Technical area

The present invention relates to a system and a method for the evacuation of fluid in a vehicle. The invention relates also to a vehicle, a computer program and a computer program product.

Background to the invention

A common operation in modern vehicles is to transfer through a pipeline and by means of a pump an amount of fluid from a tank to a dosage arrangement for subsequent supply in doses. One example of the above is the supply of fuel to a fuel pump for its subsequent injection into the cylinders of a combustion engine. A further example, particularly relevant for commercial vehicles such as trucks, buses and construction vehicles, is the supply of reducing agent to the dosage system, for its subsequent injection into the exhaust gas system of the diesel engine.

When the transfer of fluid has been completed, fluid may remain not only in the pipeline that connects the tank and the dosage unit but also in the dosage unit itself. This residual fluid may constitute a risk of fire, particularly if the fluid is readily flammable, such as vehicle fluid, and the vehicle is used for special purposes, such as military vehicles and fire-response vehicles.

At low temperatures the remaining fluid can, furthermore, freeze and block the pipeline. Blockage of pipelines that arises in this manner is normally avoided through keeping the pipelines warm, preferably with the aid of electrical coils. This solution, however, suffers from several disadvantages, such as an increased technical complexity of the system and increasing energy consumption. Blockage of pipelines can take place also at higher temperatures. This takes place in particular when fluid, such as reducing agent, remains in the pipeline for a long time and crystallises. It is, furthermore, not uncommon that the fluid, in particular when it is present in the liquid phase, has corrosive properties and can thus corrode the pipeline in which it is located during long-term contact, leak out and damage neighbouring metallic components. It is known also that components of electrical heating systems, such as electrical coils, often experience short-circuits caused by fluids with corrosive properties, such as reducing agent.

US2012/0031073A1 discloses an arrangement to supply reducing agent to the exhaust gas system of a vehicle. The arrangement comprises a pump arranged between a working tank and a storage tank, and a dosage unit for reducing agent that is connected to the working tank through a pipeline. The reducing agent is pumped from the working tank to the dosage unit when the engine is operating. After the engine has been stopped, the action of the pump leads to unused reducing agent being recirculated to the working tank from both the reducing agent dosage unit and the pipeline.

The solution that is described in US2012/0031073A1 requires, thus, that the arrangement comprise a pump that is in operation also when the engine has been switched off. This condition, known as "after run", should be avoided in order to minimise the energy consumption of the vehicle and to make it possible to switch off the main switch immediately after driving. Furthermore, the design solution with a reversible pump makes it impossible to use non-return valves, and consequently requires a two-tank system to prevent the pump becoming worn out prematurely.

The arrangement is therefore relatively complex. Furthermore, control of such an arrangement, comprising a pump and two fluid tanks, is complicated.

The purpose of the present invention is thus to provide a technically simple solution with as few components as possible, and one that removes, in particular, remaining fluid from the pipelines and/or the dosage unit in an energy-efficient manner. Summary of the invention

According to a first aspect, the purpose described above is at least partially achieved through a method for the evacuation of fluid in a vehicle according to claim 1 .

The system thus comprises a first tank intended for pressurised air, a second tank intended for a fluid that is to be supplied to a fluid dosage unit, a valve

arrangement, a first fluid pathway that connects a source of pressurised air with the valve arrangement, a second fluid pathway that connects the valve

arrangement and the first tank, a third fluid pathway that connects the second tank and the valve arrangement, a fourth fluid pathway that connects the valve arrangement with the fluid dosage unit, whereby the system in response to a control signal is arranged to be placed into a first condition, in which the valve arrangement is in a first condition in which pressurised air flows from the source of pressurised air to the first tank through the valve arrangement and through the first and the second fluid pathways, and the fluid flows from the second tank to the fluid dosage unit through the valve arrangement and through the third and the fourth fluid pathways, or into a second condition, in which the valve arrangement is in a second condition in which pressurised air flows from the first tank to the fluid dosage unit through the valve arrangement and through the second and the fourth fluid pathways, and to the second tank through the valve arrangement, and through the second, the third and a part of the fourth fluid pathways. The system according to the invention comprises a valve arrangement that alternates between two conditions, a first condition in which fluid is supplied to the dosage unit and in which the first tank is filled with pressurised air, and a second condition in which the fluid pathways, i.e. the pipelines that transport the fluid, and the dosage unit are blown clean. The process of purging is carried out solely with pressurised air that has been supplied to the system at the same time as the fluid is supplied to the dosage unit. A simple and effective design is in this way obtained. Furthermore, the design and the extent of each fluid pathway and the positioning of the valve arrangement lead to a fluid connection between the second, the third and the fourth fluid pathways being created during the purging operation. In this way pressurised air from the first tank can flow through also the third and the fourth fluid pathways. The remaining fluid from the third fluid pathway is then recirculated to the second tank. The air that flows through the fourth fluid pathway also lead to this fluid pathway and the dosage unit that is arranged in connection with the outlet of the pathway being emptied of remaining fluid, which subsequently, in one variant, is taken back to the second tank. The requirement of a dedicated, energy-consuming component of the system, such as a pump, to recirculate residual fluid to the fluid tank is in this way eliminated.

According to a second aspect, the purpose described above is achieved, at least partially, through a method for the evacuation of fluid in a system intended for a vehicle, whereby the system comprises a first tank intended for pressurised air, a second tank intended for a fluid that is to be supplied to a fluid dosage unit, a valve arrangement, a first fluid pathway that connects a source of pressurised air with the valve arrangement, a second fluid pathway that connects the valve arrangement and the first tank, a third fluid pathway that connects the second tank and the valve arrangement, a fourth fluid pathway that connects the valve arrangement with the fluid dosage unit, whereby the method comprises the reception of a control signal and, in response to the control signal, to place the system into a first condition, in which the valve arrangement is in a first condition in which pressurised air flows from the source of pressurised air to the first tank through the valve arrangement and through the first and the second fluid pathways, and the fluid flows from the second tank to the fluid dosage unit through the valve arrangement and through the third and the fourth fluid pathways, or into a second condition, in which the valve arrangement is in a second condition in which pressurised air flows from the first tank to the fluid dosage unit through the valve arrangement and through the second and the fourth fluid pathways, and to the second tank through the valve arrangement, and through the second, the third and a part of the fourth fluid pathways. According to a third aspect, the purpose is at least partially achieved through a computer program, P, where the said computer P comprises program code to cause a computer to carry out the steps according to the method. According to a fourth aspect, the purpose is at least partially achieved through a computer program product comprising a program code stored on a non-transient medium that can be read by a computer in order to carry out the method steps, when the said programme is run on a computer. According to a fifth aspect, the purpose is achieved at least partially through a vehicle that comprises the system according to the invention.

Various preferred embodiments are described in the dependent claims and in the detailed description.

Brief description of the attached drawings

The invention will be described below with reference to the attached drawings, of which: Figure 1 shows a schematic view from above of a vehicle comprising tanks intended for air and reducing agent, and a reducing agent dosage unit.

Figure 2a shows a block diagram that represents a system for the evacuation of fluid according to one embodiment of the present invention where the system has been placed into a first condition.

Figure 2b shows a block diagram that represents the system in a second condition.

Figure 3 is a flow diagram containing the method steps according to one embodiment of the present invention.

Detailed description of preferred embodiments of the invention

Figure 1 shows a schematic view from above of a vehicle. The vehicle 1 is displayed here in the form of a truck or drawing vehicle with a chassis 9 and two pairs of wheels 10A and 10B. The truck is displayed here solely as an example, and the vehicle 1 may instead be, for example, an SUV, a working vehicle or similar. A driver's cabin 7 is located at the front of the truck. A combustion engine 41 is located under the driver's cabin 7. The exhaust gases that are generated during combustion are led into an exhaust gas system 42. Also tanks 4, 5 intended for pressurised air and reducing agent are mounted on the chassis 9. Trucks and other commercial vehicles typically have a pneumatic brake system that comprises a tank 14 that contains pressurised air. As is shown in Figure 1 , also the air tank 14 normally mounted on the chassis 9. The air tank 14 of the brake system may, in one embodiment, be used as a source of pressurised air. The pressurised air is then supplied to the tank 4 through a pipeline 53.

A dosage unit 20 for reducing agent is typically arranged in the flow of exhaust gases downstream of the combustion engine 41 . To be more specific, the dosage unit 20 for reducing agent is often located inside a silencer 43 that is normally arranged in connection with the exhaust gas system 42. A tank 5 provides the dosage unit 20 for reducing agent with reducing agent through a pipeline 51 . The dosage unit 20 for reducing agent injects at least a part of the reducing agent that has been supplied into the flow of exhaust gases in order in this way to contribute to reducing the emission of harmful nitrogen oxides. In one embodiment, the reducing agent flows in a closed circuit. This embodiment also includes a return pipeline 21 through which unconsumed reducing agent is recirculated to the reducing agent tank 5. In this context, the product name AdBlue® is usually used in Europe when referring to reducing agent. The reducing agent is here used solely for the purpose of giving an example, and the tanks may contain instead other relevant fluids, such as diesel fuel.

At least the second tank 5 is equipped with at least one sensor (not shown in Figure 1 ) that measures the amount of reducing agent in the tank 5. The sensor may be, for example, a level sensor, i.e. an arrangement that measures the level of the fluid in the tank, or an arrangement that determines the weight or the volume of the fluid. This tank 5 accommodates in the normal case approximately 80 litres of reducing agent, while the tank 4 that is intended for pressurised air accommodates approximately 10 litres. The second tank 5 may be equipped also with a valve, preferably a non-return valve, that opens when the internal pressure in the tank 5 exceeds a predetermined value.

The transfer of reducing agent is normally controlled by a control unit 19 that is shown schematically in Figure 1. As has been mentioned above, it is desirable to maintain the pipeline and the dosage unit itself free from reducing agent when the transfer operation has been stopped. In order to achieve this, a system 100 is used, which will now be explained with reference to Figures 2a-2b.

Figure 2a shows a block diagram that represents a system 100 for the evacuation of fluid, such as reducing agent, where the system 100 is in a first condition. The system 1 00 comprises a first tank 4 intended for pressurised air and a second tank 5 intended for reducing agent that is to be supplied to a dosage unit 20 for reducing agent and a valve arrangement 1 1 . Fluid pathways in the form of pipelines extend such that a first pipeline 13 connects a source of pressurised air 14 with the valve arrangement 1 1 , a second pipeline 15 connects the valve arrangement 1 1 with the first tank 4, a third pipeline 17 connects the second tank 5 with the valve arrangement 1 1 and a fourth pipeline 18 that connects the valve arrangement 1 1 with the reducing agent dosage unit 20. In particular the pipelines 13, 1 5, 17, 18, but also the tanks 4, 5 and/or the dosage unit for reducing agent, may be manufactured from material that resists the corrosive properties of the reducing agent and/or internally coated with an appropriate corrosion-preventative substance.

The valve arrangement 1 1 may be a five-port valve, such as a 5/2-valve as is shown in Figure 2a. The valve arrangement may be operated in various ways, such as, for example, with the aid of a solenoid and/or a spring arrangement (not shown in the drawings). Alternatively, a 5/3-valve may be used. The designator "5/2" denotes that the valve has five ports, i.e. openings in the valve casing, and two conditions. With reference to the five-port valve that is shown in Figure 2a, three of the ports: the first 22, second 24 and third 26, are arranged on the side of the valve that faces towards the dosage unit 20 for reducing agent. A fourth 28 and a fifth 30 port are arranged on the opposite side. Depending on the condition in which the valve has been placed, the ports 22, 24, 26, 28, 30 serve as inlets or outlets for air and/or reducing agent.

With continued reference to Figure 2a, the system 100 is shown in a first, active, condition, which means that the valve arrangement 1 1 is in a first condition. A segment of the first pipeline 13 extends from a source of air 14 to a pressure- regulation arrangement 23. This arrangement 23 may be in practice a valve, preferably a pressure-operated valve. A further segment of the first pipeline 13 extends between the pressure-regulation arrangement 23 and the third port 26 of the five-port valve. The third 26 and the fifth 30 valve ports are in fluid

communication such that the pressurised air that flows in the first pipeline 13 can flow through the second pipeline 15 in order finally to reach the first tank 4.

Also the second port 24 and the fourth port 28 are in fluid communication in the first condition. This leads to the reducing agent being pumped out of the second tank 5, flowing through the third pipeline 1 5 and entering the valve arrangement 1 1 through the fourth valve port 28. The fourth pipeline 18 of the system, which extends between the valve arrangement 1 1 and the reducing agent dosage unit 20, comprises, according to one embodiment, a main pipeline 180 that branches at a branchpoint FP into a first pipeline branch 181 and a second pipeline branch 182. The branch 181 connects the branchpoint FP and the second port 24 of the valve arrangement 1 1 while the branch 182 connects the branchpoint FP and the first port 22 of the valve arrangement 1 1 . As previously mentioned, the second port 24 and the fourth port 28 are in fluid communication. The reducing agent flows consequently through the first pipeline branch 181 and the main pipeline 180 in order eventually to reach the dosage unit 20 for reducing agent. The first valve port 22 is closed in this condition. In summary, the reducing agent can be transferred from the second tank 5 to the dosage unit 20, the location and function of which have been described in association with Figure 1 . This takes place through the valve arrangement 1 1 and through the third pipeline 17 and a part of the fourth pipeline 18. The first tank 4 in parallel with this process is filled with pressurised air until the pressure in the tank 4 exceeds a predetermined value. In the embodiment that is shown in Figure 2a the system comprises also a fifth pipeline 21 that connects the dosage unit 20 with the second tank 5 such that reducing agent flows in a closed circuit that is constituted by the third pipeline 1 7, the first branch 181 and the main pipeline 180 belonging to the fourth pipeline 18, and the fifth pipeline 21 . This configuration leads to reducing agent that has not been consumed being recirculated to the second tank 5. Reducing agent that has not been consumed can then be used as cooling agent. Quantification of this return flow can, furthermore, be used to discover whether the supply of reducing agent to the dosage unit 20 is functioning as planned. In an alternative

embodiment (not shown in the drawings) that makes a simpler design possible, the system 100 lacks the fifth pipeline 21 , and the excess reducing agent is dealt with in another manner.

The pressurised air of the system may be delivered from an air tank 14 that is mounted on the vehicle. In one embodiment, the source of pressurised air is the air tank that is a component of the pneumatic brake system of the vehicle and that has been described in association with Figure 1 . Due to the robust design of the solution, the magnitude of the pressure is not of primary significance as long as the pressurised air can empty the pipelines and the dosage unit. SUVs and other vehicles that lack an air tank may be equipped with an air compressor that provides pressurised air. Alternatively, the pressurised air may consist of or comprise exhaust gases that are produced in the exhaust gas system of the vehicle.

The system 100 in Figure 2b is in a second, active, condition, and the valve arrangement 1 1 is in a second condition. The extents and designs of the pipelines 13, 1 5, 17, 18 are unchanged from those shown in Figure 2a. The first 22 and the fourth 28 valve ports are in fluid communication, as are the second 24 and the fifth 30 valve ports. This means that the pressurised air from the first tank 4 flows via the valve arrangement 1 1 through the second pipeline 15 and the first pipeline branch 181 up to the branchpoint FP, after which a first part of the pressurised air flows through the second pipeline branch 182, passes the valve arrangement 1 1 , and finally reaches, via the third pipeline 17, the second tank 5. The remaining fluid from the second pipeline branch 182 and the third pipeline 17 is then recirculated to the second tank 5. At the same time, a second part of the pressurised air flows from the branchpoint FP to the fluid dosage unit 20 through the main pipeline 180 that belongs to the fourth pipeline 18. This lead to also the first pipeline branch 181 , the main pipeline 180 and the dosage unit 20, which is arranged in connection to the main pipeline, being emptied of remaining fluid, which is subsequently, in an embodiment that is shown in Figures 2a and 2b, taken back to the second tank 5. The third valve port 26 in this condition is closed. The system 100 changes its condition in response to a control signal. To be more specific, an electronic control unit 19 may be arranged to generate a first control signal to place the system 100 into the first condition and a second control signal to place the system 100 into the second condition. In one embodiment, the control unit 19 generates a first control signal when the engine of the vehicle is started. The first control signal activates the valve arrangement 1 1 , which takes up a first condition, after which reducing agent starts to be transferred to the dosage unit 20 and the first tank 4 is filled with pressurised air until the pressure in the tank 4 exceeds a predetermined value, as described above in association with Figure 2a. In a further, closely related, embodiment, the control unit 19 generates a second control signal when the engine of the vehicle is switched off. The second control signal activates the valve arrangement 1 1 , which takes up a second condition, after which the pipelines 17, 18 are blown clean as described above in association with Figure 2b. As an alternative, the valve arrangement 1 1 , which is operated by mechanical and electrical activation when the engine is switched off, i.e. when there is no current in the system, can be placed into a second condition by purely mechanical activation. This is typically achieved by a force being applied with the aid of a spring. The counteracting force, which is normally generated by the electrical control means, such as a solenoid, is not present when the engine is switched off and the system has become currentless. This leads to the valve arrangement 1 1 being set into a condition such that the pressurised air in the first tank 4 starts to flow. According to one embodiment, the control unit 19 is arranged to control also the pressure-regulation arrangement 23.

The control unit 19 may be an integral part of the system 100. The control unit 19 comprises further a processor unit 29 and a memory unit 39 that is connected to the processor unit 29. A computer program P is stored on the memory unit 39, which computer program can cause the control unit 19 to carry out the steps according to the method that is described here. According to one embodiment, the memory unit 39 is a part of the processor unit 29. The processor unit 29 may be constituted by one or several CPUs (central processing units). The memory unit 39 may comprise a non-transient memory, such as a flash memory or RAM (random access memory). The memory unit 39 comprises instructions to cause the processor unit 29 to execute the method steps that are described here.

According to one embodiment, the control unit 19 is arranged to place the system 100 into the second condition for a predetermined period of time, such as 10, 20, 30 or 40 seconds.

The system 100 may be arranged, furthermore, to be placed into a passive condition (not shown in the drawings), which means that no fluid, i.e. neither reducing agent nor pressurised air, is transferred between the second tank 5 and the dosage unit 20 for reducing agent.

The control unit 19 and one or several control units that activate the valve arrangement 1 1 and the pressure-regulation arrangement 12 may communicate with each other by, for example, a bus, such as a CAN-bus (controller area network), which uses a message-based protocol. Examples of other

communication protocols that can be used are TTP (time-triggered protocol), Flexray, etc. Signals and data as described above can in this way be exchanged between various units in the vehicle 1 . Signals and data can instead be transferred in a wireless manner, for example, between the various units. Figure 3 shows a flow diagram containing the method steps according to the present invention. The flow diagram shows a method for the transfer of fluid in the system 1 00 that has previously been described with reference to Figures 2a and 2b. The method comprises receiving 50 a control signal and, in response to the control signal, placing 60 the system into a first condition 70 or a second condition 80.

In a first condition 70 a first valve arrangement 1 1 is in a first condition. Reducing agent flows in this condition 70 from a second tank 5 to a dosage unit, i.e. a dosage unit 20 for reducing agent, through the valve arrangement 1 1 and through a third 17 fluid pathway and a fourth 18 fluid pathway, i.e. pipelines. Reducing agent that is transferred in this way to the fluid dosage unit, i.e. to the dosage unit 20, is used for injection into the exhaust gas system of the vehicle. At the same time, pressurised air flows from a source 14 of pressurised air to a first tank 4 through the valve arrangement 1 1 and through the first 13 and the second 15 pipelines, according to Figure 2a. The first tank 4 is filled with pressurised air until the pressure in the tank 4 exceeds a predetermined value.

In a second condition 80, in which the valve arrangement 1 1 is in a second condition in which pressurised air flows from the first tank 4 to the fluid dosage unit 20 through the valve arrangement 1 1 and through the second 1 5 and the fourth 18 fluid pathways. The pressurised air also flows to the second tank 5 through the valve arrangement 1 1 , and through the second 15, the third 17 and a part of the fourth 18 fluid pathways. As has been mentioned above, the fluid pathways in the form of pipelines 13, 15, 17, 18 and their designs and extents are the same, independently of the condition. The design and the extent of each fluid pathway 13, 15, 17, 18 and the positioning of the valve arrangement 1 1 lead to a fluid connection between the second 15, the third 1 7 and the fourth 18 fluid pathways being created in the second condition 80. In this way pressurised air from the first tank 4 can flow through not only the third 17 but also the fourth 18 fluid pathways. The remaining fluid from the third 17 fluid pathway is then recirculated to the second tank 5. The air that flows through the fourth 18 fluid pathway leads to also this fluid pathway and the dosage unit 20 that is arranged in connection with the outlet of the pathway being emptied of remaining fluid.

The present invention is not limited to the embodiments described above. Various alternatives, modifications and equivalents can be used. For this reason, the embodiments named above do not limit the scope of the invention, which is defined by the attached patent claims.