SE536316C2 - Method and apparatus for removing fuel from a metering unit of an HC metering system - Google Patents

Description

535,316 according to drivers stored in a control unit of the vehicle. In order to more easily regulate the pressure at small or no dosage amounts, the system also consists of a return hose which is arranged from a pressure side of the system back to the container. According to possible dosing unit by means of said diesel which during cooling fl pours from the container via the pump and the dosing unit back to the container. In this way an active cooling of the dosing unit is provided. The return flow from the dosing valve to the container is today substantially constant. this configuration is cooling During operation of the HC dosing system, thermal energy is stored in the exhaust system.

This thermal energy can be transferred to e.g. the dosage unit.

Since the dosing unit is currently arranged at the exhaust system of the vehicle, which exhaust system during operation of the vehicle is heated depending on e.g. load on the engine, the dosing unit risks overheating. Overheating of the dosage unit may result in degradation of the same consideration functionality, which may result in degraded performance thereof.

During certain operating cases, where a cooling flow for the dosing unit is insufficient, there is a risk that the dosing unit is functionally degraded, overheated and permanently damaged, or even completely breaks down. Even at temperatures that are not critical for hardware in the HC dosing system, there is a risk that the fuel in it will be adversely affected by excessive temperatures.

The dosing unit today comprises electrical components, some of which include a circuit board. Said circuit boards can e.g. be provided for controlling the dosing of diesel to the exhaust system of the vehicle. These electrical components are sensitive to high temperatures for several reasons. Excessive temperatures of the dosing unit can result in degradation of the electrical components, which can lead to costly repairs at a service workshop. Furthermore, diesel present in the dosing unit can at least partially change to solid form at too high temperatures, which can lead to clogging of the dosing unit. According to one example, said diesel in the dosing unit undergoes pyrolysis, said diesel being at least partially converted to coke. Thus, at least a part of said diesel can boil. It is therefore of the utmost importance that the temperature of the dosing unit of the DPF system does not exceed a critical temperature.

Cooling of the dosing unit of a DPF system in vehicles today takes place continuously during ordinary operation of the vehicle as said diesel is circulated within the DPF system in the manner indicated above. To some extent, cooling of the dosing unit during operation of the vehicle today works satisfactorily.

However, there is always a need to improve the performance of existing subsystems, e.g.

DPF systems, in vehicles, not least from a competition point of view.

When shutting down the vehicle and thus after shutting off the exhaust gas i in the exhaust system, the dosing unit for diesel is cooled by means of said diesel in the same way as during ordinary operation for a predetermined time, such as e.g. 30 minutes.

WO 2009/020541 describes a system for discharging a reducing substance from an injection system. The system has a heater connected to an injector, where the purpose of the heater e.g. is to vaporize the substance from the injector to avoid blockage in the injection system. However, the heater is space consuming and its operation is associated with costs regarding development, installation, monitoring during operation and maintenance.

WO 2008/006840 describes a system for storing and supplying an additive in an exhaust system.

There is a need to improve the current HC dosing system to reduce or eliminate the above mentioned disadvantages. SUMMARY OF THE INVENTION An object of the present invention is to provide a new and advantageous method for improving the performance of an HC dosing system.

An object of the present invention is to provide a new and advantageous dosing system, where a cooling fate of a dosing unit is missing or insufficient. Another object of the invention is to provide a new and advantageous device of an HC dosing system and a new and advantageous computer program for improving the performance of an HC dosing system.

Another object of the invention is to provide a new and advantageous device of an HC dosing system and a new and advantageous computer program for improving the performance of an HC dosing system, where a cooling flow of a dosing unit is missing or insufficient.

An object of the present invention is to provide a method of an HC dosing system, which method provides a reduced risk for the functional HC dosing system and / or a risk of clogging of components, e.g. a dosing unit, of the HC dosing system with respect to a fuel. undesired degradation of components of reduced Another object of the invention is to provide an alternative method of an HC dosing system and an alternative computer program of an HC dosing system and an alternative device of an HC dosing system. These objects are achieved by a method of HC metering system for purifying exhaust gases from an engine, comprising a metering unit for supplying a fuel to an exhaust duct, according to claim 1.

According to one aspect of the invention there is provided a method of an HC metering system for purifying exhaust gases from an engine, comprising a metering unit for supplying a fuel to an exhaust duct, comprising a metering unit for supplying a fuel to an exhaust duct, comprising the step of determining whether an undesired temperature level of said dosing unit is present, said determination whether said undesired temperature level is present being carried out after switching off an exhaust gas flow. The method also comprises the step of, if said undesired temperature level is determined to exist, removing heated fuel from said dosing unit by supplying said fuel to said exhaust duct, and thereby calculating an amount of fuel to be removed on the basis of a prevailing temperature of the dosing unit and removing said fuel dosing unit by means of a self-pressure of said HC dosing system, or by means of a self-pressure of said HC dosing system removing a predetermined amount of fuel from said dosing unit to said exhaust duct.

This reduces the risk of the fuel in the dosing unit boiling. Coking could otherwise lead to operational disturbances, such as e.g. error codes in control system.

Coke of the fuel in the dosing unit could otherwise also result in a regeneration of the particle filter being adversely affected, since a smaller amount of fuel can be dosed, whereby a temperature of the exhaust system drops. In this case, it takes longer to carry out a desired regeneration of the particle filter. In this case, it also becomes more difficult to regulate a desired temperature of the exhaust system during regeneration.

Said determination of whether said undesired temperature level is present is performed after switching off an exhaust gas flow. In the case of operation where the engine of the HC dosing system is switched off after operation with a high power outlet, a 535 315 evacuation of heated fuel in the dosing unit can contribute to lowering an undesirably high temperature of the dosing unit.

The method may comprise the step of continuously cooling said dosage unit by means of a waste of said fuel. By combining continuous cooling of the dosing unit by means of said fuel and dosing of heated fuel of the dosing unit into the exhaust duct, positive synergy effects are obtained, which lead to improved cooling of the dosing unit, especially after the engine of the HC dosing system has been switched off.

The method may comprise the step of intermittently removing fuel from said dosing unit by supplying said fuel to said exhaust duct.

By intermittently removing fuel, a heat transfer between the dosing unit and the fuel can be allowed under controlled conditions. In this way, an energy value of the fuel can be increased. At appropriate times, at least a portion of the heated fuel of the metering unit may be metered into the exhaust duct of the HC metering system.

The amount of fuel removed should be so limited that a not too large amount of fuel is supplied to the exhaust duct, in particular after switching off an exhaust gas flow at the exhaust duct. At a start-up of the HC dosing system, the exhaust duct will be heated and help to vaporize the amount of fuel removed for use in a conventional manner.

Said undesired temperature level may be within a predetermined range, e.g. within 80-130 degrees Celsius. Said undesired temperature level can be selected to a suitable value depending on the properties of the fuel in question.

The method may include the step of continuously determining a prevailing temperature of the dosage unit, to continuously determine whether an undesired temperature level of a dosage unit is present. This provides a reliable method in an HC dosing system, where 536 3'G calculations of the amount of fuel to be removed can be performed on relevant input data.

The method may comprise the step of calculating an amount of fuel to be removed on the basis of a prevailing temperature of the dosing unit. In this case, an optimized amount of fuel can be removed from the dosing unit into the exhaust duct. The calculated amount of fuel can be dosed at a set appropriate time. The calculated amount of fuel can be dosed intermittently in a suitable manner.

The method may comprise the step of removing a predetermined amount of fuel from said dosage unit. The predetermined amount of fuel may be substantially all of the available heated fuel of the dosage unit. This step has the advantage that a less computationally heavy variant is provided.

Said fuel is a hydrocarbon-based fuel, such as diesel.

According to one aspect of the invention, there is provided an apparatus of an HC metering system for purifying exhaust gases from an engine, comprising a metering unit for supplying a fuel to an exhaust duct, comprising means for determining whether an undesired temperature level of said metering unit is present. said determining whether said undesired temperature level is present is performed after shutting off an exhaust flow, and means for, if said undesired temperature level of said dosing unit is present, removing heated fuel from said dosing unit by supplying said self-exhaust gas to said self-exhaust valve. HC dosing system.

The device may comprise means for continuously cooling said dosing unit by means of a flow of said fuel. The device may comprise means for intermittently removing fuel from said dosing unit by supplying said fuel to said exhaust duct.

The device may comprise means for continuously determining a prevailing temperature of a dosing unit, for continuously determining whether an undesired temperature level of a dosing unit is present.

The device may comprise means for calculating an amount of fuel to be removed on the basis of a prevailing temperature of the dosing unit.

The device may comprise means for removing a predetermined amount of fuel from said dosing unit.

The device may comprise means for removing fuel from said dosing unit by means of the existing fuel under pressurization of the dosing unit.

The feed device may include a feed device which is arranged to supply fuel to an injection system of an engine. In this case, an already significant feeding device of the vehicle can be used for a new purpose.

Alternatively, a separate feeding device can be used.

The above objects are also achieved with a motor vehicle incorporating the features of the device of an HC dosing system described herein.

The motor vehicle can be a truck, bus or car.

According to one aspect of the invention, there is provided a computer program of HC dosing system for purifying exhaust gases from an engine, comprising a dosing unit for supplying a fuel to an exhaust duct, said computer program comprising program code stored on a computer readable medium for causing an electronic control unit or other computer connected 536 315 to the electronic control unit to perform the steps according to any one of claims 1-6.

According to one aspect of the invention, there is provided a computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-6, when said computer program is run on an electronic control unit or another computer connected to the electronic control unit. .

The procedure is easy to implement in existing motor vehicles. Software for HC dosing systems for exhaust gas purification according to the invention can be installed in a control unit of the vehicle during its manufacture. A buyer of the vehicle can thus be given the opportunity to choose the function of the procedure as an option.

Alternatively, software comprising program code for performing the innovative method of HC metering system for purifying exhaust gases from an engine, including a metering unit for supplying a fuel to an exhaust duct, may be installed in a control unit of the vehicle when upgrading at a service station. In this case, the software can be loaded into a memory in the control unit. Implementing the innovative procedure is thus cost-effective, especially since no additional sensors or components need to be installed in the vehicle.

The required hardware is already arranged in the vehicle today.

The invention thus provides a cost-effective solution to the above problems.

Software that includes program code in HC metering systems for purifying exhaust gases from an engine, including a metering unit for supplying a fuel to an exhaust duct, can be easily updated or replaced. Furthermore, different parts of the software comprising program code in HC dosing systems for purifying exhaust gases from an engine, including a dosing unit for supplying a fuel to an exhaust duct, can be replaced independently of each other. This modular configuration is advantageous from a maintenance perspective. Additional objects, advantages and novel features of the present invention will become apparent to those skilled in the art from the following details, as well as through the practice of the invention. While the invention is described below, it should be understood that the invention is not limited to the specific details described. Those skilled in the art having access to the teachings herein will recognize additional applications, modifications, and incorporations within other fields, which are within the scope of the invention. SUMMARY DESCRIPTION OF THE DRAWINGS For a more complete understanding of the present invention and further objects and advantages thereof, reference is now made to the following detailed description which is to be read in conjunction with the accompanying drawings in which like reference numerals refer to like parts throughout the several diagrams. 1 schematically illustrates a vehicle, according to an embodiment of the invention; Figure 2 schematically illustrates a subsystem of the vehicle shown in Figure 1, according to an embodiment of the invention; Figure 3a schematically illustrates a fate diagram of a method, according to an embodiment of the invention; Figure 3b schematically illustrates in further detail a fate diagram of a method, according to an embodiment of the invention; and Figure 4 schematically illustrates a computer, according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE FIGURES Referring to Figure 1, a side view of a vehicle 100 is shown. The exemplary vehicle 100 consists of a tractor 110 with an engine 150 and a trailer 112. The vehicle may be a heavy vehicle, such as a truck or a bus. The vehicle can alternatively be a car. 536 316 11 It should be noted that the invention is suitable for use with any suitable HC dosing system and is not sold limited to DPF systems in motor vehicles. The innovative method and the innovative device according to an aspect of the invention are well suited for platforms which include an HC dosing system other than motor vehicles, such as e.g. watercraft. The watercraft can be of any suitable type, such as e.g. motorboats, ships, ferries or ships.

The innovative method and the innovative device according to an aspect of the invention are also well suited for e.g. systems including industrial engines and / or motorized industrial robots.

The innovation in an HC dosing system and the innovative device of a device according to an aspect of the invention are also well suited for different types of power plants, such as e.g. an electric power plant comprising a diesel generator.

The innovation of an HC dosing system and the innovative device of a device are well suited for any suitable engine system which includes an engine and an HC dosing system, such as e.g. at a locomotive or other platform.

The innovative method and device are well suited for any suitable system including a particulate generator (eg an internal combustion engine) and an HC dosing system.

The innovative method and the innovative device are well suited for any suitable system which includes any suitable system which produces exhaust gases with particles and an alter which stores particles which are combusted during a regeneration of said filters, in particular during an active regeneration of said fi lter. 536 315 12 Here, the term "link" refers to a communication link which may be a physical line, such as an optoelectronic communication line, or a non-physical line, such as a wireless connection, for example a radio or microwave link.

Here, the term "lead" refers to a passage for holding and transporting a fl uid, such as e.g. a fuel in the liquid form. The conduit can be a pipe of any suitable dimension. The conduit may consist of any suitable material, such as e.g. plastic, rubber or metal.

Here, the term "fuel" refers to an agent used to actively regenerate a particle filter in an HC dosing system. Said fuel is according to one embodiment diesel. Of course, other types of hydrocarbon-based fuels can be used. Here, diesel is cited as an example of a fuel, but one skilled in the art will recognize that the innovative process and device can be realized for other types of fuels, with the required boiling temperature for selected fuels, in control algorithms to execute software code in accordance with the innovative process. adaptations, such as e.g. adaptations to adequate Although the term HC dosing system is used herein to indicate a particulate filter system, the invention is not limited to the use of a diesel particulate filter. On the contrary, other types of particle filters can be used according to the invention. One skilled in the art will recognize what kind of fuel is best suited for regenerating the selected particulate filter.

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

The subsystem 299 is arranged in the tractor 110. The subsystem 299 may form part of an HC dosing system. The subsystem 299 according to this example consists of a container 205 which is arranged to contain a fuel. The container 205 is arranged to contain a suitable amount of fuel and is further arranged to be able to be refilled if necessary. The container can hold e.g. 200 or 1500 liters of fuel.

A first line 271 is arranged to lead the fuel to a pump 230 from the container 205. The pump 230 may be any suitable pump. The pump 230 may be a diaphragm pump comprising at least one filter. The pump 230 is arranged to be driven by means of an electric motor. The pump 230 is arranged to pump the fuel from the container 205 via the first line 271 and via a second line 272 supply said fuel to a dosing unit 250.

The dosing unit 250 comprises an electrically controlled dosing valve, by means of which a flow of fuel added to the exhaust system can be controlled. The pump 230 is arranged to pressurize the fuel in the second line 272.

The dosing unit 250 is provided with a throttling unit, against which said pressure of the fuel is built up in the subsystem 299.

The dosing unit 250 is arranged to supply said fuel to an exhaust system (not shown) of the vehicle 100. More specifically, the dosing unit 250 is arranged to supply in a controlled manner a suitable amount of fuel to an exhaust system of the vehicle 100. According to this embodiment, a particle filter (not shown) shown), e.g. a DPF, arranged downstream of a position of the exhaust system where the supply of fuel is provided. The amount of fuel supplied to the exhaust system is intended to be used in a conventional manner in the HC dosing system for active regeneration of the paiticle filter.

The dosing unit 250 is arranged at e.g. an exhaust pipe arranged to direct exhaust gases from the internal combustion engine 150 of the vehicle 100 to said particulate matter. The dosing unit 250 is arranged in thermal contact with the exhaust system of the vehicle 100. This means that thermal energy is stored in e.g. an exhaust pipe, muffler, particulate filter and SCR catalyst can then be led to the dosing unit 250. The dosing unit 250 comprises an electronic control card, which is arranged to handle communication with a control unit 200.

The dosing unit 250 also includes plastic and / or rubber components, which may melt or otherwise be adversely affected at excessive temperatures.

The dosing unit 250 is itself sensitive to temperatures above a certain temperature value, 120 degrees Celsius. Since the exhaust duct 240, the muffler and the particulate filter of the vehicle 100 exceed this temperature value, there is a risk that the dosing unit may overheat during operation of the vehicle or after operation of the vehicle unless cooling such as e.g. for example hence achieved.

It should be noted that fuel present in the dosage unit 250 may be adversely affected at temperatures significantly lower than the 120 degrees Celsius indicated above. At temperatures exceeding e.g. 70 degrees Celsius, the fuel can become unstable, so that at slightly higher temperatures it may start to boil and in the long run possibly cause clogging of the dosing unit 250.

A third conduit 273 is preferably provided between the metering unit 250 and the container 205. The third conduit 273 is arranged to return a certain amount of fuel supplied to the metering valve 250 to the container 205. With this configuration, advantageous cooling of the metering unit 250 is provided. The dosing unit 250 is cooled by means of a flow of the fuel as it is pumped through the dosing unit 250 from the pump 230 to the container 205. Cooling of the dosing unit, by means of a return de of the third line, can also be used after the vehicle has been switched off and the exhaust flow has ceased. If this cooling proves to be insufficient for the dosing unit 250, the innovative method can be used to advantage, including the step of evacuating at least a part of the fuel heated in the dosing unit 250 to the exhaust duct 240.

A first control unit 200 is arranged for communication with a first temperature sensor 220 via a link 221. The first temperature sensor 220 is arranged to detect a prevailing temperature of the dosing unit 250.

The first temperature sensor 220 is arranged to continuously send signals to the first control unit 200 including information about a prevailing first temperature T1 of the dosing unit 250.

The first control unit 200 is arranged for communication with the pump 230 via a link 231. The first control unit 200 is arranged to control operation of the pump 230 in order to e.g. regulate the flows of fuel within the subsystem 299.

The first control unit 200 is arranged to control an operating power of the pump 230 by controlling the electric motor thereby.

The first control unit 200 is arranged for communication with a second temperature sensor 280 via a link 281. The second temperature sensor 280 is arranged to detect a prevailing temperature T2 of the exhaust duct 240.

The second temperature sensor 280 is arranged to continuously send signals to the first control unit 200 including information about the prevailing temperature T2 of the exhaust duct 240.

The first control unit 200 is arranged to calculate a prevailing temperature of the dosing unit 250 on the basis of the signals received from the second temperature sensor 280.

The first control unit 200 is arranged for communication with the dosing unit 250 via a link 251. The first control unit 200 is arranged to control operation of the dosing unit 250 in order to e.g. regulating the supply of fuel to the exhaust system of the vehicle 100. According to one example, the first control unit 200 is arranged to control the operation of the dosing unit 250 in order to e.g. regulate the re-supply of fuel to the tank 205.

According to one embodiment, the first control unit 200 is arranged that, on the basis of the signals received from the first temperature sensor 220 and / or the second temperature sensor 280, if necessary, i.e. temperature level of said dosing unit is present, remove fuel from an unwanted said dosing unit by supplying said fuel to said exhaust duct, in accordance with an aspect of the innovative process. In particular, the first control unit 200 according to an embodiment is arranged to, on the basis of the signals received from the first temperature sensor 220 and / or the second temperature sensor 280, calculate, if necessary, an amount of fuel to be removed on the basis of a prevailing temperature of the dosing unit. in accordance with one aspect of the innovative process.

A second control unit 210 is arranged for communication with the first control unit 200 via a link 201. The second control unit 210 may be detachably connected to the first control unit 200. The second control unit 210 may be a control unit external to the vehicle 100. The second control unit 210 may be arranged to perform the innovative method steps according to the invention. The second control unit 210 can be used to upload software to the first control unit 200, in particular software for performing the innovative method. The second control unit 210 may alternatively be arranged for communication with the first control unit 200 via an internal network in the vehicle. The second control unit 210 may be arranged to perform substantially the same functions as the first control unit 200. such as e.g. to determine whether an undesired temperature level of the dosing unit 250 is present, and if said undesired temperature level is present, dosing an appropriate amount of fuel of the dosing unit into the exhaust duct 240. The innovative procedure can be performed by the first control unit 200 or the 536 3'IE ~ 17 second control unit 210, or by both the first control unit 200 and the second control unit 210.

According to this embodiment, a source of compressed air 260 is arranged to supply pressurized air to the dosing unit 250 via a line 261. The dosing unit 250 is arranged to use said supplied pressurized air to further atomize the fuel being dosed. The compressed air can also be used to at least partially drive the dosing unit to dose said fuel into the exhaust duct. The compressed air can also be used to, where applicable, blow out e.g. the dosage unit 250 with respect to fuel contained therein. This can occur during operation of motor 150, or after motor 150 has been turned off.

According to one embodiment, the container 205 may be the vehicle's fuel tank, with parts of the vehicle's volatile fuel system being used in accordance with the present invention. According to another example, the container may be a separate container, i.e. not the same container as the vehicle's fuel tank.

According to one embodiment, the dosing unit 250 is arranged directly at the exhaust duct 240 of the HC dosing system. According to another example, the dosing unit 250 is arranged with a passive nozzle presumably arranged through said exhaust duct 240 for dosing said fuel directly into the exhaust duct.

According to one embodiment, said pump 230 is the same pump that normally generates fuel pressure for an injection system of the engine 150. According to another example, said pump 230 is a separate pump, i.e. not the same pump that normally generates the fuel pressure to the injection system.

According to one example, a precatalyst and / or oxidation catalyst is mounted in series with the particulate filter. In this case, said precatalyst and / or oxidation catalyst are arranged upstream of said particle filter. Figure 35a schematically illustrates a flow chart of a process in an HC metering system for purifying exhaust gases from an engine, comprising a metering unit for supplying a fuel to an exhaust duct, according to an embodiment of the invention. The method comprises a first method step s301. Step s301 includes the steps of determining whether an undesired temperature level of said dosage unit is present, and if said undesired temperature level is determined to exist, removing fuel from said dosage unit by supplying said fuel to said exhaust duct. After step s301, the process is terminated.

Figure 3b schematically illustrates a flow chart of a process in an HC dosing system for purifying exhaust gases from the engine 150, comprising the dosing unit 250 for supplying a fuel to the exhaust duct 240, according to an embodiment of the invention.

The method includes a first method step s310. The process step s310 includes the step of determining a prevailing temperature of the dosing unit 250. This is done by directly measuring the prevailing temperature at the dosing unit 250. In process step s310, a first temperature value T1 representing a prevailing temperature of the dosing unit 250 is measured.

Method step s320 includes the step of determining an estimated prevailing temperature of the dosing unit 250 indirectly. This is done by measuring the temperature at a component other than the dosing unit 250 of the HC dosing system. In s310 a temperature value T2 of a component other than the dosing unit 250 is measured.

By means of the measured temperature T2, a first estimated prevailing temperature T1est of the dosing unit 250 can be determined. According to an alternative, a second estimated prevailing temperature T2est of the dosing unit 250 can be determined (calculated) by means of a calculation model which has other process steps other parameters than the temperature of a component of the HC dosing system as input value. Such an input parameter can e.g. be a prevailing load on the motor 150. It should be noted that steps s310 and s320 can be performed substantially simultaneously, or in reverse order. It should also be pointed out that according to one embodiment it is possible to use only the measured temperature T1 of the dosing unit 250 to determine a maximum temperature value Tmax as below. In some cases it is advantageous to use both the measured temperature T1 and at least one of the estimated prevailing temperatures T1est and T2est to determine a maximum temperature value Tmax as below because a more robust process is thereby obtained.

After the process step s320, a subsequent process step s330 is performed.

Process step s330 includes the step of comparing the determined first temperature T1 and at least one of the estimated prevailing temperatures T1est and T2est of the dosing unit 250. After the process step s330, a subsequent process step s340 is performed.

The process step s34O comprises the step of selecting the highest value of the values on the basis of a result of said comparison between the determined first temperature T1 and at least one of the estimated prevailing temperatures T1est and T2est. This highest temperature value is also called Tmax.

Method step s340 also includes the step of determining whether an unwanted one is present, wherein the dosing unit 250 is arranged to supply fuel to an exhaust duct.

This can be done by a comparison with a limit value Tth, such as a predetermined temperature value, e.g. 70 or 100 degrees Celsius, depending on the type of fuel used in the HC dosing system. If Tmax is greater than or equal to Tth, it may be determined that an undesired temperature level of the dosage unit is present. If Tmax is less than Tth, it can be determined that an undesired temperature level of the dosage unit does not exist. After the process step s340, a subsequent process step s350 is performed. temperature level of the dosing unit 536 306 According to an alternative embodiment, it can be determined as described above whether an undesired temperature level of the dosing unit 250 exists on the basis of only the measured temperature T1 of the dosing unit. According to this embodiment, a less complex procedure is provided, according to one aspect of the invention.

The method step s350 includes the step of, on the basis of the selected value Tmax, calculating an amount of fuel to be removed from the dosing unit 250. This can be performed by means of stored calculation models. In this case, a suitable dosage configuration can be determined, e.g. regarding the amount of fuel to be removed at the respective different times. After the process step s350, a subsequent process step s360 is performed.

The process step s360 comprises the step of, on the basis of the selected value Tmax, taking a measure for influencing the temperature of the dosing unit 250. In this case, a fixed amount of fuel is removed at a suitable time.

It appears here that a number of different amounts of fuel can be dispensed at the respective fixed time. After the procedure step s360, the procedure is terminated.

Referring to Figure 4, there is shown a diagram of an embodiment of a device 400. The controllers 200 and 210 described with reference to Figure 2 may in one embodiment include the device 400. The device 400 includes a non-functional memory 420, a data processing unit 410, and a read / write memory 450. The non-usable memory 420 has a first memory portion 430 in which a computer program, such as an operating system, is stored to control the operation of the device 200. Further, the device 400 includes a bus controller, a serial communication port , I / O means, an A / D converter, a time and date input and transfer unit, an event counter and an interrupt controller (not shown). The non-volatile memory 420 also has a second memory portion 440. A computer program P is provided which includes routines for determining whether an undesired temperature level of the dosage unit 250.

The program P comprises routines for, if said undesired temperature level is determined to exist, removing fuel from said dosing unit by supplying said fuel to said exhaust duct, according to an aspect of the innovative method. The program P includes routines for continuously determining a prevailing temperature of the dosing unit, for continuously determining whether an undesired temperature level of a dosing unit is present.

The program P includes routines for calculating an amount of fuel to be removed on the basis of a prevailing temperature of the dosing unit.

The program P includes routines for continuously cooling the dosing unit 250 by means of a waste of said fuel.

The program P comprises routines for intermittently removing fuel from said dosing unit by supplying said fuel to said exhaust duct.

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

When it is described that the data processing unit 410 performs a certain function, it is to be understood that the data processing unit 410 performs a certain part of the program which is stored in the memory 460, or a certain part of the program which is stored in the read / write memory 450.

The data processing device 410 can communicate with a data port 499 via a data bus 415. The useless memory 420 is intended for communication with the data processing unit 410 via a data bus 412. The separate memory 460 is intended to communicate with the data processing unit 410 via a data bus 411. Read / write memory 450 is arranged to communicate with the data processing unit 410 via a data bus 414. To the data port 499, e.g. links 201, 221, 231, 251 and 281 are connected (see Figure 2). When data is received on the data port 499, it is temporarily stored in the second memory part 440. Once the received input data has been temporarily stored, the data processing unit 410 is arranged to perform code execution in a manner described above. According to one embodiment, signals received at the data port 499 include information about a first measured temperature T1 of the dosing unit 250. According to one embodiment, signals received at the data port 499 include information about a second measured temperature T2 of a component of the HC dosing system in addition to the dosing unit 250. The received signals at the data port 499 can be used by the device 400 to, where applicable, remove fuel from the metering unit 250 of the HC metering system.

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

The foregoing description of the preferred embodiments of the present invention has been provided for the purpose of illustrating and describing the invention. It is not intended to be exhaustive or to limit the invention to the variations described. Obviously, many modifications and variations will occur to those skilled in the art. The embodiments were selected and described to best explain the principles of the invention and its practical applications, thereby enabling those skilled in the art to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims (15)

10 15 20 25 30 535 ENG 23 PATENT REQUIREMENTS A method of an HC metering system for purifying exhaust gases from an engine (150), comprising a metering unit (250) for supplying a hydrocarbon-based fuel to an exhaust duct (240), comprising the step of: - determining (s340) whether an undesired temperature level of said dosing unit (250) is present, said determining whether said undesired temperature level is present, exhaust gas flow is performed after switching off a characteristic of the steps that: - if said undesired temperature level is determined to exist, remove (s360) heated dosing fuel from said 250 by supplying said fuel to said exhaust duct (240), and thereby - calculating (s350) an amount of fuel to be removed on the basis of a prevailing temperature of the dosing unit (250) and removing (s360) fuel from said dosing unit by means of a self-pressure of said HC dosing system, or - by means of a self-pressure of said HC dosing system remove (s360) a predetermined amount of fuel from said dosing system unit (250) to said exhaust duct. The method of claim 1, comprising the step of continuously cooling said dosage unit (250) by a flow of said fuel. A method according to claim 1 or 2, comprising the step of intermittently removing (s360) fuel from said dosing unit (250) by supplying said fuel to said exhaust duct (240). A method according to any one of the preceding claims, wherein said undesired temperature level is within a predetermined range, e.g. within 80-130 degrees Celsius. 10 15 20 25 30 535 3'l6 24 A method according to any one of the preceding claims, comprising the step of: - continuously determining a prevailing temperature of the dosing unit (250), to continuously determine whether an undesired temperature level of the dosing unit (250) is present. A method according to any one of the preceding claims, wherein said fuel is diesel. An apparatus of an HC metering system for purifying exhaust gases from an engine (150), comprising a metering unit (250) for supplying a hydrocarbon-based fuel to an exhaust duct (240), comprising: - means (200; 210; 400) for determining whether an undesired temperature level of said dosage unit (250) is present, said determining whether said undesired temperature level exists, is performed after shutting off an exhaust gas fl, characterized by: - means (200; 210; 400) for, if said undesired temperature level of said dosing unit (250) is determined to be present, removing heated fuel from said dosing unit (250) by supplying said fuel to said exhaust duct (240), comprising - means (200; 210; 400) for calculating an amount of fuel to be removed on a basis of a prevailing temperature of the dosing unit (250) or means (200; 210; 400) for removing a predetermined amount of fuel from said dosing unit (250), and means (200; 210; 400) for removing br from the said dosing unit by means of a self-pressure of said HC dosing system. Device according to claim 7, comprising: - means (230) for continuously cooling said dosing unit (250) by means of a flow of said fuel. Apparatus according to claim 7 or 8, comprising: means (200; 210; 400) for intermittently removing fuel from said dosing unit (250) by supplying said fuel to said exhaust duct (240). . Device according to any one of claims 7-9, wherein said undesired temperature level is within a predetermined range, e.g. within 80-130 degrees Celsius. Device according to any one of claims 7-10, comprising: - means (200; 210; 400) for continuously determining a prevailing temperature of the dosing unit (250), for continuously determining the presence of an undesired temperature level of the dosing unit (250). Motor vehicle (100; 110) comprising a device according to any one of claims 7-11. A motor vehicle (100; 110) according to claim 12, wherein the motor vehicle is something of a truck, bus or passenger car. A computer program (P) in an HC metering system for purifying exhaust gases from an engine (150), comprising a metering unit (250) for supplying a hydrocarbon-based fuel to an exhaust duct (240), said computer program (P) comprising program code for cause an electronic control unit (200; 400) or another computer (210; 400) connected to the electronic control unit (200; 400) to perform the steps according to any one of claims 1-6. A computer program product comprising a program code stored on a computer readable medium for performing the method steps of any of claims 1-6, when said computer program is run on an electronic control unit (200; 400) or another computer (210; 400) connected to the electronic control unit (200; 400).