WO2011124579A1

WO2011124579A1 - Method for monitoring the injection of an additive into a fuel system for an internal combustion engine

Info

Publication number: WO2011124579A1
Application number: PCT/EP2011/055290
Authority: WO
Inventors: Pierric Besnard; Hervé RUNARVOT; Thierry Rouxel
Original assignee: Inergy Automotive Systems Research (Société Anonyme)
Priority date: 2010-04-07
Filing date: 2011-04-05
Publication date: 2011-10-13
Also published as: EP2561202A1

Abstract

Method for monitoring the injection of an additive into a fuel system for an internal combustion engine operating with a liquid fuel and comprising a fuel tank, an additive tank, an additive pump, an injector for injecting the additive into the fuel tank and a feed line connecting the pump and the injector, according to which the pressure in the feed line is measured continuously, during the injection of the additive, and is compared to a reference pressure.

Description

Method for monitoring the injection of an additive into a fuel system for an internal combustion engine

The invention relates to supplying internal combustion engines with liquid fuels.

It relates more specifically to a method for monitoring the injection of an additive into a fuel system for an internal combustion engine.

The desire for increased environmental protection has led national and international authorities of many regions of the world to tighten the legislative standards relating to pollutant emissions in multiple fields, in particular in the field of motor vehicle transport. Thus, motor vehicle manufacturers have undertaken research with a view to reducing the emissions of particulates (in particular in the case of diesel engines) and certain pollutant gases (NOx, CO, etc.). This research has, in particular, culminated in the addition of certain additives (such as certain metal salts, urea, ammonia, carbamates, etc.) to the fuel, to the engine, to the exhaust gases, etc.

In the case of vehicles propelled by a diesel engine, motor vehicle manufacturers have found a solution to the problem of the emission of particulates by equipping these vehicles with particulate filters placed in the exhaust line down which the combustion gases are exhausted to the atmosphere. In order to regenerate the filtering capability of these particulate filters, the particulates partially clogging the filters need to be burnt off at regular intervals. In order to be able to automate the periodic cycle of particulate filter

regeneration, it has been necessary to find a means of lowering the combustion temperature of these particulates so that it is compatible with the highest temperatures that can be obtained in the exhaust gases by a suitable and temporary adjustment of the combustion parameters of the engine itself. The use of a certain amount of chemical combustion additive has been recognized as being necessary in order that the combustion temperature of the solid particulates can be lowered in the exhaust gases to a temperature level that is compatible with the combustion in the engine and with the complete elimination of the particulates. Liquid-additive tanks, small in volume by comparison with the fuel tank, have been designed to be mounted on, in, or near the fuel tank of diesel- engine vehicles. Additives that give good results are those sold under the tradenames Eolys® and Infmeum; these are ceria-based compounds developed by Rhodia and Infmeum, which lower the natural combustion temperature of the particulates to 350°C instead of 600°C, i.e. around 250°C lower than their natural combustion temperature. In particular, the Eolys Powerflex® and

Infmeum F7995 grades give good results in practice. In order to remove the risk of insufficient additive addition into the diesel for a vehicle equipped with a particulate filter, it may be necessary to monitor the amount of additive actually injected into the fuel tank. However, this type of compound is viscous, especially at low temperature, which makes the usual flow rate or pressure measurements difficult or even impossible, or too slow. Another parameter which makes these conventional measurements unusable in practice is the fact that the injectors that are available commercially exhibit considerable dispersion (which may range up to 10% of the absolute value of the pressure) and that therefore using "absolute" values (such as the pressure or the average flow rate) does not make it possible to develop a universal and reliable diagnostic method.

Since it is a concentrated additive, injected drop by drop into the fuel, counting of the drops could be envisaged, but this is only possible if the injector is not submerged in the fuel, and in addition it is greatly disturbed by the movements of the fuel. The Applicant has also considered measuring the level of dilution (concentration) of the additive in the fuel using a sensor, but such a sensor is not commercially available and, besides, its response time would not make it possible to correct the command during the metering operation, and, finally, it is highly probable that its accuracy would be insufficient too.

The Applicant has, on the other hand, observed that by using a

"continuous" pressure measurement (within mechanical and electronic constraints) by means of a sensor that emits therefore a continuous signal illustrative of the instantaneous value of the pressure, the main metering problems were able to be detected rapidly and reliably. In other words, the Applicant discovered that monitoring the metering operation can be carried out by analysing the signal of the pressure in the additive feed line during said metering operation.

Consequently, the invention relates to a method for monitoring the injection of an additive into a fuel system for an internal combustion engine operating with a liquid fuel and comprising a fuel tank, an additive tank, an additive pump, an injector for injecting the additive into the fuel tank and a feed line connecting the pump and the injector, according to which the pressure in the feed line is measured continuously, during the injection of the additive, and is compared to a reference pressure.

In the present document, the fuel system is a set of elements that are intended to be incorporated into an automotive vehicle or into a stationary power plant and that have the main role of storing, purifying, measuring or transporting a fuel intended for supplying an internal combustion engine. The automotive vehicle may be a motor vehicle (a car, lorry, motorcycle, river boat, sea-going ship, or aeroplane for example) or a vehicle constrained to run on a track (for example a railway locomotive). The stationary power plant may for example be the engine of an electric power generator or the motor of a machine tool.

The term "fuel" is understood to mean a hydrocarbon suitable for powering internal combustion engines.

The expression "liquid hydrocarbon" denotes a hydrocarbon that, under the standard operating conditions of the engine, is in the liquid state in the fuel tank of the fuel system.

The expression "volatile liquid hydrocarbon" denotes a liquid hydrocarbon (according to the aforementioned definition) that has a saturation vapour pressure of greater than 1 bar at 293 K (20°C). Volatile liquid hydrocarbons commonly used for powering internal combustion engines of motor vehicles are those sold commercially under the name "petrol" and intended for spark-ignition internal combustion engines.

The expression "heavy liquid hydrocarbon" denotes a liquid hydrocarbon that has a saturation vapour pressure of less than 1 bar at 293 K (20°C). Heavy liquid hydrocarbons commonly used for powering the internal combustion engines of motor vehicles are those sold commercially under the names "diesel" or "gasoil" and intended for self-ignition internal combustion engines operating on the diesel cycle.

In the case where the metering system has the role of dispensing the additive into the fuel tank, it does this for example in an amount that is a mathematical function (usually, but not necessarily, a proportional function) of the instantaneous fuel consumption of the engine. This amount is generally calculated by an on-board computer or a specific control unit. Alternatively, the metering operation may take place in a single step, just after the filling operation, as a function of the amount of fuel introduced during the filling operation. In this case, the computer or control unit can be connected to a device that makes it possible to detect the opening and closing of the fuel filling system. Such a device may comprise a magnet linked to a moving part (typically a cap or any other manual or automatic closure system) and a sensor able to detect the presence/absence of the magnet. This presence/absence is detected by the on- board computer which stores the content of the tank at the moment when it is informed thereof. If the position of the cap when it is closed corresponds to a rest condition for the control unit, it is able to calculate a difference in volume of fuel introduced, between the moment when the system is activated and the moment when it stabilizes. This volume serves as a basis for the calculation (carried out after closure of the cap) of the amount that needs to be metered out in order to maintain a constant additive concentration.

Alternatively, the computer or control unit can receive a signal from a level gauge measuring dynamically the fuel level in the tank so that it can calculate the amount of fuel introduced into the tank and hence, calculate the amount of additive to be metered.

In one preferred variant of the invention, the method comprises the steps consisting in:

- continuously measuring the pressure between the pump outlet and the injector during additive injection so as to obtain a signal;

- analysing this signal in order to detect drifts characteristic of operational anomalies and/or to detect the end of the priming operation.

This signal analysis may be carried out by:

- comparing the pressure measured to a reference service pressure; and/or

- comparing the pressure drift to a reference gradient.

Preferably, in the event of an anomaly being detected, a warning is sent to the CPU (central processing unit or on-board computer) and/or to the instrument panel of the vehicle. A new (second) injection trial may be performed before sending such a warning.

The purpose of the appended Figures 1 to 9 is to illustrate the invention in a non-limiting manner. They were obtained at 20°C, under atmospheric pressure, with the Eolys Powerflex® additive but not necessarily on one and the same additive addition/injector system (which explains the differences in the absolute values of the average pressure from one curve to the next). It is important therefore to look at the general appearance of the curves and not at the absolute values measured. Each of these curves illustrates a continuous pressure signal (pressure curve plotted as a function of time), under particular conditions, namely:

Figure 1 : comparison of the increase in pressure at the start of a metering operation, respectively with a defective pump and/or in the presence of air (bubbles) in the system, and with a "normal" pump and a system free of air (bubbles).

Figure 2: comparison of the pressure during metering, respectively with a defective pump (for example: having an incomplete piston stroke, with internal leaks, etc.) and with a "normal" pump.

- Figure 3: comparison of the pressure signal, respectively with a system where the filter upstream of the pump is clogged, and with a "normal" system.

Figure 4: comparison of the increase in pressure at the start of metering, respectively with a system where the injector has got stuck after drying of additive residues, and with a "normal" system.

Figure 5 : pressure evolution during metering with a system where the injector is stuck because of dry additive residues. Figure 6: comparison of the pressure signal, respectively with a system where the feed line is pinched and/or partially clogged, and with a "normal" system.

Figure 7: comparison of the pressure signal, respectively with a system where the feed line is split or disconnected, and with a "normal" system.

Figure 8: pressure evolution during metering with a system where the pump gets unprimed

Figure 9: pressure evolution with a system where the pump is priming.

In these figures, when there are two of them, the normal operation is illustrated on the right and the malfunctioning operation on the left.

An example of malfunction detection based on the pressure increase gradient at the start of metering is illustrated in Figure 1 appended to the present document. In this figure, the left-hand graph illustrates a loss of efficiency of the pump or the presence of an air bubble whereas the right-hand graph represents the reference (normal) operation. It can be seen in this figure that it is possible to detect an insufficient flow rate during this operating phase by calculating the pressurization gradient (gradient of the pressure increase). The following figures (2 to 9) respectively illustrate:

Figure 2: that with a defective pump, the pressure peaks during various pulses of the pump are lower (15 mbar between p(max) and p(average), compared to 29 mbar).

- Figure 3 : that with a system where the filter upstream of the pump is clogged, the pressure peaks during various pulses of the pump are also lower (15 mbar between p(max) and p(average), compared to 70 mbar); moreover, the average pressure drops, but only slowly, which makes the diagnostic resulting from this measurement slower.

Figure 4: that with a system where the injector has got stuck as a result of the additive drying out, a peak is observed at the end of the pressurization, which is absent in normal operation.

Figure 5 : that with a system where the injector has got stuck as a result of the additive drying out, the pressure increases up to the performance limit of the pump.

Figure 6: that with a system where the feed line is pinched or partially clogged, the average pressure value increases during metering.

- Figure 7: that with a system where the feed line is split or

disconnected, there is no increase in pressure at the start of metering and that the average pressure value in service drops greatly.

Figure 8: that during injection, the pressure drops when the pump gets unprimed (for instance hen the tank is empty)

Figure 9: that when the pump is priming, the pressure increases as soon as additive gets through the injector, and stabilizes when said priming is completed (allowing hence to detect the end of the priming operation).

These figures show that although certain metering defaults can be identified by measuring the average pressure during metering, measuring and analysing a continuous pressure signal generally makes it possible to diagnose them more rapidly and/or to identify more of them, and to obtain a "universal" method, free from the dispersions encountered from one system (pump, injector, etc.) to another.

The present invention has the following advantages: reduction in the risk of the particulate filter overheating, which risk may lead to the outbreak of fire;

advantage in terms of quality;

the fact that the pressure measurement makes it possible to detect the end of priming and thus makes it possible to guarantee complete priming and to avoid excessive quantities being metered during priming as a result of pump dispersion.

Claims

C L A I M S

1 - Method for monitoring the injection of an additive into a fuel system for an internal combustion engine operating with a liquid fuel and comprising a fuel tank, an additive tank, an additive pump, an injector for injecting the additive into the fuel tank and a feed line connecting the pump and the injector, according to which the pressure in the feed line is measured continuously, during the injection of the additive, and is compared to a reference pressure.

2 - Method according to Claim 1, characterized in that it comprises the steps consisting in: - continuously measuring the pressure between the pump outlet and the injector during the injection of the additive, so as to obtain a signal;

3 - Method according to Claim 2, characterized in that the signal analysis is carried out by:

- comparing the pressure measured to a reference service pressure; and/or

- comparing the pressure drift to a reference gradient.

4 - Method according to Claim 2 or 3, characterized in that the combustion engine is that of a vehicle and in that, in the event of an anomaly being detected, a warning is sent to the CPU and/or to the instrument panel of the vehicle, eventually after having performed a second injection trial.