FR2786813A1 - METHOD FOR CONTROLLING AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

Method for controlling an internal combustion engine of a vehicle, in which the detection of a risk of leakage triggers a means of alerting the driver, a limitation of the performance of the engine, and a delayed stop of the engine.

Description

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  Method of controlling an internal combustion engine.

  The present invention relates to the field of methods for controlling internal combustion engines, in particular engines equipped

  a high pressure fuel injection system.

  The injection systems for so-called "common rail" engines integrate pipes containing fuel at very high pressure levels, from one to several hundred bars. A fuel leak on these circuits by failure of one of the components resulting in a leak or overpressure liable to generate a leak, therefore presents a serious risk for the user of untimely stopping of the engine and / or of vehicle fire. It is therefore necessary, if this type of problem occurs, to be able to quickly inform the driver and to stop the fuel supply and consequently the vehicle while maintaining as much safety as possible for its passengers and for its

outdoor environment.

  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 garage mechanic and erasing of the memorized fault, the performances of the engine in order: * to encourage the user to have his vehicle checked quickly, * to oblige him, 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 to

  vehicle occupants and the environment.

  The injection systems known for common rail engines have strategies for monitoring the pressure prevailing in the

fuel system.

  If these strategies reveal a fault, the computer reacts by immediately interrupting the fuel supply, and by placing all the actuators of the fuel circuit in the off position, leading to a stop

  engine operation snapshot.

  The previous solutions lead, in the event of a suspected leak in 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 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, rapid driving on the left lane of a highway, cornering, etc. In addition, if the vehicle is equipped with an automatic transmission, it will react to the engine shutdown by uncoupling. The engine will therefore no longer be driven by the vehicle. The driving assistance systems driven by the engine, steering assistance, braking assistance, will therefore become inoperative, which will accentuate

still the danger of the situation.

  Finally, after an engine shutdown caused by the engine control computer on leak detection, the engine can be restarted, without

  that its operation is affected by the previous failure. That-

  it can therefore happen again at any time, without the driver being

  warned by a particular operation of the engine.

  The object of the present invention is to propose a method for controlling an internal combustion engine overcoming the drawbacks

known methods.

  The object of the present invention is to propose a control method in which the driver is warned of the fault while giving him time to stop the vehicle under satisfactory safety conditions. The method of controlling an internal combustion engine of a vehicle, according to the invention, comprises the following steps: the detection of a risk of leakage triggers the triggering of a means of alerting the driver! engine performance limitation, and delayed stop

of the motor.

  Advantageously, an indicator light indicating an engine fault is activated, an indicator light is activated indicating to the driver to stop immediately, and anti-jolting means of the engine are deactivated. Advantageously, the power supplied by the motor is limited as a function of the time elapsed since the detection of the risk of leakage. We can limit the power supplied by the engine decreasingly depending on the time elapsed since the detection of the risk of leakage. It is possible to limit the power supplied by the engine to a very low value for a determined 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 engine is stopped when the fuel pressure in a fuel injection system

  motor becomes below a predetermined threshold.

  In one embodiment of the invention, the engine is stopped 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 limit is

  engine speed after detection of a risk of leakage and engine shutdown.

  In another embodiment of the invention, the limit is

  engine torque after detecting a risk of leakage and stopping the engine.

  The solution proposed makes it possible, when the engine control system detects a suspected leak in the fuel system, to warn the driver, and to allow him sufficient time and engine operation to stop his vehicle. in improved safety conditions for vehicle passengers and for

the external environment.

  This solution does not involve modifications to the fuel system pressure monitoring and leak detection strategies specific to each engine control computer, but

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  only the reaction of the system to the detection of such a fault. It also has no impact on the engine stopping strategies of each

engine control computer.

  The proposed solution allows * to warn the driver in advance of an imminent engine shutdown by the immediate lighting of a warning light (specific or shared) À by "degraded" engine operation but allowing to temporarily continue driving by a gradual reduction in engine performance * allowing him to adapt his behavior accordingly * consequently, limiting the stress of the driver and his apprehension vis-à-vis this type of failure * limit the risk of vehicle fire by Interrupting the fuel supply to the engine Rapid collapse of the fuel pressure levels in the high pressure engine circuit 20. possibly triggering a fire extinguishing system under engine cover * to intentionally cause engine shutdown only, whichever comes first: the fuel pressure measured in the high pressure circuit is become lower, from an adjustable time to an adjustable pressure value (minimum pressure allowing the opening of the injectors) after the passage of a time sufficient for the driver to be able to place his vehicle in driving conditions such as engine shutdown does not place it in an immediate danger situation the vehicle has reached such a situation, vehicle stopped or running at very low speed * in the event of a new engine start without prior repair, to severely limit engine performance, see

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  to prohibit starting, in order to avoid an uninformed driver from using a potentially dangerous vehicle under unsafe conditions of use 5. to allow (depending on the choice of authorization or not a start without repair) the driver to join

a garage on its own.

  The present invention will be better understood on studying the

  detailed description of an embodiment of the invention taken as

  of nonlimiting example and illustrated by the appended drawings, in which: FIG. 1 is a diagram of the monitoring of the fuel circuit; 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 FIG. 6 is a reaction diagram after memorization of the

risk of leakage.

  As can be seen in Figure 1, the engine control system includes a high pressure monitoring module capable of outputting a Boolean value called risk-leak which describes generically the presence of any failure , detected by the high pressure monitoring module and which could indicate a leak in the fuel system. The high pressure monitoring module receives as input the set injection pressure, measured injection pressure, engine speed, pressure control and engine start values. For example, a risk of leakage can occur in the event of a measured pressure below a minimum pressure or above a maximum value, or in the event of deviation from the regulation loop. The risk-leak-mem value is of boolean type and describes generically the presence in memory of a failure

  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 driver's will and therefore of engine performance, see Figure 4, and a

  engine shutdown procedure caused, see Figure 5.

  As can be seen in Figure 3, when the variable risk-

  leak takes the value 1, a system fault warning light is generally present on the vehicle dashboard and indicates a failure of the engine control system. This indicator, depending on the type of engine control and / or the vehicle considered, may or may not be shared with other electronic systems or be multifunctional. This warning light can be used for example in the event of a fault in the injection system and as a warning light

preheating.

  Depending on the definition of the vehicle and / or the engine control system, an alert light may also be provided, possibly shared with other systems, intended to warn the driver of a danger and ask him to stop immediately, for example a STOP indicator of

Red color.

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

jolts.

  As can be seen in Figure 4, the time-leakage variable totals the time since the appearance of the fault, that is to say 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 in: - millivolts of voltage linked to the position of the accelerator pedal, - load percentage, milligrams of fuel injected by injection,

- Newtons-meters.

  Depending on the time-leakage variable, a limitation-leakage map provides a maximum value which limits the driver's wishes. Excluding a fault that could mean a leak, that is to say if the risk-leakage variable is 0, this maximum value is replaced by a Will-max calibratable value. We can thus physically warn the driver of the presence of a major fault by a complete or almost complete cut of the injection for a short time by limiting the Will-conductor variable to a very low or even zero value for a few milliseconds after l 'appearance of the fault, suddenly very noticeable, and eventually gradually reduce the performance of the engine. We therefore benefit from a great flexibility of

  calibration in the management of this degraded mode.

  In other words, in normal operation, risk of leakage = 0, the Willingness-driver variable is not modified, except when reaching maximum values not to be exceeded linked to the engine itself and corresponding to the Willingness variable. max. In the event of a fault, risk of leakage =

  1, engine performance is limited to the limit-leakage value.

  FIG. 5 illustrates under what conditions the engine control causes the engine to stop in the event of a risk of leakage. The engine is stopped when the fault, risk-leakage = 1, has appeared for more than one

  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 various criteria: time after which it is feared, in the case of an actual leak, that the fuel may reach parts of the vehicle hot enough to cause its ignition; - time estimated sufficient to allow the driver to place his vehicle in operating conditions such that a shutdown of the engine does not pose a serious risk for the occupants of the vehicle

and / or its external environment.

  When the fuel pressure measured in the common rail (measured pressure) has been lower for more than a certain time Tmax2-leakage to a minimum calibratable value Pmin-injection, we

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  again causes the engine to stop. 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 the

engine shutdown.

  - pressure outside the engine operating range, such as lower pressure, under normal operating conditions,

  supposes a very significant leak on 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 calibrable value Vmin-stop. In the event of a fault in the vehicle speed sensor illustrated by the variable Speed-valid = 0, the value of the vehicle speed measured Speed-vehicle is toggled with a replacement value Speed-fill, in order to avoid cutting the

high speed motor.

  The Tmax-stop delay makes it possible to avoid stopping the engine in the event of a temporary disturbance of the vehicle speed sensor or in the event of a brief slowdown of the vehicle, for example in the event of

  wheel lock during braking.

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

  memorized, risk-leakage-mem = 1. From the type-leakage information-

  mem, a Tab-mod-deg table selects one of the three degraded modes

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  possible 1 / refusal to refuel the fuel: the fuel supply circuit is kept inactive, for example by keeping the

  electric fuel pump. 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 pressure

minimum injection.

  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 amount of fuel emitted outside, provided that this fuel does not flow towards parts

engine heat.

  3 / limitation of the maximum torque: the Will variable -

  driver 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 fault of the overpressure type. Indeed, this type of failure mainly occurs during a high pressure demand, that is to say

at high load.

  Obviously, if one of these degraded modes is active and a new fault occurs in the fuel pressure monitoring, the

  previously described strategy applies again.

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Claims (9)

  1. Method for controlling an internal combustion engine of a vehicle, in which the detection of a risk of leakage triggers a means of alerting the driver, a limitation of   engine performance, and delayed engine shutdown.   2. Method according to claim 1, in which an indicator light is activated indicating an engine fault, an indicator light is activated indicating   driver to stop immediately and deactivate anti-to- engine knocks.   3. Method according to any one of the claims   above, in which the power supplied by the motor is limited by   function of the time elapsed since the detection of the risk of leakage.   4. Method according to any one of the claims   previous, in which the engine is stopped after a delay   predetermined time since the detection of the risk of leakage.   5. Method according to any one of the claims   above, in which the engine is stopped when the fuel pressure in an engine injection system falls below a predetermined threshold.   6. Method according to any one of the claims   above, in which the engine is stopped when the vehicle speed is below a predetermined threshold for a predetermined period.   7. Method according to any one of the claims   previous, in which a restart is prohibited after detection of a   risk of engine leakage and stopping.   8. Method according to any one of claims   previous, in which the engine speed is limited after detection   risk of engine leakage and shutdown.   9. Method according to any one of the claims   previous, in which the torque of the motor is limited after detection   risk of engine leakage and shutdown.