TECHNICAL FIELD

5

The present invention relates to a method pertaining to an HC (hydrocarbon) dosing system. The invention relates also to a computer programme product containing programme code for a computer for implementing a method according to the invention. The invention relates also to an HC dosing 10 system and a motor vehicle which is equipped with the HC dosing system.

BACKGROUND

In vehicles today, diesel fuel is used as fuel in DPF (diesel particulate filter) 15 systems which comprise a particle filter. The particle filter is adapted to capturing, for example, diesel particles and soot. During active regeneration of the particle filter, diesel fuel is supplied to an exhaust pipe downstream of an engine and is led into an oxidation catalyst, also called DOC. In the oxidation catalyst, said diesel fuel is ignited and burnt and causes a rise in 20 the temperature of the exhaust system. Active regeneration of the particle filter situated downstream of the oxidation catalyst can thus be effected.

One type of DPF system comprises a container for diesel fuel. The DPF system may also have a pump adapted to drawing said diesel fuel from the

25 container via a suction hose and to supplying it via a pressure hose to a dosing unit situated adjacent to an exhaust system of the vehicle, e.g. adjacent to an exhaust pipe of the exhaust system. The container may be the vehicle's fuel tank or a separate container of the DPF system. The dosing unit is adapted to injecting a necessary amount of diesel fuel into the

30 exhaust pipe upstream of the particle filter according to operating routines stored in a control unit of the vehicle. To make it easier to regulate the pressure when no or only small amounts are being dosed, the system also comprises a return hose which runs back from a pressure side of the system to the container. This configuration makes it possible to cool the dosing unit by means of said diesel fuel which, during cooling, flows from the container via the pump and the dosing unit and back to the container. This results in active cooling of the dosing unit. The return flow from the dosing valve to the container is currently substantially constant.

In certain conditions, air may enter the DPF system upstream of the pump. This may for example occur during start-up of the DPF system after its initial fitting, in which case there will be air in the suction hose.

Air may also enter the suction hose when the DPF system has used up all the available fuel in the separate container, in which case the container will be empty of fuel, the pump runs dry and air is drawn into it via the suction hose.

Another example is that air may enter the suction hose in situations where there is a limited amount of fuel left in the separate container in the DPF system and said DPF system moves in such a way that splashing occurs in the container, in which case air may be drawn into the pump via the suction hose.

A further example is that the suction hose may be incorrectly fitted to the pump such that air leakage occurs on the upstream side of the pump. Here again air may be drawn into the pump via the suction hose or at a faulty or damaged seal between the suction hose and the pump.

An example is that the suction hose may itself be frayed or defective in such a way as to allow air to be drawn into the pump via the hose. Any air entering the pump on an inlet side of it will adversely affect the fuel flow in the DPF system, thereby reducing a cooling power of the dosing unit, with potential risk of overheating of temperature-sensitive components of the dosing unit.

Regeneration of the DPF system's particle filter may also be adversely affected by presence of air in the pump in that the fuel supply to the oxidation catalyst will be limited, with consequent lowering of the temperature. In such cases, any desired regeneration will take more time. It will also be more difficult to regulate a temperature of the DPF system.

Any presence of air in the pump in the DPF system adversely affects a working pressure of the dosing unit. Building up a normal working pressure of the DPF system also currently takes quite a long time when there is air in the pump.

As the dosing unit is currently situated adjacent to the vehicle's exhaust system which becomes warm during operation of the vehicle, e.g. depending on the engine's load, there is risk of the dosing valve becoming overheated. Overheating of the dosing unit may entail degradation of its functionality, potentially impairing its performance.

The dosing unit currently comprises electrical components, certain of them being provided with a circuit card. Said circuit card may for example be adapted to controlling the dosing of diesel fuel to the vehicle's exhaust system. For various reasons, these electrical components are sensitive to high temperatures. Too high temperatures of the dosing unit may result in degradation of the electrical components, potentially leading to expensive repairs at a service workshop. Moreover, diesel fuel present in the dosing unit may at least partly convert to solid form at too high temperatures, potentially leading to obstruction of the dosing unit. According to an example, said diesel fuel undergoes pyrolysis in the dosing unit and is thereby at least partly converted to coke. Thus at least part of said diesel fuel may carbonise. It is therefore of the utmost importance that the temperature of the dosing unit of the DPF system should not exceed a critical level.

There is thus a need to improve current DPF systems in order to reduce or eliminate the above disadvantages.

SUMMARY OF THE INVENTION

An object of the present invention is to propose a novel and advantageous method for improving the performance of an HC dosing system.

An object of the present invention is to propose a novel and advantageous method for improving the performance of a DPF system.

Another object of the invention is to propose a novel and advantageous HC dosing system and a novel and advantageous computer programme for improving the performance of a HC dosing system.

Another object of the invention is to propose a novel and advantageous DPF system and a novel and advantageous computer programme for improving the performance of a DPF system. An object of the present invention is to propose a novel and advantageous method for improving regeneration of a particle filter of an HC dosing system when there is air in said HC dosing system.

A further object of the invention is to propose an alternative method pertaining to an HC dosing system and an alternative computer programme pertaining to an HC dosing system, and an alternative HC dosing system. Another object of the invention is to propose a method pertaining to an HC dosing system whereby a working pressure of the fuel can be built up more quickly than in the state of the art when there is air in a feed device. These objects are achieved with a method pertaining to an HC dosing system whereby fuel in liquid form is supplied to a feed device via which fuel is supplied to at least one consumption point from a container, according to claim 1. An aspect of the invention proposes a method pertaining to an HC dosing system whereby fuel is supplied to a feed device via which fuel is supplied to at least one consumption point from a container, comprising the step of continuously detecting the feed pressure furnished by the feed device, and of controlling the operation of the feed device on the basis of changes in said feed pressure, with the object of reducing the impact of unwanted air supply at the feed device. This makes it possible for a working pressure of the fuel to be built up more quickly than in the state of the art in the presence of air supplied upstream to a feed device. The method may further comprise the step of altering the operation of the feed device in correlation with the changes in said feed pressure. This makes it possible for a working pressure of the fuel to be built up more quickly in the presence of air supplied upstream to a feed device than in the state of the art. In cases where the feed pressure drops because air is for various reasons supplied upstream of the feed device, a speed of the pump may also thereupon be lowered. In cases where the feed pressure increases after having been temporarily reduced because air has for various reasons been supplied upstream of the feed device, a speed of the pump may thereupon also be increased. This makes it possible for the operation of the feed device to be altered in a correlated way in response to the changes in said feed pressure according to the invention. Control of the operation of said feed device may be by means of a pump speed of the feed device. The result is an effective way of controlling the feed device according to an aspect of the invention. Pump speed may also be called pump rate or pump frequency.

Control of the operation of said feed device may be relative to a predetermined level of the feed pressure which the feed device is intended to furnish. This predetermined level denotes a predetermined working pressure at which the HC dosing system is intended to operate. Said predetermined level of the working pressure which the feed device is intended to furnish may be any desired suitable level. The result is a flexible solution which is easy to adapt to different types of HC dosing systems. The result is a versatile solution to the above problems. Control of the operation of said feed device may be based on the time derivative of said detected feed pressure. Continuously taking into the account the time derivative of the feed pressure and controlling the operation of the feed device on the basis thereof results in an effective method according to the invention. This solution does not involve much calculation capacity, since a time derivative of the feed pressure can quickly and easily be determined by calculation means intended for the purpose. The result is a method which can quickly adapt the control of the feed device in response to sudden changes in the feed pressure caused by presence of air at the feed device.

The method may further comprise the steps of

- determining presence of air supplied upstream to the feed device, and

- when such presence is found, controlling the operation of the feed device on the basis of changes in said feed pressure.

Thus optimising the HC dosing system's start-up time in the presence of air supplied to the feed device means that regeneration of the DPF filter can be improved and made more effective in certain applications where the HC dosing system is used to supply a fuel to a DPF system. Start-up time means a time from when presence of air at the feed device is detected to when a desired working pressure of the HC dosing system is reached. According to an aspect of the invention, the start-up time may with advantage be shorter than, for example, three minutes.

The method may further comprise the step of

- determining said presence on the basis of detected operating power of a power source which is adapted to powering said feed device and/or on the basis of a determined time during which deviant operation of the feed device takes place.

Detecting feed device behaviour characterised by presence of air at the feed device makes it possible for the feed device to be controlled according to the invention in order thereby to improve or optimise the HC dosing system's start-up time.

The feed device may be a diaphragm pump. The feed device may be any suitable pump, e.g. a gear pump.

Said at least one consumption point may be a dosing unit.

To minimise the impact of air or air bubbles on the HC dosing system, the innovative method may be applied to continuously adapt an operating power of the feed device to a prevailing situation, particularly taking into account the time derivative of the feed pressure of the feed device. A positive effect of the innovative method is that a better mean efficiency of the feed device in the presence of air at it can be achieved.

The method is easy to implement in existing motor vehicles. Software pertaining to an HC dosing system whereby fuel is supplied to a feed device via which fuel is supplied to at least one consumption point from a container according to the invention may be installed in a control unit of the vehicle during the manufacture of the vehicle. A purchaser of the vehicle may thus have the possibility of selecting the function of the method as an option. Alternatively, software which comprises programme code for applying the innovative method pertaining to an HC dosing system whereby fuel is supplied to a feed device via which fuel is supplied to at least one consumption point from a container may be installed in a control unit of the vehicle on the occasion of upgrading at a service station, in which case the software may be loaded into a memory in the control unit. Implementing the innovative method is therefore cost-effective, particularly as no further sensors or components need be installed in the vehicle. Relevant hardware is currently already provided in the vehicle. The invention therefore represents a cost-effective solution to the problems indicated above.

Software comprising programme code pertaining to a HC dosing system whereby fuel in liquid form is supplied to a feed device via which fuel is supplied to at least one consumption point from a container is easy to update or replace. Various parts of the software comprising programme code pertaining to an HC dosing system whereby fuel is supplied to a feed device via which fuel is supplied to at least one consumption point from a container may also be replaced independently of one another. This modular configuration is advantageous from a maintenance perspective. An aspect of the invention proposes an HC dosing system adapted to supplying fuel in liquid form to a feed device which is itself adapted to supplying fuel to at least one consumption point from a container, comprising: - means for continuously detecting the feed pressure furnished by the feed device, and

- means for controlling the operation of the feed device on the basis of changes in said feed pressure, with the object of reducing the impact of unwanted air supply at the feed device. The HC dosing system may further comprise means for altering the operation of the feed device in correlation with the changes in said feed pressure. In the HC dosing system, control of the operation of said feed device may be by means of a pump speed of the feed device.

In the HC dosing system, control of the operation of said feed device may be relative to a predetermined level of the feed pressure which the feed device is intended to furnish.

In the HC dosing system, control of the operation of said feed device may be based on the time derivative of said detected feed pressure. The HC dosing system may further comprise

- means for determining presence of air supplied upstream to the feed device, and

- means for, when such presence is found, controlling the operation of the feed device on the basis of changes in said feed pressure.

The HC dosing system may further comprise

- means for determining said presence on the basis of detected operating power of a power source which is adapted to powering said feed device, and/or on the basis of a determined time during which deviant operation of the feed device takes place.

The feed device may be a diaphragm pump. Said at least one consumption point may be a dosing unit. The above objects are also achieved with a motor vehicle which comprises the HC dosing system. The vehicle may be a truck, bus or passenger car. An aspect of the invention proposes a computer programme pertaining to an HC dosing system whereby fuel in liquid form is supplied to a feed device via which fuel is supplied to at least one consumption point from a container, which programme contains programme code stored on a computer-readable medium for causing an electronic control unit or another computer connected to the electronic control unit to perform steps according to any of claims 1-9.

An aspect of the invention proposes a computer programme pertaining to an HC dosing system whereby fuel in liquid form is supplied to a feed device via which fuel is supplied to at least one consumption point from a container, which programme contains programme code for causing an electronic control unit or another computer connected to the electronic control unit to perform steps according to any of claims 1 -9. An aspect of the invention proposes a computer programme product containing a programme code stored on a computer-readable medium for performing method steps according to any of claims 1-9 when said programme is run on an electronic control unit or another 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 restricted to the specific details described. Specialists having access to the teachings herein will recognise further applications, modifications and incorporations within other fields, which are within the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

Figure 2 illustrates schematically a subsystem for the vehicle depicted in Figure 1 , according to an embodiment of the invention;

Figure 3a is a schematic flowchart of a method according to an embodiment of the invention;

Figure 3b is a more detailed schematic flowchart of a method according to an embodiment of the invention;

Figure 4a is a schematic diagram of feed pressure as a function of time; Figure 4b is a schematic diagram of pump speed as a function of time; and Figure 5 illustrates schematically a computer according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 depicts a side view of a vehicle 100. The exemplified vehicle 100 comprises a tractor unit 110 with an engine 150 and a trailer 112. The vehicle may be a heavy vehicle, e.g. a truck or a bus. The vehicle may alternatively be a passenger car.

It should be noted that the invention is applicable to any suitable HC dosing system and is therefore not restricted to DPF systems of motor vehicles. The innovative method and the innovative device according to an aspect of the invention are well suited to other platforms which have an HC dosing system 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 HC dosing system according to an aspect of the invention are also well suited to, for example, systems which comprise industrial engines and/or engine-powered industrial robots.

The innovative method and the innovative HC dosing system according to an aspect of the invention are also well suited to various kinds of power plants, e.g. an electric power plant comprising a diesel generator.

The innovative method and the innovative HC dosing system are well suited to any engine system which comprises an engine and an HC dosing system, e.g. on a locomotive or some other platform.

The innovative method and the innovative device are well suited to any system which comprises a particle generator (e.g. a combustion engine) and an HC dosing system. The innovative method and the innovative device are well suited to any system which comprises any kind of system which generates exhaust gases with particles and a filter which stores particles, which particles are burnt during regeneration of said filter, particularly during active regeneration of said filter.

It should be noted that the HC dosing system may be any HC dosing system, although it is herein exemplified as an HC dosing system pertaining to a DPF system of a vehicle. The feed device may be any desired feed device and need not be a diaphragm pump as herein described. The fuel of the HC dosing system may be any desired fuel such as oil, e.g. lubricating oil, diesel fuel or some other carbon-based fuel, e.g. petrol, ethanol or methanol etc. 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 fuel in liquid form. The line may be a pipe of any suitable size. The line may be made of any suitable material, e.g. plastic, rubber or metal.

The term "fuel" refers herein to an agent used for active regeneration of a particle filter of an HC dosing system. Said fuel according to a version is diesel fuel. Other kinds of hydrocarbon-based fuels may of course be used. Diesel fuel is herein cited as an example of a fuel, but one skilled in the art will appreciate that the innovative method and the innovative device are feasible for other types of fuels, subject to necessary adaptations, e.g. adaptations to adequate carbonisation temperatures for fuels adopted, in control algorithms for executing software code in accordance with the innovative method.

Although the term "HC dosing system" is used herein to denote a particle filter system, the invention is not restricted to use of a diesel particle filter. On the contrary, other types of particle filter may be used according to the invention. One skilled in the art will appreciate which kind of fuel is best suited to regenerating the particle filter adopted.

Figure 2 depicts a subsystem 299 of the vehicle 100. The subsystem 299 is situated in the tractor unit 110. The subsystem 299 may form part of an HC dosing system, e.g. a DPF system. The subsystem 299 consists according to this example of a container 205 adapted to containing a fuel. The container 205 is adapted to containing a suitable amount of fuel and to being replenishable as necessary. The container may accommodate, for example, 200 or 1500 litres of fuel. A first line 271 is adapted to leading 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 provided with at least one filter. The pump 230 is adapted to being driven by an electric motor. The pump 230 is adapted to drawing the fuel from the container 205 via the first line 271 and supplying it via a second line 272 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 adapted to pressurising the fuel in the second line 272. The dosing unit 250 is provided with a throttle unit against which said pressure of the fuel is built up in the subsystem 299. This pressure is herein referred to as the working pressure of the HC dosing system.

The dosing unit 250 is adapted to supplying said fuel to an exhaust system (not depicted) of the vehicle 100. More specifically, the dosing unit 250 is adapted to supplying a suitable amount of fuel in a controlled way to an exhaust system of the vehicle 100. According to this version, a particle filter (not depicted) in the form of a DPF is situated downstream of a location in the exhaust system where the fuel supply is effected. The amount of fuel supplied in the exhaust system is intended to be used in a conventional way for active regeneration of the particle filter.

The dosing unit 250 is situated adjacent to, for example, an exhaust pipe which is itself adapted to leading exhaust gases from the combustion engine 50 of the vehicle 100 to an oxidation catalyst situated upstream of said particle filter. The dosing unit 250 is situated in thermal contact with the exhaust system of the vehicle 100. This means that thermal energy stored in, for example, an exhaust pipe, silencer, particle filter and a downstream SCR catalyst can thus be led to the dosing unit.

The dosing unit 250 is provided with an electronic control card which is adapted to handling communication with a control unit 200. The dosing unit 250 also comprises plastic and/or rubber components which might melt or be otherwise adversely affected as a result of too high temperatures.

The dosing unit 250 is sensitive to temperatures above a certain value, e.g. 120 degrees Celsius. As for example the exhaust pipe, the silencer and the particle filter of the vehicle 100 exceed this temperature value, there is risk that the dosing unit 250 might become overheated during or after operation of the vehicle if not provided with cooling. A third line 273 runs between the dosing unit 250 and the container 205. The third line 273 is adapted to leading back to the container 205 a certain amount of the fuel fed to the dosing valve 250. This configuration achieves with advantage cooling of the dosing unit 250. The dosing unit 250 is thus cooled by a flow of the fuel when it is pumped through the dosing unit 250 from the pump 230 to the container 205.

A first control unit 200 is arranged for communication with a pressure sensor 220 via a link 293. The pressure sensor 220 is adapted to detecting a prevailing pressure of the fuel where the sensor is fitted. According to this version, the pressure sensor 220 is situated adjacent to the second line 272 in order to measure a working pressure of the fuel downstream of the pump 230. The pressure sensor 220 is adapted to continuously sending signals to the first control unit 200 which contain information about a prevailing pressure of the fuel.

The first control unit 200 is arranged for communication with the pump 230 via a link 292. The first control unit 200 is adapted to controlling operation of the pump 230 in order for example to regulate the fuel flows within the subsystem 299. The first control unit 200 is adapted to controlling an operating power of the pump 230 by regulating its associated electric motor. The first control unit 200 is adapted to determining a prevailing operating power of the pump's electric motor, which operating power may be altered in response to presence of air at the pump 230. If air enters the first line 271 , a supply current to the pump is altered on the basis thereof. The first control unit 200 is adapted to monitoring the pump 230 in order to be able to detect behaviour which is due to presence of air at the feed device. In a similar way, the first control unit 200 is adapted to monitoring a working pressure of the fuel in order to be able to detect behaviour which is due to presence of air at the feed device. The first control unit 200 is arranged for communication with the dosing unit 250 via a link 291. The first control unit 200 is adapted to controlling operation of the dosing unit 250 in order for example to regulate fuel supply to the exhaust system of the vehicle 100. The first control unit 200 is adapted to controlling operation of the dosing unit 250 in order for example to regulate fuel return supply to the container 205.

The first control unit 200 is adapted, according to a version, to using the signals received which contain a prevailing pressure of the fuel in the region of the pressure sensor 220 as a basis for controlling the pump 230 in accordance with an aspect of the innovative method. In particular, according to a version, the first control unit 200 is adapted to using the signals received which contain a prevailing pressure of the fuel in the region of the pressure sensor 220 as a basis for controlling operation of the pump 230 at reduced power compared with ordinary operation when there is found to be air at the inlet of the pump 230 or in the pump 230, in accordance with an aspect of the innovative method. The first control unit 200 is adapted, according to a version, to using the signals received from the pump 230 which contain information about a prevailing actual operating power of the pump 230 as a basis for controlling said pump 230 in accordance with an aspect of the innovative method. In particular, the first control unit 200 is adapted, according to a version, to using the signals received which contain a prevailing actual operating power of the pump 230 as a basis for controlling the latter's operation at reduced power compared with ordinary operation when there is found to be air at the inlet of the pump 230 or in the pump 230, in accordance with an aspect of the innovative method.

A second control unit 210 is arranged for communication with the first control unit 200 via a link 290. 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 adapted to performing the innovative method steps according to the invention. The second control unit 210 may be used to cross-load software to the first control unit 200, particularly software for applying 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 adapted to performing substantially similar functions to those of the first control unit 200, e.g. using the signals received which contain a prevailing pressure of the fuel in the region of the pressure sensor 220 as a basis for controlling operation of the pump 230 at reduced power compared with ordinary operation when there is air at the pump 230. The innovative method may be applied by the first control unit 200 or the second control unit 2 0, or by both the first control unit 200 and the second control unit 210. According to this version, a compressed air source 260 is provided to supply compressed air to the dosing unit 250 via a line 261. The dosing unit 250 is adapted to using said compressed air supply in order to divide more finely the fuel being dosed. The compressed air may also be used for at least partly powering the dosing unit to dose said fuel into the exhaust duct. The compressed air may also be used, where appropriate, to blow out, for example, the dosing unit 250. This may be done during operation of the engine 150 or after the engine 150 has been switched off.

According to a version, the container 205 may be the vehicle's fuel tank, in which case portions of the vehicle's existing fuel system are utilised according to 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 a version, the dosing unit 250 is situated immediately adjacent to an exhaust duct of the HC dosing system. According to another example, the dosing unit 250 is provided with a passive nozzle running through said exhaust duct for direct dosing of said fuel into the exhaust duct.

According to a version, said pump 230 is the same pump as 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 as normally generates the fuel pressure for the injection system.

According to an example, a precatalyst and/or oxidation catalyst are/is fitted in series with, and upstream of, the particle filter.

Figure 3a is a schematic flowchart of a method pertaining to an HC dosing system whereby fuel is supplied to a feed device via which fuel is supplied to at least one consumption point from a container, according to an embodiment of the invention. The method comprises a first step s301. Method step s301 comprises the steps of continuously detecting the feed pressure furnished by the feed device, and of controlling the operation of the feed device on the basis of changes in said feed pressure, with the object of reducing the impact of unwanted air supply at the feed device. The method ends after step s301.

Figure 3b is a schematic flowchart of a method pertaining to an HC dosing system whereby fuel in liquid form is supplied to a feed device via which fuel is supplied to at least one consumption point from a container, according to an embodiment of the invention.

The method comprises a first step 310. Method step s310 comprises the step of initiating operation of the pump 230. Step s310 is followed by a step s320.

Method step s320 comprises the step of determining a number of values for at least one operating parameter. This operating parameter may for example be a prevailing feed pressure P of the HC dosing system's fuel downstream of the pump 230. Another operating parameter might be an actually prevailing operating power of the pump 230. Step s320 is followed by a step s330. Method step s330 comprises the step of using the values for the at least one parameter as a basis for deciding whether a first state is fulfilled. The first state may be a state characterised by presence of air at the pump 230. The first state may be a state which comprises presence of air supplied to the pump 230. According to an example it may be decided that the first state is fulfilled if a prevailing feed pressure of the HC dosing system's fuel begins to drop from a prevailing level. According to another example it may be decided that the first state is fulfilled if an actually prevailing operating power of the pump 230 is altered from a value which represents an operating power of it during ordinary operation to a value which is below a predetermined value. If the first state is fulfilled, a subsequent step s340 is performed. Alternatively, the first state may be determined if a change of sign of the first- order time derivative of the feed pressure may be found, indicating that the feed pressure is dropping. According to an example the first state may be determined if the second-order time derivative of the feed pressure is equal to zero (0), indicating that the feed pressure is neither increasing nor decreasing. According to an example the first state may be determined if a change of sign from positive to negative of the second-order time derivative is found, indicating that the previously increasing feed pressure is beginning to drop.

If the first state is not fulfilled, step s310 is performed again.

According to a version, method steps s310-s330 are optional, which means for example that the innovative method may begin at the step s340 described below.

Method step s340 comprises the step of determining a value for the feed pressure P of the fuel downstream of the pump 230. This may be done by means of the pressure sensor 220. The pressure sensor 220 is adapted to sending to the first control unit 200 a signal which contains information about a prevailing feed pressure P of the fuel downstream of the pump 230. Step s340 is followed by a step s350.

Method step s350 comprises the step of determining a value for the first- order time derivative P' of the feed pressure P determined at step s340. Determination of the first-order time derivative P' may be by means of the first control unit 200. Step s350 is followed by a step s360.

Method step s360 comprises the step of controlling the operation of the feed device on the basis of changes in said feed pressure P, with the object of reducing the impact of unwanted air supply at the pump 230. This entails a speed of the pump 230 being adapted on the basis of the value of said first- order time derivative P' of the feed pressure P, according to an aspect of the invention. Step s360 is followed by a step s370.

Method step s360 comprises the step of determining whether the method should end or not. If it is found that it should, the method ends. If it is found that the method should not end, step s340 is performed again, making it possible to continuously control a speed of the pump 230 on the basis of changes in the feed pressure P of the fuel downstream of the HC dosing system's pump 230.

According to the invention, the adaptive method described makes it possible to relatively quickly restore a desirable working pressure of the HC dosing system by controlling the speed of the pump 230 on the basis of changes in the feed pressure as above, particularly when there is air at the pump 230.

Figure 4a is a schematic diagram of feed pressure P of the fuel downstream of the pump 230 as a function of time T. The HC dosing system is adapted to being operated at a predetermined feed pressure Pshould (the HC dosing system's desired working pressure). When the pump 230 starts running, the feed pressure downstream of it increases until a time T1 at which unwanted air enters the pump 230. Thereupon the pressure drops until a second time T2 at which the pump is once again able to begin to build up the feed pressure. At a third time T3, air enters the pump 230 again, whereupon the feed pressure drops until a fourth time T4 at which the pump is again able to begin building up the feed pressure to a desired working pressure Pshould.

Figure 4b is a schematic diagram of the speed PV of the pump 230 as a function of time T. It should be noted that the first control unit 200 is adapted to continuously determining the first-order time derivative P' of the continuously detected values of the feed pressure P. The first control unit 200 is also adapted to determining the second-order time derivative P" of the continuously detected values of the feed pressure P. At time T1 it may be found that air has entered the pump 230. There are various ways in which this might happen. According to an example a change of sign of the first- order time derivative may be found, indicating that the feed pressure is dropping. According to an example it may be found that the second-order time derivative is equal to zero (0), indicating that the feed pressure is neither increasing nor decreasing. According to an example a change of sign from positive to negative of the second-order time derivative may be found, indicating that the previously increasing feed pressure is beginning to drop. On the basis of the magnitude of the first-order time derivative of the feed pressure P, the first control unit 200 can control the speed PV of the pump 230. According to a preferred example, the first control unit 200 may control the speed PV of the pump 230 on the basis of a magnitude of the first-order time derivative P' of the speed PV in a correlated way, which means that if the feed pressure P drops at a certain rate a pump speed may be lowered correspondingly. Similarly, the first control unit 200 may control the speed PV of the pump 230 on the basis of a magnitude of the first-order time derivative P' of the feed pressure P in a correlated way when the feed pressure increases, which means that if the feed pressure P increases at a certain rate a pump speed may be increased correspondingly.

The diagram shows the pump speed PV being controlled on the basis of changes in the feed pressure P until a desirable working pressure Pshould is reached.

It shows the pump speed PV dropping until time T1. It shows the pump speed PV as relatively low between the first time T1 and the second time T2. It shows the pump speed PV increasing after time T2 when the feed pressure P begins to increase, before subsequently dropping to a relatively low level at the third time T3. It shows the pump speed PV as relatively low between the third time T3 and the fourth time T4. It shows the pump speed PV increasing after time T4 when the feed pressure P begins to increase, before subsequently decreasing again to any suitable level when the feed pressure P stabilises.

According to an example the curve of the pump speed PV follows relatively well the shape of a curve for the first-order time derivative P' of the feed pressure P. This means that a main principle of the invention is that the faster the feed pressure P rises the higher the pump speed PV becomes. Similarly, the pump speed PV is reduced on the basis of how quickly the feed pressure drops. When the feed pressure P is dropping, the pump speed PV is relatively low.

The pump speed may be controlled in any suitable way on the basis of the first-order derivative of the feed pressure P. The result is adaptive control of the speed of the pump in order in an effective way to make it possible to build up the HC dosing system's feed pressure to a desirable level when there is air at the pump 230, according to an aspect of the invention.

A positive effect is that the innovative method makes it possible to shorten a period of time between two peaks of the feed pressure, e.g. the period T1-T3. The result is that the desirable working pressure Pshould can be built up more quickly than in the state of the art when there is air at the pump 230.

Figure 5 is a diagram of a version of a device 500. The control units 200 and 210 described with reference to Figure 2 may in a 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 programme, e.g. an operating system, is stored for controlling the function of the devices 200 and/or 210. 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. A proposed computer programme P comprises routines for the purpose, where fuel is supplied to a feed device via which fuel is supplied to at least one consumption point from a container of an HC dosing system, of continuously controlling the operation of the pump on the basis of changes in a continuously detected feed pressure of fuel downstream of the pump 230 in the HC dosing system, with the object of reducing the impact of unwanted air supply at the feed device. The programme P comprises routines for continuously controlling a speed of the pump on the basis of values for time derivatives of a continuously detected feed pressure of fuel downstream of the pump 230 in the HC dosing system, with the object of reducing the impact of unwanted air supply at the feed device.

The programme P comprises routines for altering the operation of the feed device in correlation with the changes in said feed pressure, in accordance with the innovative method. The programme P comprises routines for controlling the operation of said feed device, e.g. by influencing a prevailing pump speed, towards a predetermined level of the feed pressure which the feed device is intended to furnish. The programme P comprises routines for determining presence of air supplied upstream to the feed device and, when such presence is found, for controlling the operation of the feed device on the basis of changes in the continuously detected feed pressure of fuel downstream of the HC dosing system's pump 230.

The programme P may be stored in an executable form or in a compressed form in a memory 560 and/or in a read/write memory 550. Where the data processing unit 510 is described as performing a certain function, it means that the data processing unit 510 effects a certain part of the programme stored in the memory 560, or a certain part of the programme 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 510 via a data bus 511. The read/write memory 550 is adapted to communicating with the data processing unit 510 via a data bus 514. The data port 599 may for example have the links 290, 292 and 293 connected to it (see Figure 2). When data are received on the data port 599, they are stored temporarily in the second memory element 540. When input data have been temporarily stored, the data processing unit 510 is prepared to effect code execution as described above. According to a version, signals received on the data port 599 contain information about actually prevailing operating power of the pump 230. According to a version, signals received on the data port 599 contain information about a feed pressure of the fuel. Said feed pressure is a prevailing feed pressure downstream of the pump 230. The signals received on the data port 599 may be used by the device 500 to determine presence of air supplied to the pump 230 and, when such presence is found, to control the operation of the feed device on the basis of changes in said feed pressure, with the object of reducing the impact of unwanted air supply at the feed device.

Parts of the methods herein described may be effected by the device 500 by means of the data processing unit 510 which runs the programme stored in the memory 560 or the read/write memory 550. When the device 500 runs the programme, methods 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 or to restrict the invention to the variants described. Many modifications and variants will obviously be apparent to one skilled in the art. The embodiments have been chosen and described in order best to explain the principles of the invention and its practical applications and hence make it possible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.