WO2009068770A1

WO2009068770A1 - Estimation of the evaporation effects of a fuel diluted in oil in an internal combustion engine

Info

Publication number: WO2009068770A1
Application number: PCT/FR2008/051981
Authority: WO
Inventors: Vasco Afonso; Gérard LELONG; Emmanuel Premier; Emmanuel Retailleau
Original assignee: Renault S.A.S.
Priority date: 2007-11-05
Filing date: 2008-11-03
Publication date: 2009-06-04
Also published as: FR2923266A1

Abstract

The invention relates to a device for estimating the effects of the evaporation of a fuel diluted in the oil of an internal combustion engine (1), characterised in that it comprises a means (9) for comparing the temperature of the engine (1) oil with a temperature threshold, and a means for calculating the maximum fuel-air ratio deviation if the measure of the oil temperature is higher than said temperature threshold.

Description

ESTIMATING THE EFFECTS OF THE EVAPORATION OF

FUEL DILUTED IN THE OIL OF A MOTOR A

INTERNAL COMBUSTION

The invention relates to estimating the effects of evaporation of the diluted fuel in the oil of an internal combustion engine. More particularly, the invention relates to estimating such effects on the operating efficiency of an internal combustion engine.

It should be noted, however, that the invention relates essentially to internal combustion engines that can operate with several types of fuel. The engines thus concerned may be spark ignition engines that can operate with gasoline, ethanol, methanol or any mixture of these constituents. But these engines can also be compression ignition that can run on diesel or biodiesel.

Whatever the type of internal combustion engine, the term "richness of operation", the ratio between the mass of fuel and the mass of oxidant used by the engine during combustion. The richness of engine operation is an essential parameter to control the operating conditions of the engine. It allows, among other things, to control the rate of pollutant emissions, fuel consumption, the quality of combustion or even the mechanical reliability of the parts involved in the combustion. The control of the operating wealth depends, in general, control of the amount of fuel injected during combustion. In particular, the richness of operation depends on the following parameters:

The estimation of the intake air flow

Estimation of the stoichiometric ratio of fuel injected

Estimation of failures of the engine fuel supply

The estimation of the fuel flow from the organs attached to the engine (in particular a canister and the circuit recirculation of gasoline vapors mixed with engine oil).

The phenomenon of "blow-by" by which the oil vapors mix with the gasoline vapors has a significant influence on the richness of operation. It appears when a certain quantity of pressurized gas, during the compression phase, escapes by the multiple passages which are offered to these gases, such as those left between the segments and the shirts, or by the guides valves, or by bearings, to end up in the crankcase where they mix with the oil vapors. Blow-by vapors are thus understood to mean the leakage gases that come from the mixture of the gasoline vapors with the oil vapors in the engine casing. These leaking gases can be recycled via a rebreathing circuit, which collects said vapors, for mixing with fresh air at the intake manifold or the air filter. It is therefore necessary to know the contribution of the parameters stated above, on the one hand to control the richness of operation of the engine, but also to not distort the estimates established by other engine control strategies that can use said settings .

Some recent technological developments contribute to an increase in the amplitude of the "blow-by" phenomenon, among which we can mention: the diesel particulate filter, which requires regeneration phases, or even bioethanol (E85 / E100) which requires high cold operating efficiencies, which therefore require a greater amount of fuel diluted in the engine oil. Although the phenomenon of "blow-by" is well known at the present time, its quantification has not yet presented any absolute necessity. In practice, it is considered that the amplitude of the phenomenon is limited, or that its duration only concerns the heating phase of the engine, or that it is not necessary to finely estimate the parameters of the cold engine. The conventional solution consists in conditioning the various estimation strategies related to the richness of operation of the engine only in the hot phase of the engine. But for engines with a high proportion of Bioethanol (E85 or El OO), the problem is all the more different. that in the absence of an ethanol rate sensor, it is essential to be able to exploit as soon as possible a wealth of operation information without waiting for the hot phase of the engine. Moreover, the patent application EP 1 710 419 describes a method of modeling the phenomenon of "blow-by", but it is a principle to estimate the evaporated fuel content present in the crankcase as a function of the temperature of the engine. engine water and manifold pressure. However, this method does not take into account the significant influence of engine oil on the estimation of the evaporated fuel content.

The object of the invention is therefore to meet the needs mentioned above and, in particular, to quantify the phenomenon of "blow-by" and its impact on the richness of engine operation but also on engine control strategies based on this parameter.

Another object of the invention is to know these effects when the engine is started, that is to say during the heating phase of the engine.

The invention relates to a method for estimating the effects of evaporation of the fuel diluted in the oil of an internal combustion engine. The method comprises a step of comparing a temperature of the engine oil with a temperature threshold and a step of calculating the maximum wealth drift if said measurement of the oil temperature is greater than said temperature threshold.

By taking into account the temperature of the engine oil, it is possible to determine the influence of the phenomenon of "blow-by" on the richness of engine operation. Indeed, this consideration makes it possible to define risk windows in which the oil vapors mixed with the gasoline vapors are likely to influence the richness of operation.

Such a method also makes it possible to optimize the engine control strategies based on the parameter of richness of operation of the engine. It notably makes it possible to improve the estimation of the evaporated fuel content present in the crankcase of the engine. According to another embodiment, the method comprises a step of calculating the absolute wealth drift carried out before said step of comparing the temperature of the engine oil and in which the calculation of the maximum wealth drift is a function of said absolute wealth drift and the operating point of the engine.

According to another embodiment, the method comprises a step of saving in non-volatile memory variables after each calculation step and wherein, said calculation of the absolute wealth drift being a function of the value saved and a temperature water of said engine.

According to another mode of implementation, the method comprises a step of setting the variables to zero after the completion of said step of calculating the maximum wealth drift.

According to another mode of implementation, one initialises each engine startup said variables with a default value if access to the nonvolatile memory is defective.

According to one embodiment, the subject of the invention is a device for estimating the effects of the evaporation of the fuel diluted in the oil of an internal combustion engine. The device includes means for comparing the engine oil temperature with a temperature threshold and means for calculating the maximum drift of wealth if said oil temperature measurement is greater than said temperature threshold. With this device, it can be produced a parameter determining the existence of a significant amount of fuel diluted in the engine oil.

According to another embodiment, the device comprises means for calculating the absolute wealth drift and means for calculating the maximum wealth drift according to said absolute wealth drift and the operating point of the engine.

According to another embodiment, the device comprises means for saving in nonvolatile memory the variables after each calculation and in which, said calculation of the absolute wealth drift is a function of the value saved and a water temperature of said engine. According to another embodiment, the device comprises means for setting variables to zero after completion of the calculation of the maximum wealth drift and means for initializing said variables with a default value if access to the non-volatile memory is defective.

Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIG. 1 is a diagrammatic view of an internal combustion engine equipped with an estimation device according to the invention; and FIG. 2 is a flowchart illustrating the main phases of the estimation method according to the invention.

FIG. 1 diagrammatically shows an internal combustion engine 1 comprising an air intake duct 2 for the admission of air into the engine 1 and a gas exhaust manifold 3 intended to evacuate. the combustion gases to the outside.

The engine 1 is provided with an estimation device, for example, installed in a management computer for the operation of the engine. The estimation device is intended to estimate the effects of the evaporation of the fuel diluted in the oil on the richness of the fuel air mixture admitted to the engine cylinders. It comprises, an air pressure sensor 5 delivered by the air intake duct 2, a speed sensor 6 for measuring the rotational speed of the engine and a sensor 8 for measuring the oxygen content of the air. gas carried by the gas exhaust manifold 3, also called oxygen probe.

These sensors are connected to an electronic control unit 9, called ECU or on-board computer on board the vehicle.

The pressure sensor 5 transmits a signal for measuring the pressure of the air through a connection 5a towards the ECU 9.

The speed sensor 6 transmits a motor rotation speed signal via a connection 6a towards the ECU 9. The oxygen sensor 8 transmits a signal for measuring the oxygen content via a connection 8a in the direction of the UCE 9. In addition, the device comprises an oil temperature sensor 10, which transmits a signal for measuring the temperature of the engine oil via a connection 10a towards the ECU 9 and a water temperature sensor 1 1 which transmits a signal for measuring the temperature of the engine water via a connection 11a in the direction of the ECU 9.

The ECU 9 also comprises means for controlling at least one fuel injector 4 of the engine via a connection 4a. The ECU 9 also comprises a non-volatile memory for saving the variable values, not shown in the figure, which may be of powered RAM, EEPROM or flash-EEPROM type.

The engine 1 is also equipped with a rebreathing circuit 12 for recovering the vapors, and in particular a mixture of gasoline vapors and oil vapors, through a recovery duct 13, so that they can be recycled by mixing them together. with the air of the air intake duct 2 via a recirculation duct 14.

The ECU 9 comprises means for recording the measurements from the various sensors 5, 6, 8, 10 and 1 1 of the device. It further comprises means for performing operations on the various measurements, in particular calculating variables from the measurements from said sensors 5, 6, 8, 10 and 1 1. The ECU 9 also comprises means for comparing the calculated variables with pre-stored threshold values in the non-volatile memory.

FIG. 2 shows a flowchart of the steps of a method according to the invention implemented by the device which has just been described.

This method can be implemented in an on-board computer on board the vehicle, called UCE (Electronic Control Unit).

The first step 100 corresponds to the start of the process. Each new calculation session is initialized when the engine starts.

This step 100 continues with a step 101 of testing a non-volatile memory. This non-volatile memory makes it possible to save the state of the variables used in the process and may be of any type (powered RAM, EEPROM, flash-EEPROM). The purpose of this backup in memory is to allow the process to take into account the history of operation of the engine on previous routes. In case of memory failure, a default value will be used. In this step 101, a memory access test is therefore performed.

If it is determined that the access to the memory is defective, a default initialization step 102 is performed. In this case, an initialization of a variable parameter DO corresponding to the drift of rich maximum absolute bound to the phenomenon of "blow - by", and of a second variable parameter CO corresponding to a counter, called the counter of steam capital, for determining a running time of a subsequent calculation step 107, described below.

During the default initialization step 102, the variables DO and CO take default values that are respectively COd and DOd. The memory DO and CO are then stored in memory (step 103). In the following step 104, the variable CO is calculated which corresponds to the maximum value between the memorized variable DO and a variable D0 _water which corresponds to an absolute wealth drift as a function of the water temperature. engine. The variable D0 _water can be extracted from a table obtained by apprenticeship or is derived from a linear interpolation in the table. In this step 104, the result of the sum of the stored value DO and the variable D0 _water is also assigned to the variable DO. During this step 104, a Boolean BO is initialized to an "OFF" value, then in the next step 105, the variables BO, DO and CO elaborated previously are saved in memory.

A step 106 is then performed to compare the engine oil temperature, denoted T _HUI U, with a temperature threshold SHO. The temperature of the engine oil You _m y may be derived, in particular, the oil temperature sensor or may be modeled from other sensors. This temperature threshold SHO can be constant or calculated according to the fuel used. If the Tuuiie oil temperature is above this SHO threshold, proceed to a calculation of the following variables. In the opposite case, the comparison of the oil temperature is carried out again.

Thus, when the oil temperature is greater than the threshold SHO, a calculation step 107 is carried out, in particular for determining a variable D _np , corresponding to a maximum drift of wealth related to the "blow-by", continuously and in successive steps, that is to say iteratively. In this case, it is considered that the production of vapors can generate a risk of errors in the engine control strategies that use the signals of the probes, or sensors, richness of the operation of the engine. This presence of a vapor production is called "window at risk".

In step 107, the variable BO has the value "ON". This value corresponds to a signal to indicate the fact that one enters a "window of risk".

At each computation step, the variable CO is decremented by a value dCO. This step of decrementing dCO may be a function of engine speed and load. In particular, dCO can be calculated by interpolation using a map.

As indicated above, the variable D _np corresponds to the maximum drift of wealth related to the "blow-by" phenomenon, and this for an operating point of the engine. The calculation of the variable D _np is performed as a function of the value of the variable OD and a weighting factor PFM which is a function of the speed and the load of the engine. In particular, the PFM weighting factor can be calculated by interpolation using a map. After calculation, the variables DO, D _np and CO are saved (step 108).

It performs the steps 107 and 108, and in particular the variable calculations D _np, CO and BO, CO as the variable is greater than zero. In this case, it is considered that the "window at risk" is not completed. This control is performed in the next step 109, which compares the value of the variable CO with zero.

When the variable CO is zero, a step 1 is performed to reset the variables BO, CO and DO, which are then stored (step 1 1 1). Thus, after each variable calculation step, the values are saved in memory, during steps 103, 105, 108 and 11 1, so that in the event of stopping the engine, or the calculator, the variables can be used. new calculation basis for starting the next engine. This backup in non-volatile memory can be carried out continuously.

The process is then stopped at the stop step 1 12. The process can stop at this stop step 1 12. It can also be stopped during a shutdown of the engine or the shutdown of the computer.

Thanks to the determination of a "window of risk" defined in particular by the variable CO, one can optimize the control strategies of the engine.

Advantageously, the value of the variable D _{np can be made available} for the recognition strategy of the alcohol content in the fuel. Indeed, one can freely allow, or not, the estimates made during this strategy when certain conditions are met. If the strategy detects that a fuel used results in an estimate of the engine running power below D _np , the estimates of the strategy will or will not be stored.

In addition, concerning the fuel diagnostic strategies based on the exploitation of the engine operating wealth drift, they will be able to use the variables BO, CO and D _np to modulate their detection thresholds. In particular, the variable BO can be used to inhibit a diagnosis and the variable D _np can be used to inhibit the tests on the average drift of richness in a dead band, between 0 and D _np .

Also, for a strategy for estimating vapors from the canister, the variable BO can be used as an activation condition, in addition to the conditions specific to this strategy, in order not to memorize a wealth drift of the engine operation related to a production of "blow-by" vapors.

Claims

1. A method for estimating the effects of evaporation of the diluted fuel in the oil of an internal combustion engine, characterized in that it comprises a step of comparing a temperature of the engine oil with a threshold of temperature and a step of calculating the maximum wealth drift if said measurement of the oil temperature is greater than said temperature threshold.

2. Method according to claim 1, comprising a step of calculating the absolute wealth drift carried out before said step of comparing the engine oil temperature and wherein the calculation of the maximum wealth drift is a function of said drift. of absolute richness and the operating point of the engine.

3. Method according to claim 2, comprising a step of saving in nonvolatile memory variables after each calculation step and wherein, said calculation of the absolute wealth drift being a function of the value saved and a water temperature. said engine.

4. Method according to claim 3, comprising a step of setting the variables to zero after the completion of said step of calculating the maximum wealth drift.

5. Method according to claim 4, wherein, at each engine startup, said variables are initialized with a default value if the access to the non-volatile memory is defective.

6. Apparatus for estimating the effects of the evaporation of the fuel diluted in the oil of an engine (1) with internal combustion characterized in that it comprises means (9) for comparing the temperature of the oil of the motor (1) with a temperature threshold and means for calculating the maximum wealth drift if said oil temperature measurement is above said temperature threshold.

Device according to claim 6, comprising means (9) for calculating the absolute wealth drift and means (9) for calculating the maximum wealth drift as a function of said absolute wealth drift and the operating point of the engine ( 1).

8. Device according to claim 7, comprising means for saving in nonvolatile memory the variables after each calculation and wherein, said calculation of the absolute wealth drift is a function of the value saved and a water temperature of said engine (1).

9. Device according to claim 8, comprising means (9) for zeroing variables after the end of the calculation of the maximum wealth drift and means (9) for initializing said variables with a default value if the access to nonvolatile memory is defective.