FR3110638A1 - PROCEDURE FOR REPOSITIONING A THERMAL ENGINE CRANKSHAFT BEFORE RE-STARTING - Google Patents

Abstract

The invention relates to a method for controlling a hybrid drive train (10) of a motor vehicle comprising at least: a step of verifying a condition according to which a speed of the motor vehicle is greater than a threshold of configurable speed, - a step of checking a condition according to which an available level of electrical energy is greater than a threshold allowing an electrical machine (12, 14) to restart the heat engine (11), - a step of verifying a condition according to which an angular position of the crankshaft is located outside at least one optimal angular range (A, B) for which a starting time of the heat engine (11) is minimized, and - if the preceding conditions are satisfied, a step of controlling the electric machine (12, 14) so as to move the crankshaft of the heat engine (11) in the optimum angular range (A, B). Figure 1

Description

METHOD FOR REPOSITIONING A THERMAL ENGINE CRANKSHAFT BEFORE RE-STARTING

The present invention relates to a method for repositioning a heat engine crankshaft before restarting. The invention finds a particularly advantageous, but not exclusive, application with motor vehicle hybrid powertrains.

In a manner known per se, a motor vehicle hybrid traction chain comprises a heat engine and an electric traction motor mounted on a train of the motor vehicle, in particular a front train fitted with wheels.

A clutch, called engine interconnection clutch, is interposed between the heat engine and an electric traction motor. The electric traction motor is connected to a primary shaft of a gearbox. A secondary shaft of the gearbox is connected to the wheels of the vehicle via a differential. The electric traction motor may be integrated inside a casing of the gearbox.

The engine interconnection clutch can pass from an open state in which the electric traction motor is decoupled from the heat engine, to a closed state in which the electric traction motor is coupled to the heat engine. In the open state, the clutch makes it possible to isolate the electric traction motor with respect to the heat engine when the electric motor ensures traction of the vehicle in an electric driving mode. The clutch is closed in a thermal driving mode or a hybrid driving mode.

The document FR2806757 teaches a process for positioning the crankshaft of the heat engine in a stop position facilitating the restarting of the heat engine. The invention aims to improve this method in the context of its application to a hybrid traction chain in order to facilitate the restarting of the heat engine when the traction chain will again need said heat engine to ensure the traction of the vehicle alone or in combination with the electric traction motor.

To this end, the subject of the invention is a method for controlling a hybrid traction chain of a motor vehicle comprising a heat engine equipped with a crankshaft and an electric machine, the motor vehicle operating in an electric traction mode. while the heat engine is stopped and awaiting restart, said method comprising at least:
- a step of verifying a condition according to which a speed of the motor vehicle is greater than a configurable speed threshold,
- a step of verifying a condition according to which a level of electrical energy available is greater than a threshold allowing an electric machine to ensure a restart of the heat engine,
- a step of verifying a condition according to which an angular position of the crankshaft is located outside at least one optimum angular range for which a starting time of the heat engine is minimized, and
- if the previous conditions are verified, a step of controlling the electric machine so as to move the crankshaft of the thermal engine in the optimum angular range.

The invention has an economical character, insofar as it can be implemented by implementing a program in the engine computer which will manage the various authorization conditions. In addition, the additional electrical energy cost of the heat engine crankshaft repositioning authorization function can be put to the benefit of better responsiveness of the motor vehicle, which improves driving pleasure.

According to an implementation of the invention, said method further comprises a step of verifying a condition according to which a difference between the angular position of the crankshaft and a reference value located in the optimal angular range is greater than an angular threshold configurable.

According to an implementation of the invention, said method further comprises a step of verifying a condition according to which a position gradient of an accelerator pedal is less than a configurable gradient threshold.

According to an implementation of the invention, said method further comprises a step of verifying a condition according to which a position of the accelerator pedal is below a configurable position threshold.

According to an implementation of the invention, said method further comprises a step of verifying a condition according to which a position of the vehicle corresponds to an urban zone imposing operation of the motor vehicle in electric mode.

According to an implementation of the invention, said method further comprises a step of verifying a condition according to which an oil temperature is greater than a temperature threshold.

According to one implementation of the invention, the heat engine has two optimum angular ranges for the crankshaft.

According to an implementation of the invention, if the electric machine is capable of rotating in a clockwise direction and an anti-clockwise direction, said method comprises a step of calculating differences between the position of the crankshaft and reference values located in the two optimum angular ranges, and a step of repositioning the crankshaft in the closest optimum range for which the difference is the smallest.

The invention also relates to a computer comprising a memory storing software instructions for the implementation of the method for controlling a hybrid traction chain of a motor vehicle as defined above.

The invention further relates to a motor vehicle comprising a computer as defined above.

The invention will be better understood on reading the following description and on examining the accompanying figures. These figures are given only by way of illustration but in no way limit the invention.

Figure 1 is a schematic representation of a motor vehicle hybrid traction chain implementing the method according to the invention for repositioning a heat engine crankshaft before restarting;

Figure 2 is a schematic representation of the different functional modules allowing the implementation of the method according to the invention for repositioning a heat engine crankshaft before restarting;

FIG. 3 is a schematic representation of the functional modules implemented to manage an authorization condition for implementing the method according to the invention linked to the driver's need for acceleration;

FIG. 4 is a schematic representation of the functional modules implemented to manage an authorization condition for implementing the method according to the invention linked to a charge level of the battery or batteries of the traction chain;

FIG. 5 is a schematic representation of the functional modules implemented to manage an authorization condition for implementing the method according to the invention linked to a need for implementing the method according to the invention;

FIG. 6 is a graphic representation of an example of distribution of stop positions of the crankshaft of the heat engine illustrating optimum ranges of positions of the crankshaft of the heat engine.

Identical, similar or analogous elements retain the same reference from one figure to another.

FIG. 1 shows a traction chain 10 for a motor vehicle comprising a heat engine 11 and an electric traction motor 12 mounted on a wheel set 13, in particular a front wheel set. The heat engine 11 may for example comprise three or four cylinders, or even more than four cylinders. The heat engine 11 may be associated with an alternator-starter 14 capable of operating in generator mode to recharge the battery or batteries of the motor vehicle and in engine mode to ensure a restart of the heat engine 11. The alternator-starter 14 is for example coupled to the heat engine 11 via a belt 15 belonging to an accessory facade. The belt 15 cooperates with a pulley of the alternator-starter 15 and a pulley mounted on the crankshaft 11.1 of the heat engine 11.

The electric traction motor 12 and the alternator-starter 14 may be powered by a common battery 16 or independent batteries 16, 16'.

A clutch 17, called engine interconnection clutch, is interposed between the heat engine 11 and a gearbox 18 integrating the electric traction motor 12. The electric traction motor 12 is thus arranged inside a casing of the gearbox 18. The electric traction motor 12 is connected to a primary shaft of a gearbox 18 via a motion transmission system 19 with belt, chain, or gears. A gearbox secondary shaft 18 is connected to the wheels of the vehicle via a differential. Alternatively, the electric traction motor 12 may be arranged outside the gearbox 18.

The gearbox 18 is preferably a dual-clutch gearbox fitted with a first clutch K1 associated with the odd gears and a second clutch K2 associated with the even gears.

The engine interconnection clutch 17 can pass from an open state in which the electric traction motor 12 is decoupled from the heat engine 11, to a closed state in which the electric traction motor 12 is coupled to the heat engine 11. the open state, the clutch 17 makes it possible to isolate the electric traction motor 12 with respect to the heat engine 11 when the electric motor 12 ensures traction of the vehicle in an electric driving mode. The clutch 17 is closed in a thermal driving mode or a hybrid driving mode. The clutch 17 also allows take-off by sliding between the heat engine 11 and the gearbox 18.

Furthermore, it will be possible to provide a starter 23 to ensure cold starts of the heat engine 11. To this end, the starter 23 comprises a pinion intended to cooperate with a starter ring 24 of the heat engine 11.

A computer 21, in particular the engine computer, is capable of controlling the various components of the traction chain 10. This computer 21 comprises a memory storing software instructions for implementing the method according to the invention for controlling a machine electric so as to move the crankshaft 11.1 of the heat engine 11 in an optimum angular range for which a starting time of the heat engine 11 is minimized. By "electric machine" is meant the electric traction motor 12 or the alternator-starter 14 which can be controlled as desired to angularly move the crankshaft 11.1 of the heat engine 11 into a desired optimal position. The electric machines 12, 14 can also restart the heat engine 11.

The computer 21 receives a signal from a bidirectional engine speed sensor 22 which makes it possible to determine the angular positioning of the crankshaft 11.1 of the thermal engine 11. The possible optimum angular range(s) will be mapped in the computer 21.

The computer 21 implements a plurality of functional blocks allowing the implementation of the method according to the invention. The functional blocks are preferably implemented in software but could alternatively be implemented in an equivalent manner by electronic components.

Authorization to reposition the crankshaft 11.1 of the heat engine Aut_rep_mth is given if conditions relating to the motor vehicle Cond_veh, conditions relating to the heat engine Cond_mth, and conditions relating to the implementation of the control strategy Cond_strat are verified.

To this end, the module M1 in the form of an AND logic gate receives as input Boolean variables relating to the conditions Cond_veh, Cond_mth, and Cond_strat. The module M1 generates at output a Boolean variable relating to the authorization Aut_rep_mth for repositioning the crankshaft 11.1 of the thermal engine 11. According to an example of implementation, a Boolean variable equals 0 in the case where a condition is not verified and 1 if a condition is verified. Alternatively, the states could be reversed.

With regard to the conditions relating to the motor vehicle Cond_veh, it is possible to take into account the speed of the vehicle V_veh to control the repositioning of the crankshaft 11.1 of the heat engine 11. Indeed, there is a risk that the repositioning operation of the crankshaft 11.1 can generate noise (mainly by the electric motor and the clutches). If the vehicle is stationary, the driver may consider that something abnormal is happening to the vehicle. In order to avoid this, the operation of repositioning the crankshaft 11.1 is carried out when the speed of the vehicle V_veh is greater than a configurable speed threshold S_V. The configurable speed threshold S_V is for example between 20 km/h and 30 km/h. These two values V_veh and S_V can be compared by means of the comparison module M2. Thus, the noise generated during the movement of the crankshaft 11.1 will be masked by the rolling noise.

Another condition for performing the crankshaft repositioning operation 11.1 referenced Cond_bes_cl is linked to the fact that the driver does not need to accelerate his vehicle. Because if, on the contrary, the driver needs to accelerate strongly, the torque request at the wheel could require restarting the heat engine 11, which would abort the repositioning of the heat engine 11. An ET type module M3 receives as input a Boolean variable from module M2 and a Boolean variable relating to the driver's need for acceleration Cond_bes_cl.

As represented in FIG. 3, in order to identify the driver's need for acceleration Cond_bes_cl, it is possible for example to compare the position gradient of the accelerator pedal Grad_pos_ped with a parameterizable position gradient threshold S_grad_pos. The position gradient threshold is for example between 4 and 6%/s. The comparison between these two values Grad_pos_ped and S_grad_pos is performed by means of a module M4. Thus, if pressure on the pedal is low (gradient below the threshold), the driver relieves the torque request at the wheel, which provides a window for performing the repositioning maneuver of the heat engine 11.

A condition linked by a logical AND via an M5 module on the position of the accelerator pedal Pos_ped makes it possible to robustify an operating range. The position of the accelerator pedal Pos_ped is compared with a parameterizable position threshold S_pos_ped by means of the M6 module. Thus, if the pressure on the accelerator pedal is important, that is to say that it is greater than the threshold S_pos_ped, this means that the driver has a very dynamic driving and that he risks requesting torque to the wheel requiring a start of the heat engine 11.

Another condition linked by a logical OR via a module M7 relates to the position of the vehicle Pos_veh determined using a geolocation system, for example of the GPS type (for "Global Positioning System"). The module M8 makes it possible to identify whether the position of the vehicle Pos_veh corresponds to an urban zone Pos_urb imposing operation of the motor vehicle in electric mode. It will then be easy to reposition the crankshaft 11.1 of the heat engine 11 without the risk of having to restart it.

The level of charge of the available battery or batteries 16, 16' is an essential element in order to be able both to use energy to reposition the motor when stationary, and also to have a reserve of energy to be able to launch reboot if needed.

It is therefore checked whether a level of electrical energy available is greater than a threshold allowing an electric machine 12, 14 to ensure a restart of the heat engine 11. This condition is referenced Cond_SOC in FIG. 2.

As illustrated in FIG. 4, a distinction is made, via a switching module M9 associated with the configuration of the Conf_batt batteries, if the alternator-starter 14 and/or the electric traction motor 12 are powered by a common battery 16, for example a 48V battery, or are powered by independent batteries 16 and 16'.

If the batteries 16, 16' are separate, the module M10 compares the charge level of the battery 16 of the starter-alternator SOC_batt_P0 with a minimum charge threshold S_soc1. Furthermore, the module M11 compares the charge level of the battery 16' of the electric traction motor SOC_batt_P2 with a minimum charge threshold S_soc2. The outputs of the comparison modules M10 and M11 are applied to the input of an OR logic module referenced M12, the output of which is connected to the switching module M9.

In the case where the battery 16 is common to the alternator-starter 14 and to the electric traction motor 12, the module M13 compares the level of charge of the common battery SOC_batt_com with a minimum charge threshold S_soc3.

The output of the M9 module is connected to a second switching module M14 associated with the configuration of the Conf_CT traction chain. The module M15 compares the charge level of the battery of the electric motor SOC_batt_P2 with a minimum charge threshold S_soc4.

The minimum charge thresholds S_soc1, S_soc2, S_soc3, S_soc4 authorizing the movement of the crankshaft 11.1 in the optimum angular range are for example between 90% and 95% battery charge. As a variant, the minimum load thresholds S_soc1, S_soc2, S_soc3, S_soc4 could however be lower than these values.

The output of the module M15 is linked to the switching module M14 which generates at output a Boolean variable relating to the charge condition of the Cond_SOC battery or batteries.

As shown in FIG. 2, a Boolean variable relating to the conditions of the heat engine Cond_mth is obtained by means of a module in the form of an AND logic gate referenced M16. To this end, module M16 receives as input the Boolean variable relating to the charge condition of the battery(ies) Cond_SOC, as well as a Boolean variable relating to the state of the thermal engine E_mth (cf. module M17 which checks that the motor state E_mth corresponds to the stopped state E_mth_ar). The module M16 also receives as input a Boolean variable relating to the engine oil temperature T_hu greater than a minimum temperature threshold S_hu (cf. module M18 which compares the oil temperature T_hu with the minimum temperature threshold S_hu). The minimum oil temperature threshold S_hu is for example between 60° C. and 70° C.

We detail below, with reference to Figure 5, the authorization conditions linked to the need to implement the strategy according to the invention of repositioning the Bes_strat crankshaft.

Two conditions are linked by an M19 module in the form of an AND logic gate. The first condition is linked to the fact that the position of the crankshaft 11.1 of the heat engine Pos_vil is not in an optimal range for which a starting time of the heat engine 11 is minimized. The optimal range(s) are calibrated in a VECT vector format via the M20 module. The M21 module corresponds to a NOT logic gate.

It is also checked that a difference Ec determined by the module M22 between the position of the crankshaft 11.1 of the thermal engine 11 Pos_vil and a reference value located in an optimal angular range Pos_opt (which will be determined by a transfer function FT via the module M23 ) is greater in absolute value than a configurable angular threshold S_ang. The angular threshold S_ang is for example between 20 and 30 crankshaft degrees.

Indeed, if the crankshaft 11.1 of the combustion engine 11 is stopped very close to an optimum range, it might not be worthwhile to carry out the repositioning operation due to the electrical cost necessary to carry out this operation.

The comparison between these two values Ec and S_ang can be carried out by means of the module M24. The absolute value ABS of the deviation Ec is calculated by the M25 module.

As shown in Figure 2, the Boolean variable corresponding to the need for implementing the Bes_strat strategy is combined, by means of the module M26 in the form of an AND logic gate, with a Boolean variable representing the state of activation of the strategy. For this purpose, the M27 module checks that the activation state of the Act_strat strategy is at state 1.

FIG. 6 is a graphic representation of an example of the distribution of stop positions of the crankshaft 11.1 of the heat engine 11. FIG. 6 illustrates optimal ranges of positions A and B of the crankshaft 11.1 of the heat engine 11 as well as an example any position of the crankshaft 11.1 of the heat engine 11. The number of occurrences Occ is represented on the ordinate and the angular position of the crankshaft Pos_vil expressed in degrees is indicated on the abscissa. In this case, the optimal range A is between 20 and 40 degrees while the optimal range B is between 160 and 180 degrees.

In this example, the crankshaft 11.1 of the combustion engine 11 is stopped in a Pos_vil position located outside the optimum range B.

In addition, the difference Ec between the position of the crankshaft Pos_vil and an optimal position of reference Pos_opt corresponding to the center of the optimal range B is greater than the threshold S_ang, which authorizes the repositioning of the crankshaft 11.1 by one of the electric machines 12, 14 As a variant, the optimal reference position Pos_opt corresponds to another value of the optimal range, in particular a limit of the optimal range.

If the alternator-starter 14 or the electric traction motor 12 is able to rotate clockwise and counterclockwise, it is possible to provide a function making it possible to determine in which direction to rotate the electric machine 12 or 14 to minimize an electrical cost. of the crankshaft displacement operation 11.1. For this purpose, the deviations between the position of the crankshaft 11.1 and values situated in the optimum ranges are calculated. The crankshaft 11.1 is then repositioned in the closest optimum range for which the deviation Ec previously calculated is the smallest.

On the other hand, if only one direction of rotation is authorized for the electric machines 12, 14, the crankshaft 11.1 is moved into the closest optimum range A, B in the only possible direction of rotation.

Claims (10)

Method for controlling a hybrid traction chain (10) of a motor vehicle comprising a heat engine (11) fitted with a crankshaft (11.1) and an electric machine (12, 14), characterized in that the motor vehicle operating in an electric traction mode while the heat engine (11) is stopped and awaiting restart, said method comprising at least:
- a step of verifying a condition according to which a speed of the motor vehicle (V_veh) is greater than a configurable speed threshold (S_V),
- a step for verifying a condition according to which a level of electrical energy available (SOC_batt_P0, SOC_batt_P2) is greater than a threshold allowing an electric machine (12, 14) to restart the heat engine (11),
- a step of verifying a condition according to which an angular position of the crankshaft (11.1) is located outside at least one optimum angular range (A, B) for which a starting time of the heat engine (11) is minimized, and
- if the previous conditions are verified, a step of controlling the electric machine (12, 14) so as to move the crankshaft (11.1) of the heat engine (11) in the optimum angular range (A, B). Method according to claim 1, characterized in that it further comprises a step of verifying a condition according to which a difference (Ec) between the angular position of the crankshaft (11.1) and a reference value (Pos_opt) situated in the optimal angular range (A, B) is greater than a configurable angular threshold (S_ang). Method according to Claim 1 or 2, characterized in that it further comprises a step of verifying a condition according to which a position gradient of an accelerator pedal (Grad_pos_ped) is less than a configurable gradient threshold ( S_grad_pos). Method according to any one of Claims 1 to 3, characterized in that it further comprises a step of verifying a condition according to which a position of the accelerator pedal (Pos_ped) is lower than a parameterizable position threshold (S_pos_ped). Method according to any one of Claims 1 to 4, characterized in that it further comprises a step of verifying a condition according to which a position of the vehicle (Pos_veh) corresponds to an urban area (Pos_urb) imposing operation of the motor vehicle in electric mode. Method according to any one of Claims 1 to 5, characterized in that it also comprises a step of verifying a condition according to which an oil temperature (T_hu) is greater than a temperature threshold (S_hu). Method according to any one of Claims 1 to 6, characterized in that the heat engine (11) has two optimum angular ranges (A, B) for the crankshaft (11.1). Method according to Claim 7, characterized in that if the electric machine (12, 14) is capable of rotating in a clockwise direction and an anti-clockwise direction, the said method includes a step of calculating the differences (Ec) between the position of the crankshaft (Pos_vil) and reference values (Pos_opt) located in the two optimal angular ranges (A, B), and a step of repositioning the crankshaft (11.1) in the closest optimal range (A, B) for which the deviation (Ec) is the lowest. Computer (21) comprising a memory storing software instructions for implementing the method for controlling a hybrid powertrain (10) of a motor vehicle as defined according to any one of the preceding claims. Motor vehicle comprising a computer (21) as defined according to claim 9.