course be used. AdBlue is herein cited as an example of a reductant, but one skilled in the art will appreciate that the innovative method and the innovative system are feasible with other types of reductants. One kind of reducing agent has a freezing temperature of about -11 degrees Celsius. Figure 2a schematically illustrates a system 299 according to an example embodiment of the invention. The system 299 is situated in the tractor unit 110 and may be part of a reducing agent provision configuration. It comprises in this example a tank 205 arranged to hold a reductant. The tank 205 is adapted to hold a suitable amount of reductant and also to being replenishable as necessary. The tank 205 may be adapted to hold e.g. 75 or 50 litres of reductant.

A first line 271 is provided to lead the reductant to a pump 230 from the tank 205. The pump 230 may also be denoted pump unit. The pump 230 may be any suitable pump. The pump 230 may be arranged to be driven by an electric motor (not illustrated). The pump 230 may be adapted to drawing the reductant from the tank 205 via the first line 271 and supplying it via a second line 272 to a dosing unit 237. The dosing unit 237 may also be referred to as a reducing agent dosing unit. The dosing unit 237 comprises an electrically controlled dosing valve by means of which a flow of reductant added to the exhaust system can be controlled. The pump 230 is adapted to pressurising the reductant in the second line 272. The dosing unit 237 is provided with a throttle unit, against which said pressure of the reductant may build up in the system 299.

A first control unit 200 is arranged for communication with the pump 230 via a link L230. The first control unit 200 is arranged to send control signals S230 via said link L230. The first control unit 200 is arranged to control operation of said pump 230 so as to for example adjust flows of the reducing agent within the system 299. The first control unit 200 is arranged to control an operational power of the pump 230 e.g. by controlling the electric motor.

The dosing unit 237 is adapted to supply said reductant to an exhaust gas system (see Fig. 2b) of the vehicle 100. More specifically, it is adapted to supplying a suitable amount of reductant in a controlled way to the exhaust gas system of the vehicle 100. In this version, one SCR-unit (see Fig. 2b) is situated downstream of the position in the exhaust gas system where the supply of reductant takes place. A third line 273 running between the dosing unit 237 and the tank 205 is adapted to leading back to the tank 205 a certain amount of the reductant fed to the dosing unit 237. This configuration results in advantageous cooling of the dosing unit 237. The dosing unit 237 is thus cooled by a flow of the reductant when it is pumped through it from the pump 230 to the tank 205.

The first control unit 200 is arranged for communication with the dosing unit 237 via a link L237. The first control unit 200 is arranged to send control signals S237 via said link L237. The first control unit 200 is arranged to control operation of said dosing unit 237 so as to for example control dosing of the reducing agent to the exhaust gas system of the vehicle 100. The control unit 200 is arranged to control operation of the dosing unit 237 so as to for example adjust return flow of said reducing agent to the tank 205.

A first temperature sensor 242 is provided at the tank 205. According to one example the first temperature sensor 242 is provided at a bottom of the tank 205. The first temperature sensor 242 is arranged to determine a prevailing temperature Ttank of the reductant held in the tank 205. The first temperature sensor 242 is arranged to continuously or intermittently send signals S242 to the first control unit 200 via a link L242. Said signals S242 comprise information about the prevailing temperature Ttank of the reductant held in the tank 205. A second temperature sensor 243 is provided at the dosing unit 237. According to one example the second temperature sensor 243 is provided within said dosing unit 237. The second temperature sensor 243 is arranged to determine a prevailing temperature

Tdosingunit of the reductant within the dosing unit 237. The second temperature sensor 243 is arranged to continuously or intermittently send signals S243 to the first control unit 200 via a link L243. Said signals S243 comprise information about the prevailing temperature Tdosingunit of the reductant in the dosing unit 237.

A second control unit 210 is arranged for communication with the first control unit 200 via a link L210. It may be releasably connected to the first control unit 200. It may be a control unit external to the vehicle 100. It may be adapted to performing the innovative steps according to the invention. It may be used to cross-load software to the first control unit 200, particularly software for applying the innovative method. It may alternatively be arranged for communication with the first control unit 200 via an internal network on board the vehicle. It may be adapted to performing functions corresponding to those of the first control unit 200, such as e.g. determining safe start-up of the reducing agent provision configuration.

Figure 2b schematically illustrates a system 289 of the vehicle 100 shown i Figure 1 according to an embodiment of the invention. The system 289 comprises a catalytic configuration for emission control.

A combustion engine 231 is during operation generating an exhaust gas flow which is lead via a first passage 235 to a DOC-unit 240. A second passage 245 is arranged to convey said exhaust gas flow from said DOC-unit 240 to a DPF-unit 250. A third passage 255 is arranged to convey said exhaust gas flow from said DPF-unit 250 to an SCR-unit 260. A fourth passage 265 is arranged to convey said exhaust gas flow from said SCR-unit 260 to an environment of the catalytic configuration. In alternative embodiments, the catalytic configuration may comprise any of said components downstream said engine 231, including at least one member presenting catalytic features.

Said dosing unit 237 is arranged to provide said reductant to said third passage 255 upstream of said SCR-unit 260 and downstream of said DPF-unit 250. The first control unit 200 is arranged to control operation of said dosing unit 237 so as to, when applicable, dose reducing agent into the third passage 255.

Said SCR-unit 260 may comprise a vaporizing module (not shown) which is arranged to vaporize said dosed reducing agent so as to achieve a mixture of exhaust gas and reducing agent for treatment by means of an SCR-portion of the SCR-unit 260. Said vaporizing module may comprise a mixer (not shown) for mixing said vaporized reducing agent with the exhaust gas. Said vaporizing module may be formed in any suitable way. Said vaporizing module is configured to achieve a most effective vaporizing of provided reducing agent as possible. Herein said vaporizing module is providing large surfaces where vaporizing of provided reducing agent may be performed in an effective way. Said vaporizing module may consist of a metal or a metal alloy. Said SCR-unit 260 may according to one possible configuration comprise an ammonia slip catalyst ASC (not illustrated).

One or more NO _x -sensors may be provided so at to detect a prevailing NO _x content in any of the three passages.

Said second temperature sensor 243 is provided at the dosing unit 237, see also Figure 2a.

A third temperature sensor 236 is provided at the engine 231. According to one example the third temperature sensor 236 is provided at the engine for determining a prevailing temperature Tengcoolant of an engine coolant fluid. This engine coolant fluid is the one which is led via the lines 320 and 330 so as to heat the reducing agent in said tank 205 (see also Figure 2c). The third temperature sensor 236 is arranged to continuously or

intermittently send signals S236 to the first control unit 200 via a link L236. Said signals S236 comprise information about the prevailing temperature Tengcoolant of the engine coolant fluid at said engine 231.

A fourth temperature sensor 238 is provided at any suitable position at the vehicle 100. The fourth temperature sensor 238 is arranged to measure a prevailing temperature Tamb of ambient air. The fourth temperature sensor 238 is arranged to continuously or

intermittently send signals S238 to the first control unit 200 via a link L238. Said signals S238 comprise information about the prevailing temperature Tamb of the ambient air.

Said first control unit 200 is arranged to determine if a temperature of characteristic parts of said reducing agent provision configuration and/or a prevailing ambient temperature is below a predetermined level. The first control unit 200 is arranged to compare the prevailing temperature detected by any of the first temperature sensor, second temperature sensor, third temperature sensor and/or fourth temperature sensor with said predetermined level. The first control unit 200 is arranged to determine that at least a portion of said reducing agent held by said tank 205 is in a solid state if at least one of said detected temperature values is below said predetermined level. According to one example the first control unit 200 is arranged to determine that at least a portion of said reducing agent held by said tank 205 is in a solid state if at least one of said detected temperature values has been below said predetermined level during at least a predetermined period of time. Said first control unit 200 is arranged to activate heating of a reducing agent held in said tank 205 to at least a level above a freezing temperature of said reducing agent. The level above a freezing temperature of said reducing agent may be a predetermined level Tth. The first control unit 200 is arranged to control heating of the reducing agent provided in the tank 205 by e.g. controlling the operation of the engine 231 and the operation of the pump unit 230. Heating of the reductant in said tank 205 is further explained with reference to Figure 2c. After said heating of the reductant to at least a level Tth above a freezing temperature of said reducing agent has been performed a portion of the reducing agent in said tank 205 will be in a liquid state. The prevailing temperature of the liquid reducing agent is measured by the first temperature sensor 242. Paying regard to the position of the first temperature sensor 242, namely at the bottom of the tank 205 and in a close proximity of a heating member (line 320), the first temperature sensor 242 may measure molten reductant while a portion of frozen reductant may be present further from the heating member, which frozen reductant may provide outer surfaces of the volume of molten reductant. Said first control unit 200 is arranged to de-activate heating of said reducing agent. This is performed when the temperature of the portion of the reducing agent being in a liquid state in the tank 205 has a temperature being at least a level Tth above a freezing temperature of said reducing agent. Given that the freezing temperature of the reductant is -11 degrees Celsius said level Tth above a freezing temperature may correspond to e.g. -8 degrees Celsius, -5 degrees Celsius or 0 (zero) degrees Celsius.

Said first control unit 200 is arranged to determine a temperature change rate Tprim of a determined reducing agent temperature after de-activating heating of said reducing agent. Said first control unit 200 is according to one example arranged to determine said temperature change rate Tprim during a certain, predetermined, period of time and to determine a mean value of temperature change rate according to one embodiment. Said first control unit 200 is arranged to determine a level H of said reducing agent in said tank 205. The first control unit 200 is hereby arranged to determine a height H of the liquid portion of the reducing agent. This level H is to be taken as the height of a configuration representing the shape of the fluid/liquid/molten portion of the reducing agent within said tank 205. The level H is measured by means of a level measuring device 310 (see Fig. 2c).

Said first control unit 200 is arranged to determine a heat transfer coefficient Coeff relating to heat transfer between frozen reducing agent and fluid reducing agent. The heat transfer coefficient Coeff is according to one example a predetermined value. The heat transfer coefficient Coeff is predetermined on the basis of characteristics of the reducing agent. Said first control unit 200 is arranged to determine a configuration Config of fluid reducing agent in said tank 205. The configuration Config is relating to a shape, or basic geometry, of the fluid reducing agent portion. The configuration Config may be a predetermined configuration, such as a cylinder, cone, pyramid, sphere or other. The configuration Config may be determined on the basis of the shape of the line 320. With reference to Figure 2c the shape of the line 320 is substantially a helical spiral. According to this example shape it is determined that the configuration Config is a cylinder, also illustrated in Figure 2c.

Said first control unit 200 is arranged to determine a size of the outer surface A of said configuration Config of fluid reducing agent in said tank on the basis of said determined temperature change rate Tprim, said determined level H of said fluid reducing agent in said tank 205, said determined heat transfer coefficient Coeff and said determined configuration of fluid reducing agent in said tank.

Said first control unit 200 is arranged to determine a volume V of fluid reducing agent in said tank 205 on the basis of said determined size of the outer surface A of said configuration Config of fluid reducing agent in said tank and said configuration Config of fluid reducing agent in said tank 205.

Said first control unit 200 is arranged to, if the thus determined volume V exceeds a predetermined value Vth, allowing operation of said reducing agent provision configuration. According to one example said predetermined value Vth is a predetermined value, such as 5 or 10 litres. The predetermined value Vth is set so that when starting operation of the reducing agent dosing system 299 the volume of fluid reducing agent in the tank 205 would be sufficient for adequate operation.

Said first control unit 200 is arranged to, if the thus determined volume V does not exceed said predetermined value Vth, estimating a need of additional energy supply for obtaining a volume of fluid reducing agent exceeding said predetermined value Vth.

Said first control unit 200 is arranged to re-activate heating of said reducing agent held in said tank 205. Said first control unit 200 is arranged to reactivate heating after a time period determined on the basis of said estimated need of additional energy supply for obtaining a volume of fluid reducing agent exceeding said predetermined value Vth. Said first control unit 200 is arranged to perform the process steps depicted herein, comprising the process steps which are detailed with reference to Figure 4b.

Figure 2c schematically illustrates a portion of the reducing agent provision configuration 299. The pump unit 230 is arranged to by means of suction draw liquid reducing agent from the tank 205 by the line 271 and to provide the reducing agent to the dosing unit 237 (not shown in Fig. 2c) via the line 272. At least a portion of the reducing agent fed by the pump unit 230 to the dosing unit 237 is led back to the tank via the line 273.

An engine coolant fluid for cooling the engine 231 is led from the engine 231 (not shown in Fig. 2c) via a line 320 to the pump unit 230. The pump unit 230 is arranged to pressurize the coolant and provide it back to the engine 231 via a line 330 for cooling of the engine 231. The lines 320 and 330 form a closed circuit for conveying the engine coolant fluid. The line 320 is according to one embodiment configured in a spiral shape within the tank 205. In this way the engine coolant fluid, which is heated by the engine 231 is used for heating, and where applicable melting, the reducing agent held by the tank 205. The line 320 is also referred to as heating member. The line 320 may have any suitable form within the tank 205. The actual form of the line 320 within the tank 205 will affect the form of the molten reducing agent in the tank during heating. The configuration Config of fluid reducing agent in said tank may thus be predetermined on the basis of the form of the line 320 within the tank 205.

A reducing agent level measuring device 310 is slidebly mounted on a support member 311. The device 310 is a floating device being positioned at a top surface of the reducing agent. The level measuring device 310 is arranged to continuously or intermittently determine a prevailing level of reducing agent in the tank 205 and to communicate this information to the first control unit 200 via a suitable link (not shown). Hereby the level measuring device 310 is arranged to determine a height H of the molten portion of the reducing agent in the tank 205. Herein the radius r of the configuration Config (the radius of the illustrated cylinder) is illustrated. Other reducing agent level measuring device may be used according to other examples of the invention.

According to this example embodiment configuration Config has the shape of a cylinder. However, according to other embodiments the configuration may have any other geometrical form, such as a sphere, cone or pyramid. It is advantageous to arrange the line 320 in such a way that a basic geometry is formed during heating of frozen reductant in said tank 205, for computational purposes.

Herein the total surface area A refers to the outer surface of the configuration Config.

Figure 3a schematically illustrates a graph presenting a prevailing temperature T of the reducing agent in said tank 205 given in degrees Celsius as a function of time t given in seconds s. The temperature T is according to this example the temperature Ttank which is measured by the first temperature sensor 242 at the bottom of said tank 205.

At time t=t0 a prevailing temperature of the reducing agent at the first temperature sensor 242 is TO degrees Celsius. According to this example the temperature TO is below freezing temperature of the reducing agent, such as -20 or -30 degrees Celsius. The first control unit 200 is hereby arranged to determine that heating of the reducing agent is necessary before circulation of the reducing agent within the reducing agent dosing configuration and subsequent dosing is allowable. Hereby heating of the at least partly frozen reducing agent in the tank is activated. This is performed by means of said first control unit 200 by controlling a flow of said engine coolant fluid in said line 320.

Hereby the prevailing temperature of the reducing agent closest to the line 320 is increasing. At a first point of time tl the temperature of the reducing agent measured by the first temperature sensor 242 has reached the melting temperature Tl of the reducing agent. Hereby the heating of said reducing agent in the tank 205 is further continued during a certain time period. Hereby the temperature T is increasing to a level above said freezing temperature of said reducing agent. The freezing temperature is the same as the above mentioned melting temperature. Said certain time period of continued heating from said first point Tl of time may be a predetermined time period. Said level above said freezing temperature of said reducing agent may be a predetermined temperature level. According to one example said predetermined time period of continued heating may be determined on the basis of e.g. prevailing temperature of the engine coolant fluid, mean coolant flow in the line 320 and operation parameters of the pump unit 230. Such an operation parameter may be e.g. average power of the pump unit 230.

At a second point of time t2 the prevailing temperature T of the reducing agent reaches a temperature T2, which is a level above said freezing temperature Tl of said reducing agent. Said level may be a predetermined level. Said level above freezing temperature of said reducing agent may be e.g. 5 or 10 degrees Celsius above said temperature Tl. Hereby it is determined that at least a part of the reducing agent provided in said tank 205 is in a liquid phase.

At the second point of time t2 heating of the reducing agent in the tank 205 is

deactivated/shut off. After the heating of the reducing agent in said tank 205 has been turned/switched off heat transfer from a volume of reducing agent being in a liquid phase to surrounding reducing agent being in a solid phase is present. Hereby the prevailing temperature T of the reducing agent in liquid phase will start to drop, which is indicated in the graph after the second point of time t2.

According to one example a temperature change rate of the determined fluid reducing agent temperature Ttank after de-activating heating of said reducing agent is determined. According to one example a temperature change rate Tprim of the determined reducing agent temperature determined between the second point of time t2 and a third point of time t3. Hereby said temperature change rate of the determined reducing agent is set to be a mean temperature change rate during said period of time. The third point of time t3 may be any suitable point of time. The third point of time t3 may be determined on the basis of said second point of time t2. Hereby said third point of time t3 may be determined such that a time interval t3-t2 is equal to a predetermined value, e.g. 2, 5 or 10 minutes.

According to one example the temperature change rate Tprim of the determined fluid reducing agent temperature Ttank is determined at a point of time being within the time interval t2-t3.

With reference to Figure 3 and the teachings herein a theoretical example relating to the innovative method is detailed below.

EXAMPLE 1 Herein it is assumed that the molten reducing agent within the tank 205 has a cylindrical shape, which is illustrated schematically with reference to Figure 2c. The cylindrical configuration Config is a representation of a fluid volume surrounded by frozen reducing agent.

The surface area A of the cylinder can be determined by known formulas: A(H, r), where H is the height of the cylinder and r is the radius.

Just as a comment: In case it is assumed that the molten reducing agent within the tank 205 has a spherical shape, the surface area A of the sphere can be determined by known formulas: A(r), where r the radius (actually r=H/2).

There is assumed that the temperature at an interface between molten reducing agent and frozen reducing agent is Ti _C e=-ll[°C].

The prevailing temperature of the fluid reducing agent is continuously measured, T _me it [°C]

A temperature difference between frozen reducing agent and molten reducing agent is thus: ΔΤ = Tmelt - Tii,ce

A heat transfer coefficient Coeff relates to a heat transfer rate from molten reducing agent to frozen reducing agent: C melt->ice [Js/m ² K].

The heat capacity of the molten portion reducing agent relates to the required energy for a given temperature change rate of the molten reducing agent: C _p [J/kgK]

At a time point to heating of the reducing agent within the tank is deactivated. A

measurement and calculating process is relating to a subsequent time point t.

The amount of energy transferred from the molten portion of reducing agent to the frozen portion of the reducing agent:

Change of energy content in the molten portion of reducing agent during the time period t- to:

E(t) — C _p * m _melt * (T _me i _t (t _Q — T _melt (t))

This gives two equations and three unknown, Energy E, radius r and the mass of the molten portion of reducing agent m _me i _t .

By assuming that the shape of the molten portion of the reducing agent is a basic geometry (in this case a cylinder) it is possible to calculate the volume on the basis of the radius r and height H : V(H, r).

Further the density of the reducing agent is known: p.

Hereby the mass of the molten reducing agent m _me i _t may be expressed as a function of the radius r: m _me it = V(h,r)* p

This gives: E(t) = A(h, r) * C _melt→ice AT(t)dt

E(t) = C _p * V(h, r) * p * (T _melt (t ₀ ) - T _melt (t))

which is an solvable equation system with two equations and two unknown parameters (E, r). Hereby the radius r of the molten portion (cylinder) is determined. Hereby the mass of the molten portion of the reducing agent m _me it may be determined in accordance with above.

This method is applicable for all geometries of the molten portion of the reducing agent where both surface area and volume may be defined by one unknown variable besides potentially measurable parameters, e.g. the height H. EN D OF EXAMPLE 1

Figure 4a schematically illustrates a flow chart of a method for determining safe start-up of a reducing agent provision configuration comprising a reducing agent tank 205, a pump unit 230, at least one dosing unit 237 for providing said reducing agent to an engine emission control system of a combustion engine 231.

The method comprises a first method step s401. The method step s401 comprises the steps of:

- activating heating of a reducing agent held in said tank 205 to at least a level above a freezing temperature of said reducing agent; - de-activating heating of said reducing agent;

- determining a temperature change rate Tprim of a determined reducing agent temperature Ttank after de-activating heating of said reducing agent;

- determining a level H of said reducing agent in said tank;

- determining a heat transfer coefficient Coeff relating to heat transfer between frozen reducing agent and fluid reducing agent; - determining a configuration Config of fluid reducing agent in said tank 205;

- determining a size of the outer surface A of said configuration Config of fluid reducing agent in said tank 205 on the basis of said determined temperature change rate Tprim, said determined level H of said reducing agent in said tank, said determined heat transfer coefficient Coeff and said determined configuration Config of fluid reducing agent in said tank;

- determining a volume V of fluid reducing agent in said tank 205 on the basis of said determined size of the outer surface A of said configuration Config of fluid reducing agent in said tank 205 and said configuration Config of fluid reducing agent in said tank 205; and - if the thus determined volume V exceeds a predetermined value Vth, allowing operation of said reducing agent provision configuration.

After the method step s401 the method ends/is returned.

Figure 4b schematically illustrates a method for determining safe start-up of a reducing agent provision configuration comprising a reducing agent tank 205, a pump unit 230, at least one dosing unit 237 for providing said reducing agent to an engine emission control system of a combustion engine 231. It should be noted that the reducing agent provision configuration hereby has been shut off/de-activated for a certain amount of time, thus providing a possibility that at least a portion of said reducing agent provided in said tank 205 is frozen. Naturally the likelihood that least a portion of said reducing agent provided in said tank is frozen is higher if the ambient air is relatively cold, such as below -20 or -30 degrees Celsius. According to one embodiment all of the reducing agent in said tank 205 is frozen.

The method comprises a first method step s405. The method step s405 comprises the step of determining if a temperature of at least one characteristic part of said reducing agent provision configuration and/or a prevailing ambient temperature is/are below a

predetermined level. Said predetermined level may correspond to the freezing temperature of said reducing agent. Said predetermined level may correspond to any suitable

temperature value below which it is likely that at least a portion of said reducing agent is in a solid state (frozen). According to one example said characteristic part of the reducing agent provision

configuration is at said line 320 at the bottom of said tank 205. A prevailing temperature Ttank of the reducing agent at a bottom said tank 205 is hereby measured by means of said first temperature sensor 242. According to one example said characteristic part of the reducing agent provision

configuration is said dosing unit 237. A prevailing temperature Tdosingunit of the reducing agent in said dosing unit 237 is hereby measured by means of said second temperature sensor 243.

According to one example said characteristic part of the reducing agent provision

configuration is at an engine coolant fluid line configuration at said engine 231. A prevailing temperature Tengcoolant of the engine coolant fluid at said engine 231 is hereby measured by means of said third temperature sensor 236.

According to one example a prevailing temperature Tamb of ambient air is measured and compared to said predetermined level. It is according to an example assumed that said reducing agent has the same temperature as the characteristic part of said reducing agent provision configuration and/or a prevailing ambient temperature.

If it is determined that at least one characteristic part of said reducing agent provision configuration and/or a prevailing ambient temperature is/are below a predetermined level it assumed that at least a portion of said reducing agent in said tank 205 is in a solid state and a subsequent method step s410 is performed. The predetermined temperature level may be a level below freezing temperature of the reducing agent, such as 5 or 10 degrees Celsius below freezing temperature of the reducing agent. According to one example operation of the reducing agent provision configuration may be initiated directly if it is determined that the temperature of said least one characteristic part of said reducing agent provision configuration and/or a prevailing ambient temperature is/are above said freezing

temperature of the reducing agent.

The method comprises a method step s410. The method step s410 comprises the step of activating heating of the reducing agent held in said tank 205 to at least a level above a freezing temperature of said reducing agent. Hereby heating of the reducing agent in said tank 205 is performed by means of a heating member, namely the line 320. Hereby heating of said reducing agent is performed until said first temperature sensor 242 is detecting that a prevailing temperature Ttank of the reducing agent is above a predetermined temperature value. Said predetermined temperature value is according to one example a freezing temperature of said reducing agent. In a case where said reducing agent is Adblue said predetermined temperature value may be -11 degrees Celsius. Hereby it may be assumed that at least a portion of said reducing agent is in a liquid phase.

After the method step s410 a subsequent method step s415 is performed.

The method step s415 comprises the step of de-activating heating of said reducing agent. This is performed by means of said first control unit 200. Hereby heat transfer from said liquid state reducing agent will result in a temperature drop of the molten reducing agent in said tank 205. After the method step s415 a subsequent method step s420 is performed.

The method step s420 comprises the step of determining a temperature change rate Tprim of a determined reducing agent temperature after de-activating heating of said reducing agent. This naturally gives a measure of how fast the temperature of the liquid portion of the reducing agent in the tank 205 is decreasing due to that it is cooled by the surrounding frozen portion of the reducing agent. The temperature change rate determination is performed by means of said first control unit 200. This is also depicted in greater detail with reference to Figure 3.

After the method step s420 a subsequent step s425 is performed.

The step s425 comprises the step of determining a level H of said reducing agent in said tank 205. This may be performed by means of the reducing agent level measuring device 310, the support member 311 and the first control unit 200. The level H is corresponding to the height of the configuration Config. According to one example the configuration Config has the shape of a cylinder. After the method step s425 a subsequent step s430 is performed.

The step s430 comprises the step of determining a heat transfer coefficient Coeff relating to heat transfer between frozen reducing agent and fluid reducing agent. The heat transfer coefficient Coeff may be a predetermined value, which is stored in a memory of the first control unit 200. The heat transfer coefficient may be determined on the basis of known characteristics of the reducing agent. After the method step s430 a subsequent step s435 is performed.

The method step s435 comprises the step of determining a configuration Config of fluid reducing agent in said tank 205. This may be performed by means of the first control unit 200. The configuration Config may be a predetermined configuration, i.e. a predetermined basic shape or geometry, such as a cylinder or a cone. Alternatively the configuration may be a tetrahedron, octahedron, dodecahedron, icosahedron, sphere, segment of a sphere, or any other suitable configuration. Information regarding the predetermined configuration Config may be stored in a memory of the first control unit 200. According to one embodiment the method step s435 comprises the step of choosing one predetermined configuration Config out of a set of predetermined configurations. This may be performed by means of the first control unit 200. After the method step s435 a subsequent step s440 is performed

The method step s440 comprises the step of determining a size of the outer surface A of said configuration Config of fluid reducing agent in said tank 205 on the basis of said determined temperature change rate Tprim, said determined level H of said reducing agent in said tank 205, said determined heat transfer coefficient Coeff and said determined configuration

Config of fluid reducing agent in said tank 205. This may be performed by means of the first control unit 200.

After the method step s440 a subsequent step s445 is performed The method step s445 comprises the step of determining a volume V of fluid reducing agent in said tank 205 on the basis of said determined size of the outer surface A of said

configuration Config of fluid reducing agent in said tank 205 and said configuration Config of fluid reducing agent in said tank 205. This may be performed by means of the first control unit 200.

After the method step s445 a subsequent step s450 is performed

The method step s450 comprises the step of, if the thus determined volume V exceeds a predetermined value Vth , allowing operation of said reducing agent provision configuration. This may be performed by means of the first control unit 200.

The method step s450 may comprise the step of, if the thus determined volume V does not exceed said predetermined value Vth, estimating a need of additional energy supply for obtaining a fluid volume exceeding said predetermined value Vth. The method step s450 comprises the step of re-activating heating of said reducing agent held in said tank 205.

After the step s450 the method is ended/returned.

Figure 5 is a diagram of one version of a device 500. The control units 200 and 210 described with reference to Figure 2a and Figure 2b may in one version comprise the device 500. The device 500 comprises a non-volatile memory 520, a data processing unit 510 and a read/write memory 550. The non-volatile memory 520 has a first memory element 530 in which a computer program, e.g. an operating system, is stored for controlling the function of the device 500. The device 500 further comprises 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 interruption controller (not depicted). The non-volatile memory 520 has also a second memory element 540. The computer program P comprises routines for determining safe start-up of a reducing agent provision configuration comprising a reducing agent tank 205, a pump unit 230, at least one dosing unit 237 for providing said reducing agent to an engine emission control system of a combustion engine 231. The computer program P may comprise routines for activating heating of a reducing agent held in said tank 205 to at least a level above a freezing temperature of said reducing agent. The computer program P may comprise routines for controlling heating of the reducing agent held in said tank 205 to at least a level above a freezing temperature of said reducing agent. The computer program P may comprise routines for de-activating heating of said reducing agent. The computer program P may comprise routines for de-activating heating of said reducing agent when it has been detected that said reducing agent has been heated to a temperature exceeding said level above a freezing temperature of said reducing agent.

The computer program P may comprise routines for determining a temperature change rate Tprim of a determined reducing agent temperature after de-activating heating of said reducing agent. The computer program P may comprise routines for determining a temperature change rate Tprim of a determined reducing agent temperature after deactivating heating of said reducing agent during a predetermined time period after deactivation of heating of said reducing agent has been performed. The computer program P may comprise routines for determining a level H of said reducing agent in said tank 205. The computer program P may comprise routines for determining a height H of a configuration Config of fluid reducing agent in said tank 205.

The computer program P may comprise routines for determining a heat transfer coefficient Coeff relating to heat transfer between frozen reducing agent and fluid reducing agent. The computer program P may comprise routines for determining a configuration Config of fluid reducing agent in said tank 205.

The computer program P may comprise routines for determining a size of the outer surface A of said configuration Config of fluid reducing agent in said tank 205 on the basis of said determined temperature change rate Tprim, said determined level H of said reducing agent in said tank, said determined heat transfer coefficient Coeff and said determined configuration Config of fluid reducing agent in said tank 205.

The computer program P may comprise routines for determining a volume V of fluid reducing agent in said tank 205 on the basis of said determined size of the outer surface A of said configuration of fluid reducing agent in said tank 205 and said configuration Config of fluid reducing agent in said tank 205.

The computer program P may comprise routines for, if the thus determined volume V exceeds a predetermined value Vth, allowing operation of said reducing agent provision configuration. The computer program P may comprise routines for determining if a temperature of characteristic parts of said reducing agent provision configuration and/or a prevailing ambient temperature Tamb is below a predetermined level. Said predetermined level may correspond to the freezing temperature of said reducing agent.

The computer program P may comprise routines for, if the thus determined volume V does not exceed said predetermined value Vth, estimating a need of additional energy supply for obtaining a fluid volume exceeding said predetermined value Vth. The computer program P may comprise routines for re-activating heating of said reducing agent held in said tank.

The computer program P may comprise routines for performing any of the process steps detailed with reference to Figure 4b. The program P may be stored in an executable form or in compressed form in a memory 560 and/or in a read/write memory 550.

Where it is stated that the data processing unit 510 performs a certain function, it means that it conducts a certain part of the program which is stored in the memory 560 or a certain part of the program which is stored in the read/write memory 550.

The data processing device 510 can 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 to communicate with the data processing unit via a data bus 511. The read/write memory 550 is arranged to communicate with the data processing unit 510 via a data bus 514. The links L210, L230, L231, L236, L237, L242, L243 and L248, for example, may be connected to the data port 599 (see Fig. 2a-c). When data are received on the data port 599, they are stored temporarily in the second memory element 540. When input data received have been temporarily stored, the data processing unit 510 will be prepared to conduct code execution as described above.

Parts of the methods herein described may be conducted by the device 500 by means of the data processing unit 510 which runs the program stored in the memory 560 or the read/write memory 550. When the device 500 runs the program, method steps and process steps herein described are executed.

The foregoing description of the preferred embodiments of the present invention is provided for illustrative and descriptive purposes. It is not intended to be exhaustive, nor to limit the invention to the variants described. Many modifications and variations will obviously suggest themselves to one skilled in the art. The embodiments have been chosen and described in order to best explain the principles of the invention and their practical applications and thereby make it possible for one skilled in the art to understand the invention for different embodiments and with the various modifications appropriate to the intended use.

The components and features specified above may within the framework of the invention be combined between different embodiments specified.