EP3207238B1 - Method for interrupting the injection of fuel to an internal combustion engine - Google Patents

Description

Technical field of the invention

The present invention relates to the control of internal combustion engines. The invention relates more particularly to a method for cutting off the injection of fuel into an internal combustion engine in a decelerating vehicle.

The invention applies to the field of command control of vehicles fitted with a petrol or diesel thermal powertrain (GMP) with a manual (BVM), automated (BVA), piloted (BVMP) or double clutch (DCT).

The figure 1 shows schematically the powertrain fitted to a vehicle. The powertrain includes a heat engine 1. On the figure 1 , the heat engine is connected to a transmission 2 conventionally comprising a gearbox and a clutch device of which only a connecting element with the engine 1 is presented. The heat engine can be petrol or diesel. The gearbox can be manual (BVM), automated (BVA), piloted (BVMP) or dual clutch (DCT). Transmission 2 ensures the transfer of a torque generated by the engine to the wheels, not shown. The heat engine 1 is conventionally placed on engine spacers 3. Engine torque is called the torsional phenomenon 4 of the transmission elements 2 between the moment when the heat engine 1 lands on its shims 3 and the moment when the heat engine drives the wheels during acceleration transients.

In other words, the engine clearances are the tilting of the heat engine 1 on its wedges 3 during the acceleration transients. There is always a motor tilt when torque is applied when there was none, for example during an acceleration request from a so-called `` off the cuff '' situation, i.e. without depressing the accelerator pedal, or when decelerating when the foot is lifted completely. The engine clearances thus correspond to the applied torque for which neither the heat engine nor the wheel drive with each other during a transient acceleration phase.

Such vehicles are equipped with a computer making it possible to automatically adapt the operating point of each of the components of the vehicle, in particular the heat engine, in order to comply with the driver's wishes in terms of the torque required and obtain approval for determined conduct.

To obtain optimal driving pleasure, the computer conventionally implements two types of filtering of the torque requested by the driver, carried out using a first filter module called preventive of the engine torque and a second filter module of the motor torque says curative.

The first preventive filtering module filters a setpoint torque corresponding to the driver's wishes in order to pass the engine clearances by limiting the jolts of the traction chain as much as possible.

The second curative filter module makes it possible to attenuate any oscillations in the engine speed resulting from the passage of the engine clearances in acceleration and deceleration. To this end, it generates a corrective torque in phase opposition with the engine speed oscillation.

Thus during deceleration, the second curative filter module attenuates the oscillations of the speed during the passages of engine clearances. For this attenuation not to be perceptible by the driver, this phase would have to last several seconds. However, for reasons of fuel economy, a compromise must be made between a curative correction and a reasonable filtering time. This can therefore degrade the driving pleasure felt by the customer where the duration is reduced compared to the optimal.

The Figures 2a, to 2d illustrate this phenomenon during a deceleration phase. When the driver releases the accelerator pedal ( Figure 2a , at t0), the preventive torque ( figure 2c ) provides filtering during the passage of the engine clearances. At the end of the filtering, the injection is cut off (this instant is shown in the four figures by the axis 5 in dotted lines), which allows fuel savings. However, the tilting of the motor being so strong that rebounds 6, 6 '( figure 2b ) are to be filtered. A healing couple ( figure 2d ) in phase opposition with the engine speed is thus applied in order to attenuate the oscillations resulting from the tilting of the engine. In the interests of fuel economy, a compromise is made between preventive and curative approval in order to minimize oscillations in the system. However, rebounds of the order of 50 to 100 rpm on the engine speed may then remain, degrading the pleasure for the driver. In addition, this compromise is often difficult to find and the filtering can then last for several seconds, which consumes a great deal of fuel to obtain nominal approval.

We also know of the document JP2005171942A a process according to the preamble of claim 1.

There is therefore a need to maintain nominal approval while greatly reducing fuel consumption during deceleration.

Consequently, the problem underlying the invention is to propose a strategy making it possible to maintain nominal driving pleasure while greatly reducing the fuel consumption during the vehicle's deceleration phase.

1. a) une étape détection d'une demande de décélération du véhicule,
2. b) une étape de détermination d'un couple curatif destiné à atténuer les oscillations du régime moteur pendant la décélération en générant un couple correctif en opposition de phase avec l'oscillation de régime moteur et qui commence toujours par une phase croissante,
3. c) une étape de détection du premier maximum de couple curatif, et suite à la détection de ce premier maximum de couple curatif,

caractérisé en ce qu'il comprend :

• une étape de détermination d'un couple préventif destiné à limiter le basculement du moteur sur ses cales,
• une étape de détection de l'atteinte d'un seuil prédéterminé de couple préventif qui indique que le moteur débute son basculement sur ses cales,

l'étape c) de détection du premier maximum de couple curatif étant initiée que lorsque le seuil prédéterminé de couple préventif est atteint,
d) une étape de demande de coupure d'injection dès que, suite à ce premier maximum le couple curatif atteint une valeur proportionnelle à ce premier maximum de couple curatif.To solve this problem, there is provided according to the invention a method for cutting off the injection of fuel into an internal combustion engine on a vehicle in the deceleration phase comprising:

1. a) a step of detecting a request for deceleration of the vehicle,
2. b) a step of determining a curative torque intended to attenuate the oscillations of the engine speed during deceleration by generating a corrective torque in phase opposition with the engine speed oscillation and which always begins with an increasing phase,
3. c) a step of detecting the first maximum of the healing couple, and following the detection of this first maximum of the healing couple,

characterized in that it comprises:

• a step of determining a preventive torque intended to limit the tilting of the engine on its chocks,
• a step of detecting the reaching of a predetermined threshold of preventive torque which indicates that the engine is starting to tilt on its chocks,

step c) of detecting the first maximum curative torque being initiated only when the predetermined threshold of preventive torque is reached,
d) an injection cut-off request step as soon as, following this first maximum, the healing torque reaches a value proportional to this first maximum of healing torque.

The technical effect is to authorize the injection cut before the end of the preventive approval, which allows a gain in fuel, while choosing during deceleration the appropriate moment so that the approval is satisfactory.

Preferably, the proportional value is established with a proportionality factor of between 1 and -1.

More preferably, the proportional value of curative torque is established with a proportionality factor between 0.75 and -0.5.

More preferably, the proportional value of curative torque is established with a proportionality factor equal to 0.5.

• une étape de détermination d'un couple préventif destiné à limiter le basculement du moteur sur ses cales,
• une étape de détection de l'atteinte d'un seuil prédéterminé de couple préventif qui indique que le moteur débute son basculement sur ses cales,

l'étape c) de détection du premier maximum de couple curatif étant initiée que lorsque le seuil prédéterminé de couple préventif est atteint.In a variant, the engine being placed on wedges, the method comprises:

• a step of determining a preventive torque intended to limit the tilting of the engine on its chocks,
• a step of detecting the reaching of a predetermined threshold of preventive torque which indicates that the engine is starting to tilt on its chocks,

step c) of detecting the first maximum curative torque being initiated only when the predetermined threshold of preventive torque is reached.

In a variant, the engine being coupled to a transmission, the preventive torque follows a predetermined decreasing trajectory, which is defined from a trajectory with three successive slopes, as a function of the engine speed and of the gear ratio engaged. Preferably this predetermined decreasing trajectory is defined by three successive linear slopes.

In a variant, the start of the third slope corresponds to the predetermined threshold of preventive torque.

In a variant, the method includes a step of verifying that the detected deceleration request corresponds to a request for total deceleration of the vehicle.

The invention also relates to an internal combustion engine comprising a computer comprising the acquisition, processing and control means required for implementing a method according to any of the variants described above.

The invention also relates to a vehicle comprising an internal combustion engine of the invention.

Brief description of the drawings

• La figure 1 est une représentation schématique d'un moteur thermique relié à un élément transmission.
• La figure 2a, 2b, 2c, 2d sont des chronogrammes illustrant au cours d'une décélération l'évolution simultanée en fonction du temps respectivement de la consigne de pédale d'accélérateur, du régime moteur, du couple préventif et du couple curatif, selon l'art antérieur.
• La figure 3 une représentation schématique un système de gestion de la commande en couple d'un moteur thermique selon l'invention.
• Les figures 4a à 4d sont des chronogrammes illustrant au cours d'une décélération l'évolution simultanée en fonction du temps respectivement de la consigne de pédale d'accélérateur, du régime moteur, du couple préventif et du couple curatif, selon l'invention.

Other particularities and advantages will appear on reading the following description of a particular, non-limiting embodiment of the invention, made with reference to the figures in which:

• The figure 1 is a schematic representation of a heat engine connected to a transmission element.
• The figure 2a, 2b, 2c, 2d are chronograms illustrating during a deceleration the simultaneous evolution as a function of time respectively of the accelerator pedal setpoint, the engine speed, the preventive torque and the curative torque, according to the prior art.
• The figure 3 a schematic representation of a system for managing the torque control of a heat engine according to the invention.
• The figures 4a to 4d are chronograms illustrating during a deceleration the simultaneous evolution as a function of time respectively of the accelerator pedal setpoint, the engine speed, the preventive torque and the curative torque, according to the invention.

detailed description

The invention applies to a powertrain of a vehicle comprising an internal combustion engine operating on petrol or diesel (also commonly known as Diesel) and a transmission disposed between this engine and the wheels of the vehicle. The internal combustion engine is placed on blocks which support it.

The transmission can in particular be a manual gearbox (BVM), automatic gearbox (BVA), manual piloted gearbox (BVMP) or double clutch gearbox. or DCT).

A computer in this vehicle makes it possible to automatically adapt the operating point of each of the powertrain members, in particular the torque supplied by the internal combustion engine, in order to comply with the driver's instructions. Concretely, when the driver presses the accelerator pedal, a torque is calculated according to the engine speed and the gearbox engaged. The computer comprises the acquisition, processing and control means required for implementing the method of the invention detailed below.

The figure 3 presents a system 10 for managing the torque control of an internal combustion engine integrated in the computer. This system 10 includes a module 11 for interpreting the driver's wishes, a module 12 for preventive approval, as well as a module 13 for conversion to the indicated torque and a module 14 for curative approval interacting with a decision module 15 injection cutoff.

The figure 3 with the figures 4a to 4d illustrate the steps of a process for cutting off the fuel injection of an internal combustion engine for a decelerating vehicle according to the invention.

• une consigne conducteur Pacc, telle que par exemple la position d'une pédale ou d'un levier d'accélération du véhicule,
• un régime Nmot du moteur thermique,
• un rapport Rbv de démultiplication de la transmission.

The first step of the method, carried out here in module 11, therefore consists in detecting a request for deceleration of the vehicle by the driver. On the figure 4a , the deceleration request begins at time t0. A setpoint torque Cc is then calculated as a function of several input data making it possible to interpret the driver's wishes. This input data includes by way of example:

• a driver instruction Pacc, such as for example the position of a pedal or of a vehicle acceleration lever,
• an Nmot engine speed,
• an Rbv transmission reduction ratio.

The next step, carried out in module 12, is to filter the setpoint torque Cc calculated in module 11 to determine a preventive torque Cp making it possible to cross the engine clearances by limiting jolts and to respect a more or less dynamic predefined typing of the vehicle. Thus, in the event of a deceleration request, for example by lifting the driver's foot, the calculated preventive torque Cp makes it possible to carry out a phase of progressive adaptation of the actual engine torque to the setpoint torque, Cc, from the moment of the request deceleration (at t0 on the figure 4a ), according to a predetermined trajectory as a function of the gearbox ratio, Rbv and of the Nmot regime.

The preventive torque Cp can be determined from a map stored in the computer which establishes this torque as a function of the driver's instruction, Pacc, the engine speed Nmot, and the gear engaged, Rbv.

In the next step, performed in module 13, the preventive torque Cp is then converted into a torque setpoint indicated Ci by taking into account a couple of losses from the heat engine. The torque loss Cpm from the engine is the minimum torque necessary to move the vehicle forward. The torque loss Cpm generally takes into account the internal mechanical friction of the engine as well as that of accessories, such as an alternator, linked to the engine.

The indicated torque Ci is equal to the sum of the preventive torque Cp and the loss torque Cpm of the heat engine: $$\mathrm{This}=\mathrm{Cp}+\mathrm{Cpm}$$

In the next step, performed in module 14, a curative approval function monitors the evolution of the engine speed, Nmot. This curative approval function determines, when the engine speed oscillates, a corrective torque, Ccor, intended to attenuate the oscillations of the engine speed, the evolution of the corrective torque being in phase opposition with this engine speed oscillation. The final torque setpoint Cf of the motor is then equal to the sum of the indicated torque Ci and the corrective torque Ccor: $$\mathrm{Cf}=\mathrm{This}+\mathrm{Ccor}$$

The final torque, Cf, is then converted into a command for the various injection members (quantity to be injected, injection pressure, etc.).

In principle, the invention makes it possible, during a request for total deceleration, to cut off the injection at a determined moment during the clearance passage phase, in other words during the engine tilting phase on its chocks, before preventive approval is completed to save fuel while maintaining satisfactory driving pleasure for the customer. In practice, in the case of a deceleration with lifted foot, the preventive approval is considered to be terminated when the preventive torque, Cp, has joined the engine loss torque, since we are in effective torque which corresponds to a specified torque Ci (motor torque) equal to 0.

Advantageously, to avoid false detections, we first check the achievement of certain conditions:
A first condition is to verify that the detected deceleration request corresponds to a request for total deceleration of the vehicle. To this end, it is verified that the driver setpoint, which is between a minimum setpoint and a maximum setpoint (for example 0 to 100%) Pacc, is less than a threshold S1 (cf. figure 4a ) suitable to be sure that the driver's wishes correspond to a request total deceleration. For example, in the case where the driver's instruction indicates the position of an accelerator pedal, the threshold is chosen so as to confirm that the driver has his foot raised from this pedal. On the figure 4a , the threshold S1 is reached at time t1. The threshold S1 may for example be 2% of the maximum setpoint, but depending on the vehicle, the type of sensor, etc. this can vary to 3% or 4%.

A second condition is to verify that the preventive torque has reached a determined threshold S2 (cf. figure 4c ) which indicates that the engine begins to tilt on its chocks, in other words that we are at the beginning of the passage of the engine clearances. On the figure 4c , the threshold S2 is reached at time t2. For an automotive application, the threshold S2 of preventive torque between may be between 5 and 10 Nm, and rather 5 Nm on petrol, and rather 10 Nm on diesel.

The threshold S2 can be easily predefined if the preventive torque Cp itself follows a predetermined decreasing trajectory. As illustrated in the figure 4c , the trajectory of the preventive torque Cp is for example advantageously defined as a function of the engine speed, Nmot, and of the gear transmission engaged, Rbv, from a decreasing trajectory at three successive slopes. In this example, the start of the portion of the third slope corresponds to the predetermined threshold S2.

From the moment when these two conditions are preferably satisfied, the examination of the value of the healing couple, Ccor, is initiated in order to determine when to cut the injection. Indeed, thanks to the oscillations of the curative torque, we can determine the moment when the engine will rock on its chocks. Cutting the injection at this time allows it to remain on its holds and therefore to avoid rebounds which are harmful for the pleasure of driving.

• suivre l'évolution du couple curatif, Ccor ; pour détecter le premier maximum de couple curatif, Ccormax. Sur la figure 4d le premier maximum de couple curatif, Ccormax, est détecté à l'instant t3, postérieur à t1 et t2 (cf. figure 4d). On recherche un maximum car le couple curatif, Ccor, commence toujours par une phase croissante. Le couple curatif, Ccor, est « l'image » en opposition de phase du régime moteur, or puisque que l'on est en décélération, le régime décroit donc le couple curatif augmente.
• mémoriser la valeur de ce premier maximum de couple curatif, Ccormax.
• demander la coupure d'injection dès que, suite à ce premier maximum de couple, Ccormax, le couple curatif Ccor atteint une valeur proportionnelle à ce premier maximum de couple curatif, Ccormax.

More precisely, from the moment when the two aforementioned conditions are verified, the process comprises the steps consisting in:

• follow the evolution of the healing couple, Ccor; to detect the first maximum healing torque, Ccormax. On the figure 4d the first maximum of curative torque, Ccormax, is detected at time t3, after t1 and t2 (cf. figure 4d ). We are looking for a maximum because the healing couple, Ccor, always begins with an increasing phase. The healing torque, Ccor, is the “image” in phase opposition of the engine speed, but since we are decelerating, the speed therefore decreases the healing torque increases.
• memorize the value of this first maximum curative torque, Ccormax.
• request the injection cutoff as soon as, following this first maximum of torque, Ccormax, the healing torque Ccor reaches a value proportional to this first maximum of healing torque, Ccormax.

The proportional value is established with a proportionality factor between 1 and -1. A value close to 1 promotes consumption gain at the expense of pleasure while a value close to -1 favors driving pleasure at the expense of consumption gain.

Because it can be advantageous not to cut the injection at the same time as passing the maximum curative torque, while having a good compromise between driving pleasure and the gain in consumption thanks to the injection cut, the proportional value can be established with a proportionality factor between 0.75 and -0.5.

The best compromise between driving pleasure and fuel consumption thanks to the injection cut-off is achieved with a proportionality factor equal to 0.5.

The invention makes it possible to cut the injection during the passage of the games in the deceleration phase so that the engine remains on its chocks. This has the effect of preventing the motor from bouncing on its chocks and therefore generating rebounds. Consequently, filtering of preventive and curative approval is no longer necessary and a gain in fuel consumption of the order of 0.5 to 1 second is possible.

The invention improves driving pleasure and the performance of the vehicle during transient deceleration phases for a vehicle equipped with a thermal powertrain.

The invention does not entail any additional material cost.

Claims (9)

1. A method for interrupting the injection of fuel to an internal combustion engine in a vehicle during a deceleration phase, the engine being placed on blocks, including:

   a) a detection step of a request to decelerate the vehicle,

   b) a step of determining a corrective torque (Ccor) intended to attenuate the oscillations of the engine speed during the deceleration by generating a corrective torque in phase opposition with the oscillation of the engine speed and which always begins by an increasing phase,

   c) a step of determining a preventive torque (Cp) intended to limit the rocking of the engine on its blocks,

   d) a detection step of the reaching of a predetermined threshold (S2) of preventive torque (Cp) which indicates that the engine is starting its rocking on its blocks,

   e) a detection step of the first maximum corrective torque (Ccormax), this detection step of the first maximum corrective torque (Ccormax) being initiated when the predetermined threshold (S2) of preventive torque is reached, and following the detection of this first maximum corrective torque (Ccormax),

   f) a step of requesting the interruption of the injection as soon as, following this first maximum, the corrective torque (Ccor) reaches a value proportional to this first maximum corrective torque (Ccormax).
2. The method according to Claim 1, in which the proportional value is established with a proportionality factor comprised between 1 and -1.
3. The method according to Claim 2, in which the proportional value is established with a proportionality factor comprised between 0.75 and -0.5.
4. The method according to Claim 3, in which the proportional value is established with a proportionality factor equal to 0.5.
5. The method according to one of the preceding claims, the engine being coupled to a transmission, characterized in that the preventive torque (Cp) follows a predetermined decreasing trajectory, which is defined from a trajectory with three successive linear gradients, as a function of the speed of the engine (Nmot) and of the engaged transmission ratio (Rbv).
6. The method according to the preceding claim, characterized in that the start of the third gradient corresponds to the predetermined preventive torque threshold (S2).
7. The method according to any one of the preceding claims, characterized in that it includes:

   - a step of verification that the detected deceleration request corresponds to a total deceleration request of the vehicle.
8. An internal combustion engine, characterized in that it includes a computer including the means for acquisition, processing and command required for implementation of a method according to any one of the preceding claims.
9. A vehicle, characterized in that it includes an internal combustion engine according to the preceding claim.

Images