DE102020119265A1 - A liquid injection system for a vehicle - Google Patents

Abstract

Aspects of the present invention relate to a liquid injection system (26, 28), to a control unit (11), to a vehicle (20) and to a method. The liquid injection system (26, 28) comprises one or more injection nozzles (2a, 2b) for injecting a dose of pressurized liquid into an exhaust system (24) or into an engine (22). The system (26, 28) also comprises a pump (3) for pressurizing the liquid injection system (26, 28) and also for relieving the pressure of the liquid injection system (1), a line (4) for transporting liquid between the pump (3) and the Injector (the injectors) (2a, 2b) and a pressure sensor (5) for measuring the liquid pressure within the liquid injection system (26, 28). The liquid within the system can contain gas bubbles that are entrained within it. The control unit (11) is configured to instruct the injector (s) (2a, 2b) to close, operate the pump (3) to depressurize the system and use the pressure sensor (5) to record the rate of depressurization during depressurization. The regulator (11) can calculate the amount of gas carried in the liquid from this pressure reduction rate.

Description

TECHNICAL PART

The present disclosure relates to a liquid injection system, particularly, but not exclusively, to a urea injection system for treating nitrogen oxides in vehicle exhaust gases and to a method for measuring gas entrainment in a liquid injection system. Aspects of the invention relate to a control device, to a system, to a vehicle and to a method.

BACKGROUND

Vehicle exhaust aftertreatment systems for diesel engines typically use a selective catalytic reduction process (SCR) in which nitrogen oxides (NOx) react with ammonia to produce less toxic nitrogen and water compounds and thus comply with the legally prescribed limit values for NOx emissions. Ammonia is usually supplied in the form of a measured dose of urea, which is usually referred to as Diesel Exhaust Fluid (DEF, trade name AdBlue) and is injected into the exhaust gas flow upstream of the catalytic converter. The same technology can be used on ultra-lean gasoline engines.

It is known that in such systems urea is injected into the flue gas by an injector upstream of one or more catalytic converters. The injector is a valve that receives pressurized urea, which is delivered through a pipe from a container and a pump. Stricter laws require more complex exhaust gas treatment systems with multiple injectors and branches in the line to convey the urea to the various injectors.

After any assembly or maintenance work and before such an injection system can be used, the system would normally have to undergo a priming operation, which usually consists of opening the injection nozzles and using the pump to pump urea into the piping and injection nozzles and so as to expel gas to bring the entire system into a liquid-filled state ready to inject measured doses of urea. In cold weather, an injector can be damaged if the liquid in it can freeze, so current systems typically perform a flush operation when the vehicle is turned off. A purging process usually consists of running the pump backwards to draw gas back through an open injector to evacuate urea from part or all of the system. Flushing the entire system including the pump is undesirable as this would require the entire system to be primed again before liquid injection can resume, which increases pump wear, consumes excessive energy and generates noise, which might be undesirable. Therefore, the desired normal state of the system after a flushing process consists in the system being filled with gas in the area of the injection nozzles and filled with urea in the area of the pump, with a clear boundary between the two areas, which is maintained by the surface tension of the urea.

However, the inventors have found that this desirable state does not always occur in practice, since the introduction of gas into the system can lead to bubbles in the urea itself being entrained and this gas being distributed in the system in ways that are difficult to predict and control can.

When the system is pressurized to perform the liquid injection, the presence of gas entrainment in the urea reduces the pressurization of the system, and this loss of pressure, as well as the presence of a gas fraction, greatly reduces the injection dose. Hence, the unexplained variability in gas input is a problem to ensure that urea dosing is optimal and emissions are adequately controlled.

It is an object of the present invention to overcome the drawbacks associated with known systems.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide a controller, system, method and vehicle as claimed in the appended claims.

In one aspect of the present invention, a regulator for operating a liquid injection system is provided. The liquid injection system comprises at least one injector for injecting a dose of pressurized liquid, a pump device for delivering liquid in a forward direction to pressurize the liquid injection system for performing the liquid injection, and for delivering liquid in a reverse direction to the liquid injection system to make pressureless, a line for pumping liquid between the pump device and the at least one injector, a pressure sensor for measuring the Fluid pressure within the fluid injection system.

The regulator is configured to: command the at least one injector to close, control the pump device to run in reverse to depressurize the system, and determine a depressurization rate during depressurization.

The present invention is advantageous in that it enables the hydraulic stiffness of the contents of the liquid injection system to be measured. It follows from physical principles that a nominally closed system containing a mixture of gas and liquid has a stiffness that depends essentially on the average compressibility of the contents of the closed system. The reverse running pump apparatus thus develops a pressure change within the system, so that the pressure decreases when the pump apparatus is operating. Assuming that other factors remain essentially constant, the rate of pressure reduction is an indicator of the compressibility of the entire system content. Other factors referred to include the duty cycle or speed of the pumping system, compliance with system limits such as pipes and valves, and also system leakage, which is nominally zero.

The present invention can be used to advantage with various types of liquid injection systems.

• mindestens einen elektronischen Prozessor mit einem elektrischen Eingang zum Empfangen von Informationen, die mit dem Druck der Flüssigkeit innerhalb des Flüssigkeitseinspritzsystems zusammenhängen; und
• mindestens eine elektronische Speichervorrichtung, die elektrisch mit dem mindestens einen elektronischen Prozessor gekoppelt ist und in der Befehle gespeichert sind;
• und wobei der mindestens eine elektronische Prozessor so konfiguriert ist, dass er auf die mindestens eine Speichervorrichtung zugreift und die Befehle darauf ausführt, um das Steuersystem zu veranlassen, das Flüssigkeitseinspritzsystem in Abhängigkeit von der Information zu steuern.

The controller can consist of one or more controllers. The one or more controllers are composed of one or more controllers:

• at least one electronic processor having an electrical input for receiving information related to the pressure of the liquid within the liquid injection system; and
• at least one electronic storage device electrically coupled to the at least one electronic processor and having instructions stored therein;
• and wherein the at least one electronic processor is configured to access and execute the instructions on the at least one memory device to cause the control system to control the liquid injection system in dependence on the information.

The controller can be configured to derive a measurement of an amount of gas entrained in the liquid from the rate of pressure reduction and to output a signal indicating the amount of gas entrained in the liquid.

The beneficial effect of this feature of the invention is that it enables the monitoring and then control of the amounts of gas within a liquid injection system.

The controller can be configured such that it controls the pump device so that it runs in the forward direction in order to carry out a liquid injection by determining an opening duration of the at least one injector and / or a delivery rate of the pump device and / or an operating time of the pump device as a function of controls the measurement of the amount of gas entrained in the system.

The beneficial effect of this feature of the invention is that the liquid injection process is modified to account for the amount of gas entrained in the liquid, thereby allowing more precise control of the liquid dosage to be applied by the system.

The controller can be configured to control the duration of a subsequent purging process based on the measurement of the amount of gas entrained in the system.

The advantageous effect of this feature of the invention is that flushing processes are carried out which remove gas or can control the gas content within the limit values to be expected.

The controller can be configured to control a system that includes at least two injectors, the controller configured to run in reverse to depressurize the system, with only a first injector open to dispense fluid evacuating a length of tubing feeding the first injector and then running the pump in reverse to depressurise the system with only a second injector open to evacuate fluid from the tubing feeding the second injector.

The advantageous effect of this property of the invention is that multi-injector systems can be partially flushed by liquid, while the controller can simultaneously derive measurements for the amount of gas in the various parts of the system.

In one aspect, a system is provided that comprises a controller as described above and a liquid injection system, the liquid injection system being a urea injection system for is an exhaust gas treatment system of an internal combustion engine.

In a further aspect, a system is provided which comprises a controller as described above and a liquid injection system, the liquid injection system being a water injection system for an internal combustion engine.

In a further aspect, a vehicle having an internal combustion engine and a urea injection system or a water injection system is provided.

In accordance with another aspect of the invention, a method of operating a liquid injection system is provided, the system comprising
at least one injector for injecting a dose of pressurized liquid,
a pump device for pumping liquid in a forward direction to pressurize the liquid injection system to perform the liquid injection and for pumping liquid in a reverse direction to depressurize the liquid injection system,
a pipe for conveying liquid between the pump device and the at least one injector,
a pressure sensor for measuring the pressure of the liquid within the liquid injection system, the method comprising
Closing the at least one injector,
Controlling the pumping device to run in reverse to depressurize the system and determining a depressurization rate during depressurization.

The method may include deriving a measurement of an amount of gas entrained in the liquid from the pressure reduction rate and outputting a signal indicative of the amount of gas entrained in the liquid.

The method may include controlling the pump device so that it runs in the forward direction in order to carry out a liquid injection by setting an opening duration of the one or more injectors and / or a delivery rate of the pump device and / or an operating time of the pump device depending on the measurement of the The amount of gas entrained in the system is controlled.

The method can include adapting the duration of a subsequent flushing process as a function of the measurement of the amount of gas entrained in the system.

The method of operating a liquid injection system can be applied to a system having at least two injection nozzles and may include controlling the pump device to run in reverse to depressurize the system with only a first injection nozzle open to Evacuate fluid from a length of pipe feeding the first injector and then control the pump assembly to run in reverse to depressurize the system with only a second injector open to feed fluid from a length of pipe that feeds the second injector, to evacuate.

In another aspect, a non-transitory computer readable medium is provided that contains computer readable instructions which, when executed by a processor, provide the performance of the method described above.

In the context of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set forth in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular their individual features, independently or in any desired manner Combination can be taken. This means that all embodiments and / or features of each embodiment can be combined in any way and / or in any combination, unless these features are incompatible. Applicant reserves the right to amend an originally filed claim or to file a new claim accordingly, including the right to amend an originally filed claim to depend on a feature of another claim and / or a feature of another claim although it was not originally claimed in this way.

Figure list

• zeigt ein Fahrzeug mit einem Harnstoffeinspritzsystem, das am Auspuff eines Verbrennungsmotors angebracht ist;
• Bild 2 zeigt ein Harnstoffeinspritzsystem und einen Regler für ein Harnstoffeinspritzsystem;
• zeigt die Abfolge der Ereignisse zur Durchführung einer Messung des Gaseintrags;
• ist ein Diagramm, das den Betrieb der Pumpe und den zugehörigen Systemdruck für zwei verschiedene Gasfraktionen der gasmitgerissenen Flüssigkeit während des in dargestellten Prozesses zeigt.
• zeigt den Ablauf bei der Injektion einer Flüssigkeitsdosis.
• zeigt die Abfolge der Ereignisse zur Durchführung einer selektiven Spülung der Druckleitungen, die jeden Injektor speisen.
• zeigt ein Fahrzeug mit einem am Verbrennungsmotor angebrachten Wassereinspritzsystem;
• Bild 8 zeigt einen Regler für ein Flüssigkeitseinspritzsystem.
• , , und zeigen eine Vielzahl von möglichen Gaseintragsszenarien in einem Flüssigkeitseinspritzsystem

One or more embodiments of the invention will now be described only by way of example with reference to the accompanying drawings, in which:

• Figure 11 shows a vehicle having a urea injection system attached to the exhaust of an internal combustion engine;
• Figure 2 shows a urea injection system and a controller for a urea injection system;
• shows the sequence of events for carrying out a measurement of the gas input;
• Figure 3 is a diagram showing the operation of the pump and associated system pressure for two different gas fractions of the gas-entrained liquid during the in process shown.
• shows the procedure for injecting a dose of liquid.
• shows the sequence of events to carry out a selective flush of the pressure lines feeding each injector.
• Figure 11 shows a vehicle with a water injection system attached to the internal combustion engine;
• Figure 8 shows a controller for a liquid injection system.
• , , and show a variety of possible gas entry scenarios in a liquid injection system

DETAILED DESCRIPTION

A liquid injection system, vehicle, and method in accordance with embodiments of the present invention is described herein with reference to the accompanying drawings to described.

In the discussion that follows, the term duty cycle (sometimes called duty cycle) is used to refer to the control of the pump or an injector, where operation can be intermittent rather than continuous, and duty cycle then refers to the operating time as a percentage of the available Time. A common way to implement a variable duty cycle is to use pulse width modulation (PWM) to intermittently turn the device on and off. For example, a square-wave pulse sequence used in PWM with the same on (high) and off (low) duration would result in a duty cycle of 50%, since the device is switched on (in operation) for half the available time. Other pulse duty factors can then be achieved by means of similarly periodic but asymmetrical waves. For example, a 10 Hz pulse train with a duty cycle (high) of 0.09 seconds in a 0.1 second cycle would result in a duty cycle of 90%. Continuous operation (always on / in operation) therefore corresponds to a pulse duty factor of 100%. In this way, the PWM duty cycle control can be used to continuously change the dosage between 0 and 100% while the system is running, e.g. to gradually increase the duty cycle as the exhaust gas flow increases at higher engine speeds and loads. The pulse duty factor of injector and pump is used to control the urea liquid dose supplied to the exhaust gas.

In the following discussion, the term “prime” is used to fill a system or part of a system with liquid so that it is ready for liquid to be injected, which would normally be achieved by running the pump in the forward direction. In this way, the priming of the system avoids an operational delay in applying a dose due to liquid flowing through the lines for the first time. Similarly, the term purging is used to remove fluid from a system or part of a system, which is normally accomplished by operating the pump in reverse.

shows a vehicle 20th with a urea injection system 26th for injecting urea into an exhaust system 24 for treating exhaust gases from an engine 22nd be ejected in the vehicle.

2 shows a urea injection system 26th with a urea reservoir 6 , the stored urea 7th contains that through an inlet pipe 8th a pump device 3 is supplied, the outlet of which 1 pressurized urea in the forward direction through the lines 4th , 10a , 10b and their connector 9 to the urea injectors 2a , 2 B promotes. The urea injectors 2a , 2 B inject urea into an exhaust system that is in is not shown. Those skilled in the art will appreciate the length of the common supply pipe 4th probably on the order of 1 to 3 meters and therefore in relation to the length of the individual supply pipes 10a , 10b very long ( 12th ), although this depends on the location of the pump system in the vehicle. A pressure sensor 5 is arranged so that it reduces the pressure in the delivery line 4th measures. Dashed lines in indicate signals going to or from a control unit 11 are conducted, the at least one sensor input from the pressure sensor 5 and the outputs to the pump device 3 and to the injectors 2a , 2 B controls. The control outputs can be in the form of a PWM signal, which determines the duty cycle of the injector 2a , 2 B or the pump device 3 controls.

It is welcomed that the inlet pipe 8th and the pump outlet 1 are named according to the forward direction of the urea and that, under certain circumstances, the urea can otherwise be conveyed in the reverse direction; in this case the functions of the inlet pipe 8th and the pump outlet 1 conversely, while the physical part names are unchanged for ease of reference.

It is estimated that the controller 11 can receive additional input signals and send additional output signals, of which none is shown in the figures. For example, the control unit can also send a signal from a sensor in the urea reservoir 6 received, which shows the remaining urea level in the container, and so output a warning signal to other systems in the vehicle or to the display of the vehicle driver if the urea level is below a defined threshold value. The controller also receives signals indicative of the urea dosage required or signals that enable the controller to calculate the urea dosage required, such as engine operating conditions, exhaust gas temperature, and exhaust gas constituents.

Although not shown in the figures, for reasons of manufacturability and cost, the pump device 3 and the pressure sensor 5 in the same assembly with each other and / or in the same assembly as the reservoir 6 to be built in. The pumping unit 3 can be placed inside the container so that on an inlet tube 8th can be dispensed with entirely; the inlet to the pumping unit 3 is thus located directly in the body of the stored urea 7th . The storage container 6 will normally be provided with an access port for topping up urea during operation. In other embodiments, the pumping device 3 have multiple outlets that connect to the supply lines 10a and 10b are connected so that the common supply line 4th becomes superfluous. In such a configuration, the pressure sensor can be connected directly to the pump device 3 connected to measure the pressure in the feed line. The pressure sensor 5 may also include a plurality of pressure sensors that have different pressure sensor capabilities or may be distributed at multiple locations within the system, however such distributed pressure sensor systems would be understood to provide the same pressure signal to the controller 11 that shows the printing of the system's contents.

It is estimated that in other variants the pumping device 3 alternatively, may include various configurations that enable the functionality of a reversible pump capable of pumping liquid in either a forward or reverse direction. The pumping device 3 may include a unidirectional pump coupled to a reversing valve to ensure the forward and reverse direction of the liquid flow. The pumping device 3 may further include two pumps, one pump configured to pump liquid in the forward direction and the other pump configured to pump liquid in the reverse direction. Such pumps can include positive displacement pumps or centrifugal pumps.

shows two injectors 2a , 2 B , but other variants are possible with just one injector or with more than two injectors. Multiple injectors are increasingly used to allow better control of urea dosing as exhaust emission regulations become more stringent. For example, two injectors may be required to apply urea to two separate SCR devices within an exhaust system. Any system with more than one injector requires that the common supply pipe 4th at one or more connection points 9 in at least two individual feed tubes 10a , 10b ... 10n is divided, each having a flow to an injector 2a , 2 B ... deliver 2n. The individual feed pipes can be of the same length or of different lengths and are usually shorter than the common feed pipe 4th .

With the injection nozzles 2a , 2 B in it can be valves that control the urea flow by their degree of opening or by controlling their duty cycle. These valves can be opened and closed with the help of an electromagnet. Liquid injectors can also be referred to as dosing modules by those working in the field. The urea dose applied by an injector depends on the flow characteristics of the valve, the total operating time, the work cycle and also on the pressurization and flow capacities of the pump system. 3. Every gas entrained in the liquid also has an effect on the dose of the applied liquid active substance.

If the urea pressure in the system is lower than the gas pressure in the exhaust system, the gas flows backwards through an open injector into the pipes 10a , 10b and 4th the urea injection system as well as in the pump system 3 . This situation can occur when gas is leaking from a nominally closed injector or when the pumping device 3 is operated in reverse direction to purge an injection nozzle of urea while the injection nozzle is open. During a purging process, an injector, as described above, can be open to the lumen of the exhaust system, or some injectors have a separate valve that opens to atmospheric air. Flushing the single feed tube 10a that has the injector 2a feeds can by closing the injector 2 B and opening the injector only 2a done while the pumping device 3 runs backwards. In this way, different sections of the supply line 4th , 10a , 10b and the inlet pipe 8th purged of urea and filled with gas.

Flushing operations are required to avoid problems with urea freezing in the urea injectors 2a , 2 B to avoid. However, there is still other reasons gas may be present within the injection system, such as leakage. The injectors themselves are prone to gas leaks, so the purging process usually returns urea to each junction 9 pulls in the line of systems with multiple injectors, as this minimizes the hydrostatic pressures acting on the injectors and reduces the resulting gas leaks at the injectors. Gas is also present in injection systems during assembly or maintenance, and some of the gas can be retained if the system is insufficiently primed. In all these cases, the supply lines 4th , 10a , 10b and connections 9 Gas included. The branches 9 and other discontinuities or surface irregularities in the supply lines 4th , 10a , 10b , the injectors 2a , 2 B , the pressure sensor 5 or the pumping device 3 can disrupt the flow of urea and allow the air to form discrete bubbles that are entrained in the urea even when the system is fully aspirated. For these reasons, gas influx is difficult to predict and control. Different scenarios for gas entry are in the to shown.

shows the inventive method implemented by the controller for measuring the gas entrainment in the liquid of the system. In the first step, S1 , all injectors are closed to isolate a single contiguous test volume that is the internal volumes of the supply lines 4th , 10a , 10b , the connections 9 , the pump device 3 , the pressure sensor 5 and includes all other auxiliary elements that can provide a volume in continuity with the volume to be tested. At this junction, the pressure within the system may previously have been raised above atmospheric pressure by the pumping device 3 was pumped in the forward direction. The second step S2 , consists in the pumping device 3 operate in reverse to withdraw liquid containing either liquid, gas, or a combination of liquid and gas. During step S2 is executed, the output data of the pressure sensor 5 from the controller 11 recorded to the depressurization rate, represented as a step S3 to derive.

The next step S4 The method consists in deriving a measurement of the amount of gas entrained from the rate of pressure reduction. In an ideal system, the rate of pressure reduction depends on the pump flow rate, the total test volume, and the gas fraction of the contents within the test volume. In reality the system is not ideal and other factors such as the elasticity of the pipes, leakage from the valves and pump, the composition and compressibility of the contents all have an impact on the rate of pressure reduction. Provided that these other factors that make the system less than ideal are adequately controlled, the rate of pressure reduction will largely depend on the fraction of gas within the test volume.

Since the test volume and the pump flow rate are known in advance, the controller is able to calculate the gas fraction based on the above theoretical basis. Alternatively, it is also possible to configure the controller so that it calculates the gas fraction by comparing it with test data. In this case, a look-up table with test data is provided in the regulator, which assigns a specific pressure reduction rate or a specific range of pressure reduction rates to a specific gas fraction or a specific range of gas fractions. Alternatively, an empirical equation relating the gas fraction to the rate of pressure reduction can be derived from the test data. Whichever practical means is desirable or best suited for a particular application, calculating the gas fraction from the depressurization rate takes advantage of this relationship and is in step S4 from picture 3 shown.

After a value for the gas entrainment amount has been calculated, the last step is S5 the value as a data value in the memory of the control unit 11 or output as a signal to another part of the control unit or to another control unit in the vehicle, for example via a data bus known in the automotive industry such as LIN (Local Interconnect Network), CAN bus (Controller Area Network), Ethernet or the like. This step is called a step S5 in picture 3 shown.

shows the state of various elements of the system along a time axis 33 during the method of , in which the injectors are continuously closed and the initial state of the system pressure is stable 37 . The pumping apparatus is between times t34 and t35 operated in reverse direction. In the upper diagram shows the state of the pumping device 30th than either running backwards 31 or stopped 32 . The diagram below illustrates the outcome 36 of the pressure sensor 5 for two different examples - a relatively high degree of gas entrainment at which the pressure slowly drops 38 , and a relatively low level of gas entrainment where the pressure drops faster 39 . The rate of pressure reduction 38 , 39 is then from the controller 11 recorded.

If you compare the and so is the closing of the injectors S1 the before starting the pumping device in reverse at the time t34 the completed. As soon as the Pumping device at t34 in has started, the pumping device runs as in step S2 in and printing is as in step S3 in described monitored until the pumping device at the time t35 in is switched off. The pressure reduction speed will be as in step S4 of 3 described after the point in time t35 of 4th then the signal indicating the amount of entrained gas is determined in step S5 of 3 issued.

Although not shown, a variation of the method can be used by first starting the operation of the reverse pump system before closing the injectors. Therefore, although the system was reached in a different order of steps, the system is then in the same state as S2 in with the pump running and the injectors closed. The rate of pressure drop S3 can then be measured as before. In this case it is unlikely that the pressure will be stable before the injectors at t34 are closed. During the period t34 to t35 however, the pressure will still decrease at a rate that depends on the amount of gas entrained in the system.

Instead of up t35 in to wait, the rate of pressure reduction can alternatively be used to perform the calculation in step S4 in intermittently or continuously during the period t34 to t35 in perform. In this case you can follow the steps S2 , S3 and S4 occur simultaneously. In this case the step S4 several times between t34 and t35 of 4th occur so that several intermediate values of gas entrainment are generated before a final value is generated.

The output of step S5 can step at any time S4 be generated. Indeed, the steps can S2 , S3 , S4 and S5 take place at the same time, producing a time varying output signal indicative of gas entrainment. At each point in time at which the determination of the pressure reduction rate has been completed, the signal indicating the amount of entrained gas in step S5 are issued.

As mentioned earlier, if urea contains entrained gas bubbles, this affects the dose of urea that is administered during the subsequent dosing process. This effect occurs directly as a result of the gas content in the liquid; e.g. a nominal gas fraction of 10% means that only nominally 90% of the injected liquid is urea, although this ratio also depends on the pressure. The gas fraction effect can also occur indirectly, in that the flow and pressure properties of the injection system are impaired. Thus, the measurement of gas entrainment in a subsequent injection of a dose of urea can be taken into account to ensure that the applied dose is corrected for gas entrainment. This can include correcting the proportion of gas in the injected liquid and / or correcting changes in the flow properties of the gas-entrained liquid.

shows an example of how gas entrainment is taken into account in subsequent dosing processes, e.g. by changing the duty cycle of the injector (s) and pump apparatus. In step S6 receives the control unit 11 a requirement for the urea metering of the exhaust gas, this requirement being dependent on the temperature, the flow rate and the composition of the exhaust gas or the expected exhaust gas. In step S7 calculates the control unit 11 the required pump and injector duty cycles using the value of the gas fraction that was previously calculated from a previous measurement, e.g. with the method of . In step S8 the pump device is operated in the forward direction to pressurize the urea injection system according to the calculated duty cycle, and in step S9 one or more urea injection nozzles are operated according to the calculated pulse duty factor in order to ensure the correct urea metering as in step S6 required to deliver.

During urea injection, the degree of gas entrainment will likely change as gas entrained urea is injected into the exhaust system. Therefore, the initial duty cycle of the pumping equipment and injectors can be adjusted in response to this change in gas entrainment. The steps S8 and S9 can be reversed or occur simultaneously.

In an alternative example, only one of the pump and injector duty cycles is changed. In this case, step S7 only the duty cycle to be changed is calculated.

If partial flushing processes are carried out as described below, the injection process can also take into account all sections of the flushed (evacuated) pipeline as well as the gas entrainment in a line that still contains urea. This may require an adjustment to the duty cycle of the pump system or the injector or an extension of the operating time.

shows a method for flushing the urea system. In step S10 becomes one of the injectors 2a open and close all others, then step in S11 the pumping device operated in reverse to remove urea from the supply pipe 10a to wash. When the control system with information about the volume of the supply line and the flow rate of the pumping device is preconfigured, step S11 to be used, only the supply line 10a to flush so that the flush can be stopped when the urea reaches the junction 9 is withdrawn. At this point the pumping device can, as in step S12 specified to be stopped while the injector is open 2a closed and another 2b, as in step S13 shown is opened. The pumping device is then operated in reverse to remove urea from the supply pipe 10b in step S14 rinse out. If there are more than two injectors, the steps can S12 to S14 be repeated to rinse their supply lines. As with the first flushing of the feed line 10a can the controller 11 operated to return urea to the branch 9 to rinse, but no further. Alternatively, the control unit 11 operated in such a way that urea via the common supply line 4th back to the pump system 3 and beyond into the inlet pipe 8th is rinsed.

The measurement of the pressure reduction and discharge of the gas fraction, as in the steps S3 and S4 of shown, can be used at the beginning, at the end or during a flush, as in shown to be performed. For example, it may be desirable to have the urea only from a single feed line 10a to rinse by just following the steps S10 , S11 and S12 of and then the measurement of the gas fraction according to the steps S3 and S4 carry out the gas fraction in the individual feed line 10b and the common feed line 4th to determine. It may also be desirable to remove the urea from the two individual feed pipes 10a and 10b to rinse as in the steps S10 to S14 in shown, and then perform the measurement to find the gas fraction in the common feed pipe 4th according to the steps S3 and S4 to confirm. In this way it is possible to manipulate the state of the system so that it has separate areas for gas and urea, the urea area, however, possibly containing entrained gas bubbles. By the control unit 11 It is the control unit that provides data such as the volume of the pipes and the flow rate of the pump device for different work cycles 11 possible to calculate the fraction of gas within a urea range for a system that contains separate ranges of both gas and urea. These calculations require that the controller 11 Has access to additional data that correlates the rate of pressure reduction with a particular gas fraction for each of the conditions under test.

This correlation can be in the form of look-up tables or an empirical equation based on test data or a theoretical calculation based on system volumes such as the volumes of the pipes 10a , 10b and 4th depending on the condition to be checked. With these different methods, the system can reach different states, as in the , , or shown.

Based on measurements of gas entrainment, the controller can 11 Perform advanced flushing operations to remove urea from one or more of the supply pipes 4th , 10a , 10b , the pump device 3 and the inlet pipe 8th to evacuate.

After partial or complete flushing of the urea injection system 26th can the control unit 11 perform a priming operation to one or more of the supply lines 4th , 10a , 10b , Pump device 3 and inlet pipe 8th to fill again with urea.

The to show a variety of possible gas entry scenarios in a liquid injection system. In shows a liquid injection system that consists of a reservoir 6 with liquid 7th and a pump 3 with integrated pressure sensor 5 consists, the liquid in a common feed line 4th feeds, which is then connected to a connection 9 into two separate feed lines 10a , 10b shares that with two injectors 2a , 2 B are connected. The content of each feed pipe 10a , 10b contains small gas bubbles 32 with areas 31 with liquid between the gas bubbles 32 . The common supply pipe 4th contains liquid that does not contain gas 30. has the same distinguishing features as , but the gas bubbles 32 are so big that they are better than leftovers from liquid 31 in a gas-filled area of the individual supply pipes 10a and 10b can be described. These alternatives are then viewed as essentially the same scenario, but differ in their extent. These types of situations can arise from leakage of air into the system through injectors, possibly due to differential pressure acting on the injector. Alternatively, these situations can arise from a partially effective flushing process, perhaps because a liquid becomes trapped in the coils of the system. Or these situations may arise because of a partially effective suction process, perhaps because some gas is trapped in the small discontinuities in the internal surfaces of the system. These are just sample illustrations, and those skilled in the art will understand that a variety of scenarios are possible.

shows the system of after a successful flush of was carried out. In this case, the individual feed lines 10a and 10b of all liquid evacuated, so they just take the gas 33 contained during the flushing process through the injectors 2a and 2 B has been sucked into the system. The common feed pipe 4th contains the liquid 31 with gas bubbles 32 in the individual feed pipes before the flushing process 10a and 10b were present ( ). The pressure drop measured during the flushing process provides an indication of the amount of gas in the common feed line 4th which is taken into account in subsequent injection or flushing processes as described above. Similarly shows the system of after a successful flush of was carried out.

Figure 3 shows an alternate embodiment of a liquid injection system that is used to inject water into an internal combustion engine 22nd of a vehicle 20th is used to control engine temperatures and combustion. Water injection systems experience problems similar to urea injection systems, such as damage to the injectors when water freezes and expands inside the injector, so the water injectors are flushed to correct this problem. This can also lead to gas entrainment, which can affect the dose of water supplied to the engine. Therefore, the method described above is also useful for water injection systems. In this case the liquid injection system would be shown in Fig 7th than a water injection system 28 described, which has the same arrangement and the same characteristic features as in Fig 2 except that instead of urea 7th Water is used as the injection medium. The injector is then arranged to inject water into an engine instead of urea into an exhaust. The experienced user would appreciate having system specifications such as pressure, flow rates and material specifications between a urea injection system 26th in and and a water injection system 28 in would be different.

The methods described above for application to a urea injection system 26th can usefully use such a water injection system 28 be applied. In particular, the measurement of the pressure reduction and the discharge of the gas fraction, as in can be shown in an in water injection system shown. In such a water injection system 28 are the injectors 2a , 2 B Water injectors and the storage tank 6 a water storage tank, and the operating principles and control methods as described here and in the , and shown remain the same. The control unit 11 also receives signals that are not shown in the figures and that indicate the required water dosage, or signals that it sends to the control unit 11 allow the required water dosage to be calculated, such as engine operating conditions and engine speed and torque requirements.

picture 8th shows a schematic representation of the controller 11 from picture 2 . In picture 8th includes the controller 11 a single processor 100 , but in other embodiments of the invention the controller can 11 more than one processor 100 include. The controller 11 comprises at least one electronic storage device 101 in which the commands 102 are stored and the electronic processor 100 is with the at least one electronic storage device 101 electrically coupled so that he is on the commands 102 can access.

The control unit 11 includes an electrical input 103 to receive signals from the sensors (not shown) which are configured to at least sense the pressure in the system. The control unit 11 also includes an electrical output 104 to provide output signals for at least the injectors 2a , 2 B and the pumping device 5 in the execution of .

The processor 100 is configured in such a way that it accesses the in the memory chip 101 stored instructions 102 accesses and executes the instructions so that he is able to use the previously described and in the flowcharts of the , and to perform combined functions for measuring gas entrainment, for performing liquid injection and for performing flushing processes.

For the purpose of this disclosure, it should be understood that the controller described herein 11 may comprise a control unit or a computing device with one or more electronic processors. A vehicle and / or a system thereof can comprise a single control unit or a single electronic control device, or alternatively various functions of the control device can be used 11 embodied in various control units or control devices or housed in these. A set of instructions could be provided which, when executed, cause the control device or control unit (s) to implement the control techniques (including the method (s) described) described herein. The instruction set can be embedded in one or more electronic processors or, alternatively, the instruction set could be provided as software that is executed by one or more electronic processors. For example, a first controller can be implemented in software that runs on one or more electronic processors and one or more other controllers can also be implemented in software that runs on one or more electronic processors, optionally on the same processor or processors as the first controller. However, it will be appreciated that other arrangements will also be useful, and therefore, it is not intended that the present disclosure be limited to any particular arrangement. In any event, the set of instructions described above may be embedded in a computer readable storage medium (e.g., non-transitory computer readable storage medium) that may include any mechanism for storing information in a form readable by a machine or electronic processor / computing device, including, but not limited to: a magnetic storage medium (e.g., floppy disk); optical storage medium (eg CD-ROM); magneto-optical storage medium; Read Only Memory (ROM); Random Access Memory (RAM); erasable programmable memory (e.g. EPROM and EEPROM); Flash memory; or electrical or other types of media for storing such information / instructions.

It is appreciated that various changes and modifications can be made in the present invention without departing from the scope of the present application.

The ones in the , and The blocks shown can be steps in a method and / or sections of code in the computer program 102 represent. The illustration of a particular order of the blocks does not necessarily mean that there is a required or preferred order for the blocks, and the order and arrangement of the blocks can be varied. In addition, some steps may be left out.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be understood that changes may be made in the examples given without departing from the scope of the invention as claimed.

The features described in the preceding description can be used in combinations other than those expressly described.

Although functions have been described with reference to certain features, those functions may be performed by other features, whether described or not.

Although features have been described with reference to particular embodiments, those features may also be present in other embodiments, whether described or not.

Although the foregoing description attempts to draw attention to those features of the invention that are believed to be of particular importance, it should be understood that the applicant claims protection in respect of any patentable feature or combination of features to which in Reference is made to and / or shown in the drawings, whether or not particular emphasis is placed thereon.

Claims (9)

A control device for operating a liquid injection system, the liquid injection system comprising: at least one injector for injecting a dose of pressurized liquid, a pumping device for pumping liquid in a forward direction to pressurize the liquid injection system to perform liquid injection and for pumping liquid in a reverse direction to depressurize the liquid injection system, a pipe for conveying liquid between the pump device and the at least one injector, a pressure sensor for measuring the pressure of the liquid within the liquid injection system, the controller configured to: instructs the at least one injector to close, controls the pumping device to run in reverse to depressurize the system, and determine a rate of pressure reduction during depressurization. Control unit after Claim 1 wherein the controller is configured to derive a measurement of an amount of gas entrained in the liquid from the rate of pressure reduction and to output a signal indicative of the amount of gas entrained in the liquid. Control device according to one of the preceding claims, wherein the control device is configured to control the pump device so that it runs in a forward direction to perform a liquid injection by determining an opening duration (s) of the at least one injector and / or a delivery rate of the Pump device and / or an operating time of the pump device controls depending on the measurement of the amount of gas entrained in the system. Control unit after Claim 2 , wherein the controller is configured to control the duration of a subsequent purging process as a function of the measurement of the amount of gas entrained in the system. Control unit after Claim 4 for a system having at least two injectors, wherein the controller is configured to control the pump device to run in reverse to depressurize the system, with only a first injector open to dispense fluid from a piece of pipe that feeds the first injector, and then controls the pump device to run in reverse to depressurize the system, with only a second injector open to dispense fluid from a length of pipe feeding the second injector, to evacuate. A system comprising the control device according to any one of the preceding claims and a liquid injection system, the liquid injection system being a water injection system for an internal combustion engine or a urea injection system for an exhaust gas treatment system of an internal combustion engine. Vehicle with an internal combustion engine and a system according to Claim 6 . A method of operating a liquid injection system, the system comprising at least one injector for injecting a dose of pressurized liquid, a pump device for pumping liquid in a forward direction to pressurize the liquid injection system to perform the liquid injection and for pumping liquid in a reverse direction to depressurize the liquid injection system, a pipe for conveying liquid between the pump device and the at least one injector, a pressure sensor for measuring the pressure of the liquid within the liquid injection system, the method comprising: Closing the at least one injector, Controlling the pumping device to run in reverse to depressurize the system and determining a depressurization rate during depressurization. Non-transitory computer-readable medium containing computer-readable instructions which, when executed by a processor, enable the method to be performed Claim 8 effect.

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