EP4731879A1

EP4731879A1 - Method of controlling operation of a hydraulic metering system, computer program, computer-readable medium, control arrangement, hydraulic metering system, an engine, and a vehicle

Info

Publication number: EP4731879A1
Application number: EP24826356.8A
Authority: EP
Inventors: Hans RIETZ; Per Bremberg
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2023-06-20
Filing date: 2024-06-14
Publication date: 2026-04-29
Also published as: CN121773260A; SE546697C2; SE2350752A1; WO2024263080A1

Abstract

A method (100) of controlling operation of a hydraulic metering system (10) is disclosed, wherein the hydraulic metering system (10) is configured to supply a liquid into an exhaust conduit (12) of an engine (14). The hydraulic metering system (10) comprises a reservoir (16) configured to store the liquid, a supply path (11), a pump (13) configured to pump liquid from the reservoir (16) into the supply path (11), and a supply opening (15) configured to supply the liquid into the exhaust conduit (12) of the engine (14). The supply path (11) comprises a valve (17) controllable between an open state in which liquid is supplied from the supply path (11) through the supply opening (15) and a closed state in which liquid is blocked from flowing from the supply path (11) through the supply opening (15). The method (100) comprises the steps of obtaining (110) data indicative of freezing of liquid in the supply path (11), and performing (120) at least a first supply of a predetermined first amount of liquid into the exhaust conduit (12) via the supply opening (15) by controlling the valve (17) between the closed and open states if the data is indicative of freezing of liquid in the supply path (11).is disclosed The present disclosure further relates to a computer program, a computer-readable medium (200), a control arrangement (21), a hydraulic metering system (10), an engine (14), and a vehicle (2).

Description

Method of controlling operation of a hydraulic metering system, Computer Program, Computer-readable medium, Control Arrangement, Hydraulic Metering System, an Engine, and a Vehicle

TECHNICAL FIELD

The present disclosure relates to a method of controlling operation of a hydraulic metering system. The present disclosure further relates to a computer program, a computer-readable medium, a control arrangement for controlling the operation of a hydraulic metering system, a hydraulic metering system, an engine, and a vehicle comprising an engine.

BACKGROUND

Internal combustion engines are a common type of engines which converts chemical energy into kinetic energy through the combustion of a fuel. Internal combustion engines, such as four-stroke internal combustion engines, comprise one or more cylinders and a piston arranged in each cylinder. The pistons are connected to a crankshaft of the engine and are arranged to reciprocate within the cylinders upon rotation of the crankshaft. The engine usually further comprises one or more inlet valves and outlet valves as well as one or more fuel supply arrangements. The one or more inlet valves and outlet valves are controlled by a respective valve control arrangement usually comprising one or more camshafts rotatably connected to a crankshaft of the engine, via a belt, chain, gears, or similar. A four-stroke internal combustion engine completes four separate strokes while turning a crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. Internal combustion engines, such as diesel engines or Otto engines are commonly used in different types of motor vehicles, such as trucks and buses, cars, vessels, etc. Internal combustion engines may also be stationary engines, used in e.g. a pump or an electric generator. Such internal combustion engines are used in many industrial applications.

General problems when designing an internal combustion engine is the emission levels from the engine and the fuel consumption of the engine. The emission levels of carbon dioxide CO2 are directly correlated to the fuel consumption of the engine. Moreover, exhausts from an engine can comprise carbon monoxide CO from incomplete combustion, hydrocarbons HC from unburnt fuel, nitrogen oxides NOx from high combustion temperatures, and particulate matter which is usually abbreviated PM and consists mostly of soot/smoke.

Environmental concerns, as well as emissions standards for motor vehicles, have led to the development of combustion engine assemblies using exhaust additives, such as reducing agents for diesel, and/or ethanol, exhaust gases. Reducing agents may comprise an aqueous urea solution and may be used as a consumable in a Selective Catalytic Reduction SCR in order to lower nitrogen oxides NOx concentration in exhaust emissions from the internal combustion engine. A selective catalytic reduction arrangement is a means of converting nitrogen oxides NOx with the aid of a catalyst into diatomic nitrogen N2, and water H2O using a reduction agent added to a stream of exhaust gas which is adsorbed onto a catalyst substrate of the SCR catalyst. The reduction agent may comprise a gaseous reductant, typically anhydrous ammonia, aqueous ammonia, or urea.

The reduction agent is often stored in liquid form in a reservoir and delivered into the exhaust conduit of an engine through the use of e.g. an injector. The injector may e.g. comprise a supply opening configured to receive the reduction agent from the reservoir supply and deliver the reduction agent into the exhaust conduit of the engine. A pump may be used to deliver the reduction agent to the supply opening. The supply opening may comprise a valve in order to control when the reduction agent is to be delivered to the exhaust conduit. Such a system comprising the reservoir, pump, valve and supply opening of the reduction agent may e.g. be called a hydraulic metering system or a reduction agent delivery system. When the reduction agent is exposed to the heat of the exhaust gases it evaporates, into e.g. ammonia gas which may then react with the NOx in the catalyst. If the temperature in the exhaust gas is insufficient to convert the reduction agent or if an excess of reduction agent is introduced into the exhaust conduit there is a risk of crystallization of reduction agent in the exhaust conduit, i.e. that the reduction agent solidifies in a crystal structure on a substrate, e.g. the wall of the exhaust conduit of the engine. Such crystallization may lead to increased backpressure in the exhaust conduit and/or inefficient NOx conversion, leading to higher NOx emissions.

In cold climate the reduction agent may freeze within the hydraulic metering system. Since the reduction agent is aqueous it may expand during the phase transition from liquid to solid form during freezing. This expansion may cause damage to components of the hydraulic metering system since considerable force may be applied to the components of the system due to the increased volume required by the solid reduction agent. This damage may lead to a malfunctioning hydraulic metering system which may even start to leak. In any case, the ability of the hydraulic metering system to provide the reduction agent to the exhaust conduit and the exhaust aftertreatment system will be impacted resulting in lowered ability to reduce the emissions produced by the engine. The system must then be repaired at considerable cost and downtime. In order to avoid this, certain hydraulic metering systems will purge the reduction agent from the more fragile components by e.g. injecting the remaining reduction agent into the exhaust conduit of the engine, or pump the reduction agent back into the reservoir. However, introducing a large amount of reduction agent into the exhaust conduit for purging purposes may lead to crystal formation in the exhaust conduit. Furthermore, the temperature of the exhaust conduit may be low at times when the purging need to be performed, thereby increasing the risk of crystal formation. Pumping the reduction agent back into the reservoir may introduce exhaust gas into the hydraulic metering system, with associated risk of crystal formation in the metering system.

Other systems are arranged with components capable of handling the forces associated with the liquid freezing at ambient pressures. However in such systems a blockage of the supply path of the hydraulic metering system may form due to frozen reduction agent. When the hydraulic metering system is to be used for supplying reduction agent into the exhaust conduit again there is a risk that the blockage has not had time to thaw. In this case components may be damaged if the pressure is increased further in the hydraulic metering system due to e.g. the pump operating while the blockage is still existing.

Hydraulic metering system are vital components to achieve the emission reductions required and are burdensome and costly to service, maintain, and repair. Therefore, it is an advantage if at least some operational aspects of a hydraulic metering system can be controlled, to prevent wear, tear, and damage of components of the hydraulic metering system and the thereto associated systems and arrangements.

SUMMARY

It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a method of controlling operation of a hydraulic metering system, the hydraulic metering system being configured to supply a liquid into an exhaust conduit of an engine. The system comprises a reservoir configured to store the liquid, a supply path, a pump configured to pump liquid from the reservoir into the supply path, and a supply opening configured to supply the liquid into the exhaust conduit of the engine. The supply path comprises a valve controllable between an open state in which liquid is supplied from the supply path through the supply opening and a closed state in which liquid is blocked from flowing from the supply path through the supply opening. The method comprises the steps of: obtaining data indicative of freezing of liquid in the supply path, and performing at least a first supply of a first amount of liquid into the exhaust conduit via the supply opening by controlling the valve between the closed and open states if the data is indicative of freezing of liquid in the supply path.

Thereby a method is provided capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, a method is provided capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. This is because a first amount of liquid is supplied to the exhaust conduit when data indicates freezing of liquid in the supply path. Thus, the risk of a too large pressure being built up in the system is reduced, and therefore the risk of damage to the components is also reduced.

Accordingly, a method is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Optionally, the first amount of liquid is predetermined. The predetermined first amount of liquid may be determined based on an estimate of crystal formation in the exhaust conduit when supplying the predetermined first amount of liquid to the exhaust conduit. Thereby the risk of crystal formation may be reduced compared to supplying the liquid to the exhaust conduit without taking the crystal formation aspect into consideration.

The estimate may be based on computational or analytical modelling of crystal formation, or based on empirical data stored in look-up tables etc.

The amount of crystal formation in the exhaust conduit is inter alia dependent on the amount of liquid being supplied to the exhaust conduit. Thereby, the amount of crystal formation in the exhaust conduit for a given amount of liquid being supplied to the exhaust conduit can be estimated. Thus, the predetermined first amount of liquid may be determined based on this estimate. The predetermined first amount of liquid may thus be determined based on an estimate of an amount of crystal formation in the exhaust conduit for that amount of liquid being supplied to the exhaust conduit.

Thereby, since a predetermined amount of liquid which is based on an estimate of crystal formation in the exhaust conduit is supplied to the exhaust conduit the risk of crystal formation in the exhaust conduit can be reduced, since the predetermined amount can be chosen to achieve this, e.g. by supplying a lower amount of liquid at times when it is expected that there is an increased risk of crystal formation. Thereby the NOx conversion efficiency in the catalyst may be maintained, thus reducing the risk of an increase in emission, particularly NOx emissions.

The predetermined first amount of liquid may alternatively or in additionally be determined based on the pressure reduction in the hydraulic metering system when supplying the predetermined first amount of liquid to the exhaust conduit.

Thereby the pressure in the hydraulic metering system can be reduced in a quick manner, resulting in a method being provided capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path.

Preferably, the predetermined first amount of liquid may be determined based on both the pressure reduction in the hydraulic metering system and an estimate of crystal formation in the exhaust conduit, when supplying the predetermined first amount of liquid to the exhaust conduit.

Since the predetermined first amount of liquid is determined based on both the pressure reduction in the hydraulic metering system and an estimate of crystal formation in the exhaust conduit, when supplying the predetermined first amount of liquid to the exhaust conduit, the amount of liquid can be accurately determined such that the risk of crystal formation in the exhaust conduit is minimized while at the same time the pressure reduction in the hydraulic metering system is maximized, thereby reducing the risk for damage to the components of these systems and avoiding or at least alleviating the risk of reduced NOx conversion efficiency

Optionally, the method comprises the step of setting the predetermined first amount of liquid based on one or more of, a current operational condition of the engine, current physical properties prevailing in the exhaust conduit, current physical properties prevailing in the hydraulic metering system, and current ambient physical properties. Here, an estimate of the amount of crystal formation may be based one or more of these parameters. The predetermined first amount of liquid may thus be determined based on an estimate of an amount of crystal formation in the exhaust conduit for that amount of liquid being supplied to the exhaust conduit, given one or more of, a current operational condition of the engine, current physical properties prevailing in the exhaust conduit, current physical properties prevailing in the hydraulic metering system, and current ambient physical properties. The crystal formation dependence on the parameters given above has been extensively studied in the art and will therefore not be further described herein.

Preferably, the predetermined first amount of liquid may be determined based on an estimate of an amount of crystal formation in the exhaust conduit for that amount of liquid being supplied to the exhaust conduit, given the current physical properties prevailing in the exhaust conduit.

Thereby, a method is provided capable of controlling the system such that the risk of damage to the hydraulic metering system is reduced.

Moreover, a method is provided capable of controlling the hydraulic metering system such that a reduction in the aftertreatment system efficiency is avoided or at least alleviated. This is because the amount of liquid supplied to the exhaust conduit is tailored to the specific conditions prevailing at the time when the control is performed. Since the predetermined first amount of liquid is set based on one or more of the physical conditions or properties itemized above the amount of liquid can be accurately determined such that the risk of crystal formation in the exhaust conduit is minimized while at the same time the pressure reduction in the hydraulic metering system is maximized, thereby reducing the risk for damage to the components of these systems and avoiding or at least alleviating the risk of reduced NOx conversion efficiency.

The predetermined first amount may be based on only one of the current operational condition of the engine, the current physical properties prevailing in the exhaust conduit, the current physical properties prevailing in the hydraulic metering system, and the current ambient physical properties. The predetermined first amount may alternatively be based on several or all of these properties. The predetermined first amount may be based on a function taking one, several or all of the physical properties outlined above as input variables in order to determine as an output the first amount of liquid to be supplied to the exhaust conduit.

The current operational condition of the engine may e.g. be an indication of whether the engine is on or off, a rotational speed of the engine, or a load of the engine.

Optionally, the physical properties prevailing in the exhaust conduit may comprise one or more of the temperature in the exhaust conduit, the exhaust flow rate in the exhaust conduit, and the pressure in the exhaust conduit. Furthermore, the physical properties prevailing in the hydraulic metering system may comprise one or more of the pressure in the hydraulic metering system, the flow rate of liquid in the hydraulic metering system, and the temperature in the hydraulic metering system. Additionally, the ambient physical properties may comprise one or more of the ambient temperature, the ambient pressure, and the ambient humidity

Thereby, a method is provided capable of controlling the system such that the risk of damage to the hydraulic metering system is reduced. Moreover, a method is provided capable of controlling the hydraulic metering system such that a reduction in the aftertreatment system efficiency is avoided or at least alleviated. This is because the amount of liquid supplied to the exhaust conduit is tailored to the specific conditions prevailing at the time when the control is performed. A low temperature in the exhaust conduit may e.g. indicate that an increased risk of crystal formation is at hand. This would indicate that the predetermined first amount of liquid supplied into the exhaust conduit should be below a certain value to avoid or at least alleviate crystal formation. Similarly, a high pressure in the hydraulic metering system may e.g. indicate an increased risk of damage to the hydraulic metering system components. This would indicate that the predetermined amount of liquid supplied into the exhaust conduit should be above a certain value to reduce the risk of damage to the components. Several such considerations may be performed and weighed together in order to set the predetermined first amount of liquid. The predetermined first amount of liquid to be supplied to the exhaust conduit may therefore be a compromise between competing constraints or targets. By taking all of this data into consideration the predetermined first amount of liquid can be chosen and set such that an optimum value is chosen given the constraints. Since the predetermined first amount of liquid is set based on one or more of the physical parameters or properties itemized above the amount of liquid can be even more accurately determined such that the risk of crystal formation in the exhaust conduit is minimized while at the same time the pressure reduction in the hydraulic metering system is maximized, thereby reducing the risk for damage to the components of these systems and avoiding or at least alleviating the risk of reduced NOx conversion efficiency.

The predetermined first amount may be based on only one of the current operational condition of the engine, the temperature in the exhaust conduit, the exhaust flow rate in the exhaust conduit, the pressure in the exhaust conduit, the pressure in the hydraulic metering system, the flow rate of liquid in the hydraulic metering system, the temperature in the hydraulic metering system, the ambient temperature, the ambient pressure, and the ambient humidity. The predetermined first amount may alternatively be based on several or all of these properties. The predetermined first amount may be based on a function taking one, several or all of the physical properties outlined above as input variables in order to determine as an output the predetermined first amount of liquid to be supplied to the exhaust conduit.

Optionally, the method further comprises the step of, after the step of performing the at least first supply of the first amount of liquid: performing a number of second supplies of a second amount of liquid into the exhaust conduit via the supply opening by controlling the valve between the closed and open states.

Thereby a method is provided capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, a method is provided capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. Additionally, a method is provided capable of reducing the pressure in the hydraulic metering system in an efficient and controlled manner. This is achieved by supplying the liquid into the exhaust conduit in a number of controlled supply steps. Thereby the amount of liquid being supplied to the exhaust conduit during each supply can be controlled in an accurate manner. In this way it can be ensured that the pressure in the hydraulic metering system can be successively reduced while avoiding over-supply of liquid into the exhaust conduit which could result in crystal formation with the associated problems outlined above.

Optionally, the method further comprises the step of, after the step of performing the at least first supply of the first amount of liquid: performing a number of second supplies of a second amount of liquid into the exhaust conduit required for reaching a pressure in the hydraulic metering system below a first threshold pressure.

Thereby a method is provided capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, a method is provided capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. Additionally, a method is provided capable of reducing the pressure in the hydraulic metering system to a first threshold pressure in an efficient and controlled manner. This is achieved by supplying the liquid into the exhaust conduit in a number of controlled supply steps until the first threshold pressure is reached. Thereby the amount of liquid being supplied to the exhaust conduit during each supply can be controlled in an accurate manner. In this way it can be ensured that the pressure in the hydraulic metering system can be successively reduced to the first threshold pressure while avoiding over-supply of liquid into the exhaust conduit. Moreover, by choosing the first threshold pressure judicially and reducing the pressure in the system to the first threshold pressure it can be ensured that the system will not be damaged by the pressure prevailing in the hydraulic metering system. The first threshold pressure may e.g. be between 1 and 5 bar, preferably 1 bar.

Optionally, the method comprises the step of: setting the second amount of liquid based on one or more of a current operational condition of the engine, current physical properties prevailing in the exhaust conduit, current physical properties prevailing in the hydraulic metering system, and current ambient physical properties.

Thereby a method is provided capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, a method is provided capable of reducing the pressure in the hydraulic metering system to a target pressure in an efficient and controlled manner. Additionally, a method is provided capable of controlling the hydraulic metering system such that a reduction in the aftertreatment system efficiency is avoided or at least alleviated. This is because the amount of liquid supplied to the exhaust conduit is tailored to the specific conditions prevailing at the time when the control is performed. Since the second amount of liquid is set based on one or more of the physical conditions or properties itemized above the amount of liquid can be accurately determined such that the risk of crystal formation in the exhaust conduit is minimized while at the same time the pressure reduction in the hydraulic metering system is maximized, thereby reducing the risk for damage to the components of these systems. The second amount may be set once or several times, e.g. before each successive supply. The second amount may also be set at other intervals, e.g. every other supply, every third supply or every fourth supply. The second amount may also be set based on elapsed time, i.e. after x amount of time has passed the second amount is set, or set again. The second amount may also be set based on changes of the physical properties measured, e.g. if the temperature or pressure in the exhaust conduit and/or in the hydraulic metering system changes by a certain amount, reaches or exceeds a threshold value etc. All of the physical properties mentioned above based on which the second amount of liquid is set can be used also for determining to set the second amount of liquid again, i.e. updating or setting a new value for the second amount of liquid. In this way, the second amount of liquid may be tailored to the conditions prevailing at the time of supply, thereby an accurate amount of liquid can be supplied to the exhaust conduit at each supply event, reducing the risk for crystal formation while at the same time reducing the pressure in the hydraulic metering system in an optimal manner. Thereby the risk for damage to the components of the hydraulic metering system is reduced and a reduction in the aftertreatment system efficiency is avoided or at least alleviated.

The second amount of liquid may be based on only one of the current operational condition of the engine, the current physical properties prevailing in the exhaust conduit, the current physical properties prevailing in the hydraulic metering system, and the current ambient physical properties. The second amount of liquid may alternatively be based on several or all of these properties. The second amount of liquid may be based on a function taking one, several or all of the physical properties outlined above as input variables in order to determine as an output the second amount of liquid to be supplied to the exhaust conduit.

Optionally, the physical properties prevailing in the exhaust conduit comprise one or more of the temperature in the exhaust conduit, the exhaust flow rate in the exhaust conduit, and the pressure in the exhaust conduit, and wherein the physical properties prevailing in the hydraulic metering system comprises one or more of the pressure in the hydraulic metering system, the flow rate of liquid in the hydraulic metering system and the temperature in the hydraulic metering system, and wherein the ambient physical properties comprises one or more of the ambient temperature, the ambient pressure, and the ambient humidity.

Thereby a method is provided capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, a method is provided capable of reducing the pressure in the hydraulic metering system to a target pressure in an efficient and controlled manner. Moreover, a method is provided capable of controlling the hydraulic metering system such that a reduction in the aftertreatment system efficiency is avoided or at least alleviated. This is because the amount of liquid supplied to the exhaust conduit is tailored to the specific conditions prevailing at the time when the control is performed. Since the second amount of liquid is set based on one or more of the physical conditions or properties itemized above the amount of liquid can be accurately determined such that the risk of crystal formation in the exhaust conduit is minimized while at the same time the pressure reduction in the hydraulic metering system is maximized, thereby reducing the risk for damage to the components of these systems.

The second amount of liquid may be based on only one of the current operational condition of the engine, the temperature in the exhaust conduit, the exhaust flow rate in the exhaust conduit, the pressure in the exhaust conduit, the pressure in the hydraulic metering system, the flow rate of liquid in the hydraulic metering system, the temperature in the hydraulic metering system, the ambient temperature, the ambient pressure, and the ambient humidity. The second amount of liquid may alternatively be based on several or all of these properties. The second amount of liquid may be based on a function taking one, several or all of the physical properties outlined above as input variables in order to determine as an output the second amount of liquid to be supplied to the exhaust conduit.

Optionally, the hydraulic metering system comprises a heating arrangement configured to heat the hydraulic metering system, wherein the method comprises the step of: activating the heating arrangement if the data is indicative of freezing of liquid in the supply path.

Thereby, a method is provided capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. The heating arrangement will aid in thawing the frozen liquid, thereby ensuring that the liquid may be supplied to the exhaust conduit. The heating arrangement may be activated prior to, at the same time as, or after the step of performing at least a first supply of a predetermined first amount of liquid into the exhaust conduit.

Optionally, the method comprises the step of, prior to the step of performing at least a first supply of a first amount of liquid into the exhaust conduit via the supply opening: deactivating the pump.

Thereby, a method is provided capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. By deactivating the pump, the pressure in the hydraulic metering system will be reduced rapidly when performing the first supply of the first amount of liquid, thereby aiding in the reduction of pressure in the hydraulic metering system.

Optionally, the method comprises the step of: performing the first supply of the first amount of liquid based on a pressure in the hydraulic metering system for obtaining a pressure in the hydraulic metering system below a second threshold pressure when the first amount of liquid has been supplied to the exhaust conduit.

Thereby, a method is provided capable of controlling the system such that the risk of damage to the hydraulic metering system is reduced. Moreover, a method is provided capable of reducing the pressure in the hydraulic metering system quickly. The second threshold pressure may e.g. be a pressure which the hydraulic metering system is configured to withstand. Thereby the pressure in the system may very quickly be reduced down to a pressure which the hydraulic metering system can withstand without elevated risk for damages to the hydraulic metering system. The second threshold pressure may be between 1-5 bar. This step may be performed when there is indication that the pressure need to be reduced quickly, e.g. when there is an increased risk of damage to the hydraulic metering system. More concretely, the step may comprise setting the predetermined first amount of liquid based on a pressure in the hydraulic metering system for obtaining a pressure in the hydraulic metering system below a second threshold pressure when the predetermined first amount of liquid has been supplied to the exhaust conduit if data indicates an increased or imminent risk of damage to the hydraulic metering system. This step may thus e.g. be performed when the pressure in the hydraulic metering system is above a certain value which indicates a high risk of damage to the system, and the engine has been turned off. The step may also be performed based on indications that a certain time has passed since the pump was started in combination with indications that the engine has been turned off.

When the method comprises the step of performing a number of second supplies of a second amount of liquid into the exhaust conduit via the supply opening, the method may further comprise the step of setting the second amount of liquid based on a pressure in the hydraulic metering system for obtaining a pressure in the hydraulic metering system below the second threshold pressure when one supply of the second amount of liquid into the exhaust conduit has been performed. More concretely, the step may comprise setting the second amount of liquid based on a pressure in the hydraulic metering system for obtaining a pressure in the hydraulic metering system below a second threshold pressure when the second amount of liquid has been supplied to the exhaust conduit if data indicates an increased or imminent risk of damage to the hydraulic metering system. Thereby the pressure in the hydraulic metering system may be reduced quickly. This step may be performed based on the same considerations as has been explained in conjunction with setting the first predetermined amount of liquid above.

According to a second aspect of the invention, the object is achieved by a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer program comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments described herein, a computer program is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks. As a result, the above-mentioned object is achieved.

According to a third aspect of the invention, the object is achieved by a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer-readable medium comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments described herein, a computer-readable medium is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks. As a result, the above-mentioned object is achieved.

According to a fourth aspect of the invention, the object is achieved by a control arrangement for controlling the operation of a hydraulic metering system, the hydraulic metering system being configured to supply a liquid into an exhaust conduit of an engine. The system comprises a reservoir configured to store the liquid, a supply path, a pump configured to pump liquid from the reservoir into the supply path, and a supply opening configured to supply the liquid into the exhaust conduit of engine. The supply path comprises a valve controllable between an open state in which liquid is supplied from the supply path through the supply opening and a closed state in which liquid is blocked from flowing from the supply path through the supply opening. The control arrangement is configured to: obtain data indicative of freezing of liquid in the supply path, and perform at least a first supply of a first amount of liquid into the exhaust conduit via the supply opening by controlling the valve between the closed and open states if the data is indicative of freezing of liquid in the supply path.

Thereby the control arrangement is capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, the control arrangement is capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. This is because a first amount of liquid is supplied to the exhaust conduit when data indicates freezing of liquid in the supply path. Thus, the risk of a too large pressure being built up in the system is reduced, and therefore the risk of damage to the components is also reduced.

Accordingly, a control arrangement is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved. It will be appreciated that the various embodiments described for the method are all combinable with the control arrangement as described herein. That is, the control arrangement according to the fourth aspect of the invention may be configured to perform any one of the method steps of the method according to the first aspect of the invention.

According to a fifth aspect of the invention, the object is achieved by a hydraulic metering system configured to supply a liquid into an exhaust conduit of an engine.

The system comprises a reservoir configured to store the liquid, a supply path, a pump configured to pump liquid from the reservoir into the supply path, and a supply opening configured to supply the liquid into the exhaust conduit of the engine. The supply path comprises a valve controllable between an open state in which liquid is supplied from the supply path through the supply opening and a closed state in which liquid is blocked from flowing from the supply path through the supply opening. The hydraulic metering system comprises a control arrangement configured to: obtain data indicative of freezing of liquid in the supply path, and perform at least a first supply of a first amount of liquid into the exhaust conduit via the supply opening by controlling the valve between the closed and open states if the data is indicative of freezing of liquid in the supply path.

Thereby the control arrangement of the hydraulic metering system is capable of controlling the operation of the hydraulic metering system in a simple, effective and accurate manner. Moreover, the control arrangement is capable of controlling the hydraulic metering system to avoid the risk of damage to the hydraulic metering system when liquid has frozen in the supply path. This is because a first amount of liquid is supplied to the exhaust conduit when data indicates freezing of liquid in the supply path. Thus, the risk of a too large pressure being built up in the system is reduced, and therefore the risk of damage to the components is also reduced.

Accordingly, a hydraulic metering system is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above- mentioned object is achieved.

According to a sixth embodiment of the invention, the object is achieved by an engine comprising an exhaust conduit and a hydraulic metering system according to some embodiments of the present disclosure. Since the engine comprises an hydraulic metering system according to some embodiments, an engine is provided having at least some of the above-mentioned advantages.

Accordingly, an engine is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

According to a seventh embodiment of the invention, the object is achieved by a vehicle comprising an engine according to some embodiments of the present disclosure.

Since the vehicle comprises an engine according to some embodiments, a vehicle is provided having at least some of the above-mentioned advantages.

Accordingly, a vehicle is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:

Fig. 1 schematically illustrates a vehicle according to some embodiments,

Fig. 2 schematically illustrates a hydraulic metering system according to some embodiments, Fig. 3 schematically illustrates schematically illustrates a method of controlling operation of a hydraulic metering system,

Fig. 4 schematically illustrates two graphs showing the pressure of a hydraulic metering system as a function of time,

Fig. 5 schematically illustrates a computer-readable medium.

DETAILED DESCRIPTION Aspects of the present invention will now be described more fully. Like reference signs refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 schematically illustrates a vehicle 2 according to some embodiments. According to the illustrated embodiments, the vehicle 2 is a truck, i.e. a type of heavy road vehicle as well as a type of heavy commercial vehicle. According to further embodiments, the vehicle 2, as referred to herein, may be another type of heavy or lighter type of manned or unmanned vehicle for water-based or land-based propulsion such as a boat, lorry, a bus, a construction vehicle, a tractor, a car, or the like.

The vehicle 2 comprises an internal combustion engine 14. The internal combustion engine 14 is configured to provide motive power to the vehicle 2 via wheels 47 of the vehicle 2. The vehicle 2 may further comprise one or more electric machines for providing motive power to the vehicle 2. The vehicle 2 may thus comprise a hybrid electric powertrain comprising one or more electric propulsion motors in addition to the internal combustion engine 14 for providing motive power to the vehicle 2.

Fig. 2 illustrates a hydraulic metering system 10 of an engine 14. The hydraulic metering system 10, will alternatively be referred to as the system 10 below. The engine 14 may be an internal combustion engine 14. The engine 14, may be an engine of a vehicle, e.g. of the vehicle illustrated in Fig. 1. According to some embodiments, the internal combustion engine 14, as referred to herein, may be configured to power another type of unit or system than a vehicle, such as for example an electric generator.

According to the illustrated embodiments, the internal combustion engine 14 is a diesel engine, i.e. a type of compression ignition engine. The internal combustion engine 14 may thus be configured to operate on diesel or a diesel-like fuel, such as biodiesel, biomass to liquid (BTL), or gas to liquid (GTL) diesel. Diesel-like fuels, such as biodiesel, can be obtained from renewable sources such as vegetable oil which mainly comprises fatty acid methyl esters (FAME). Diesel-like fuels can be produced from many types of oils, such as rapeseed oil (rapeseed methyl ester, RME) and soybean oil (soy methyl ester, SME).

According to further embodiments, the internal combustion engine 14, as referred to herein, may be an Otto engine with a spark-ignition device, wherein the Otto engine may be configured to run on petrol, alcohol, similar volatile fuels, or combinations thereof. Alcohol, such as ethanol, can be derived from renewable biomass. Alternatively the internal combustion engine may be a hydrogen internal combustion engine configured to run on hydrogen.

The hydraulic metering system 10 is configured to supply a liquid into an exhaust conduit 12 of the engine 14. The exhaust conduit 12 may have a first inlet configured to receive exhaust gas from an outlet of the engine 14. The exhaust conduit 12 may have a first outlet configured to supply exhaust gas flowing through the exhaust conduit 12 to an exhaust aftertreatment system (not shown) of the engine 14. The exhaust aftertreatment system may for that purpose comprise one or more of a catalytic converter, a selective catalytic reduction arrangement, a diesel oxidation catalyst, a particulate filter, or the like. The exhaust aftertreatment system may be configured to reduce the amount of emissions in the exhaust gas in a manner known per se and will not be further explained herein.

The hydraulic metering system 10 further comprises a reservoir 16 configured to store the liquid. The liquid may be a reduction agent, e.g. an aqueous urea solution such as DEF. The reservoir 16 may e.g. be a tank or a cannister.

The hydraulic metering system 10 further comprises a supply path 11 and a pump 13 configured to pump liquid from the reservoir 16 into the supply path 11. The supply path 11 may e.g. comprise flexible tubes and/or rigid pipes. As is illustrated in Fig. 2, the supply path 11 may have a first inlet configured to receive liquid from the reservoir 16. The supply path 11 may thus be connected with the reservoir 16. Thus, whenever the pump 13 operates liquid will flow from the reservoir 16 into the supply path 11. The supply path 11 may furthermore have a first outlet configured to supply liquid to the reservoir 16. Thus, the supply path 11 may be connected with the reservoir 16 at two points, thereby creating a circular hydraulic metering system 10 where liquid can flow from the reservoir 16 into and along the supply path 11 and back into the reservoir 16.

The hydraulic metering system 10 further comprises a supply opening 15 configured to supply the liquid into the exhaust conduit 12 of the engine 14. The supply opening 15 may thus be configured to extend into the exhaust conduit 12 of the engine 14. The supply opening 15 may be comprised in an injector arrangement. The injector arrangement may then be configured to extend into the exhaust conduit 12 of the engine 14. The hydraulic metering system 10 may comprise more than one supply opening 15, e.g. two supply openings 15. This is not shown in Fig. 2. According to the embodiment illustrated in Fig. 2, the supply path 11 comprises a valve 17. The valve 17 is controllable between an open state in which liquid is supplied from the supply path 11 through the supply opening 15 and a closed state in which liquid is blocked from flowing from the supply path 11 through the supply opening 15. Thus, when the valve 17 is in the open state, liquid being pumped by the pump 13 from the reservoir 16 will be supplied into the exhaust conduit 12 of the engine 14. When the valve 17 is in the closed state, liquid being pumped by the pump 13 from the reservoir 16 will not be supplied into the exhaust conduit 12 of the engine 14. The liquid will then be returned to the reservoir 16 via the supply path 11. The valve 17 may be capable of being opened partially to allow for a portion of the liquid flow in the supply path 11 to be supplied into the exhaust conduit 12 of the engine 14.

According to the embodiment illustrated in Fig. 2 the hydraulic metering system 10 comprises a control arrangement 21. The control arrangement 21 is configured to obtain data indicative of freezing of liquid in the supply path 11. This data is used to determine whether there is a risk that frozen liquid in the hydraulic metering system 10 may damage the system. If that is the case, action should be taken to lower the pressure in the hydraulic metering system 10. In short, the actions taken may comprise turning of the pump 13 (if it is active) and reducing the pressure in the hydraulic metering system 10 by opening the valve 17 in order to let the liquid in the system 10 flow into the exhaust conduit 12. Furthermore, the hydraulic metering system 10 may need to be heated in order to unfreeze the frozen liquid in the system 10 prior to or simultaneously with opening the valve 17. This idea will be described in greater detail below.

The control arrangement 21 can receive input signals from sensors 19, 20, 22, 23.

According to the embodiment illustrated in Fig. 2 there are two sensors 19, 20 configured to collect data indicative of the physical properties prevailing in the exhaust conduit 12. There may however be fewer or more sensors configured to collect data indicative of the physical properties prevailing in the exhaust conduit 12, e.g. one, three, four, five, or more sensors. The sensor 19 may be a sensor configured to collect data indicative of the temperature in the exhaust conduit 12. The sensor 20 may be a sensor configured to collect data indicative of the flow rate of exhaust gas in the exhaust conduit 12. As has been described above there may be more or less than two sensors. These sensors may additionally or alternatively be configured to collect data indicative of other physical properties prevailing in the exhaust conduit 12 than the temperature or flow rate, e.g. the pressure in the exhaust conduit 12. Although the data are for the purposes of this embodiment described as obtained from sensors, it is also contemplated that the physical parameters may be modelled as well. According to the embodiment illustrated in Fig. 2 there are two sensors 22, 23 configured to collect data indicative of the physical properties prevailing in the hydraulic metering system 10. There may however be fewer or more sensors configured to collect data indicative of the physical properties prevailing in the hydraulic metering system 10, e.g. one, three, four, five, or more sensors. The sensor 22 may be a sensor configured to collect data indicative of the temperature in the hydraulic metering system 10. The sensor 23 may be a sensor configured to collect data indicative of the pressure in the hydraulic metering system 10. As has been described above there may be more or less than two sensors. These sensors may additionally or alternatively be configured to collect data indicative of other physical properties prevailing in the hydraulic metering system 10 than the temperature or pressure, e.g. the flow rate of liquid in the hydraulic metering system 10. The control arrangement 21 may also receive data indicative of the operational condition of the pump 13, this data may e.g. include whether the pump 13 is on or off, the pumping rate of the pump 13, and the load of the pump 13. Furthermore, stored historical data regarding the operational condition of the pump 13 can be used as well, e.g. in combination with current data. Moreover, the control arrangement may also receive data indicative of the operational condition of a heating arrangement 18. The operational condition of the heating arrangement 18 may e.g. include whether the heating arrangement 18 is on or off, the power being supplied to or by the heating arrangement 18, and the temperature of the heating arrangement 18.

The control arrangement 21 may also receive data indicating current ambient physical properties, such as the ambient temperature, whether there is precipitation, the humidity, the current ambient pressure etc. This data may be received from relevant sensors configured to collect this type of data, e.g. temperature sensors, humidity or rain sensors. These sensors are not shown in Fig. 2.

The control arrangement 21 is configured to perform at least a first supply of a first amount of liquid into the exhaust conduit 12 via the supply opening 15 by controlling the valve 17 between the closed and open states if the data is indicative of freezing of liquid in the supply path 11.

Thereby the control arrangement 21 can control the operation of the hydraulic metering system 10 in a simple, effective and accurate manner. Moreover, control arrangement 21 is capable of controlling the hydraulic metering system 10 to avoid the risk of damage to the hydraulic metering system 10 when liquid has frozen in the supply path 11. This is because a first amount of liquid is supplied to the exhaust conduit 12 when data indicates freezing of liquid in the supply path 11. Thus, the risk of a too large pressure being built up in the hydraulic metering system 10 is reduced, and therefore the risk of damage to the components of the hydraulic metering system 10 is also reduced.

The first amount of liquid may be predetermined. The predetermined first amount of liquid may be determined based on an estimate of crystal formation in the exhaust conduit when supplying the predetermined first amount of liquid to the exhaust conduit. The crystal formation in the exhaust conduit is inter alia dependent on the amount of liquid supplied to the exhaust conduit, as will be explained in greater detail below. Thereby, since a predetermined amount of liquid is supplied to the exhaust conduit 12 the risk of crystal formation in the exhaust conduit 12 can be reduced, since the predetermined amount of liquid can be chosen to achieve this, e.g. by supplying a lower amount of liquid at times when it is expected that there is an increased risk of crystal formation. Thereby the NOx conversion efficiency in the catalyst may be maintained, thus reducing the risk of an increase in emission, particularly NOx emissions.

According to some embodiments, the control arrangement 21 is configured to set the predetermined first amount of liquid based on one or more of, a current operational condition of the engine 14, current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties. The physical properties prevailing in the exhaust conduit 12 may comprise one or more of the temperature in the exhaust conduit 12, the exhaust flow rate in the exhaust conduit 12, and the pressure in the exhaust conduit 12. The physical properties prevailing in the hydraulic metering system 10 may comprise one or more of the pressure in the hydraulic metering system 10, the flow rate of liquid in the hydraulic metering system 11, and the temperature in the hydraulic metering system 10. The ambient physical properties may comprise the ambient temperature, the ambient pressure, and the ambient humidity.

The input signals from the sensors 19, 20, 22, 23 sent to the control arrangement 21 is indicative of whether freezing of liquid in the supply path 11 has occurred, are occurring or is imminent to occur. In a preferred embodiment of the present disclosure, an indication that the liquid in the supply path 11 has already frozen will be a requirement for triggering the first supply of the first amount of liquid.

Freezing of liquid, e.g. that the liquid has already frozen, may be indicated by considering e.g. the temperature prevailing in the hydraulic metering system 10 and comparing this temperature to the freezing point of the liquid in the hydraulic metering system 10. Furthermore, the freezing point of the liquid may vary depending on pressure, therefore pressure data may additionally or alternatively be considered for the determination of whether freezing of liquid has occurred. Other indications of freezing having occurred in the supply path 11 may e.g. be found from data regarding the pump 13, e.g. the load of the pump 13, the pumping rate of the pump 13, the flow rate of liquid in the supply path 11 and other parameters. How these parameters vary over time may also be taken into consideration. Moreover, other data may be used, such as the current ambient temperature and/or pressure and the physical properties prevailing in the exhaust conduit 12, such as the temperature, pressure or flow rate of exhaust gas. It is contemplated that a multitude of these sensor data is collected and processed together in order to determine whether there is an indication of freezing of liquid in the supply path 11, this may be referred to as sensor-fusion since data from a number of different sensors are used. A function may be used which takes as input a number of parameters and as output gives a determination of whether there is freezing or not in the supply path 11, e.g. by providing a Boolean or a flag indicating freezing. Historical data may also be used in the determination of whether there is freezing. Furthermore, the control arrangement may obtain information of whether the pump 13 has been active before or during the freezing of the liquid to thereby indicate a risk of a large pressure having been built up in the hydraulic metering system. Thus, the control arrangement 21 may be configured to perform the at least first supply of the first amount of liquid into the exhaust conduit 12 only if the pump 13 had been activated within a certain proximity in time to the freezing having occurred, i.e. so that the pressure in the system had been built up before the freezing occurred.

Data of physical properties prevailing in the exhaust conduit 12 may preferably be used for determining whether there is an increased risk of crystal formation in the exhaust conduit 12. This data may include, but is not limited to, one or more of the flow rate of exhaust gas in the exhaust conduit 12, the temperature of the exhaust gas in the exhaust conduit 12, and the pressure in the exhaust conduit 12. The temperature in the exhaust conduit 12 in close proximity to the supply opening 15 is preferably used. Furthermore, the temperature of the exhaust conduit 12 walls may alternatively or additionally be taken into consideration.

The risk of crystallization is also dependent on the amount of liquid being introduced into the exhaust conduit 12, e.g. the amount of liquid being supplied per time unit. Thereby a maximum amount of liquid which can be introduced into the exhaust conduit 12 per time unit without elevating the risk of crystal formation may be determined based on the data received from the sensors 19, 20. The predetermined first amount of liquid may then be set to be lower than said maximum amount of liquid. The predetermined first amount of liquid may thus be determined based on an estimate of an amount of crystal formation in the exhaust conduit 12 for that amount of liquid being supplied to the exhaust conduit 12, given one or more of, a current operational condition of the engine, current physical properties prevailing in the exhaust conduit, current physical properties prevailing in the hydraulic metering system, and current ambient physical properties. Preferably, the predetermined first amount of liquid may be determined based on an estimate of an amount of crystal formation in the exhaust conduit 12 for that amount of liquid being supplied to the exhaust conduit 12, given the current physical properties prevailing in the exhaust conduit 12.

The supply of the correct predetermined first amount of liquid may be achieved in a number of ways, e.g. by setting a time during which the valve 17 is in an open state. The time the valve 17 needs to be opened is determined by considering the physical properties which influence the amount of liquid being supplied per time unit when the valve 17 is in the open state. Data which may be taken into consideration for this determination is the pressure in the hydraulic metering system 10, temperature at the point of supply in the exhaust conduit 12, and the flow rate of the exhaust gas in the exhaust conduit 12. The valve 17 will then be controlled to the open state for the determined time and after the determined time has elapsed the valve will be controlled to the closed state. Thereby the correct predetermined first amount of liquid will be supplied to the exhaust conduit 12. The pressure in the hydraulic metering system 10 will then be reduced while at the same time an amount of liquid is supplied to the exhaust conduit 12 which reduces the risk of the liquid being crystallized in the exhaust conduit 12.

According to some embodiments, the control arrangement 21 is configured to, after having performed the at least first supply of the first amount of liquid, perform a number of second supplies of a second amount of liquid into the exhaust conduit 12 via the supply opening 15 by controlling the valve 17 between the closed and open states.

Thereby, the control arrangement 21 is capable of reducing the pressure in the hydraulic metering system 10 in an efficient and controlled manner. This is achieved by supplying the liquid into the exhaust conduit 12 in a number of controlled supply steps. Thereby the amount of liquid being supplied to the exhaust conduit 12 during each supply can be controlled in an accurate manner. In this way it can be ensured that the pressure in the hydraulic metering system 10 can be successively reduced while avoiding over-supply of liquid into the exhaust conduit 12 which could result in crystal formation with the associated problems outlined above.

The predetermined first amount of liquid may alternatively or in additionally be determined based on the pressure reduction in the hydraulic metering system 10 when supplying the predetermined first amount of liquid to the exhaust conduit 12.

Preferably, the predetermined first amount of liquid may be determined based on both the pressure reduction in the hydraulic metering system 10 and an estimate of crystal formation in the exhaust conduit 12, when supplying the predetermined first amount of liquid to the exhaust conduit 12. In this way a balance can be struck between quickly lowering the pressure in the hydraulic metering system 10 and minimizing the risk of crystal formation in the exhaust conduit 12, as will be explained in greater detail below.

According to some embodiments, the control arrangement 21 is configured to, after having performed the at least first supply of the first amount of liquid, perform a number of second supplies of a second amount of liquid into the exhaust conduit 12 required for reaching a pressure in the hydraulic metering system below a first threshold pressure P1.

Thereby, the control arrangement 21 is capable of reducing the pressure in the hydraulic metering system 10 to a first threshold pressure P1 an efficient and controlled manner. This is achieved by supplying the liquid into the exhaust conduit 12 in a number of controlled supply steps until the first threshold pressure P1 is reached. Thereby the amount of liquid being supplied to the exhaust conduit 12 during each supply can be controlled in an accurate manner. In this way it can be ensured that the pressure in the hydraulic metering system 10 can be successively reduced to the first threshold pressure P1 while avoiding over-supply of liquid into the exhaust conduit 12. Moreover, by choosing the first threshold pressure P1 judicially and reducing the pressure in the system 10 to the first threshold pressure P1 it can be ensured that system 10 will not be damaged by the pressure prevailing in the hydraulic metering system 10. The first threshold pressure P1 may e.g. be between 1 and 10 bar, preferably 1 bar.

According to some embodiments, the control arrangement 21 is configured to, set the second amount of liquid based on one or more of a current operational condition of the engine 14, , current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties. The physical properties prevailing in the exhaust conduit 12 may comprise one or more of the temperature in the exhaust conduit, the exhaust flow rate in the exhaust conduit, and the pressure in the exhaust conduit. The physical properties prevailing in the hydraulic metering system may comprise one or more of the pressure in the hydraulic metering system, and the temperature in the hydraulic metering system. The ambient physical properties may comprise the ambient temperature, the ambient pressure, and the ambient humidity.

Thereby, the control arrangement 21 is capable of reducing the pressure in the hydraulic metering system 10 to a first threshold pressure P1 in an efficient and controlled manner. Additionally, the control arrangement 21 is capable of controlling the hydraulic metering system 10 such that a reduction in the aftertreatment system efficiency is avoided or at least alleviated. This is because the second amount of liquid supplied to the exhaust conduit 12 is tailored to the specific conditions prevailing at the time when the control is performed. Since the second amount of liquid is set based on one or more of the physical conditions or properties itemized above the second amount of liquid can be accurately determined such that the risk of crystal formation in the exhaust conduit 12 is minimized while at the same time the pressure reduction in the hydraulic metering system 10 is maximized in each supply of liquid. Thereby the risk for damage to the components of the hydraulic metering system 10 is reduced. The second amount of liquid may be set once or several times, e.g. before each successive supply. The second amount may also be set at other intervals, e.g. every other supply, every third supply or every fourth supply. The second amount may also be set based on elapsed time, i.e. after x amount of time has passed the second amount is set. The second amount may also be set based on changes of the physical properties measured, e.g. if the temperature or pressure changes by a certain amount etc. In this way, the second amount may be tailored to the conditions prevailing at the time of supply, thereby an accurate amount of liquid can be supplied to the exhaust conduit 12 at each supply, reducing the risk for crystal formation while at the same time reducing the pressure in the hydraulic metering system 10 in an optimal manner. Thereby the risk for damage to the components of the hydraulic metering system 10 is reduced and a reduction in the aftertreatment system efficiency avoided or at least alleviated.

The second amount of liquid may be set in the same manner, having the same considerations in mind, as have been described in conjunction with the setting of the predetermined first amount of liquid above.

As has been described above, according to some embodiments, the hydraulic metering system 10 comprises a heating arrangement 18 configured to heat the hydraulic metering system 10. The heating arrangement 18 may heat the hydraulic metering system 10 directly or indirectly. For instance, the heating arrangement 18 may comprise an electric heater configured to heat the liquid in the hydraulic metering system 10, or it may comprise a heat exchanger heating the liquid in the hydraulic metering system 10. The control arrangement 21 may then be configured to activate the heating arrangement 18 if the data is indicative of freezing of liquid in the supply path 11. The heating arrangement 18 may be activated before, during or after the valve 17 is controlled by the control arrangement 21.

According to some embodiments, the control arrangement 21 is configured to, deactivate the pump 13 prior to performing at least a first supply of a first amount of liquid into the exhaust conduit 12 via the supply opening 15. By deactivating the pump 13 the pressure in the hydraulic metering system 10 will be reduced rapidly when the first amount of liquid is supplied to the exhaust conduit 12. The risk of damage to the hydraulic metering system 10 is thereby reduced.

According to some embodiments, the control arrangement 21 is configured to perform the first supply of the first amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the first amount of liquid has been supplied to the exhaust conduit 12. Thereby the control arrangement 21 is capable of controlling the hydraulic metering system 10 such that the risk of damage to the hydraulic metering system 10 is reduced. Moreover, the control arrangement 21 is capable of reducing the pressure in the hydraulic metering system 10 quickly. The second threshold pressure P2 may e.g. be a pressure which the hydraulic metering system 10 is configured to withstand. In more detail, the components of the hydraulic metering system 10 may be configured to be able to withstand pressures up to and preferably above the second threshold pressure P2. Thereby the pressure in the hydraulic metering system 10 may very quickly be reduced down to a pressure which the hydraulic metering system can withstand without elevated risk for damages to the hydraulic metering system. The second threshold pressure may be between 1-7 bar, e.g. 3, 4 or 5 bar.

The control arrangement 21 may be configured to perform the first supply of thefirst amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the first amount of liquid has been supplied to the exhaust conduit 12, when there is indication that the pressure need to be reduced quickly. In other words, the control arrangement 21 may be configured to perform the first supply of the first amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the first amount of liquid has been supplied to the exhaust conduit if data indicates an increased or imminent risk of damage to the hydraulic metering system 10. This indication may be e.g. that the pressure in the hydraulic metering system 10 is above a certain value, e.g. 8-12 bar, which indicates a high risk of damage to the hydraulic metering system 10 when it is frozen, together with indications that the engine 14 has been turned off. The step may also be performed based on indications that a certain time has passed since the pump 13 was started in combination with indications that the engine 14 has been turned off.

When the control arrangement 21 is configured to perform a number of second supplies of a second amount of liquid into the exhaust conduit 12 via the supply opening 15, the control arrangement 21 may further be configured to perform the supply of the second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below the second threshold pressure P2 when one supply of the second amount of liquid into the exhaust conduit 12 has been performed. Thereby the pressure in the hydraulic metering system 10 may be reduced quickly. This may be performed based on e.g. that the pressure in the hydraulic metering system 10 is above a certain value, e.g. 8-12 bar, which indicates a high risk of damage to the hydraulic metering system 10 when it is frozen, together with indications that the engine 14 has been turned off. The step may also be performed based on indications that a certain time has passed since the pump 13 was started in combination with indications that the engine 14 has been turned off.

The control arrangement 21 may thus be configured to perform the supply of the second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the second amount of liquid has been supplied to the exhaust conduit 12, when there is indication that the pressure need to be reduced quickly. In other words, the control arrangement 21 may be configured to perform a supply of the second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the second amount of liquid has been supplied to the exhaust conduit 12 if data indicates an increased or imminent risk of damage to the hydraulic metering system 10, as described above.

Fig. 4 illustrates two graphs showing two examples of a control of the hydraulic metering system 10 performed by the control arrangement 21 according to some embodiments herein. The vertical axes indicate the pressure in the hydraulic metering system 10 and the horizontal axes indicate time. The upper horizontal dashed line in both graphs, denoted “P_u” indicates a pressure value which is unsafe for the hydraulic metering system 10, especially if freezing of the liquid within the supply path 11 and components of the system 10 occur. Above this dashed line there is a high risk of damage to components of the system 10 if freezing occurs. The lower horizontal line in the upper graph indicates the first threshold pressure P1. The lower horizontal line in the lower graph indicates the second threshold pressure P2. These lines indicates that pressures below the lines are safe for components of the hydraulic metering system 10. The vertical dashed lines t1, t2, t3, t4, t5, t6 and t7 indicate different points in time. The jagged line show the pressure prevailing in the hydraulic metering system 10 as a function of time.

The upper graph of Fig. 4 show an example of a controlled reduction of the pressure in the hydraulic metering system 10, according to some embodiments herein. At time t1 the control arrangement 21 obtains data indicative of freezing of liquid in the supply path 11. Based on one or more of the current operational condition of the engine 14, , current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties the control arrangement 21 sets the first predetermined amount of liquid to be supplied to the exhaust conduit 12, taking into consideration the risk of crystallization in the exhaust conduit 12 given the current physical properties prevailing. The first predetermined amount of liquid is set in order to reduce the pressure in the hydraulic metering system 10 as much as possible while at the same time avoiding or alleviating the risk of crystal formation in the exhaust conduit 12. The control arrangement then performs a first supply of a predetermined first amount of liquid into the exhaust conduit 12 via the supply opening 15 by controlling the valve 17 between the closed and open states. The control arrangement 21 then sets a second amount of liquid based on one or more of a current operational condition of the engine 14, a current operational condition of the pump 13, current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties. Alternatively, the second amount of liquid may be set to be the same value as the first predetermined amount of liquid. The control arrangement 21 thereby takes into consideration the risk of crystallization given the current physical properties prevailing. Thereafter the control arrangement 21 performs a number of second supplies of the second amount of liquid into the exhaust conduit 12 required for reaching a pressure in the hydraulic metering system below the first threshold pressure P1. The setting of the second amount of liquid is in the example shown in Fig. 4 performed between each successive supply of the second amount of liquid, as can be seen by the irregular shape of the jagged line, but as has been described above, the second amount of liquid may be set more seldom as well. At time t2 it can be seen that the pressure is not reduced further but rather follows a plateau. Here the control arrangement 21 , based on the parameters which it obtains (current operational condition of the engine 14 etc.), has set the second amount of liquid to be supplied very low or even zero. In this scenario the engine is idling. At time t3, the control arrangement 21 once again sets a new second amount of liquid to be supplied, based on the parameters which it obtains, and the pressure drops with each supply. Thus, the new second amount is now greater than between t2 and t3. As can be seen, the pressure is reduced in steps below the first threshold pressure P1 at time t4. In this way the pressure in the hydraulic metering system 10 can be reduced, or lowered, in a controlled manner without risking crystallization in the exhaust conduit 12.

The lower graph of Fig. 4 show an example of a less controlled reduction of the pressure in the hydraulic metering system, according to some embodiments herein. At time t5 the control arrangement 21 obtains data indicative of freezing of liquid in the supply path 11. Based on one or more of the current operational condition of the engine 14, a current operational condition of the pump 13, current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system, and current ambient physical properties the control arrangement 21 sets the first predetermined amount of liquid to be supplied to the exhaust conduit 12, taking into consideration the risk of crystallization given the current physical properties prevailing. The first predetermined amount of liquid is set in order to reduce the pressure in the hydraulic metering system 10 as much as possible while at the same time avoiding or alleviating the risk of crystal formation in the exhaust conduit 12. The control arrangement 21 then performs a first supply of a predetermined first amount of liquid into the exhaust conduit 12 via the supply opening 15 by controlling the valve 17 between the closed and open states. The control arrangement 21 then sets a second amount of liquid based on one or more of a current operational condition of the engine 14, a current operational condition of the pump 13, current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties. The control arrangement 21 thereby takes into consideration the risk of crystallization given the current physical properties prevailing, e.g. in the exhaust conduit 12. Thereafter the control arrangement 21 performs a number of second supplies of the second amount of liquid into the exhaust conduit 12. However, at time t6 data indicates that the conditions in the hydraulic metering system 10 and its environment are such that there is an imminent risk to the components of the hydraulic metering system 10, e.g. the engine 14 is turned off and the pressure in the system 10 is high, e.g. above 10 bar. The control arrangement 21 then performs a supply of a second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below the second threshold pressure P2 when the second amount of liquid has been supplied to the exhaust conduit 12. Thus, the control arrangement 21 thereafter controls the valve 17 such that the supply opening 15 is in the open state until the pressure in the hydraulic metering system 10 is below the second threshold pressure P2 at time t7. As can be seen, the pressure is then reduced continuously and rapidly between time t6 and time t7. In this way the pressure in the hydraulic metering system 10 can be reduced, or lowered, in a quick manner when it is needed. The risk of damage to the system 10 is therefore reduced.

Fig. 3 illustrates a method 100 of controlling operation of a hydraulic metering system 10 being configured to supply a liquid into an exhaust conduit 12 of an engine 14. The hydraulic metering system 10 may be a hydraulic metering system 10 as described with reference to Fig. 2. The engine 14 may be an engine 14 as described with reference to Fig. 2. The engine 14 may be arranged in a vehicle 2 as described with reference to Fig. 1. Therefore, below, simultaneous reference is made to Fig. 1 - Fig. 3. As indicated in Fig. 3, according to the illustrated embodiments.

The method 100 is a method of controlling operation of a hydraulic metering system 10 being configured to supply a liquid into an exhaust conduit 12 of an engine 14. The hydraulic metering system 10 comprises a reservoir 16 configured to store the liquid, a supply path 11, a pump 13 configured to pump liquid from the reservoir 16 into the supply path 11, and a supply opening 15 configured to supply the liquid into the exhaust conduit 12 of the engine

14. The supply path 11 comprises a valve 17 controllable between an open state in which liquid is supplied from the supply path 11 through the supply opening 15 and a closed state in which liquid is blocked from flowing from the supply path 11 through the supply opening

15. The method 100 comprises the step of: obtaining 110 data indicative of freezing of liquid in the supply path, and performing 120 at least a first supply of a first amount of liquid into the exhaust conduit via the supply opening 15 by controlling the valve 17 between the closed and open states if the data is indicative of freezing of liquid in the supply path 11.

According to some embodiments, the hydraulic metering system 10 comprises sensors 19, 20, 22, 23 configured to obtain data indicative of freezing of liquid in the supply path. The data may also be obtained from modelling the system and the parameters governing it.

According to some embodiments, the first amount of liquid is a predetermined amount of liquid. According to some embodiments, when the first amount of liquid is predetermined, the method 100 comprises the step of: setting 111 the predetermined first amount of liquid based on one or more of, a current operational condition of the engine 14, current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties.

Optionally, the physical properties prevailing in the exhaust conduit 12 comprise one or more of the temperature in the exhaust conduit 12, the exhaust flow rate in the exhaust conduit 12, and the pressure in the exhaust conduit 12, and wherein the physical properties prevailing in the hydraulic metering system 10 comprises one or more of the pressure in the hydraulic metering system 10, the flow rate of liquid in the hydraulic metering system 10, and the temperature in the hydraulic metering system 10, and wherein the ambient physical properties comprises the ambient temperature, the ambient pressure, and the ambient humidity.

According to some embodiments, the method 100 further comprises the step of, after the step of performing 120 the at least first supply of the predetermined first amount of liquid: performing 130 a number of second supplies of a second amount of liquid into the exhaust conduit 12 via the supply opening 15 by controlling the valve 17 between the closed and open states.

According to some embodiments, the method 100 further comprises the step of, after the step of performing 120 the at least first supply of the predetermined first amount of liquid: performing 131 a number of second supplies of a second amount of liquid into the exhaust conduit 12 required for reaching a pressure in the hydraulic metering system 10 below a first threshold pressure P1.

According to some embodiments, the method 100 further comprises the step of: setting 121 the second amount of liquid based on one or more of a current operational condition of the engine 14, , current physical properties prevailing in the exhaust conduit 12, current physical properties prevailing in the hydraulic metering system 10, and current ambient physical properties.

According to some embodiments, when the method 100 comprises the further steps of performing 130 a number of second supplies of a second amount of liquid into the exhaust conduit 12 via the supply opening 15 by controlling the valve 17 between the closed and open states, the step of performing 130 a number of second supplies of second amount of liquid comprises performing a supply of the second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the second amount of liquid has been supplied to the exhaust conduit 12. The valve 17 may thus be kept open until the second threshold pressure P2 is reached.

The step performing a supply of the second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the second amount of liquid has been supplied to the exhaust conduit 12, may be performed when there is indication that the pressure need to be reduced quickly. In other words, the step of performing a supply of the second amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the second amount of liquid has been supplied to the exhaust conduit 12 may be performed if data indicates an increased or imminent risk of damage to the hydraulic metering system 10.

Optionally, here the physical properties prevailing in the exhaust conduit 12 comprise one or more of the temperature in the exhaust conduit 12, the exhaust flow rate in the exhaust conduit 12, and the pressure in the exhaust conduit 12, and wherein the physical properties prevailing in the hydraulic metering system 10 comprises one or more of the pressure in the hydraulic metering system 10, the flow rate of liquid in the hydraulic metering system 10, and the temperature in the hydraulic metering system 10, and wherein the ambient physical properties comprises the ambient temperature, the ambient pressure, and the ambient humidity.

According to some embodiments, the hydraulic metering system 10 comprises a heating arrangement 18 configured to heat the hydraulic metering system 10. The method 100 may then additionally comprise the step of: activating 112 the heating arrangement 18 if the data is indicative of freezing of liquid in the supply path 11.

According to some embodiments, the method 100 further comprises the step of: setting 113 the predetermined first amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the predetermined first amount of liquid has been supplied to the exhaust conduit 12.

The step of setting 113 the predetermined first amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the predetermined first amount of liquid has been supplied to the exhaust conduit 12, may be performed when there is indication that the pressure need to be reduced quickly. In other words, the step of setting the predetermined first amount of liquid based on a pressure in the hydraulic metering system 10 for obtaining a pressure in the hydraulic metering system 10 below a second threshold pressure P2 when the predetermined first amount of liquid has been supplied to the exhaust conduit 12 may be performed if data indicates an increased or imminent risk of damage to the hydraulic metering system 10.

According to some embodiments, the method comprises a step of, prior to the step of performing 120 at least a first supply of a predetermined first amount of liquid into the exhaust conduit via the supply opening: deactivating 114 the pump 13.

By deactivating the pump 13 it is ensured that the pressure does not rise in the hydraulic metering system 10 further. Thus, the pressure in the hydraulic metering system 10 will be reduced rapidly after the valve 17 has been opened and the supply of the liquid has been initiated.

It will be appreciated that the various embodiments described for the method 100 are all combinable with the control arrangement 21 as described herein. That is, the control arrangement 21 may be configured to perform any one of the method steps 110, 111, 112, 113, 120, 121, 122, 130, and 131 of the method 100.

Fig. 5 illustrates a computer-readable medium 200 comprising instructions which, when executed by a computer, cause the computer to carry out the method 100 according to some embodiments of the present disclosure. According to some embodiments, the computer- readable medium 200 comprises a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to some embodiments. The computer may be comprised in the control arrangement 21. In some embodiments, the computer-readable medium may be a non- transitory computer-readable medium, such as a tangible electronic, magnetic, optical, infrared, electromagnetic, and/or semiconductor system, apparatus, and/or device. One skilled in the art will appreciate that the method 100 of controlling operation of a hydraulic metering system 10 being configured to supply a liquid into an exhaust conduit 12 of an engine 14 may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in the control arrangement 21 , ensures that the control arrangement 21 carries out the desired control, such as the method steps 110, 111, 112, 113, 120, 121 122, 130, and 131 described herein. The computer program is usually part of a computer program product 200 which comprises a suitable digital storage medium on which the computer program is stored, such as the computer-readable medium 200 illustrated in Fig. 5. In other words, the computer program product may be a computer readable medium 200 and the computer program may be stored in the computer readable medium 200..

The control arrangement 21 may comprise a calculation unit which may take the form of substantially any suitable type of computer, processor circuit or microcomputer, i.e. any hardware or hardware/firmware device implemented using processing circuity such as, but not limited to, a processor, Central Processing Unit (CPU), a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable gate array (FPGA), a System-on-Chip (SoC), a programmable logic unit, a microprocessor, an application-specific integrated circuit (ASIC), or any other device capable of electronically performing operations in a defined manner..

The control arrangement 21 may further comprise a memory unit, wherein the calculation unit may be connected to the memory unit, which may provide the calculation unit with, for example, stored program code and/or stored data which the calculation unit may need to enable it to do calculations. The calculation unit may also be adapted to store partial or final results of calculations in the memory unit. The memory unit may comprise a physical device utilised to store data or programs, i.e., sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors. The memory unit may comprise e.g., a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g., ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments.

The control arrangement 21 may be connected to components of the hydraulic metering system 10, components of the internal combustion engine 14, and/or other parts of the vehicle 2 receiving and/or sending input and output signals. These input and output signals may comprise waveforms, pulses, or other attributes which the input signal receiving devices can detect as information and which can be converted to signals processable by the control arrangement 21. These signals may then be supplied to the calculation unit. One or more output signal sending devices may be arranged to convert calculation results from the calculation unit to output signals for conveying to other parts of the vehicle's control system and/or the component or components for which the signals are intended. Each of the connections to the respective components of the hydraulic metering system 10, components of the internal combustion engine 14, and/or other parts of the vehicle 2, for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g., a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection.

In the embodiments illustrated, the hydraulic metering system 10 comprises a control arrangement 21 but might alternatively be implemented wholly or partly in two or more control arrangements or two or more control units.

Control systems in modern vehicles generally comprise a communication bus system consisting of one or more communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a control system may comprise a large number of control units and taking care of a specific function may be shared between two or more of them. Vehicles of the type here concerned are therefore often provided with significantly more control arrangements than depicted in Fig. 2, as one skilled in the art will surely appreciate.

The computer program product 200 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the method steps 110, 111, 112, 113, 120, 122, 130, and 131 according to some embodiments when being loaded into one or more calculation units of the control arrangement 21. The data carrier may be, e.g. a CD ROM disc, as is illustrated in Fig. 4, or a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer program product may furthermore be provided as computer program code on a server and may be downloaded to the control arrangement 21 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems. It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components, or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims

1. A method (100) of controlling operation of a hydraulic metering system (10), the hydraulic metering system (10) being configured to supply a liquid into an exhaust conduit (12) of an engine (14), wherein the system (10) comprises a reservoir (16) configured to store the liquid, a supply path (11), a pump (13) configured to pump liquid from the reservoir (16) into the supply path (11), and a supply opening (15) configured to supply the liquid into the exhaust conduit (12) of the engine (14), wherein the supply path (11) comprises a valve (17) controllable between an open state in which liquid is supplied from the supply path (11) through the supply opening (15) and a closed state in which liquid is blocked from flowing from the supply path (11) through the supply opening (15), and wherein the method comprises the steps of: obtaining (110) data indicative of freezing of liquid in the supply path, and performing (120) at least a first supply of a first amount of liquid into the exhaust conduit (12) via the supply opening (15) by controlling the valve (17) between the closed and open states if the data is indicative of freezing of liquid in the supply path (11).

2. The method (100) according to claim 1 , wherein the first amount of liquid is predetermined, the method further comprising the step of: setting (111) the predetermined first amount of liquid based on one or more of, a current operational condition of the engine (14), current physical properties prevailing in the exhaust conduit (12), current physical properties prevailing in the hydraulic metering system (10), and current ambient physical properties.

3. The method (100) according to claim 2, wherein the physical properties prevailing in the exhaust conduit (12) comprise one or more of the temperature in the exhaust conduit (12), the exhaust flow rate in the exhaust conduit (12), and the pressure in the exhaust conduit (12), and wherein the physical properties prevailing in the hydraulic metering system (10) comprises one or more of the pressure in the hydraulic metering system (10), the flow rate of liquid in the hydraulic metering system (10), and the temperature in the hydraulic metering system (10), and wherein the ambient physical properties comprises one or more of the ambient temperature, the ambient pressure, and the ambient humidity.

4. The method (100) according to any one of the preceding claims, wherein the method (100) further comprises the step of, after the step of performing (120) the at least first supply of the first amount of liquid: performing (130) a number of second supplies of a second amount of liquid into the exhaust conduit (12) via the supply opening (15) by controlling the valve (17) between the closed and open states.

5. The method (100) according to any one of the preceding claims, wherein the method (100) further comprises the step of, after the step of performing (120) the at least first supply of the first amount of liquid: performing (131) a number of second supplies of a second amount of liquid into the exhaust conduit (12) required for reaching a pressure in the hydraulic metering system (10) below a first threshold pressure (P1).

6. The method (100) according to any one of claims 4-5, wherein the method (100) comprises the step of: setting (121) the second amount of liquid based on one or more of a current operational condition of the engine (14), current physical properties prevailing in the exhaust conduit (12), current physical properties prevailing in the hydraulic metering system (10), and current ambient physical properties.

7. The method (100) according to claim 6, wherein the physical properties prevailing in the exhaust conduit (12) comprise one or more of the temperature in the exhaust conduit (12), the exhaust flow rate in the exhaust conduit (12), and the pressure in the exhaust conduit (12), and wherein the physical properties prevailing in the hydraulic metering system (10) comprises one or more of the pressure in the hydraulic metering system (10), the flow rate of liquid in the hydraulic metering system (10), and the temperature in the hydraulic metering system (10), and wherein the ambient physical properties comprises one or more of the ambient temperature, the ambient pressure, and the ambient humidity.

8. The method (100) according to any one of the preceding claims , wherein the method (100) comprises the step of, prior to the step of performing (120) at least a first supply of a first amount of liquid into the exhaust conduit (12) via the supply opening (15): de-activating (114) the pump (13).

9. The method (100) according to any one of the preceding claims, wherein the method (100) comprises the step of: performing (120) the first supply of the first amount of liquid based on a pressure in the hydraulic metering system (10) for obtaining a pressure in the hydraulic metering system (10) below a second threshold pressure (P2) when the first amount of liquid has been supplied to the exhaust conduit (12).

10. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method (100) according to any one of the claims 1 - 9.

11. A computer-readable medium (200) comprising instructions which, when executed by a computer, cause the computer to carry out the method (100) according to any one of the claims 1 - 9.

12. A control arrangement (21) for controlling the operation of a hydraulic metering system

(10), the hydraulic metering system (10) being configured to supply a liquid into an exhaust conduit (12) of an engine (14), wherein the system comprises a reservoir (16) configured to store the liquid, a supply path (11), a pump (13) configured to pump liquid from the reservoir (16) into the supply path (11), and a supply opening (15) configured to supply the liquid into the exhaust conduit (12) of the engine (14), wherein the supply path (11) comprises a valve (17) controllable between an open state in which liquid is supplied from the supply path (11) through the supply opening (15) and a closed state in which liquid is blocked from flowing from the supply path (11) through the supply opening (15), wherein the control arrangement (21) is configured to: obtain data indicative of freezing of liquid in the supply path (11), and perform at least a first supply of a first amount of liquid into the exhaust conduit (12) via the supply opening (15) by controlling the valve (17) between the closed and open states if the data is indicative of freezing of liquid in the supply path

(11).

13. A hydraulic metering system (10) configured to supply a liquid into an exhaust conduit

(12) of an engine (14), wherein the system (10) comprises a reservoir (16) configured to store the liquid, a supply path (11), a pump (13) configured to pump liquid from the reservoir (16) into the supply path (11), and a supply opening (15) configured to supply the liquid into the exhaust conduit (12) of the engine (14), wherein the supply path (11) comprises a valve (17) controllable between an open state in which liquid is supplied from the supply path (11) through the supply opening (15) and a closed state in which liquid is blocked from flowing from the supply path (11) through the supply opening (15), wherein the hydraulic metering system (11) comprises a control arrangement according (21) to claim 12.

14. An engine (14) comprising an exhaust conduit (12) and a hydraulic metering system (10) according to claim 13, wherein the hydraulic metering system (10) is configured to supply liquid into the exhaust conduit (12) of the engine (14).

15. A vehicle (20) comprising an engine (14) according to claim 14.