Method for injecting a fluid and injector system for a vehicle engine

Abstract

The invention provides a method for injecting a fluid in an internal combustion engine system comprising: an internal combustion engine; a duct; a fluid injector of a fluid in the duct or in the internal combustion engine, the fluid injector comprising: an actuation coil; and a fluid pump pressurize the fluid. The method comprising the steps of: heating (102) the actuation coil with a first heating current including a first heating intensity; then pressurizing (108) the fluid at an injection pressure with the fluid pump; heating (110) the actuation coil with a second heating current including a second heating intensity; then injecting (112) fluid through the fluid injector by feeding the actuation coil with an injection intensity of an injection current; the second heating intensity being inferior to the injection intensity in order to keep closed the fluid injector during the step of heating the actuation coil with the second heating current.

Description

Method for injecting a fluid and injector system for a vehicle engine

[0001] The invention pertains to fluid injector heating. More precisely, the invention pertains to fluid injectors for vehicle engines. The invention also provides an injection system.

[0002] A vehicle engine unit is typically equipped with fuel injectors, and auxiliary injectors which are dedicated to the injection of other functional fluids. These auxiliary injectors are typically adapted for delivering water, or water-based solutions. By way of illustration, the water-based solutions enclose aqueous urea solutions (e.g. AdBlue) which are prone to freezing. Upon freezing, the associated injector is clogged and disabled until warmer conditions are encountered or triggered.

[0003] A combustion engine forms a powerful heat source which is convenient for deicing the inner sensors or fluid injectors arranged in the gas exhaust line. However, in specific working conditions, an aqueous urea solution injector may freeze albeit the combustion engine moves the vehicle, or switched on. For example, a vehicle powered by an internal combustion engine and driving down a mountain pass in freezing condition may encounter a situation wherein at least one of its injectors freezes. Indeed, the ambient temperature is low but the energy required for driving the vehicle remains too low for heating enough the gas exhaust line.

[0004] Therefore, additionally heating the fluid injectors is required in order to alleviate the freezing events.

[0005] The document US2013275025A1 provides a method for controlling a fuel injector during start-up of a fuel injected internal combustion engine. The fuel injector has a heater element configured to heat liquid fuel, such as gasoline, ethanol, gasoline / alcohol blends, diesel, or JP-8 within the fuel injector and indicate heater temperature. The controller is configured to estimate a fuel temperature based on the heater temperature, determine a crankshaft angle at which to initiate an injection event based on the fuel temperature, and initiate the injection event at the determined crankshaft angle. The method comprises a step of determining the engine operating parameters. Based on these parameters, the method encloses a step of determining if the engine temperature is greater than an engine temperature threshold. If the engine temperature is less than the engine temperature threshold, the method proceeds to a step of activating the injector heater.

[0006] The document US2015267671A1 describes a method for controlling electrical power applied to a fuel heater. The method includes applying power to the heater, determining a value for an electrical parameter that varies as a function of the temperature of the heater, and determining a value representative of the time rate of change of the electrical parameter. The method further includes determining the value of the electrical parameter corresponding to a change in the time rate of change of the electrical parameter. The method also executes a comparison on the change in the time rate of the electrical parameter with respect to a predetermined threshold.

[0007] The document US4886032A describes a method for a vehicle engine having fuel injectors with a solenoid coil in a housing for passing fuel into the engine. The engine includes an electrical control unit with an alternate normal engine run mode and an injector heating mode and a temperature sensing switch to signal the electrical control so that the fuel pump and engine starter are deenergized and the injector coils are energized for a timed period so that the injectors are heated and subsequently the temperature of fuel passed therethrough is increased by heat transfer therefrom during a subsequent start and run mode of operation. A constant voltage is applied to the injector coil during an injector heating mode at low temperatures prior to starting the engine. The constant voltage corresponds to the maximum battery voltage. This coil energizing opens the injectors, however since the fuel pump is deactivated, no fuel sprays into the engine.

[0008] Yet, this method does not allow to heat the injectors when the pump pressurizes the fluid. In addition, the heating generates thermal shocks to the injectors.

[0009] The invention intends to improve or to solve at least one drawback of the prior art. The invention aims at allowing heating of the fluid injector when the fluid is pressurized without injecting said fluid. It is another objective of the invention to avoid the thermal shock risk for the fluid injector upon heating. The invention also aims at optimizing the thermal shock risk and the fluid flow management when the injected fluid is pressurized upstream the fluid injector.

[0010] In accordance with a first aspect, the invention provides a method for injecting a fluid in an internal combustion engine system; the internal combustion engine system comprising: an internal combustion engine; a duct; a fluid pump adapted to pressurize the fluid; a fluid injector configured for injecting a fluid from the fluid pump in the duct or in the internal combustion engine, the fluid injector comprising: an actuation coil; the method comprising the steps of: o heating the actuation coil with a first heating current including a first heating intensity; theno pressurizing the fluid at an injection pressure with the fluid pump;■ remarkable in that during the step of pressurizing the fluid, the method further comprises the steps of: o heating the actuation coil with a second heating current including a second heating intensity; then o injecting fluid through the fluid injector by feeding the actuation coil with an injection intensity of an injection current; the second heating intensity being inferior to the injection intensity in order to keep closed the fluid injector during the step of heating the actuation coil with the second heating current.

[0011] In embodiments, the at the step of heating the actuation coil with the first heating current, said first heating current comprises a first intensity peak equal to a maximum intensity of the injection current.

[0012] In embodiments, after the first intensity peak, the first heating current comprises a hold intensity between the intensity peak and the second heating intensity.

[0013] In embodiments, the hold intensity represents from 90% to 50% of the maximum intensity of the injection current, preferably from 80% to 60% of the maximum intensity of the injection current.

[0014] In embodiments, the first intensity peak comprises a gradual intensity increase up to the maximum intensity of the injection current, preferably the gradual intensity increase comprises a constant intensity increase ratio until said maximum intensity of the injection current.

[0015] In embodiments, the first heating current comprises first heating pulses, the method comprises a step of measuring a system temperature; and a step of comparing the system temperature with a first temperature threshold; if the system temperature is lower than the first temperature threshold, the first heating pulses comprise a constant heating intensity; if the system temperature is of at least the first temperature threshold, each of the first heating pulses comprise a decreasing heating intensity; preferably the system temperature is an injector temperature or an exhaust temperature.

[0016] In embodiments, the first heating current comprises first heating pulses with a variable pulse width which increases over time.

[0017] In embodiments, the method further comprises a step of measuring an ambient air temperature, the method executing the step of heating the actuation coil with the first heating current if the ambient air temperature is colder than a second temperature threshold.

[0018] In embodiments, the step of heating the actuation coil with the first heating current comprises a fixed time duration after which the step of pressurizing and the step of heating the actuation coil with the second heating current are executed.

[0019] In embodiments, the injection current comprises a series of injection pulses at an injection frequency, and the second heating current comprises a second series of second heating pulses at a second frequency which is smaller than the injection frequency.

[0020] In embodiments, the fluid is a urea aqueous solution and / or the duct is gas exhaust pipe in fluid flow communication with the internal combustion engine.

[0021] In embodiments, the fluid comprises water and / or the duct is an air intake pipe in fluid flow communication with an air inlet of the internal combustion engine.

[0022] In embodiments, the duct extends from the combustion engine, and comprises duct section which is at least at 1 m away from the combustion engine, preferably at least at 1.5 m away from the combustion engine, said duct section being in thermal exchange with the ambient air, the fluid injector being arranged along said duct section.

[0023] In embodiments, the step of pressurizing is a step of starting to pressurize the fluid.

[0024] In embodiments, the fluid is a liquid, for instance liquid fuel.

[0025] In embodiments, the fluid comprises a freezing temperature of at most 0°C, or at most -10°C.

[0026] In embodiments, the fluid injector is in fluid flow communication with the fluid injector.

[0027] In embodiments, the second heating intensity is lower than the first heating intensity, preferably the maximum of second heating intensity is lower than the minimum of the first heating intensity.

[0028] In embodiments, the step of injecting is a step of feeding the actuation coil with an opening current in order to open the fluid injector and to inject fluid through the fluid injector by means of the fluid injector and the fluid pump ; the second heating intensity being lower than the injecting intensity in order to avoid injection during the step of heating the actuation coil with the second heating current and / or in order to keep closed the fluid injector during the step of feeding the actuation coil with the second heating current.

[0029] In embodiments, the fluid injector comprises a closing element adapted to close fluid injection through the fluid injector, the actuation coil being adapted to move the closing element from a closed position to an open position allowing fluid injection.

[0030] In embodiments, the injecting current is an opening current.

[0031] It is another aspect of the invention to provide a method for injecting a fluid in an internal combustion engine system; the internal combustion engine system comprising: aninternal combustion engine; a duct; a fluid injector configured for injecting a fluid in the duct or in the internal combustion engine, the fluid injector comprising: an actuation coil; and a fluid pump adapted to pressurize the fluid upstream the fluid injector; the method comprising the steps of:• feeding the actuation coil with a first heating current in order to heat the fluid injector; then• pressurizing the fluid at an injection pressure with the fluid pump; remarkable in that during the step of pressurizing the fluid, the method further comprises the steps of:• feeding the actuation coil with a second heating current which comprises a second heating intensity in order to heat the fluid injector; then• feeding the actuation coil with an injection current comprising an injection intensity enabling fluid injection through the fluid injector; the second heating intensity being inferior to the injection intensity such that the fluid injector remains closed during the step of feeding the actuation coil with a second heating current.

[0032] It is another aspect of the invention to provide a method for injecting a fluid in an internal combustion engine system and / or of heating a fluid injector ; the internal combustion engine system comprising: an internal combustion engine; a duct; a fluid injector configured for injecting a fluid in the duct or in the internal combustion engine, the fluid injector comprising: an actuation coil; and a fluid pump adapted to pressurize the fluid upstream the fluid injector ; the method comprising the steps of:• heating the fluid injector at a first temperature; then• pressurizing the fluid at an injection pressure with the fluid pump; remarkable in that, the method further comprises the steps of• heating the fluid injector at a second temperature by powering of the actuation coil with a second current ; then optionally• injecting fluid with the fluid injector by powering said fluid injector with an injection current higher than the second current; said second current avoiding the fuel injector to inject fluid.

[0033] It is another aspect of the invention to provide a method for injecting a fluid in an internal combustion engine system; the internal combustion engine system comprising: an internal combustion engine; a duct; a fluid injector configured for injecting a fluid in the duct or in the internal combustion engine, the fluid injector comprising: an actuation coil ; and afluid pump adapted to pressurize the fluid upstream the fluid injector ; the method comprising the steps of:• feeding the actuation coil with a first heating current in order to heat the fluid injector; then• feeding the actuation coil with an injection current enabling fluid injection through the fluid injector; remarkable in that the first heating current comprises first heating pulses with a variable pulse width which increases over time.

[0034] It is another aspect of the invention to provide a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method in accordance with the invention.

[0035] It is another aspect of the invention to provide an internal combustion engine system for an automotive vehicle, the internal combustion engine system which comprises : an internal combustion engine; a duct; a fluid injector configured for injecting a fluid in the duct or in the internal combustion engine, the fluid injector comprising: an actuation coil ; and a fluid pump adapted to pressurize the fluid upstream the fluid injector; a control unit, the internal combustion engine system is remarkable in that it further comprises an electronic control unit (30) adapted to carry out the method in accordance with the invention.Brief description of the figures.

[0036] Figure 1 is a side view of an automotive vehicle with an internal combustion engine system in accordance with a preferred embodiment of the invention.

[0037] Figure 2 is a flow chart of a method in accordance with a preferred embodiment of the invention.

[0038] Figure 3 is a temporal graph illustrating the injection current and heating currents in accordance with a preferred embodiment of the invention.

[0039] Figure 4 is a temporal graph illustrating the first heating current with different pulse width modulations in accordance with a preferred embodiment of the invention.

[0040] Figure 5 is a temporal graph illustrating the first heating current with, and without, a current peak and a hold current in accordance with a preferred embodiment of the invention.

[0041] Figure 6 is a temporal graph highlighting the differences between the pulses of the injection current, the first heating current and the second heating current in accordance with a preferred embodiment of the invention.

[0042] Figure 7 is a temporal graph of a comparison of pulse profiles of the first heating current in accordance with a preferred embodiment of the invention.Description of the embodiments

[0043] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method substeps. The terms "comprising", "comprises" and "comprised of" also include the term "consisting of".

[0044] The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g., 1 to 5 can include 1, 2, 3, 4, 5 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of endpoints also includes the recited endpoint values themselves (e.g., from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

[0045] The particular features, structures, characteristics or embodiments may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments.

[0046] Throughout the description, the same reference signs will be used in order to designate similar or identical entities.

[0047] Figure 1 is a schematic representation of an automotive vehicle 10 with an internal combustion engine system 12.

[0048] The internal combustion engine system 12 is embedded in the automotive vehicle 10. The internal combustion engine system 12 comprises an internal combustion engine 14, and a plurality of ducts 16. The ducts 16 comprise an air intake pipe 18 and a gas exhaust pipe 20.

[0049] The air intake pipe 18 is in fluid flow communication with an air inlet of the internal combustion engine 14. The air intake pipe 18 provides fresh air intended to feed combustion in the internal combustion engine 14. The gas exhaust pipe 20 is in fluid flow communication with the internal combustion engine 14, and channels exhaust gas products out of the automotive vehicle 10.

[0050] A fluid is stored in a fluid tank 22. The fluid is a urea aqueous solution. Such a urea aqueous solution comprises a freezing point at -10°C. As an alternative or more generally, the fluid comprises water. The fluid is sucked from the tank 22, and pressurized toward theinternal combustion engine 14 by a fluid pump 24. The fluid pump 24 is adapted to pressurize fluids. The fluid pump 24 is adapted for pressurizing the fluid at 5 bars or more.

[0051] As an option, the internal combustion engine system 12 includes temperature measuring means. The temperature measuring means include an outer thermometer 26 adapted to measure the air temperature outside the automotive vehicle 10. The temperature measuring means include also an inner thermometer 28 adapted to measure a system temperature of the internal combustion engine system 12. For instance, the inner thermometer 28 is adapted to measure gas temperature in the gas exhaust pipe 20. The temperature measuring means may comprise further temperature sensors.

[0052] The internal combustion engine system 12 comprises at least one fluid injector 30, preferably several fluid injectors 30. For instance, the fluid injectors 30 comprise at least one fluid injector 30 equipping the air intake pipe 18 in order to inject water therein. In addition, or as an alternative; the fluid injectors 30 comprise at least one fluid injector 30 equipping the gas exhaust pipe 20 in order to spray the urea aqueous solution therein.

[0053] Each or at least one fluid injector 30 comprises body with a seat passage and a closing element therein which is adapted to open or close the seat passage; thereby allowing or preventing injection of fluid pressurized by the pump 24. The closing element may be a pintle. It may generally be a movable element mating with the seat passage. The fluid injector 30 may be configured such that the fluid pressure urges the closing element toward the opening direction. Such a fluid injector 30 is well known by the skilled person; such that its functioning will not be detailed further.

[0054] The fluid injector 30 further comprises an actuation coil; also designated as solenoid; adapted to generate a magnetic field actuating the closing element upon application of an injection current or actuation current. Due to its electric resistance, the actuation coil heats when it is powered by a current. By thermal conduction, applying a heating current to the actuation coil heats the body, and the fluid injector 30 as a whole. This also heats the fluid contained in said fluid injector 30. This heating phenomenon is intended to enable deicing, to avoid freezing of the fluid flowing through or enclosed in the fluid injector 30.

[0055] As an option, the automotive vehicle 10 comprises a fuel tank and a fuel pump (not illustrated) delivering fuel to the internal combustion engine 14. The fuel pump is separate and distinct form the liquid pump 24. The liquid pump 24 may be an auxiliary pump.

[0056] The system 10 further comprises an electronic control unit 40 (ECU). The electronic control unit 40 controls the current applied to the actuation coil. The electronic control unit 40 is configured to control the application of an injection current to the actuation coil in order to open the fluid injector 30, and to perform an injection event. The electronic controlunit 40 is configured to control a first heating current and a second heating current; at least. The electronic control unit 40 may be a computer, for instance a vehicle inboard computer. The electronic control unit 40 comprises a processor 42 and a memory 44 adapted to store a computer program. The computer program comprises instructions which, when executed by the computer and / or the electronic control unit 40, cause the internal combustion engine system 12 to carry out the injection method in accordance with the invention.

[0057] The computer program may be stored on a flash memory.

[0058] As an embodiment of the invention, the electronic control unit may comprise a programmable electronic card.

[0059] Figure 2 represents a diagram of a method for injecting a fluid in an internal combustion engine system. The injecting a fluid in an internal combustion engine system may correspond to the one as described in relation with figure 1.

[0060] The method comprises the following steps, for instance executed in the sequence as listed below:

[0061] measuring 100 an ambient air temperature; and if the ambient air temperature is colder than a so called second temperature threshold, then

[0062] heating 102 the actuation coil with a first heating current including a first heating intensity;

[0063] measuring 104 a system temperature;

[0064] comparing 106 the system temperature with a first temperature threshold which is optional warmer than the second temperature threshold;

[0065] pressurizing 108 the fluid at an injection pressure with the fluid pump toward the fluid injector; and in the meantime

[0066] heating 110 the actuation coil with a second heating current including a second heating intensity; then

[0067] injecting 112 fluid through the fluid injector by powering the actuation coil with an injection intensity of an injection current; the second heating intensity being inferior to the injection intensity in order to keep closed the fluid injector during the step of heating the actuation coil with the second heating current.

[0068] The step of measuring 100 an ambient air temperature may be initiated upon ignition of the internal combustion engine, or at a given time interval from switching on of the automobile vehicle. The method is executed provided ambient air temperature is colder than the second temperature threshold.

[0069] As an option, each of the first heating current, the second heating current and the injection current comprise current pulses. The current pulses are heating pulses whichcontribute to heat the fluid injector through its actuation coil. The current pulses are separated by current cuts, where the intensity becomes null. During the current cuts, the actuation coil, notably the fluid injector, does not heat. Its temperature remains constant or decreases depending on the environment temperature.

[0070] As an alternative, at least one of the first heating current and the second heating current comprise a constant current.

[0071] The step of heating 102 the actuation coil with the first heating current comprises a first intensity peak equal to a maximum intensity of the injection current. The maximum intensity of the injection current uses the maximum power of the power supply of the internal combustion engine system. This implies that the first intensity peak uses the maximum power available in the electric feeding circuit. Heating is thereby more efficient. The step of heating 102 the actuation coil with the first heating current may generally be a step of pre-heating.

[0072] After the first intensity peak, the first heating current comprises a hold intensity at an intensity level between the intensity peak and the second heating intensity. As an option, the first intensity peak comprises a gradual intensity increase up to the maximum intensity of the injection current. This intensity increase is a function of a constant ratio and of time. The gradual intensity increase comprises a constant intensity increase ratio until the maximum intensity of the injection current, and until the first intensity peak.

[0073] As an option, the hold intensity of the first heating current represents from 90% to 50% of the maximum intensity of the injection current, respectively the first intensity peak; preferably from 80% to 60% of the maximum intensity of the injection current, respectively the first intensity peak. Thus, heating is at higher level than a hold current of the injection current. This facet of the invention promotes heating.

[0074] The first heating current comprises first heating pulses. After the step of comparing 106, if the system temperature is lower than the first temperature threshold, the first heating pulses comprise a constant heating intensity; if the system temperature is of at least the first temperature threshold, each of the first heating pulses comprise a decreasing heating intensity. The system temperature is an injector temperature or an exhaust temperature. The exhaust temperature is an exhaust gas temperature, or an exhaust pipe temperature. The first heating pulses optionally comprise a variable pulse width which increases over time.

[0075] The step of heating the actuation coil with the first heating current comprises a fixed time duration after which the step of pressurizing and the step of heating the actuation coil with the second heating current are executed; and / or the injection current comprises aseries of injection pulses at an injection frequency, and the second heating current comprises a second series of second heating pulses at a second frequency which is smaller than the injection frequency.

[0076] As an option, during the step of pressurizing 108 the fluid, the fuel pump is disabled. It is cut. As a further option, during the steps of heating 102 the actuation coil with the first heating current and heating 110 the actuation coil with the second heating current, the fuel pump is disabled.

[0077] At the step of injecting 112, the second heating intensity represents at most 80% of the injection intensity, preferably at most 50% of the injection intensity. The injection intensity may exhibit intensity variation during injection. The second heating intensity may be of at most 80% of the minimum intensity of the injection intensity, preferably of at most 50% of the minimum intensity of the injection intensity. The difference between the injection intensity and the second heating intensity provides a safety margin in order to avoid unexpected injection by the fluid injector, while ensuring heating.

[0078] Figure 3 provides a temporal graph superposing the injection current IC, the first heating current HC1, the second heating current HC2 as applied to the actuation coil of the fluid injector as described in figure 1.

[0079] The injection current IC and the heating current each comprise heating pulses. The injection period IPE of the injection current IC is shorter than the heating period(s) HP of the heating currents HC1 and HC2, which are optionally equal. The injection period IPE may be a first period defined by the engine throttle; and the heating period HPE may generally correspond to a second period. The injection period IPE defines an injection frequency which is higher than the heating frequency. The injection period IPE varies when the engine throttle changes. The second heating current comprises a second series of second heating pulses at a second frequency which is smaller than the injection frequency, preferably at least ten times smaller than the injection frequency. The computation and the control of the heating current is easier.

[0080] By way of illustration, the injection pulses of the injection current IC comprise current peaks raising at 1.1 A, and a hold current at about 0.42 A. The current peak lasts about 3 ms to 5 ms. The injection period IPE may be of about 250 ms. The injection pulse width may be of at most 20%, preferably at most 5%.

[0081] Figure 4 offers a comparison of different pulse widths for the first heating current HC1.

[0082] The heating period HPE of the first heating current HC1 is set to 1 s. However, other durations may be selected. Upon beginning of the method for injecting fluid, the fluidinjector is heated with first a series of heating pulses which comprise a first pulse width PW1. The first pulse width PW1 may be of 40%, or more generally between 30% to 60%. The first pulse width PW1 is higher than the injection pulse width.

[0083] A pulse width is defined as a proportion of the pulse duration over the whole period between two subsequent pulse starts. The first heating pulses of the first heating current HC1 may comprise a constant intensity.

[0084] In the current example, these first heating pulses reach 0.9 A. As a further option, the may be of 1.1 A ; and / or equal to the intensity of the intensity peaks of the injection current IC. The selected first pulse width PW1 allows a gentle heating of the fluid injector, thereby mitigating the thermal shock risk.

[0085] When a predefined period of time is elapsed, or after a predefined number of first heating pulses; a pulse width modulation is applied. The pulse width increases up to a second pulse width PW2. The first heating pulses become longer. There is a duration extra time as illustrated by the arrows in dotted lines. The second pulse width PW2 may be of 80%, or more generally between 70% and 90%. Thus, the fluid injector is heated further. Its temperature is raising. The freezing risk is limited deeper while avoiding thermal shock.

[0086] Figure 5 presents different profiles of first heating pulses HPU1 of the first heating current HC1.

[0087] The first heating current HC1 comprises first heating pulses HPU1 (only one represented) with different pulse profiles depending on the injector temperature, or more generally a system temperature. If the system temperature is lower than the first temperature threshold, the first heating pulse HP1 comprises a constant current value equal to the injection current.

[0088] Otherwise, if the injector temperature is at least as high as the first temperature threshold, each of the first heating pulses comprises a current peak CP and a hold current HC; which are respectively a heating current peak and a heating hold current.

[0089] The hold current HC comprises a first hold intensity Hll and follows the current peak CP which comprises a first intensity peak I Pl. The hold current HC may be lower than the peak current PC. The first hold intensity Hll may be lower than the maximum intensity of the injection current, and thus of the current available in the electric circuit of the system. The first intensity peak IP1 is higher than the first hold intensity Hll. This aspect of the invention allows a fine tuning of the heating level, and of the temperature of the fluid injector.

[0090] Figure 6 presents a comparison of the different current levels of the current pulses of the injection current IC, of the first heating current HC1 and of the second heating current HC2. For the sake of comprehension, the injection pulse IP (plotted with a dotted line) of theinjection current IC is represented with a same duration, notably a same period, as the first heating pulse HPU1 of the first heating current HC1 and the second heating pulse HPU2 of the second heating current HC2.

[0091] Both of the injection pulse IP and the first heating pulse HP1 comprise a current peak CP at the first intensity peak IP1 and / or the maximum intensity of the injection current IC. They may have a same intensity value of 1.1 A. In practice their time durations differ. As apparent from the present figure, the injection pulse IP and the first heating pulse HP1 comprise a hold current.

[0092] The hold current HC of the injection pulse IP is intended to keep the fluid injector in an open position during a predefined duration in order to inject a targeted quantity of fluid depending on the fluid pressure. The hold current HC of the injection pulse IP comprises an injection hold intensity IHI which is the lowest level of the injection pulse.

[0093] The hold current HC of the first heating current HC1 comprises a first holding intensity Hll which is higher than the injection hold intensity IHI of the injection pulse IP. Then, heating is increased and freezing is avoided.

[0094] The second heating current HC2 comprises a second heating intensity HI2 which reaches an intensity of 0.3 A, for instance. The second heating current HC2 is lower than the injection current IC. More precisely, the second heating intensity HI2 is lower than the injection hold intensity IHI. The injection hold intensity IHI comprises an intensity level which, at least, maintains open the fluid injector. The injection hold intensity IHI is between the first holding intensity Hll and the second heating intensity HI2.

[0095] In other words, the second heating current HC2 allows heating while staying at distance from intensity conditions at which opening and injection occurs through the fluid injector. Then, uncontrolled injection is prevented while countering the effects of low temperatures. This enlarges the functionality range of the fluid injector.

[0096] Figure 7 is a temporal graph comparing temperatures of a controlled first heating phase (plotted with a dotted line) and a non-controlled first heating phase (plotted with a solid line). The time (t) is illustrated at the abscissa axis, and the temperature (T) is illustrated at the ordinate axis.

[0097] The first heating phase is followed by a second heating phase with a lower heating intensity when pressure is established. This lower heating intensity is inferior to the injection intensity in order to keep closed the fluid injector. The first heating phase is controlled by the current peaks CP, and the second heating phase is controlled by the hold currents HC. The hold currents HC follows the current peaks CP, and may result in different temperature profiles depending on the applied current peak CP.

[0098] In accordance with a first option illustrated with the solid line, the temperature profile resulting from the current peak CP exhibits a sudden temperature rise at the beginning of the first heating pulse HPU1.

[0099] In accordance with a second option illustrated with the dotted line, the temperature profile resulting from the current peak CP comprises a gradual heating increase up to an injection point. The injection point is obtained by means of the injection current, preferably reaching the maximum intensity of the injection current (not illustrated) or the first intensity peak I Pl. The gradual temperature increase comprises a substantially constant temperature increase ratio over time. This ratio is applied until reaching the maximum of the injection current and / or of the first heating current HC1. The temperature of the first heating current HC1 follows a straight temperature ramp TR (illustrated with a chain dotted line). Then, temperature is steadily increasing. This offers a compromise between high temperature and thermal shock management.

Claims

CLAIMS1. A method for injecting a fluid in an internal combustion engine system (12); the internal combustion engine system (12) comprising: an internal combustion engine (14); a duct (16) ; a fluid pump (24) adapted to pressurize the fluid; a fluid injector (30) configured for injecting a fluid from the fluid pump (24) in the duct or in the internal combustion engine (14), the fluid injector (30) comprising: an actuation coil; the method comprising the steps of: o heating (102) the actuation coil with a first heating current (HC1) including a first heating intensity (HI 1); then o pressurizing (108) the fluid at an injection pressure with the fluid pump (24);■ characterized in that during the step of pressurizing (108) the fluid, the method further comprises the steps of: o heating (110) the actuation coil with a second heating current (HC2) including a second heating intensity (HI2); then o injecting (112) fluid through the fluid injector (30) by feeding the actuation coil with an injection intensity of an injection current (IC); the second heating intensity (HI2) being inferior to the injection intensity in order to keep closed the fluid injector (30) during the step of heating (110) the actuation coil with the second heating current (HC2).

2. The method in accordance with claim 1, characterized in that at the step of heating (102) the actuation coil with the first heating current (HC1), said first heating current (HC1) comprises a first intensity peak ( I Pl) equal to a maximum intensity of the injection current (IC).

3. The method in accordance with claim 2, characterized in that after the first intensity peak, the first heating current (HC1) comprises a hold intensity between the intensity peak and the second heating intensity (HI2).

4. The method in accordance with claim 3, characterized in that the hold intensity represents from 90% to 50% of the maximum intensity of the injection current (IC).

5. The method in accordance with claim 4, characterized in that the hold intensity represents from 80% to 60% of the maximum intensity of the injection current (IC).

6. The method in accordance with any one of claims 2 to 5, characterized in that the first intensity peak ( I Pl) comprises a gradual intensity increase up to the maximum intensity of the injection current (IC).

7. The method in accordance with claim 6, characterized in that the gradual intensity increase comprises a constant intensity increase ratio until said maximum intensity of the injection current (IC).

8. The method in accordance with any one of claims 1 to 7, characterized in that the first heating current (HC1) comprises first heating pulses (HPU1), the method comprises a step of measuring (104) a system temperature; and a step of comparing (106) the system temperature with a first temperature threshold; if the system temperature is lower than the first temperature threshold, the first heating pulses (HPU1) comprise a constant heating intensity; if the system temperature is of at least the first temperature threshold, each of the first heating pulses (HPU1) comprise a decreasing heating intensity.

9. The method in accordance with claim 8, wherein the system temperature is an injector temperature or an exhaust temperature.

10. The method in accordance with any one of claims 1 to 9, characterized in that the first heating current (HC1) comprises first heating pulses (HPU1) with a variable pulse width which increases over time.

11. The method in accordance with any one of claims 1 to 10, characterized in that the method further comprises a step of measuring (100) an ambient air temperature, the method executing the step of heating (102) the actuation coil with the first heating current (HC1) if the ambient air temperature is colder than a second temperature threshold.

12. The method in accordance with any one of claims 1 to 11, characterized in that the step of heating (102) the actuation coil with the first heating current (HC1) comprises a fixed time duration after which the step of pressurizing (108) and the step of heating (110) the actuation coil with the second heating current (HC2) are executed.

13. The method in accordance with any one of claims 1 to 12, characterized in that the injection current (IC) comprises a series of injection pulses (IP) at an injection frequency, and the second heating current (HC2) comprises a second series of second heating pulses (HPU2) at a second frequency which is smaller than the injection frequency.

14. The method in accordance with any one of claims 1 to 13, characterized in that the duct (16) is a gas exhaust pipe (20) in fluid flow communication with the internal combustion engine (14).

15. The method in accordance with any one of claims 1 to 13, characterized in that the fluid is an urea aqueous solution.

16. The method in accordance with any one of claims 1 to 13, characterized in that the duct (16) is an air intake pipe (18) in fluid flow communication with an air inlet of the internal combustion engine (14).

17. The method in accordance with any one of claims 1 to 13, characterized in that the fluid comprises water.

18. The method in accordance with any one of claims 1 to 17, characterized in that the duct (16) extends from the combustion engine (14), and comprises a duct section which is at least at 1 m away from the combustion engine (14), said duct section being in thermal exchange with the ambient air, the fluid injector (30) being arranged along said duct section.

19. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method in accordance with any one of claims 1 to 18.

20. An internal combustion engine system (12) for an automotive vehicle (10), the internal combustion engine system (12) which comprises : an internal combustion engine (14) ; a duct; a fluid injector (30) configured for injecting a fluid in the duct or in the internal combustion engine (14), the fluid injector (30) comprising: an actuation coil ; and a fluid pump (24) adapted to pressurize the fluid upstream the fluid injector (30); a control unit, the internal combustion engine system (12) is characterized in that it further comprises an electronic control unit (40) adapted to carry out the method in accordance with any one of claims 1 to 18.

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