EP2799698A1 - Control method for a powertrain during a transition period of engine play - Google Patents

Abstract

In this control method (100) of a powertrain of a vehicle comprising at least one step (20) for calculating a preventive torque of a heat engine to limit jolts of the powertrain, the preventive torque dependent on a conductive setpoint, this calculation step (20) comprising a traversed state of the motor clearances when said pair is between a first threshold and a second threshold, at least one of the thresholds of the method (100) is defined as a function of a modified setpoint whose value is constant when the calculation step is in the traversed state of the engine sets and which is equal to that of the driver setpoint at the moment of entry into this state.

Description

The present invention relates to a method for controlling a powertrain of a vehicle during a motor grooming phase.

The invention belongs to the field of vehicles comprising a powertrain comprising a heat engine and a transmission disposed between this engine and the wheels of the vehicle.

Such vehicles are equipped with a computer to automatically adapt the operating point of each of the powertrain members, in particular the torque that is provided by the heat engine, in order to comply with a directive from the driver.

The operation of a power train with a combustion engine may be disturbed by engine play. This is a phenomenon of torsion of the transmission between the engine and the wheels that occurs between the moment the engine lands on its holds and the moment when the engine drives the wheels of the vehicle. The phase of crossing of the engine games is defined as the range of torque for which neither the engine nor the wheel trains each other.

In a usual manner, a preventive approval function of the powertrain control system applies a filtering treatment of the torque setpoint resulting from the driver's request. This preventive approval function comprises a state called in the rest of the "traversed state of the engine games", to apply a particular torque setpoint during the crossing phase of the engine games. Thus, it allows to cross these games by avoiding strong jerks of the powertrain.

For example, the state of the art is known from the French patent application FR-2-899-282-A1 which describes a preventive approval function of a control method of a powertrain to avoid such jolts during the crossing games.

The figure 1 illustrated by graphs, the evolution as a function of time expressed in seconds (s), of torque values expressed in Newton-meter (Nm) on the top graph and a driver setpoint expressed in percent (%) on the bottom graph.

In a control method of a known prior art powertrain, as represented by the figure 1 , the state crossed the games The engine of a preventive approval function is determined by comparing a preventive pair Cp with a first threshold S1 and a second threshold S2.

The preventive torque Cp is calculated from a setpoint torque Cc dependent on a driver setpoint Pacc such as the position of an accelerator pedal or an acceleration lever of this vehicle.

When the preventive pair Cp is between the first threshold S1 and the second threshold S2, the preventive approval function is in the traversed state of the engine games.

The first and second thresholds S1 and S2 are in particular defined as a function of the driver set point Pacc. For example, the second threshold S2 can be defined with a value of 10 Nm for a driver instruction corresponding to a depression of 10% of the accelerator pedal, and with a value of 40 Nm for a depression of 50% of this pedal. The intermediate values of the second threshold S2 are determined by continuously interpolating a map of a computer according to the position of the accelerator pedal.

Therefore, when the Pacc instruction driver evolves between a time t1 and an instant t2, respectively corresponding to the input and output times of the traversed state games of this preventive approval function, the first and second thresholds S1 and S2 evolve too.

This method has the disadvantage of extending the duration of the crossed state of the engine games of the preventive approval function in many vehicle life situations, resulting in a limitation (or loss) acceleration of the vehicle, also called hole to acceleration.

The object of the invention is to overcome the drawbacks of the prior art by setting, during the traversing phase of the engine sets, the value of the driver's command value for calculating the first and second thresholds.

For this purpose, the present invention provides a method of controlling a powertrain of a vehicle comprising at least one step of calculating a preventive torque of a heat engine to limit jolts of the powertrain, this couple preventive device dependent on a conductive setpoint, the calculation step thus defined comprising a traversed state of the engine games when the preventive torque is between a first threshold and a second threshold, the method being remarkable in that at least one of these Thresholds is defined according to a modified setpoint whose the value in the traversed state of the motor sets is constant and equal to that of the driver setpoint at the moment of entry into this state.

Thus, the invention allows the value of the thresholds to remain substantially constant in the traversed state of the engine games, which reduces the duration of this state and reduce the holes at acceleration.

According to one particular characteristic, the evolution gradient of the preventive torque is lower in the traversed state of the games of the calculation step mentioned above than outside this state.

According to a particular characteristic, at least one of the thresholds mentioned above is defined by a map whose entry is the modified setpoint.

According to a particular characteristic, at least one of these thresholds is defined by a map whose input is the engine speed.

According to a particular characteristic, at least one of the thresholds is defined by a map whose input is the gear ratio of a transmission of the powertrain.

According to a particular characteristic, the driver setpoint is a position of a pedal or a vehicle acceleration lever.

According to a particular characteristic, the engine runs on gasoline or diesel.

Still for the same purpose, the present invention also proposes a remarkable vehicle in that it comprises means adapted to implement steps of a control method of a powertrain as succinctly described above.

• la figure 1, déjà décrite, représente des graphiques illustrant l'évolution d'une consigne de couple dans une étape de calcul du couple de consigne d'un moteur dans un procédé de commande d'un groupe motopropulseur d'un véhicule selon l'art antérieur ;
• la figure 2 représente un ordinogramme illustrant des étapes de calcul du couple de consigne d'un moteur dans un procédé de commande d'un groupe motopropulseur d'un véhicule selon l'invention ;
• la figure 3 représente des graphiques illustrant l'évolution d'une consigne de couple dans une étape de calcul du couple de consigne d'un moteur dans un procédé de commande d'un groupe motopropulseur d'un véhicule selon l'invention ; et
• la figure 4 représente une machine à états d'un procédé de commande d'un groupe motopropulseur d'un véhicule selon l'invention.

The invention will be better understood and other aspects and advantages will appear more clearly on reading the following description of a particular embodiment, given by way of non-limiting example and with reference to the accompanying drawings. wherein :

• the figure 1 , already described, represents graphs illustrating the evolution of a torque setpoint in a step of calculating the target torque of an engine in a control method of a powertrain of a vehicle according to the prior art;
• the figure 2 represents a flowchart illustrating steps for calculating the target torque of an engine in a control method of a powertrain of a vehicle according to the invention;
• the figure 3 represents graphs illustrating the evolution of a torque setpoint in a step of calculating the target torque of an engine in a control method of a powertrain of a vehicle according to the invention; and
• the figure 4 represents a state machine of a control method of a powertrain of a vehicle according to the invention.

The invention applies to a powertrain of a vehicle comprising a heat engine running on gasoline or diesel fuel (also commonly called diesel) and a transmission disposed between the engine and the vehicle wheels.

The transmission may notably be a gearbox of the type manual gearbox (BVM), automated gearbox (BVA), manual gearbox (BVMP) or gearbox Double Clutch (English "Double Clutch Transmission" or DCT).

A computer of this vehicle makes it possible to automatically adapt the operating point of each of the powertrain members, in particular the torque supplied by the heat engine, in order to respect the driver's instruction.

The figure 2 illustrates the steps of a control method 100 for calculating the target torque of the engine of this powertrain 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.

A first step 10 of the control method 100 consists of interpreting the will of the driver to calculate a setpoint torque Cc as a function of several input data. This input data includes as an example:

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

A second step 20 is a preventive approval function for calculating a specified torque reference Ci.

In this second step 20, the setpoint torque Cc is first filtered to provide a preventive torque Cp to cross the motor games by limiting jolts and to respect a predefined typing more or less dynamic vehicle.

The preventive torque Cp is then converted into a given torque setpoint Ci taking into account a couple of losses of the engine. The loss torque Cpm of the engine generally takes into account the internal mechanical friction of the engine as well as those 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: $$\mathrm{This}=\mathrm{Pc}+\mathrm{CMP}$$

In a third step 30, an optional healing approval function monitors the evolution of the engine speed. This curative amenity function can for example calculate, when the engine speed is oscillating, a correction torque Ccor, in opposition to this oscillation phase. The final torque setpoint Cf of the motor is then equal to the sum of the indicated torque Ci and the corrective torque Ccor: $$\mathrm{Cf}=\mathrm{This}+\mathrm{Ccor}$$

In order to limit jolts during a traversing phase of the engine gears, a particular filtering of the setpoint torque Cc is applied for the calculation of the preventive torque Cp.

The figure 3 illustrated by graphs, the evolution as a function of time expressed in seconds (s), of torque values expressed in Newton-meter (Nm) on the top graph and a Pacc instruction set expressed in percent (%) on the bottom graph.

When the preventive pair Cp is between a first threshold S1 and a second threshold S2, the evolution gradient of the preventive pair Cp is smaller compared to that observed when this pair is outside the range defined by the thresholds S1 and S2. .

To do this, a state machine of the control method 100, for example in step 10 or step 20, provides information on the status of the preventive authorization function of the second step 20.

During the initialization of this state machine, a nonlimiting example of which is illustrated by the figure 4 , the preventive approval function is in the pending state of an acceleration 210.

When the set torque gradient Cc is greater than a predefined threshold ε, the preventive approval function goes to the state before engine games 220.

The transition from the state before engine games 220 to the traversed state of the engine sets 230 occurs when the preventive torque Cp is between the first and second thresholds S1 and S2.

When the preventive approval function is in the traversed state of the engine sets 230, if the preventive torque Cp is greater than the second threshold S2, the function then goes into the state after the engine games 240.

From this state after engine gears 240, the transition to the waiting state of an acceleration 210 is performed when the preventive torque Cp is equal to the setpoint torque Cc.

So, on the graphs of the figure 3 , the preventive approval function is in the pending state of an acceleration 210 until time t0.

At time t0, the driver setpoint Pacc and therefore the setpoint torque Cc increase and the preventive approval function goes into the state before engine games 220.

At time t1, the preventive pair Cp deviates greater than the first threshold S1. The preventive approval function is then in the traversed state of the engine sets 230 until time t2 for which the preventive torque Cp becomes greater than the second threshold S2.

Between instants t1 and t2, the evolution gradient of the preventive torque Cp is then reduced by means of a larger filter applied to the setpoint torque Cc to avoid jolts.

Between instants t2 and t3, one is in the state after engine games 240; at time t3, the preventive torque Cp is equal to the setpoint torque Cc and thus returns to the waiting state of an acceleration 210.

At least one of the first and second thresholds S1 and S2 is defined as a function of a modified setpoint Pacc_f depending on the driver setpoint Pacc.

The first S1 and / or the second threshold S2 may for example also be defined as a function of the Nmot regime of the heat engine and / or the gear ratio Rbv of the transmission.

To simplify the calculation and facilitate the development of the control method 100, a map can for example be used to determine the first threshold S1, the second threshold S2 being defined with respect to the first threshold S1 by means of an offset (in predefined English "offset"). Conversely, it is also possible to use a map to determine the second threshold S2 and to define the first threshold S1 by offset with respect to the second threshold S2.

This offset value is variable according to the heat engines. By way of nonlimiting example, it is possible to choose an offset value of between 1 and 10 Newton-meter (Nm).

Until time t1, the modified setpoint Pacc_f is equal to the value of the Pacc instruction set previously defined. From time t1, the preventive approval of the second step 20 enters the traversed state of the sets 230, the modified setpoint Pacc_f is fixed at a constant value, equal to that of the Pacc instruction setpoint observed at the moment t1. Thus, the values of the first and second thresholds S1 and S2 then vary only very slightly, for example as a function of the Nmot speed of the engine, the dynamic range of which is much slower than that of the Pacc position of the pedal or lever. acceleration.

At time t2, the preventive approval of the second step 20 exits the traversed state of the sets 230 and the modified setpoint Pacc_f then becomes equal to the current value of the driver setpoint Pacc.

Thus, the implementation of the method according to the invention makes it possible to reduce the duration of the traversed state of the engine games 230 of the preventive approval function, which reduces the holes during acceleration.

Claims (8)

A method (100) for controlling a power unit of a vehicle comprising at least one step (20) for calculating a preventive torque (Cp) of a heat engine to limit jolts of the powertrain, said torque (Cp) dependent on a conductive setpoint (Pacc), said step (20) having a traversed state of the motor sets (230) when said pair (Cp) is between a first threshold (S1) and a second threshold (S2) , said method (100) being characterized in that at least one of said thresholds (S1, S2) is defined as a function of a modified setpoint (Pacc_f) whose value in said traversed state of the engine sets (230) is constant and equal to that of said driver setpoint (Pacc) at the instant (t1) of entry into this state (230). Control method according to claim 1, characterized in that the evolution gradient of said preventive torque (Cp) is lower in said state through games (230) of said step (20) than outside this state. Control method (100) according to claim 1 or 2, characterized in that at least one of said thresholds (S1, S2) is defined by a map whose input is said modified setpoint (Pacc_f). Control method (100) according to any one of the preceding claims, characterized in that at least one of said thresholds (S1, S2) is defined by a map whose input is the speed (Nmot) of said motor. Control method (100) according to any one of the preceding claims, characterized in that at least one of said thresholds (S1, S2) is defined by a map whose input is the gear ratio (Rbv) of a transmission said power train. Control method (100) according to any one of the preceding claims, characterized in that said driver setpoint (Pacc) is a position of a pedal or a vehicle acceleration lever. Control method (100) according to any one of the preceding claims, characterized in that the engine runs on gasoline or diesel. Vehicle characterized in that it comprises means adapted to implement steps of a control method (100) according to any one of the preceding claims.

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