EP0583184A1 - Method for regulating the idle-running of an internal combustion engine - Google Patents

Abstract

Process for controlling the rotational speed of an internal-combustion engine in idling mode, characterised in that it comprises the following steps: - periodically measuring the value of the battery voltage; - deducing therefrom a mean value of the battery voltage over a given horizon; - calculating the value of a statistical amount representing the discrepancy between each mean value of battery voltage and a predetermined threshold value; - associating, with each value of the said statistical magnitude, a corresponding value of the rotational speed of the engine in the idling mode. <IMAGE>

Description

The present invention relates to a method for controlling the idle speed of an internal combustion engine fitted in particular to a motor vehicle.

A motor vehicle equipped with an internal combustion engine with positive ignition or compression ignition, must be supplied with electrical energy to be able to start at any time and have a sufficient amount of current to operate the various electrical receivers of the vehicle (ignition, lighting, engine cooling fan, etc.). To do this, the vehicle is conventionally fitted with a battery of electrochemical accumulators, this battery being permanently recharged during engine operation by means of an electric generator or alternator driven by the rotation of the engine shaft.

The generator is dimensioned in such a way as to authorize the commissioning of the different consumers of currents connected to the battery and this under critical operating conditions of the engine and in particular at the low engine rotation speed corresponding to engine idling.

Conventionally, the idling speed of an internal combustion engine of the type fitted to motor vehicles, corresponding to the released foot position of the accelerator pedal, changes little or not over time except with the temperature d 'water. This speed is determined for a given type of engine as low as possible in order to meet the consumption and pollution control requirements imposed by the legislation in force.

This therefore results in the need to equip motor vehicles with powerful alternators capable of producing a high amperage at the low rotational speed corresponding to the engine idling speeds. This large dimensioning of the alternator has many disadvantages: cost, size, weight, etc.

The method of controlling the rotation speed of the engine in idle phase makes it possible to eliminate these various drawbacks, in particular by allowing the use of alternators of class lower than those traditionally used, and this for an almost zero cost of production.

The method of controlling the rotation speed of an internal combustion engine in phase operating mode according to the invention, applies to an internal combustion engine which therefore supplies electric current to electrical consumers via an alternator and a battery and which comprises a sensor for measuring the value of the voltage of the starter battery, an engine control system comprising means for calculating and means for storing information and finally means for adjusting the idle speed controlled by said engine control system.

According to the invention, the method of controlling the speed of rotation of an engine is characterized in that the value of the speed of rotation of the engine in idle operating phase is increased from a predetermined nominal value, as a function of the value of the measured battery voltage, so as to cause the generator to produce the electricity necessary for said consumers.

Thanks to the process which is the subject of the invention, the adaptation of the idling speed makes it possible to maintain the electrical balance even with an alternator of weak characteristics. In fact, when the voltage appears too low, in particular because of the commissioning of a powerful electrical consumer, the idle rotation speed is increased. Thus the alternator is able to produce more electric current and to compensate for the consumption of electricity. Raising the engine speed at idle then relieves the battery and prevents it from being discharged, which operates in a manner repetitive causes its destruction. The rotation speed is brought back to its nominal value as soon as the battery voltage returns to its normal value.

• (a) mesurer périodiquement la valeur de la tension batterie ;
• (b) calculer à chaque nouvelle valeur de la tension batterie ainsi mesurée, la valeur d'une première grandeur statistique représentative de la moyenne des valeurs de la tension batterie sur un horizon donné de valeurs mesurées ;
• (c) calculer pour chaque valeur ainsi obtenue de ladite première grandeur statistique, l'écart de cette valeur à une valeur de seuil prédéterminée ;
• (d) calculer la valeur d'une seconde grandeur statistique représentative de la moyenne des écarts entre ladite première grandeur statistique et ladite valeur de seuil ;
• (e) associer à chaque valeur de ladite seconde grandeur statistique une valeur correspondante du régime de rotation du moteur ;
• (f) commander les moyens de réglage du régime ralenti de façon à faire coïncider à chaque instant, le régime de rotation ralenti dudit moteur avec ladite valeur de rotation du moteur déduite de la valeur de ladite seconde grandeur statistique.

According to another characteristic of the method for controlling the rotation speed of an internal combustion engine according to the invention, it comprises the following steps:

• (a) periodically measure the value of the battery voltage;
• (b) calculating at each new value of the battery voltage thus measured, the value of a first statistical quantity representative of the average of the values of the battery voltage over a given horizon of measured values;
• (c) calculating for each value thus obtained from said first statistical quantity, the deviation of this value from a predetermined threshold value;
• (d) calculating the value of a second statistical quantity representative of the average of the differences between said first statistical quantity and said threshold value;
• (e) associating with each value of said second statistical quantity a corresponding value of the engine speed;
• (f) controlling the means for adjusting the idle speed so as to make the idle rotation speed of said engine coincide at each instant with said engine rotation value deduced from the value of said second statistical quantity.

According to another characteristic of the method for controlling the rotation speed according to the invention, the measurements of the value of the voltage of battery and the calculation of the different statistical values are performed after a delay period.

According to another characteristic of the method of controlling the speed of rotation according to the invention, in accordance with step (e) the values of speed of rotation of the associated engine are deduced from a specific map contained in the engine control system.

According to another characteristic of the method for controlling the rotation speed according to the invention, step (b) is eliminated, said first statistical quantity then being directly equal to the battery voltage.

According to another characteristic of the method of controlling the rotation speed according to the invention, step (d) is eliminated, said second statistical quantity then being directly equal to the difference between the first statistical quantity and the predetermined threshold value.

• la figure 1 est une vue schématique d'un moteur à combustion interne équipé d'un dispositif de mise en oeuvre du procédé selon l'invention ;
• la figure 2 est un schéma fonctionnel précisant les différentes étapes du procédé selon l'invention ;
• la figure 3 est un graphique montrant l'incidence de la tension batterie sur l'évolution du régime de rotation du moteur au ralenti, conformément au procédé selon l'invention.

The objects, aspects and advantages of the present invention will be better understood from the description given below of an embodiment of the invention, this embodiment being given by way of non-limiting example, referring to the attached drawing, in which:

• Figure 1 is a schematic view of an internal combustion engine equipped with a device for implementing the method according to the invention;
• FIG. 2 is a functional diagram specifying the different steps of the method according to the invention;
• FIG. 3 is a graph showing the impact of the battery voltage on the evolution of the engine rotation speed at idle, in accordance with the method according to the invention.

FIG. 1 therefore describes an internal combustion engine equipped with a device implementing the method for controlling the engine rotation speed during the idling operating phases. Only the elements necessary for understanding the invention have been shown.

The internal combustion engine shown, for example of the four-stroke type and with four in-line cylinders, referenced 1, is equipped with a fuel supply device, for example of the multipoint injection type where each cylinder is supplied with fuel by a specific electro-injector 5.

The opening of each electro-injector 5 is controlled by an engine control system 7, which determines the quantity of fuel injected according to the operating conditions.

The engine control system 7 also controls the flow rate of the oxidizing gases, in particular during the idle operating phase, by means of a piloted actuator 4 making it possible to control the opening of the idle bypass.

This engine control system 7 conventionally comprises a computer comprising a CPU, a random access memory (RAM), a read only memory (ROM), analog-digital converters (A / D), and various input and output interfaces. It receives input signals relating to the operation of the engine and of the peripheral members, performs operations and generates output signals intended in particular for injectors 5 and actuator means 4.

Among the input signals is the battery voltage information, emitted by a measurement sensor 22 arranged on the connection line of the alternator 12 to the battery 3.

The engine 1 in fact conventionally drives an electric generator or alternator 12 capable of producing, during the engine operating ranges, a charging current intended for the storage battery 3.

This alternator 12 essentially comprises a rotor and a stator. The rotor driven by the motor shaft, includes electromagnets constituted by one or more excitation windings. The stator has a three-phase winding. The alternating current produced in the three-phase winding is transformed into direct current in a rectifier circuit before supplying the battery 3.

The implementation of the process object of the invention is operated by the engine control system 7. The latter thanks to a strategy implemented in the computer and to tables of values stored in its memories controls the idle speed by controlling the actuator 4 in particular as a function of the information battery voltage.

In accordance with FIG. 2, the method for controlling the idle speed of the engine as a function of the voltage of the starter battery 3, implemented by the engine control system 7, is as follows.

The battery voltage information Vbat measured periodically by the sensor 22 is processed by a low-pass first order digital filter F1, of the form 1 / (1 + cp), so as to obtain a statistical quantity VMbat representative of the average value of the battery voltage over a given measurement horizon, such as for example the last hundred measurements.

avec
   VMbat_i valeur de la grandeur statistique correspondant à l'instant Ti ( Ti = To + i * P ; avec To instant de mise en marche du véhicule et P période de mesure de la tension batterie)
   VMbat_i-1 valeur de la grandeur statistique correspondant à l'instant Ti-1 ;
   Vbat_i valeur de la tension batterie mesurée à l'instant Ti ;
   F1 constante de filtrage du filtre F1;
   et VMbat_0 = 0.The filtering formula chosen is then: $$\text{VMbat\_i = VMbat\_i-1 + (Vbat\_i - (VMbat\_i-1)) / F1)}$$

with
VMbat_i value of the statistical quantity corresponding to the instant Ti (Ti = To + i * P; with To instant of starting the vehicle and P period of measurement of the battery voltage)
VMbat_i-1 value of the statistical quantity corresponding to the instant Ti-1;
Vbat_i value of the battery voltage measured at time Ti;
F1 filter constant F1;
and VMbat_0 = 0.

The purpose of this first filtering is to take into consideration an average voltage which does not take into account the brief variations in the battery voltage, as during a headlight call.

However, in a simplified embodiment of the method which is the subject of the present invention, it is possible to eliminate this filtering and directly process the raw value of the battery voltage Vbat_i observed at time Ti. According to this variant, we then have VMbat_i = Vbat_i

The average value VMbat having thus been obtained, it is then compared by subtractor means S to one. predetermined threshold value Vs corresponding to the normal value of the battery voltage 3. The reference voltage of the starter batteries usually used is equal to 12.7 V.

The gross difference Ebat, between VMbat and Vs, is then treated by new filtering means so as to produce a second statistical value EMbat representative of the evolution of the difference between the average value of the battery voltage VMbat and the voltage setpoint Vs over a given horizon of calculated values.

This filtering uses two distinct filtering values according to the sign of the deviation. This decoupling of the processing according to the positive or negative value of the difference allows greater flexibility in the dynamic adaptation of the rotation speed in idle phase depending on the battery voltage.

The Ebat difference is therefore first treated by comparator means C which, depending on the value of the sign of the Ebat difference, positive or negative, send the latter either to the filter F2 or to the filter F3.

   et si Ebat_i < 0 $$\text{EMbat\_i = EMbat\_i-1 - (Ebat\_i) / F3)}$$

avec
   Ebat_i valeur de l'écart entre la première grandeur statistique et la valeur de seuil à l'instant Ti, Ebat_i = Vmbat_i - Vs ;
   EMbat_i valeur de la seconde grandeur statistique représentative de la moyenne des écarts à l'instant Ti ;
   EMbat_i-1 valeur de la seconde grandeur statistique à l'instant Ti-1 ;
   F2 constante de filtrage du filtre F2;
   F3 constante de filtrage du filtre F3;
   EMbat_0 = 0The filtering formula chosen is then:
if Ebat_i> 0 (again VMbat_i> Vs) $$\text{EMbat\_i = EMbat\_i-1 - (Ebat\_i / F2)}$$

and if Ebat_i <0 $$\text{EMbat\_i = EMbat\_i-1 - (Ebat\_i) / F3)}$$

with
Ebat_i value of the difference between the first statistical quantity and the threshold value at time Ti, Ebat_i = Vmbat_i - Vs;
EMbat_i value of the second statistical quantity representative of the average of the deviations at time Ti;
EMbat_i-1 value of the second statistical quantity at time Ti-1;
F2 filter constant of filter F2;
F3 filter constant of filter F3;
EMbat_0 = 0

The use of two constants makes it possible to dissociate the evolution of the values of EMbat according to the value of the Ebat difference observed. We can thus take F2> F3 so as to have faster convergence in the event of a positive deviation than a negative deviation. The reason for this difference in treatment will be specified later in the description.

Each value EMbat_i of the second statistical quantity EMbat is then converted into the engine speed Rral_i, using the addressing means A which call up, in a table stored in the memories M of the engine control system 7, the value of the engine speed corresponding to the value of the statistical quantity produced.

Figure 3 shows a possible relationship between the values of EMbat and the engine speed. The increase in the second statistical quantity corresponding to a negative variation in the difference between the observed average voltage and the normal voltage is accompanied by an increase in the rotation speed from the nominal speed corresponding to the other operating conditions of the motors and at normal battery voltage up to a maximum value allowed for engine idling.

The development of such a mapping is carried out by series of measurements on the test bench for each type of engine.

The speed value is then directly usable by the engine control system to adjust the engine idle speed as soon as the latter returns to the idle operating phase, via the actuator 4 and the injectors 5.

In accordance with what has just been described, the operation of the speed control method of rotation of the engine during idling operation is as follows.

As soon as the engine is started or preferably after a time delay period Tbat, the engine control system 7 applies the previously described treatment to the battery voltage information and thus permanently has the optimum value of the idle speed taking into account the various electrical consumers present.

When the battery voltage Vbat decreases due to the commissioning of a powerful electrical consumer, for example the activation of air conditioning, the average voltage VMbat drops consecutively and the gap Ebat with the normal voltage Vs increases. The second statistical quantity EMbat increases, which causes an increase in the engine idling speed Rral. Thus the alternator 12 is able to produce more electric current and to compensate for the consumption of electricity. Raising the engine speed at idle thus relieves the battery 3.

The rise in tension linked to the increase in speed causes a reduction in the Ebat gap and therefore a gradual halt in the increase in rotation speed.

The shutdown of electric consumers causes a strong rise in the battery voltage Vbat and by the same, the rise in the average voltage VMbat. The difference between normal voltage and average voltage then becomes largely positive, which causes a rapid decrease in the idle rotation speed. As before, the functioning of the system is regulated.

The use of two separate filtering constants for the development of EMbat according to the sign of the Ebat deviation, makes it possible to very quickly reduce the engine rotation speed to reach the nominal operating speed as soon as the electricity demand has stopped, while the ramp-up can take place more gradually.

Thus, thanks to the method according to the invention, it is possible to respond to an increase in the electric consumption of the vehicle, without increasing the class of the alternator or discharging the battery.

Of course, the invention is in no way limited to the embodiment described and illustrated, which has been given only by way of example.

On the contrary, the invention includes all the technical equivalents of the means described and their combinations if these are carried out according to the spirit.

• soit avec des composants d'électronique analogique pour lesquels les sommateurs, comparateurs et autres filtres sont réalisés à l'aide d'amplificateurs opérationnels ;
• soit avec des composants d'électronique numérique qui réaliseraient la fonction en logique câblée ;
• soit par un algorithme de traitement du signal implanté sous forme d'un module logiciel composant d'un système logiciel de contrôle moteur faisant fonctionner le microcontrôleur d'un calculateur électronique.
• soit encore, par une puce spécifique (custom) dont les ressources matérielles et logicielles auront été optimisées pour réaliser les fonctions objet de l'invention : puce microprogrammable ou non, encapsulée séparément ou bien tout ou partie d'un coprocesseur implanté dans un microcontrôleur ou microprocesseur etc.

As for the implementation of the idle speed control method, it can be carried out in various forms:

• either with analog electronic components for which the summers, comparators and other filters are produced using operational amplifiers;
• either with digital electronic components which would perform the function in wired logic;
• either by a signal processing algorithm implemented in the form of a software module component of an engine control software system operating the microcontroller of an electronic computer.
• or again, by a specific chip (custom) whose hardware and software resources will have been optimized to carry out the functions which are the subject of the invention: microprogrammable chip or not, encapsulated separately or else all or part of a coprocessor implanted in a microcontroller or microprocessor etc.

Likewise, the invention includes all the technical equivalents applied to an internal combustion engine whatever its combustion cycle (2-stroke, 4-stroke), the fuel used diesel or petrol or else, the number of its cylinders.

Claims (9)

[1] Method for controlling the rotation speed of an internal combustion engine in the idling phase, said engine (1) which supplies current to electrical consumers via an alternator (12) and d '' a battery (3), comprising a sensor (22) for measuring the voltage of the battery (3), a motor control system (7) comprising calculation means and information storage means and adjustment means (4) of the idle speed controlled by said engine control system (7), characterized in that the value of the engine rotation speed in the idle operating phase is increased from a predetermined nominal value, as a function of the reduction in voltage measured battery, so as to cause the alternator (12) to produce the electricity necessary for said consumers. [2] Method for controlling the rotation speed of an engine according to claim 1, characterized in that it comprises the following steps: (a) periodically measure the value Vbat_i of the battery voltage (Vbat); (b) calculate at each new value Vbat_i of the battery voltage (Vbat) thus measured, the value VMbat_i of a first statistical quantity (VMbat) representative of the average of the values of the battery voltage over a horizon given measured values; (c) calculating for each value VMbat_i thus obtained from said first statistical quantity (VMbat), the deviation Ebat_i from this value to a predetermined threshold value Vs; (d) calculating the value EMbat_i of a second statistical quantity (EMbat) representative of the average of the deviations Ebat_i between said first statistical quantity (VMbat) and said threshold value Vs; (e) associating with each value EMbat_i of said second statistical quantity (EMbat) a corresponding value Rral_i of the engine rotation speed; (f) controlling the means for adjusting (4) the idle speed so as to make the idle speed of said motor (1) coincide at each instant with said Rral_i value of motor rotation deduced from the EMbat_i value of said second quantity statistics (EMbat). [3] Method for controlling the rotation speed of an engine according to claim 2, characterized in that the measurements of the value of the battery voltage (3) and the calculation of the statistical values (VMbat, EMbat) are carried out after a time-out period (Tbat). [4] Method for controlling the rotation speed of an engine according to any one of claims 2 to 3, characterized in that in accordance with step (b) the values of said first statistical quantity (VMbat) are calculated at from the following formula: $$\text{VMbat\_i = VMbat\_i-1 + ((Vbat\_i - (VMbat\_i-1)) / F1)}$$

where F1 is a filter constant and where VMbat_0 = 0. [5] Method for controlling the rotation speed of an engine according to any one of claims 2 to 4, characterized in that in accordance with step (d) the values of said statistical quantity (EMbat) are calculated from with the following formula:
if Ebat_i> 0 (where Ebat_i = VMbat_i - Vs) $$\text{EMbat\_i = EMbat\_i-1 - ((Ebat\_i) / F2)}$$

and if Ebat_i <0 $$\text{EMbat\_i = EMbat\_i-1 - ((Ebat\_i) / F3)}$$

where F2 and F3 are two constants and where EMbat_0 = 0. [6] Method for controlling the rotation speed of an engine according to claim 5, characterized in that F2 is greater than F3. [7] Method for controlling the rotation speed of an engine according to any one of claims 2 to 6, characterized in that in accordance with step (e) the values Rral_i of rotation speed of the engine associated with said values EMbat_i are deduced from a specific map contained in the engine control system (7). [8] Method for controlling the rotation speed of an engine according to any one of claims 2 or 3, characterized in that step (b) is omitted, said first statistical quantity (VMbat) then being directly equal to battery voltage (Vbat). [9] Method for controlling the rotation speed of an engine according to any one of claims 2 to 4, characterized in that step (d) is omitted, said second statistical quantity (EMbat) then being directly equal to the difference between the first statistical quantity (VMbat) and the predetermined threshold value Vs.

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