WO2009004195A2

WO2009004195A2 - Device and method for estimating the amount of alcohol contained in the fuel of an engine

Info

Publication number: WO2009004195A2
Application number: PCT/FR2008/050749
Authority: WO
Inventors: Vasco Afonso; Gérard LELONG; Fabio Vicentini
Original assignee: Renault S.A.S.
Priority date: 2007-06-01
Filing date: 2008-04-24
Publication date: 2009-01-08
Also published as: WO2009004195A3; FR2916805A1; FR2916805B1

Abstract

The invention relates to a device for estimating the amount of alcohol contained in the fuel supplying a spark ignition internal combustion engine (1), characterised in that it includes a sensor (8) for measuring a parameter relating to the rotation of the engine, means for controlling the injection of different amounts of fuel into at least two cylinders (1a) of the engine and means (7) for determining the engine torque variation resulting from said injection operations, on the basis of measurements supplied by the sensor.

Description

DEVICE AND METHOD FOR ESTIMATING A QUANTITY OF ALCOHOL CONTAINED IN FUEL

OF AN ENGINE

The present invention relates to the estimation of the amount of alcohol contained in the fuel supplying a spark ignition internal combustion engine. The invention also relates to the control of the motor, that is to say the management and control of a set of sensors and actuators by means of software strategies and calibration parameters contained in an onboard computer called "Electronic Control Unit" (ECU).

More particularly, the invention relates to internal combustion engines with spark ignition that can operate with several types of fuel, namely pure gasoline, pure alcohol such as ethanol or methanol or a mixture of gasoline and alcohol. For vehicles equipped with a motor of this type, it is necessary to know at any time the exact composition of the fuel used, since the settings for the control of the operation of the engine are different according to this composition.

Indeed, the operation of such an internal combustion engine requires the realization of a mixture of air and fuel in stoichiometric proportions. However, the physicochemical characteristics of a fuel that contains a certain proportion of alcohol, whether ethanol or methanol, are very different from normal gasoline containing no alcohol. In mixtures containing alcohol, the presence of oxygen makes it possible to be in the presence of a "lean" fuel for which the stoichiometric ratio is of the order of 9, for example, for a mixture of fuel and ethanol, whereas for a fuel containing only gasoline, the stoichiometric ratio is 14.7. This means that to burn the same amount of air admitted into the cylinders of the combustion engine, it will be necessary to use more fuel. Such an increase in fuel therefore requires an increase in the fuel injection time in the cylinders. In addition, the difference in vapor pressure between the two types of fuel causes disparities during cold combustion, for example in the start-up phase.

If one wishes to allow different possibilities of use of fuel to choose, it is understood that it is necessary to determine at any time what type of mixture is present in the fuel tank of the vehicle to adapt the various parameters of combustion, such as fuel injection time, ignition timing, etc. In the absence of such a precise determination, the engine could be damaged and pollutant emissions could be increased.

Japanese Patent Application JP 1,117,740 (Mitsubishi) discloses a device for determining the amount of alcohol present in the fuel fed to a combustion engine, which uses a sensor that makes use of the electrical or optical properties of the fuel. fuels in order to differentiate them and to deduce the amount of alcohol. The cost of such a technology is high and its use requires to provide a particular location for such a sensor in the vehicle tank.

Also known are devices for determining the amount of alcohol contained in the fuel supplying a combustion engine, which use oxygen sensors mounted in the exhaust pipe of the engine and capable of measuring a quantity of oxygen in order to deduce the amount of alcohol contained in the fuel supplying the engine. Thus, US Pat. No. 5,400,762 (Chrysler) describes a method and a device for determining the percentage of alcohol of the ethanol or methanol type contained in the fuel of a vehicle by using a cathode probe. oxygen lambda type operating in "all or nothing". No. 5,970,968 (Chrysler) uses for the same purpose a proportional type oxygen probe providing a signal proportional to the amount of oxygen present in the exhaust gas. In both cases, the determination of the level of alcohol in the fuel requires an impeccable operation of the oxygen sensor, so that in case of failure or drift thereof it becomes impossible to properly differentiate the fuels used. The object of the present invention is to allow an accurate determination of the amount of alcohol contained in the fuel in the vehicle tank and supplying the combustion engine, in a more reliable manner than in the known processes and in same time in a less expensive way. The invention also relates to a determination that allows to recognize very quickly the composition of a new fuel that has been introduced into the vehicle tank, regardless of the fuel composition used during a previous operation. In one embodiment, a device for estimating a quantity of alcohol contained in the fuel supplying a spark ignition internal combustion engine, comprises a sensor for measuring a parameter relating to the rotation of the engine, means for for controlling injections of different amounts of fuel in at least two cylinders of the engine and means for determining the variation of the engine torque resulting from said injections, from measurements provided by said sensor.

The estimation of the amount of alcohol contained in the fuel is therefore carried out without the aid of an oxygen sensor which may otherwise be present for other reasons. This results in a particularly reliable estimate since it does not depend on the proper functioning of such a probe. In addition, taking into account a torque variation of the motor makes it possible to obtain the desired result without it being necessary to provide any additional specific member on the motor, which reduces the cost of the device. It is sufficient to provide an appropriate software strategy to control the fuel injections and to use the already existing means for determining an engine parameter.

For example, the measuring sensor is adapted to measure the speed of rotation of the motor from which the torque of the motor can then be deduced.

In an advantageous embodiment, the means for controlling injections of different amounts of fuel are adapted to control the injection of a larger amount of fuel into a first set of cylinders and a smaller amount of fuel into a second set of cylinders during a first period of time. Then said means can control the injection of a smaller amount of fuel into the first set of cylinders and a larger amount of fuel into the second set of cylinders for a second period of time.

The means for determining the variation of the engine torque can then be adapted to effect the difference between the engine torque resulting from the injections made during the first and second periods of time. This in fact results in a determination of the value of the derivative of the torque with respect to a change in the amount of fuel. This derivative makes it possible to deduce the richness of the mixture injected and therefore the quantity of alcohol in the fuel.

In addition, it is possible to provide a means of deactivation as a function of the phasing of the fuel injection so as not to make the estimation as long as the phasing of the injection and therefore the engine operation, are not properly stabilized over time.

In another aspect, there is provided a method of controlling fuel injection in an internal combustion engine based on an estimate of the amount of alcohol contained in the fuel. In this method, a parameter relating to the rotation of the motor, for example the speed of rotation, is measured, injections of different quantities of fuel are controlled in at least two cylinders of the engine, and the variation of the engine torque resulting from said injections is determined, from the measurements of said parameter.

Then, it is possible to control an increase or decrease in the quantity of fuel injected as a function of the variation of the engine torque thus determined so as to exactly adapt the operation of the engine to the composition of the fuel.

In one embodiment, the control of injections of different amounts of fuel is deactivated as long as the phasing of the fuel injection is not carried out and / or until the operation of the engine is stabilized.

The invention will be better understood from the study of an embodiment taken by way of nonlimiting example and illustrated by the accompanying drawings, in which: FIG. 1 schematically illustrates an internal combustion engine equipped with a estimate according to the invention;

FIG. 2 illustrates a curve showing the variations of the torque as a function of the richness of the mixture injected into a cylinder; and FIG. 3 is a functional diagram illustrating the different stages of implementation of an injection control method according to the invention. FIG. 1 very schematically illustrates a spark ignition internal combustion engine referenced 1. The various cylinders 1a, for example four in number, are fed by a mixture of air and fuel which flows into a combustion engine. intake 2, while the exhaust gases from the engine are conveyed by an exhaust pipe 3.

A fuel injector 4 is associated with each of the cylinders 1a. A pressure sensor 5 mounted in the intake duct 2 provides a signal 6 to an electronic control unit 7 via a connection 6. The electronic control unit 7 also receives signals from a sensor 8 which measures the speed rotation of the motor 1 and which is connected to the control unit 7 by a connection 9. The electronic control unit 7 is capable of transmitting control signals to the various injectors 4 by connections 10.

Finally, a sensor 12 measures the temperature of the coolant circulating in the engine 1 and transmits a signal to the electronic control unit 7 via the connection 13.

The instantaneous speed of rotation of the motor or the duration of rotation during a given period of time enables the electronic control unit 7 to establish an estimation of the instantaneous torque of the motor 1. The measurement of the instantaneous speed of rotation by means of the 8 sensor can be advantageously by means of the detection of the position of a moving target rotatably connected to the crankshaft of the engine 1, the sensor 8 having a fixed sensitive element relative to the engine block. The target may for example be provided with patterns, such as machined teeth for a magneto-reluctant sensor or a repetition of optical patterns for an optical sensor. A linear or non-linear combination of the measurements thus obtained makes it possible to estimate the instantaneous engine torque. The estimating device thus uses reliable information, determined by means of a robust sensor whose presence is in any case essential to the operation of the engine and that it is therefore not necessary to add for the needs of the estimation device of the invention.

Referring to FIG. 2, which shows a curve of evolution of the engine torque obtained for a cylinder as a function of the richness of the fuel injected into this cylinder, it can be seen that the curve has an ascending limb, a vertex and a descending branch. , the summit corresponding to a wealth of about

1, 12. The curve is established for a stabilized operation of the engine, including when the phasing of the injection is stabilized in time.

In order to estimate the quantity of alcohol contained in the fuel supplying the internal combustion engine 1, illustrated in FIG. 1, different amounts of fuel are injected into at least two of the engine cylinders. These injections, which will be referred to here as "partial injections", are made on each of the cylinders of the engine. For each partial injection, the torque difference induced on the cylinder in question is measured by the determination of the instantaneous engine torque which has been mentioned above. During a certain number of engine revolutions, two cylinders are for example supplied with a larger amount of fuel injected, thus corresponding to an enrichment. The other two cylinders are simultaneously fed with a smaller amount of fuel injected during the same number of engine revolutions, ie during the same period of time. For this first period of time, the gross engine torque determined for the depleted rolls is subtracted from the gross torque determined for the enriched cylinders. Then, during a second period of time, the enriched cylinders and the depleted cylinders are exchanged and partial injections and the same calculation are carried out.

The derivative of the torque, that is to say the variation of the engine torque as a function of the variation of the richness, is the total difference between the gross torques determined on the enriched cylinders and those determined on the depleted cylinders. For a given operating point of the engine, this variation of the engine torque as a function of the difference in wealth corresponds to the slope of the curve which expresses the value of the torque as a function of the richness.

If, for example, at the point noted A in FIG. 2, partial injections are performed which are represented by two horizontal arrows, one in the sense of a depletion, that is to say of a greater low, the other in the sense of enrichment, that is to say a greater richness, a positive slope is obtained, that is to say a positive value of the derivative of the torque function relative to to the variation of wealth. The point A is indeed in the area of the increasing curve for wealth less than 1, 12. For the point noted C, we obtain on the contrary a negative derivative value. Finally, for point B, a zero derivative value is obtained, the point B corresponding to the vertex of the curve illustrated in FIG. 2 with a richness of 1, 12, that is to say a wealth close to the value 1.

The flowchart in Figure 3 illustrates the flow of the strategy for estimating the amount of alcohol contained in the fuel injected and the resulting change in fuel control. Step 14 begins with a check on the stability of the phasing of the injections. If the phasing of the injections is suitable, proceed to step 15. If, on the other hand, a suitable phasing is not found, that is to say that the motor has not yet stabilized in its operation, we proceed to step 16 which consists of wait for the proper phasing of injections before starting. In step 15, it is checked whether the conditions for the computation for the derivative of the pair are combined. If this is not the case, go to step 17, which allows waiting for the conditions to be met to start the estimation strategy. Among these conditions, one can for example provide the following:

It can be expected that a certain delay has expired to allow a stabilized operation of the engine. Such a time delay makes it possible to avoid that, in the event of a fuel change, the partial injections are made with a residue of the old fuel that could have been stored in the injectors and the fuel supply lines between the engine and the engine. Fuel tank. This ensures that the partial injections are well made with the new fuel whose composition is to be determined.

It can also be verified that too many partial injections have not been triggered for a given period of time. This avoids too much disturbing the operation of the engine to estimate the amount of alcohol contained in the fuel.

When all the conditions are met, step 15 is passed to step 18, which consists in performing partial injections on the two sets of cylinders successively, one in the direction of an enrichment, the other in the meaning of impoverishment, as shown in Figure 2.

Then, in step 19, the derivative of the torque is calculated as a function of the wealth variation as indicated above.

In step 20, it is tested whether the derivative of the torque is negative or positive. If the result of the comparison shows that the derivative is negative, which corresponds to the position of point C of Figure 2, we then proceed to step 21 to a decrease in the duration of the injections in the engine cylinders, so as to take into account the fact that the wealth of fuel feeding the cylinders is too important compared to the wealth close to 1 that should be adopted. The operation of the engine is thus modified according to the estimate of the quantity of alcohol contained in the fuel.

If, on the contrary, the derivative of the pair is not negative, that is to say if it is positive or zero, then step 22 is carried out, where the value of the derivative of the torque is checked with respect to a threshold. If this value is greater than the threshold, proceed to step 23 and increase the duration of the injections. In this case, we find ourselves in the situation of point A illustrated in FIG. 2 and the fuel mixture is too poor, the richness being much lower than

1, 12. It is therefore necessary to increase the amount of fuel injected by increasing the injection time for proper operation of the engine, taking into account the estimated amount of alcohol contained in the fuel. If the derivative of the torque, while being positive, remains lower than or equal to the threshold tested in step 22, the duration of the injections is not increased because it is then considered that one is close to an operation with a richness of the order of 1, which does not require a change in the duration of the injections.

Step 24 allows the strategy to be resumed in step 15 as long as an iteration counter has not reached a determined value. It is thus possible to restart the calculation of the torque derivative several times in order to confirm the first conclusion, provided that the conditions provided for in step 15 are fulfilled.

The device of the invention as well as its method of implementation thus make it possible not only to easily estimate the composition of a fuel, that is to say the amount of alcohol contained in this fuel, but also to automatically modify the operation of the engine by an action on the duration of the fuel injections according to the estimated composition of the fuel .

Claims

1 - Device for estimating a quantity of alcohol contained in the fuel supplying a spark ignition internal combustion engine (1), characterized in that it comprises a sensor (8) for measuring a relative parameter to the rotation of the engine, means for controlling injections of different amounts of fuel in at least two cylinders (1a) of the engine and means (7) for determining the variation of the engine torque resulting from said injections, from the measurements provided by the said sensor.

2-Device according to claim 1 wherein the measuring sensor is adapted to measure the speed of rotation of the motor.

3-Device according to one of the preceding claims wherein the means for controlling injections of different amounts of fuel are adapted to control the injection of a larger amount of fuel in a first set of cylinders and a less fuel in a second set of cylinders, for a first period of time, then to control the injection of a smaller amount of fuel into the first set of cylinders and a larger amount of fuel into the second set of cylinders; of cylinders for a second period of time.

4-Device according to claim 3 wherein the means for determining the variation of the engine torque are adapted to effect the difference between the engine torque resulting from the injections made during the first and second periods of time.

5-Device according to one of the preceding claims further comprising a means of deactivation according to the phasing of the fuel injection. 6 - A method of controlling the injection of fuel into an internal combustion engine according to an estimation of the quantity of alcohol contained in the fuel, characterized in that a parameter relating to the rotation of the engine is measured injections of different amounts of fuel are controlled in at least two cylinders of the engine and the variation of the engine torque resulting from said injections is determined from the measurements of said parameter.

7-A method according to claim 6 wherein it controls the injection of a larger amount of fuel in a first set of cylinders and a smaller amount of fuel in a second set of cylinders during a first period of time and then controlling the injection of a smaller amount of fuel into the first set of cylinders and a larger amount of fuel into the second set of cylinders for a second period of time.

8-Process according to claim 7 wherein the difference between the engine torque resulting from the injections carried out during the first and second periods of time is made to deduce information on the amount of alcohol contained in the fuel.

9-Process according to one of claims 6 to 8 wherein it controls an increase or decrease in the amount of fuel injected as a function of the variation of the engine torque thus determined.

10-Process according to one of claims 6 to 9 wherein the control of injections of different amounts of fuel is deactivated as long as the phasing of the fuel injection is not carried out and / or as long as the operation of the engine n is not stabilized.