WO2019059831A1

WO2019059831A1 - A system and a method for determining safe start-up of a reducing agent provision configuration

Info

Publication number: WO2019059831A1
Application number: PCT/SE2018/050930
Authority: WO
Inventors: Kurt KÄLLKVIST; Per Bremberg
Original assignee: Scania Cv Ab
Priority date: 2017-09-22
Filing date: 2018-09-13
Publication date: 2019-03-28
Also published as: SE541370C2; SE1751176A1

Abstract

The invention relates to a method for determining safe start-up of a reducing agent provision configuration during relatively cold conditions.The method comprises the steps of determining a need of heating energy supply to there ducing agent provision configuration in order to provide safe start-up of there ducing agent provision configuration. This is performed on the basis of determined ambient temperature values corresponding to engine shut down and engine start as well as a determined time period during which the engine has been turned off. The invention relates also to a computer program product comprising program code (P) for a computer (200; 210; 500) for implementing a method according to the invention. The invention relates also to a system for determining safe start-up of a reducing agent provision configuration and a motor vehicle (100) equipped with the system.

Description

A system and a method for determining safe start-up of a reducing agent provision configuration

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. 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 comprising a reducing agent tank 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 the 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 the 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 the reducing agent at least a portion of the 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 it is likely that 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 the 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 the tank. If the 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 to achieve, 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 the 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.

Due to design parameters of the reducing agent provision configuration various parts will be completely defrosted at different points of time when trying to heat the configuration for operation during cold conditions. In a similar way, after the engine of the vehicle is shut down, reducing agent in different parts of the configuration will freeze at different point of times during cold conditions. If an operator of the vehicle performs frequent and/or short engine shutdowns it is difficult to decide if the configuration should be heated or not before restarting operation. One such situation may be if the operator takes a lunch/rest break and turns of the vehicle engine, in particular during cold conditions. Cold conditions may be referring to outdoor temperatures below a freezing point of the reducing agent, such as -10 or -25 degrees Celsius. Another such situation may be if the vehicle engine is shut off between two shifts, e.g. during a night, at relatively low outdoor temperatures.

US20130340409 relates to a method for determining the temperature of a reducing agent provision system.

SUMMARY OF THE INVENTION

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 comprising a reducing agent tank.

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

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 process of a reducing agent provision configuration comprising a reducing agent tank.

Yet another object of the invention is to propose a method, a system and a computer program achieving a robust and automated start-up process of a reducing agent provision configuration comprising a reducing agent tank. 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 comprising a reducing agent tank.

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 the reducing agent to an engine emission control system of a combustion engine, comprising the steps of:

- when turning off the combustion engine, determining and storing a first prevailing ambient temperature and a turning off clock time;

- when starting the combustion engine, determining and storing a second prevailing ambient temperature and a starting clock time; - determining a relevant ambient temperature value on the basis of at least one of the first prevailing ambient temperature and the second prevailing ambient temperature;

- determining a period of time during which the combustion engine has been turned off on the basis of the turning off clock time and the starting clock time;

- determining a need of heating energy supply to the reducing agent provision configuration on the basis of said determined relevant ambient temperature value and said determined period of time during which the combustion engine has been turned off, in order to provide safe start-up of the reducing agent provision configuration.

By determining a time period during which the engine has been turned off, i.e. the time period lapsed since the reducing agent provision configuration was operational, and estimating an ambient temperature regarding this time period, a heating energy supply may be determined in an accurate and reliable way.

In a case where the engine has been shut off during a relatively short time period (e.g. 2 hours), and where ambient temperatures are relatively low (below freezing temperature of the reducing agent), the reducing agent provision configuration hereby may be started quicker compared to prior art solutions.

The inventive method is applicable for relatively short engine operational stop periods (e.g. 0.5-2 hours, or e.g. 1-24 hours) as well as for relatively long engine operational stop periods (e.g. 24-72 hours, or longer). Hereby a versatile method is provided. The method may comprise the step of:

- determining that operable status of the reducing agent provision configuration is at hand prior to turning off a combustion engine of the engine emission control system. Hereby the innovative method can be activated in a reliable manner.

The method may comprise the step of: - determining the need of heating energy supply on the basis of a predetermined collection of heating energy values. The predetermined collection of heating energy values may be an empirically determined collection of heating energy values. Hereby a reliable and accurate method is provided. The heating energy values may be expressed in terms of a minimal required heating time for operation of heating devices or actual energy values

corresponding to the minimal required heating time values.

The method may comprise the step of:

- heating the reducing agent provision system according to the determined need of heating energy supply. Hereby safe start-up and operation of the reducing agent provision configuration is provided. This is particularly advantageous in relatively cold environment and relatively short engine operational stop periods.

The method may comprise the step of: - determining if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature is below a predetermined level prior to turning off the combustion engine. Hereby it advantageously may be determined if a potential need for heating of the reducing agent provision configuration is at hand.

According to one example the relevant ambient temperature value is modelled/estimated/calculated/determined on the basis of at least one of the first prevailing ambient temperature and the second prevailing ambient temperature by means of a model.

According to one example a prevailing state of matter of the reducing agent in the reducing agent provision configuration is determined by means of a model. The prevailing state of matter of the reducing agent in the reducing agent provision configuration may be determined on the basis of the determined relevant ambient temperature value, a previous state of matter of the reducing agent, and a prevailing temperature in the reducing agent provision configuration. A time of heating the reducing agent in the reducing agent provision configuration may then be determined on the basis of the prevailing state of the matter of the reducing agent and the heating energy supply by means of a model. Thus, by determining the prevailing state of matter of the reducing agent, a more accurate estimation of the time of heating may be obtained.

According to one example a previous state of matter of the reducing agent is determined on the basis of the relevant ambient temperature value and a prevailing temperature in the reducing agent provision configuration by means of a model. According to another example the previous state of matter of the reducing agent in the reducing agent provision configuration is determined by an established known state of matter of the reducing agent. The known state of matter may be modelled/established/calculated/determined on the basis of the prevailing temperature in the reducing agent provision configuration and previous consumption of reducing agent, i.e. if the reducing agent provision configuration is warm and a whole tank of reducing agent has been consumed at an expected rate, it can be concluded that the reducing agent in the whole reducing agent provision configuration is in a fluid state. The known state of matter is then established to be fluid. The models mentioned in the examples above may be stored in a memory of a control unit.

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 the reducing agent to an engine emission control system of a combustion engine, comprising:

- means arranged for, when turning off the combustion engine, determining and storing a first prevailing ambient temperature and a turning off clock time; - means arranged for, when starting the combustion engine, determining and storing a second prevailing ambient temperature and a starting clock time;

- means arranged for determining a relevant ambient temperature value on the basis of at least one of the first prevailing ambient temperature and the second prevailing ambient temperature; - means arranged for determining a period of time during which the combustion engine has been turned off on the basis of the turning off clock time and the starting clock time;

- means arranged for determining a need of heating energy supply to the reducing agent provision configuration on the basis of said determined relevant ambient temperature value and said determined period of time during which the combustion engine has been turned off in order to provide safe start-up of the reducing agent provision configuration.

The system may comprise:

- means arranged for determining that operable status of the reducing agent provision configuration is at hand prior to turning off a combustion engine of the engine emission control system. The system may comprise: - means arranged for determining the a need of heating energy supply on the basis of a predetermined collection of heating energy values. The predetermined collection of heating energy values may be an empirically determined collection of heating energy values.

The system may comprise:

- means arranged for determining if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature is below a predetermined level prior to turning off the combustion engine. According to one example the system may comprise means arranged for determining a relevant ambient temperature value modelled/estimated/calculated/determined on the basis of at least one of the first prevailing ambient temperature and the second prevailing ambient temperature, by means of a model.

According to one example the system may comprise means arranged for determining a prevailing state of matter of the reducing agent in the system by means of a model. The system may comprise means arranged for determining the prevailing state of matter of the reducing agent in the system on the basis of the determined relevant ambient temperature value, a previous state of matter of the reducing agent, and a prevailing temperature in the system.

According to an aspect of the invention there is provided a vehicle comprising a system according to what is presented herein. The 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 comprising a reducing agent tank, a pump unit, at least one dosing unit for providing the reducing agent to an engine emission control system of a combustion engine, wherein the 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 the electronic control unit or the 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 comprising a reducing agent tank, a pump unit, at least one dosing unit for providing the reducing agent to an engine emission control system of a combustion engine, wherein the 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 comprising a reducing agent tank, a pump unit, at least one dosing unit for providing the reducing agent to an engine emission control system of a combustion engine, wherein the 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 the electronic control unit or the 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 anyone of the method steps depicted herein, when the 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 the 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.

BRIEF DESCRIPTION OF THE DRAWINGS

For fuller understanding of the present invention and its further objects and advantages, 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 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. The catalytic configuration may comprise at least one SCR-unit. The catalytic configuration may comprise one or more DOC-units, DPF- units 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, the 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 the 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 the link L230. The first control unit 200 is arranged to control operation of the 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 the 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 the link L237. The first control unit 200 is arranged to control operation of the 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 the 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. The 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 the 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. The signals S243 comprise information about the prevailing temperature Tdosingunit of the reductant in the dosing unit 237.

A real time clock 280 is arranged for communication with the first control unit 200 via a link L280. The real time clock 280 is arranged to continuously provide a clock signal S280 to the first control unit 200 via the link L280. Hereby real time clock values are provided continuously to the first control unit 200. According to one embodiment the real time clock 280 is integrated in the first control unit 200.

A first heating device 291 is arranged at the second line 272. The first heating device 291 may be any suitable heating device. The first heating device 291 is arranged for heating the reducing agent at a given position. According to one embodiment the first heating device 291 comprises an electrical heater, e.g. in the shape of a helical surrounding the second line 272. The first control unit 200 is arranged to control operation of the first heating device 291. The first heating device 291 is according to one example arranged to heat the reducing agent in the second line 272 by an electrical arrangement (not shown). Hereby the reducing agent as well as the second line 272 is heated.

A second heating device 292 is arranged at the dosing unit 237. The second heating device

292 may be any suitable heating device. The second heating device 292 is arranged for heating the reducing agent at a given position. According to one embodiment the second heating device 292 comprises an electrical heater. The first control unit 200 is arranged to control operation of the second heating device 292. The second heating device 292 is according to one example arranged to heat the reducing agent in the dosing unit 237 by an electrical arrangement (not shown). Hereby the reducing agent as well as the dosing unit 237 is heated.

A third heating device 293 is arranged at the third line 273. The third heating device 293 may be any suitable heating device. The third heating device 293 is arranged for heating the reducing agent at a given position. According to one embodiment the third heating device

293 comprises an electrical heater, e.g. in the shape of a helical surrounding the third line 273. The first control unit 200 is arranged to control operation of the third heating device

293. The third heating device 293 is according to one example arranged to heat the reducing agent in the third line 273 by an electrical arrangement (not shown). Hereby the reducing agent as well as the third line 273 is heated.

The first heating device 291, the second heating device 292 and the third heating device 293 is powered by a separate power source such as a 24 V vehicle battery.

It should be noted that any number of heating devices may be provided in the system 299.

A fourth heating device 294 is arranged for heating the reducing agent held in the tank 205. The fourth heating device 294 is a reducing agent tank heating configuration 294 which is partly arranged within the tank 205. The fourth heating device 294 comprises an engine coolant fluid for cooling the engine 231. The engine coolant fluid is led from the engine 231 (not shown in Fig. 2a) via the line 294 to the pump unit 230. The pump unit 230 is arranged to convey the coolant and provide it back to the engine 231 via the line 294 for cooling of the engine 231. The line 294 forms a closed circuit for conveying the engine coolant fluid. The line 294 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 294 may have any suitable form within the tank 205. The first control unit 200 is arranged to control operation of the fourth heating device 294, e.g. by controlling operation of the pump 230. The fourth heating device 294 is according to one example arranged to heat the reducing agent in tank 205. According to an alternative embodiment the fourth heating device comprises an electrical heating arrangement (not shown).

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 the exhaust gas flow from the DOC-unit 240 to a DPF-unit 250. A third passage 255 is arranged to convey the exhaust gas flow from the DPF-unit 250 to an SCR-unit 260. A fourth passage 265 is arranged to convey the exhaust gas flow from the SCR-unit 260 to an environment of the catalytic configuration. In alternative embodiments, the catalytic configuration may comprise any of the components downstream the engine 231, including at least one member presenting catalytic features. The dosing unit 237 is arranged to provide the reductant to the third passage 255 upstream of the SCR-unit 260 and downstream of the DPF-unit 250. The first control unit 200 is arranged to control operation of the dosing unit 237 so as to, when applicable, dose reducing agent into the third passage 255.

The SCR-unit 260 may comprise a vaporizing module (not shown) which is arranged to vaporize the 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. The vaporizing module may comprise a mixer (not shown) for mixing the vaporized reducing agent with the exhaust gas. The vaporizing module may be formed in any suitable way. The vaporizing module is configured to achieve a most effective vaporizing of provided reducing agent as possible. Herein the vaporizing module is providing large surfaces where vaporizing of provided reducing agent may be performed in an effective way. The vaporizing module may consist of a metal or a metal alloy.

The 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.

The 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 line 294 so as to heat the reducing agent in the tank 205 (see also Figure 2a). The third temperature sensor 236 is arranged to continuously or intermittently send signals S236 to the first control unit 200 via a link L236. The signals S236 comprise information about the prevailing temperature Tengcoolant of the engine coolant fluid at the 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. The signals S238 comprise information about the prevailing temperature Tamb of the ambient air.

The first control unit 200 is arranged for determining if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature is below a predetermined level prior to turning off the combustion engine. These

characterizing parts are positioned where the respective four temperature sensors are provided. 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 238 with the predetermined level. The first control unit 200 is arranged for, when turning off the combustion engine, determining and storing a first prevailing ambient temperature Tl and a turning off clock time tl. The turning off may be performed manually by an operator affecting an actuator means for starting/shutting down the engine 231. The turning off may be performed automatically by means of the first control unit 200. The first prevailing ambient

temperature Tl may be determined by means of the fourth temperature sensor 238.

The first control unit 200 is arranged for, when starting the combustion engine 231, determining and storing a second prevailing ambient temperature T2 and a starting clock time t2. The starting may be performed manually by an operator affecting an actuator means for starting/shutting down the engine 231. The starting may be performed automatically by means of the first control unit 200. The second prevailing ambient temperature T2 may be determined by means of the fourth temperature sensor 238.

The first control unit 200 is arranged for determining a relevant ambient temperature value Test on the basis of at least one of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2. The first control unit 200 is arranged for determining a period of time during which the combustion engine 231 has been turned off on the basis of the turning off clock time tl and the starting clock time t2.

The first control unit 200 is arranged for determining a need of heating energy supply to the reducing agent provision configuration in order to provide safe start-up of the reducing agent provision configuration. The first control unit 200 is arranged for determining a need of heating energy supply to the reducing agent provision configuration, on the basis of the relevant ambient temperature value Test and the period of time during which the combustion engine 231 has been turned off, in order to provide safe start-up of the reducing agent provision configuration.

The first control unit 200 is arranged for determining that operable status of the reducing agent provision configuration is at hand prior to turning off a combustion engine of the engine emission control system.

The first control unit 200 is arranged for determining the need of heating energy supply on the basis of an empirically determined collection of heating energy values.

The 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 3 schematically illustrates a table (Table 1) wherein a number of predetermined time values are provided. The information content of Table 1 may be stored in a memory of the first control unit 200. The time values are each corresponding to a heating energy required to melt frozen reducing agent within the reducing agent provision configuration to such an extent that safe start-up and operation of the configuration is possible.

The Table 1 is organized as a 3x3 matrix according to this example embodiment. According to other examples any suitable NxM matrix may be used, where N and M are positive integers.

The elements of the matrix comprise information about a minimal required time for heating the reducing agent provision configuration. Hereby increasing values of time Toff during which the engine 231 has been turned off is indicated in the Figure 3. Hereby decreasing values of relevant ambient temperature value Test is indicated in the Figure 3.

Nine elements comprising information about the are presented minimal required time for heating the reducing agent provision configuration are provided, namely tla, tlb, tic, t2a, t2b, t2c, t3a, t3b and t3c. The specified minimal required time values for heating the reducing agent provision configuration are predetermined values.

The time value tla is corresponding to a relatively short shut off time and a relatively high relevant ambient temperature Test. The time value tla is thus corresponding to a relatively short time value meaning that only a small amount of heating energy needs to be provided to the reducing agent provision configuration for allowing safe start-up of the same.

The time value t3c is corresponding to a relatively long shut off time and a relatively low relevant ambient temperature Test. The time value t3c is thus corresponding to a relatively long time value meaning that a relatively large amount of heating energy needs to be provided to the reducing agent provision configuration for allowing safe start-up of the same.

Table 1 is set up so that given any value of time Toff and relevant ambient temperature value Test corresponds to an amount of heating energy (specified in a corresponding element) needed for allowing safe start-up of the reducing agent provision configuration. The amount of needed heating energy may be expressed in terms of a minimum time period required for one or more heating devices to heat the configuration sufficiently given predetermined heating capacity of the one or more heating devices. The amount of needed heating energy may be expressed in terms of a minimum time period required for a set of heating devices of the reducing agent provision configuration to heat the configuration sufficiently given predetermined heating capacity.

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 the 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:

- when turning off the combustion engine, determining and storing a first prevailing ambient temperature Tl and a turning off clock time tl; - when starting the combustion engine, determining and storing a second prevailing ambient temperature T2 and a starting clock time t2;

- determining a relevant ambient temperature value Test on the basis of at least one of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2;

- determining a period of time during which the combustion engine has been turned off on the basis of the turning off clock time tl and the starting clock time t2;

- determining a need of heating energy supply to the reducing agent provision configuration in order to provide safe start-up of the 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 the reducing agent to an engine emission control system of a combustion engine 231.

The method comprises a first method step s410. The method step s410 comprises the step of determining if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature Tamb is below a predetermined level prior to turning off the combustion engine. This may be performed by means of the first temperature sensor 242, second temperature sensor 243, third temperature sensor 236 and fourth temperature sensor 238. After the method step s410 a subsequent method step s420 is performed.

The method step s420 comprises the step of determining that operable status of the reducing agent provision configuration is at hand prior to turning off the combustion engine agent provision configuration is in a state where circulation of the reducing agent is functioning properly. Hereby it may be determined that the reducing agent provision configuration is in a state where circulation of the reducing agent is possible and allowable. Hereby it may be determined that the reducing agent provision configuration is in a state where dosing by means of the dosing unit 237 is functioning properly. Hereby it may be determined that the reducing agent provision configuration is in a state where dosing by means of the dosing unit 237 is possible and allowable. According to one example a subsequent method step s430 is performed if operable status of the reducing agent provision configuration is at hand prior to turning off the combustion engine 231. If operable status of the reducing agent provision configuration is not at hand prior to turning off the combustion engine 231 the method may be ended according to one example embodiment.

After the method step s420 a subsequent method step s430 is performed.

The method step s430 comprises the step of, when turning off the combustion engine 231, determining and storing a first prevailing ambient temperature Tl and a turning off clock time tl. The turning off clock time tl is a time value indicating when the engine 231 is turned off. This turning off clock time tl is generated by means of the real time clock 280. The first prevailing ambient temperature Tl is determined by means of the fourth temperature sensor 238. The first prevailing ambient temperature Tl and the turning off clock time tl are stored in a memory of the first control unit 200.

After the method step s430 a subsequent method step s440 is performed.

The method step s440 comprises the step of, when starting the combustion engine 231, determining and storing a second prevailing ambient temperature T2 and a starting clock time t2. The starting clock time t2 is a time value indicating when the engine 231 is turned on. This starting clock time t2 is generated by means of the real time clock 280. The second prevailing ambient temperature T2 is determined by means of the fourth temperature sensor 238. The second prevailing ambient temperature T2 and the starting clock time t2 are stored in a memory of the first control unit 200.

After the method step s440 a subsequent step s450 is performed. The step s450 comprises the step of determining a relevant ambient temperature value Test on the basis of at least one of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2. The relevant ambient temperature value Test is a temperature value representing the temperature during which the engine 231 has been turned off. The relevant ambient temperature value Test may be determined in a number of different ways.

According to one example the first prevailing ambient temperature Tl is determined to be the relevant ambient temperature value Test. According to one example the second prevailing ambient temperature T2 is determined to be the relevant ambient temperature value Test. According to one example a lowest value of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2 is determined to be the relevant ambient temperature value Test. According to one example a mean value of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2 is determined to be the relevant ambient temperature value Test. According to one example the relevant ambient temperature value Test is modelled/estimated/calculated/determined on the basis of at least one of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2 by means of a model being stored in a memory of the first control unit 200.

After the method step s450 a subsequent step s460 is performed. The step s460 comprises the step of determining a period of time Toff during which the combustion engine 231 has been turned off on the basis of the turning off clock time tl and the starting clock time t2. Hereby a time period Toff specifying an engine shut down time period is determined. The time period Toff is defined as t2-tl, given in e.g. seconds (s) or hours (h). This is performed by means of the first control unit 200. After the method step s460 a subsequent step s470 is performed.

The step s470 may comprise the step of determining a need of heating energy supply to the reducing agent provision configuration in order to provide safe start-up of the reducing agent provision configuration. The determined required heating energy is corresponding to an amount of energy necessary for heating the reducing agent provision configuration in such a way that no molten reducing agent is provided in the line 271, pump 230, line 272, dosing unit 237 and line 273. Further the determined required heating energy is

corresponding to an amount of energy necessary for providing at least a minimum amount of molten reducing agent in the tank 205, which amount of molten reducing agent in the tank 205 is enough for allowing proper and safe operation of the reducing agent provision configuration. The step s470 may comprise the step of determining the need of heating energy supply on the basis of an empirically determined collection of heating energy values. These heating energy values may be expressed in terms of a given time period during which heating is performed (s480) by means of at least one heating device (given a predetermined operational power). The need of heating energy supply may be expressed in any suitable way so that the first control unit 200 may control the heating process accordingly. This is further explained with reference to Figure 3.

After the method step s470 a subsequent step s480 is performed.

The step s480 comprises the step of heating the reducing agent provision configuration according to the determined need of heating energy supply. The first control unit 200 is arranged to control the heating process. Hereby at least one of the first heating device 291, second heating device 292, third heating device 293 and fourth heating device 294 is controlled so as to provide thermal energy to the reducing agent provision configuration for melting/heating the reducing agent. According to one embodiment all four heating devices are controlled for providing a maximal possible heating process. This means that all four heating devices are controlled so as to generate a maximal heat transfer from the respective heating device to the reducing agent provision configuration for heating the reducing agent.

The heating process of the reducing agent provision configuration is performed in accordance with the determined need of heating energy supply to the reducing agent provision configuration.

After the step s480 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 2 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, a pump unit, at least one dosing unit for providing the reducing agent to an engine emission control system of a combustion engine.

The computer program P may comprise routines for, when turning off the combustion engine, determining and storing a first prevailing ambient temperature Tl and a turning off clock time tl.

The computer program P may comprise routines for, when starting the combustion engine, determining and storing a second prevailing ambient temperature T2 and a starting clock time t2.

The computer program P may comprise routines for determining a relevant ambient temperature value Test on the basis of at least one of the first prevailing ambient temperature Tl and the second prevailing ambient temperature T2.

The computer program P may comprise routines for determining a period of time during which the combustion engine has been turned off on the basis of the turning off clock time tl and the starting clock time t2. The computer program P may comprise routines for determining a need of heating energy supply to the reducing agent provision configuration in order to provide safe start-up of the reducing agent provision configuration.

The computer program P may comprise routines for determining a need of heating energy supply to the reducing agent provision configuration, on the basis of the relevant ambient temperature value Test and the period of time during which the combustion engine 231 has been turned off, in order to provide safe start-up of the reducing agent provision

configuration.

The computer program P may comprise routines for determining that operable status of the reducing agent provision configuration is at hand prior to turning off a combustion engine of the engine emission control system.

The computer program P may comprise routines for determining the need of heating energy supply on the basis of an empirically determined collection of heating energy values.

The computer program P may comprise routines for determining if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature is below a predetermined level prior to turning off the combustion engine.

The computer program P may comprise routines for controlling heating the reducing agent provision configuration according to the determined need of heating energy supply.

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 L280, for example, may be connected to the data port 599 (see Fig. 2a and 2b). 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.

Claims

1. 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 the reducing agent to an engine emission control system of a combustion engine (231), comprising the steps of:

- when turning off the combustion engine (231), determining (s430) and storing a first prevailing ambient temperature (Tl) and a turning off clock time (tl);

- when starting the combustion engine (231), determining (s440) and storing a second prevailing ambient temperature (T2) and a starting clock time (t2); - determining (s450) a relevant ambient temperature value (Test) on the basis of at least one of the first prevailing ambient temperature (Tl) and the second prevailing ambient temperature (T2);

- determining (s460) a period of time (Toff) during which the combustion engine (231) has been turned off on the basis of the turning off clock time (tl) and the starting clock time (t2); - determining (s470) a need of heating energy supply to the reducing agent provision configuration on the basis of said determined relevant ambient temperature value (Test) and said determined period of time (Toff) during which the combustion engine (231) has been turned off, in order to provide safe start-up of the reducing agent provision

configuration.

2. The method according to claim 1, comprising the step of:

- determining (s420) that operable status of the reducing agent provision configuration is at hand prior to turning off the combustion engine (231) of the engine emission control system.

The method according to claim 1 or 2, comprising the step of: - determining (s470) the need of heating energy supply on the basis of a predetermined collection of heating energy values.

4. The method according to anyone of the preceding claims, comprising the step of:

- determining (s410) if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature (Tamb) is below a predetermined level prior to turning off the combustion engine (231).

5. A system 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 the reducing agent to an engine emission control system of a combustion engine (231), comprising:

- means (200; 210; 500) arranged for, when turning off the combustion engine (231), determining and storing a first prevailing ambient temperature (Tl) and a turning off clock time (tl);

- means (200; 210; 500) arranged for, when starting the combustion engine (231), determining and storing a second prevailing ambient temperature (T2) and a starting clock time (t2);

- means (200; 210; 500) arranged for determining a relevant ambient temperature value (Test) on the basis of at least one of the first prevailing ambient temperature (Tl) and the second prevailing ambient temperature (T2);

- means (200; 210; 500; 280) arranged for determining a period of time (Toff) during which the combustion engine (231) has been turned off on the basis of the turning off clock time (tl) and the starting clock time (t2); - means (200; 210; 500) arranged for determining a need of heating energy supply to the reducing agent provision configuration on the basis of said determined relevant ambient temperature value (Test) and said determined period of time (Toff) during which the combustion engine (231) has been turned off, in order to provide safe start-up of the reducing agent provision configuration.

6. The system according to claim 5, comprising:

- means (200; 210; 500) arranged for determining that operable status of the reducing agent provision configuration is at hand prior to turning off a combustion engine (231) of the engine emission control system.

7. The system according to claim 5 or 6, comprising:

- means (200; 210; 500) arranged for determining the need of heating energy supply on the basis of a predetermined collection of heating energy values.

8. The system according to anyone of the claims 5-7, comprising:

- means (200; 210; 500) arranged for determining if a temperature of characteristic parts of the reducing agent provision configuration and/or a prevailing ambient temperature (Tamb) is below a predetermined level prior to turning off the combustion engine (231).

9. A vehicle (100; 110) comprising a system according to anyone of claims 5-8.

10. The vehicle (100; 110) according to claim 9, which vehicle is any from among a truck, bus or passenger car.

11. A computer program (P) 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 the reducing agent to an engine emission control system of a combustion engine (231), wherein the computer program (P) comprises program code for causing an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500) to perform the steps according to anyone of the claims 1-4.

12. A computer program product containing a program code stored on a computer-readable medium for performing method steps according to anyone of claims 1-4, when the computer program is run on an electronic control unit (200; 500) or another computer (210; 500) connected to the electronic control unit (200; 500).