EP1008742B1 - Method to control an internal combustion engine - Google Patents

Description

The present invention relates to the field of methods of control of internal combustion engines, especially engines fitted a high pressure fuel injection system.

Injection systems for so-called "common rail" engines integrate piping containing fuel at very high levels of pressure, from one to several hundred bars. A fuel leak on these circuits by failure of one of the components causing a leak or overpressure likely to generate a leak, therefore presents a risk serious for the user accidental shutdown of the engine and / or fire of the vehicle. It is therefore necessary, if this type of problem occurs, to ability to promptly notify driver and stop power in fuel and consequently the vehicle by maintaining a safety as important as possible for its passengers and its outdoor environment.

• d'inciter l'utilisateur à faire rapidement contrôler son véhicule,
• de l'obliger, ou d'obliger un nouvel utilisateur du véhicule non averti de l'incident, à un roulage prudent, afin d'éviter, si le défaut réapparaít, une coupure moteur dans des conditions dangereuses pour les occupants du véhicule et l'environnement.

It may also be necessary, if a leak or a risk of leak has been detected and memorized by the engine control computer, to restrict, until verification and, if necessary, repair by a mechanic and erasure of the memorized fault, the performances of the engine so:

• encourage the user to have their vehicle checked quickly,
• to force it, or to oblige a new user of the vehicle not informed of the incident, to drive carefully, in order to avoid, if the fault reappears, an engine shutdown in conditions dangerous for the occupants of the vehicle and the 'environment.

Known injection systems for common rail engines have pressure monitoring strategies in place fuel system.

If these strategies reveal a fault, the computer reacts immediately shutting off the fuel supply, and placing in the stop position all the fuel system actuators, resulting in a stop engine operation snapshot.

Previous solutions lead, in the event of a suspected leak on the fuel system, to a sudden and unexpected engine outage for the driver. This loses all possibility of action on the engine and does not can rely more than the vehicle's brakes to stop.

This situation, which is very stressful for the driver, can be extremely dangerous depending on the driving conditions of the vehicle when it occurs for example in the event of overtaking, acceleration, fast driving on the left lane of a highway, bend, etc.

In addition, if the vehicle is equipped with a transmission automatic, it will react to the engine shutdown by uncoupling. The engine will no longer be driven by the vehicle. Systems driving assistance driven by the engine, steering assistance, brake assist, will therefore become inoperative, which will accentuate still the danger of the situation.

Finally, after an engine shutdown caused by the ECU engine check on leak detection, the engine can be restarted, without that its operation is affected by the previous failure. This one can therefore reproduce at any time, without the driver being warned by a particular engine operation.

The object of the present invention is to propose a method of control of an internal combustion engine overcoming the disadvantages known methods.

The object of the present invention is to propose a method of control in which the driver is warned of the fault while leaving him time to stop the vehicle safely satisfactory.

The method of controlling an internal combustion engine of a vehicle, according to the invention, comprises the following steps: detection of a risk of leakage triggers a means of alerting the driver, engine performance limitation, and delayed stop of the motor.

Advantageously, an indicator light is activated indicating a fault in the engine, an indicator light is activated indicating to the driver to stop immediately and deactivate anti-jerk means of the engine.

Advantageously, the power supplied by the motor is limited depending on the time elapsed since the detection of the risk of leakage. We can limit the power supplied by the motor decreasingly by function of the time elapsed since the detection of the risk of leakage. We can limit the power supplied by the motor to a very low value during a fixed duration, so as to cause a noticeable jerk by the driver.

Advantageously, the engine is stopped after a delay predetermined time since the detection of the risk of leakage.

In one embodiment of the invention, the stop is caused of the engine when the fuel pressure in an injection system of the motor becomes below a predetermined threshold.

In one embodiment of the invention, the stop is caused of the engine when the vehicle speed is below a threshold predetermined for a predetermined period.

In one embodiment of the invention, a restart after detecting a risk of leakage and stopping the engine.

In another embodiment of the invention, the engine speed after detection of a risk of leakage and engine shutdown.

In another embodiment of the invention, the engine torque after detecting a risk of leakage and stopping the engine.

The proposed solution allows, upon detection by the system engine check system for a suspected leak in the fuel system, warn the driver, and give him a time and a level of sufficient engine operation to stop the vehicle in improved safety conditions for vehicle passengers and for the external environment.

This solution does not require modifications to the fuel system pressure monitoring and leak detection on this circuit specific to each engine control computer, but only the reaction of the system to the detection of such a fault. She also has no impact on the engine shutdown strategies of each engine control computer.

• d'avertir de façon anticipée le conducteur de l'imminence d'une coupure du moteur
  • par l'allumage immédiat d'un voyant d'alerte (spécifique ou partagé )
  • par un fonctionnement du moteur "dégradé" mais permettant de poursuivre temporairement le roulage
  • par une diminution progressive des performances du moteur
• de lui permettre d'adapter son comportement en conséquence
• en conséquence, de limiter le stress du conducteur et son appréhension vis-à-vis de ce type de défaillance
• de limiter les risques d'incendie du véhicule par :
  • interruption de l'alimentation en carburant du moteur
  • effondrement rapide des niveaux de pression carburant dans le circuit haute pression du moteur
  • éventuellement, déclenchement d'un système d'extinction d'incendie sous capot moteur
• de ne provoquer volontairement la coupure du moteur que, selon la première de ces conditions réalisées :
  • la pression de carburant mesurée dans le circuit haute pression est devenue inférieure, depuis un temps réglable à une valeur de pression réglable (pression minimale permettant l'ouverture des injecteurs)
  • après l'écoulement d'un temps suffisant pour que le conducteur ait pu placer son véhicule dans des conditions de roulage telles qu'une coupure moteur ne le place pas en situation de danger immédiat
  • le véhicule a atteint une telle situation, véhicule arrêté ou roulant à très faible allure
• dans le cas d'un nouveau démarrage du moteur sans réparation préalable, de limiter fortement les performances du moteur, voire d'interdire son démarrage, afin :
  • d'éviter à un conducteur non averti d'utiliser un véhicule potentiellement dangereux dans des conditions d'utilisation non sûres
  • de permettre (selon le choix d'autorisation ou non d'un démarrage sans réparation) au conducteur de rejoindre un garage par ses propres moyens.

The proposed solution allows:

• to warn the driver in advance of the impending engine shutdown
  • by the immediate lighting of a warning light (specific or shared)
  • by an engine operation "degraded" but allowing to temporarily continue driving
  • by a gradual reduction in engine performance
• allow him to adapt his behavior accordingly
• consequently, to limit the stress of the driver and his apprehension vis-à-vis this type of failure
• limit the risk of vehicle fire by:
  • interruption of engine fuel supply
  • rapid collapse of fuel pressure levels in the engine's high pressure system
  • possibly triggering a fire extinguisher system under the engine hood
• to intentionally cause the engine to shutdown only, whichever comes first:
  • the fuel pressure measured in the high pressure circuit has become lower, since an adjustable time to an adjustable pressure value (minimum pressure allowing the opening of the injectors)
  • after sufficient time has passed for the driver to be able to place his vehicle in driving conditions such that an engine shutdown does not place him in an immediate danger situation
  • the vehicle has reached such a situation, vehicle stopped or driving at very low speed
• in the event of a new start of the engine without prior repair, severely limit the performance of the engine, or even prohibit its start, in order to:
  • to prevent an uninformed driver from using a potentially dangerous vehicle under unsafe conditions of use
  • to allow (according to the choice of authorization or not a start without repair) to the driver to join a garage by his own means.

la figure 1 est un schéma de la surveillance du circuit de carburant;

la figure 2 est un schéma de réaction en cas de risque de fuite;

la figure 3 est un schéma de la procédure d'alerte du conducteur;

la figure 4 est un schéma de limitation des performances du moteur;

la figure 5 est un schéma illustrant les conditions de coupure du moteur; et

la figure 6 est un schéma de réaction après mémorisation du risque de fuite.

The present invention will be better understood on studying the detailed description of an embodiment of the invention taken by way of nonlimiting example and illustrated by the appended drawings, in which:

Figure 1 is a diagram of the fuel system monitoring;

FIG. 2 is a diagram of reaction in the event of risk of leakage;

Figure 3 is a diagram of the driver alert procedure;

FIG. 4 is a diagram for limiting the performance of the engine;

Figure 5 is a diagram illustrating the engine shutdown conditions; and

Figure 6 is a reaction diagram after memorizing the risk of leakage.

As can be seen in Figure 1, the control system of the motor includes a high pressure monitoring module capable to output a Boolean value called risk-leakage which describes generically the presence of any fault, detected by the high pressure monitoring module which may indicate a leak on the fuel system. The high pressure monitoring module receives as input the setpoint injection pressure values, measured injection pressure, engine speed, control engine pressure and start. For example, a risk of flight can occur at measured pressure below a pressure minimum or greater than a maximum value, or in the event of a deviation from the regulation loop. The risk-leak-mem value is of boolean type and describes in general terms the presence in memory of a fault corresponding to a risk of leakage.

Figure 2 illustrates the reaction of the system to the presence of a risk of leakage on the engine fuel system (risk of leakage = 1). Thus, upon detection of a risk of leakage, three actions are triggered, a driver alert, see Figure 3, a limitation of the will of the driver and therefore engine performance, see Figure 4, and a engine shutdown procedure caused, see Figure 5.

As can be seen in Figure 3, when the risk-leakage variable takes the value 1, we light a system fault indicator present usually on the vehicle dashboard and indicating a fault of the engine control system. This indicator, depending on the type of control engine and / or the vehicle in question, may or may not be shared with others electronic systems or be multifunctional. This indicator can be used by example in the event of a fault in the injection system and as a warning light preheating.

Depending on the vehicle definition and / or the control system motor, there may also be an alert light, possibly shared with other systems, intended to warn the driver of a danger and request an immediate stop, for example a STOP indicator Red color.

Finally, engine control systems, especially engine with common rail, have strategies aimed at reducing the jolts of the engine. These strategies are immediately inhibited. This allows, if the driver is not looking at his dashboard and / or if the fault indicator system or alert was already on due to another anomaly, warn him of the fault by degraded operation of the engine presenting jolts.

• millivolts de tension liée à la position de la pédale d'accélérateur,
• pourcentage de charge,
• milligrammes de carburant injecté par injection,
• Newtons-mètres.

As can be seen in Figure 4, the time-leakage variable totals the time elapsed since the appearance of the fault, that is, since the risk-leakage variable has taken the value 1. The time- leakage is only reset to 0 after a reset of the engine control computer. The will-driver variable generally designates the driver's desire to accelerate. Depending on the engine control system, it can be expressed as:

• millivolts of voltage linked to the position of the accelerator pedal,
• load percentage,
• milligrams of fuel injected by injection,
• Newton meters.

Depending on the time-leakage variable, a mapping limitation-leakage provides a maximum value which limits the will of the driver. Excluding a fault which could mean a leak, that is to say if the risk-leakage variable is 0, this maximum value is replaced by a Will-max. We can thus physically warn the driver of the presence of a major fault by a complete shutdown or almost complete injection for a short time by limiting the variable Willingness to conduct at a very low or even zero value during a few milliseconds after the appearance of the fault, resulting in a very sudden noticeable, and eventually gradually reduce the engine performance. We therefore benefit from a great flexibility of calibration in the management of this degraded mode.

In other words, in normal operation, risk-leakage = 0, the Willingness-conductor variable is not modified, except when reaching maximum values not to be exceeded related to the engine itself and corresponding to the Will-max variable. In the event of a fault, risk of leakage = 1, engine performance is limited to the limit-leakage value.

• temps après lequel on craint, dans le cas d'une fuite réelle, que le carburant puisse atteindre des parties du véhicule suffisamment chaudes pour provoquer son inflammation;
• temps estimé suffisant pour permettre au conducteur de placer son véhicule dans des conditions de fonctionnement telles qu'une coupure du moteur ne présente pas de risque grave pour les occupants du véhicule et/ou son environnement extérieur.

FIG. 5 illustrates under which conditions the engine control causes, in the event of a risk of leakage, the engine to stop. The engine is stopped when the fault, risk-leakage = 1, has appeared for more than a certain time, that is to say if time-leakage is greater than Tmax-leakage. Tmax-leakage can be calibrated and can be chosen according to different criteria:

• time after which it is feared, in the event of an actual leak, that the fuel may reach parts of the vehicle hot enough to cause ignition;
• time estimated sufficient to allow the driver to place his vehicle in operating conditions such that a shutdown of the engine does not present a serious risk for the occupants of the vehicle and / or its external environment.

• pression minimale en deçà de laquelle les injecteurs ne s'ouvrent plus. En effet, si le système n'est plus capable d'assurer l'injection de carburant, il est inutile de maintenir l'alimentation en carburant, qui ne ferait qu'accroítre le risque d'incendie sans éviter la coupure du moteur.
• pression hors du domaine de fonctionnement du moteur, telle qu'une pression inférieure, en conditions normales de fonctionnement, suppose une fuite très importante sur le circuit de carburant du véhicule.

When the fuel pressure measured in the common rail (pressure-measured) has been lower for more than a certain time Tmax2-leakage to a minimum calibratable value Pmin-injection, the engine is again stopped. The time delay Tmax2-leak makes it possible to get rid of any pressure pulsations in the common rail. The Pmin-injection value can be chosen according to different criteria:

• minimum pressure below which the injectors no longer open. Indeed, if the system is no longer able to provide fuel injection, it is useless to maintain the fuel supply, which would only increase the risk of fire without avoiding engine shutdown.
• pressure outside the engine's operating range, such as lower pressure, under normal operating conditions, presupposes a very significant leak in the vehicle's fuel system.

Finally, the engine is stopped if the measured speed of the vehicle speed-vehicle is lower, for more than a certain time Tmax-stop at a minimum calibratable value Vmin-stop. In the event of a default vehicle speed sensor illustrated by the variable Speed-valid = 0, we toggle the value of the vehicle speed measured Speed-vehicle by a Replacement value Speed-fill, in order to avoid a cut in the high speed motor.

The Tmax-stop delay avoids cutting the motor in case of momentary disturbance of the speed sensor vehicle or in the event of a brief slowdown of the vehicle, for example in the event of wheel lock during braking.

The Vmin-stop value can be chosen according to the speed below which it is considered that an engine shutdown caused is without risk to the occupants of the vehicle and / or its environment or function of the speed below which the vehicle is considered to be stopped.

1°/ refus de gavage du carburant : le circuit d'alimentation en carburant est maintenu inactif, par exemple par maintien à l'arrêt de la pompe électrique à carburant. On interdit donc le démarrage du véhicule. Ce mode dégradé peut être sélectionné par exemple en cas de panne mémorisée de type pression inférieure à une valeur minimale, qui peut résulter d'une très forte fuite. Autoriser l'alimentation en carburant présenterait un risque majeur d'incendie, sans doute sans permettre le démarrage du moteur, la pression risquant d'être inférieure à la pression minimale d'injection.

2°/ ralenti accéléré : la variable Volonté-conducteur est forcée à 0 et le régime de ralenti prend une valeur fixe, ce qui permet au conducteur de rejoindre un garage en roulage lent. Ce mode dégradé peut par exemple être sélectionné en cas de panne mémorisée de type écart de boucle qui peut résulter d'une fuite moyenne. L'utilisation d'un ralenti accéléré permet donc d'autoriser le conducteur à rejoindre un garage par ses propres moyens, en limitant la quantité de carburant émise à l'extérieur, sous réserve que ce carburant ne s'écoule pas en direction de parties chaudes du moteur.

3°/ limitation du couple maximal : la variable Volonté-conducteur est limitée de façon permanente par une valeur maximale en fonction du régime du moteur, ce qui permet au conducteur de rejoindre un garage ou son domicile, dans des conditions de roulage moins sévères que le ralenti accéléré. Ce mode dégradé peut par exemple être sélectionné en cas de panne mémorisée de type surpression. En effet, ce type de panne se produit essentiellement lors d'une demande de pression forte, c'est-à-dire à forte charge.

FIG. 6 illustrates the reaction of the system after memorizing the risk of leakage. This reaction only occurs after the system has been reset. The type-leak-mem variable indicates the type of fault stored, for example on or under pressure, loop deviation, etc. The system fault indicator is kept on in the event of a memorized risk of leak, risk-leak-mem = 1. From the type-leak-mem information, a Tab-mod-deg table selects one of the three degraded modes possible:

1 ° / refusal to refuel the fuel: the fuel supply circuit is kept inactive, for example by keeping the electric fuel pump stopped. It is therefore prohibited to start the vehicle. This degraded mode can be selected for example in the event of a stored failure of the pressure type less than a minimum value, which may result from a very large leak. Authorizing the fuel supply would present a major fire risk, probably without allowing the engine to start, the pressure being likely to be lower than the minimum injection pressure.

2 ° / accelerated idling: the Willing-driver variable is forced to 0 and the idling speed takes a fixed value, which allows the driver to reach a garage when driving slowly. This degraded mode can for example be selected in the event of a memorized failure of the loop deviation type which may result from an average leak. The use of accelerated idling therefore allows the driver to reach a garage on his own, by limiting the quantity of fuel emitted outside, provided that this fuel does not flow towards parts engine heat.

3 ° / limitation of the maximum torque: the Willingness-driver variable is permanently limited by a maximum value depending on the engine speed, which allows the driver to reach a garage or his home, in less severe driving conditions than accelerated idling. This degraded mode can for example be selected in the event of a stored overpressure type failure. Indeed, this type of failure occurs essentially during a request for high pressure, that is to say at high load.

Obviously, if one of these degraded modes is active and one new fault occurs in the fuel pressure monitoring, the previously described strategy applies again.

Claims (9)

1. A control method for an internal combustion engine of a vehicle, in which the detection of a risk of leakage in an injection system of the engine triggers a warning means for the driver, a limitation of the engine performance, and a delayed stoppage of the engine.
2. A method as claimed in claim 1, in which a warning light indicating a defect of the engine is activated, a warning light warning the driver to stop immediately is activated and anti-jolt means of the engine are de-activated.
3. A method as claimed in any one of the preceding claims, in which the power supplied by the engine is limited as a function of the period that has elapsed since the detection of the risk of leakage.
4. A method as claimed in any one of the preceding claims, in which the engine is caused to stop after a predetermined period has elapsed since the detection of the risk of leakage.
5. A method as claimed in any one of the preceding claims, in which the engine is caused to stop when the fuel pressure in an injection system of the engine becomes lower than a predetermined threshold.
6. A method as claimed in any one of the preceding claims, in which the engine is caused to stop when the speed of the vehicle is lower than a predetermined threshold for a predetermined period.
7. A method as claimed in any one of the preceding claims, in which restarting is prohibited after detection of a risk of leakage and stoppage of the engine.
8. A method as claimed in any one of the preceding claims, in which the speed of the engine is limited after detection of a risk of leakage and stoppage of the engine.
9. A method as claimed in any one of the preceding claims, in which the torque of the engine is limited after detection of a risk of leakage and stoppage of the engine.

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