METHOD FOR CONTROLLING A MOTOR VEHICLE POWERTRAIN

Abstract

The invention relates to a method for controlling a motor vehicle powertrain (1), the powertrain (1) comprising a heat engine (2) configured to generate engine torque on a drive shaft (3), a clutch (6) configured to couple or uncouple a primary shaft (5) with the drive shaft (3), and an electric machine (7) configured to generate engine torque on the primary shaft (5). The control method comprises the following steps when the heat engine (2) drives the drive shaft (3): - a step of generating torque from the electric machine (7) on the primary shaft (5) so as to generate a resistive torque on the primary shaft (5) and produce electrical energy; - a step of supplying a starter-alternator (11) with the electrical energy produced by the electric machine (7); - a step of controlling the starter-alternator (11) in order to generate engine torque on the drive shaft (3). Figure 1

Description

Title of the invention: METHOD FOR CONTROLLING A MOTOR VEHICLE POWERTRAIN

[0001] The technical context of the present invention is that of methods for controlling a powertrain equipping a motor vehicle. More particularly, the invention relates to such a method for controlling a powertrain equipping a motor vehicle. It also relates to a powertrain for a motor vehicle which is capable of implementing such a control method. It also relates to a motor vehicle provided with such a powertrain.

[0002] In the state of the art, a method for controlling a powertrain of a motor vehicle is known, described by patent document FR3032676. The powertrain comprises a heat engine capable of supplying a first average torque associated with an acyclic torque to a drive shaft. The powertrain also comprises a gearbox coupled to a primary shaft and supporting a limit input torque depending on a gear engaged and the acyclic torque, and corresponding to a maximum accepted noise. The powertrain also comprises a prime mover capable of supplying a second torque to the primary shaft. The powertrain also comprises coupling means capable of coupling the drive shaft to the primary shaft.

[0003] The control method comprises a step in which a maximum acyclic torque is determined corresponding to the limit input torque supported in the presence of the gear engaged, then a first maximum average torque of the thermal engine is deduced from this maximum acyclic torque, which is a function of the current speed of the latter. When a torque required by the motor vehicle is greater than the first maximum average torque, the thermal engine is provided with a first average torque at most equal to the first deduced maximum average torque and the prime mover is provided with a second torque equal to the difference between the required torque and the first average torque.

[0004] The prime mover is chosen from an electric motor, a hydraulic machine, a pneumatic machine and a flywheel. It is understood that the prime mover is a non-thermal machine arranged to provide torque to move the motor vehicle, either alone or in addition to a thermal engine.

[0005] When the heat engine is ignited, the successive explosions generated by the reaction between the fuel and the oxidant transmit acyclisms to the gearbox. These acyclisms are transmitted to the shafts of all the machines of the powertrain linked to the motor vehicle's drivetrain. In some cases, these acyclisms are likely to generate noises, such as shot noises, commonly referred to as "rattle noise", particularly when the gearbox gears are free of constraints and undergo these acyclisms. These shot noises are particularly generated at the level of the gears of the prime mover.

[0006] One solution is to put the gears linked to the prime mover under stress by causing electrical recharging on electrical energy storage means, such as a motor vehicle battery.

[0007] However, when the battery is fully charged, such stressing is no longer possible, and such a solution becomes inoperative.

[0008] The object of the present invention is to propose a new control method in order to respond at least in large part to the preceding problem and to further lead to other advantages.

[0009] A first goal is to propose a simple and easy to implement control method.

[0010] A second goal is to propose a control method requiring the least possible structural modification of the powertrain.

[0011] A third aim is to propose an effective control method whatever the driving mode applied to the powertrain, including a low-load driving mode, such as a creep or take-off mode, in which the powertrain is under little stress and operates at low speed.

[0012] According to a first aspect of the invention, at least one of the aforementioned objectives is achieved with a method for controlling a motor vehicle powertrain, the powertrain comprising:

[0013] - a heat engine configured to generate a motor torque on a motor shaft;

[0014] - a gearbox coupled in rotation to a primary shaft;

[0015] - a clutch configured to selectively assume a closed configuration or an open configuration in which the input shaft and the drive shaft are respectively coupled or uncoupled;

[0016] - an electric machine configured to generate a motor torque on the shaft primary ;

[0017] the control method comprising the following steps when the heat engine is started and it rotates the engine shaft and the primary shaft, the clutch being configured in its closed configuration:

[0018] - a step of generating torque from the electric machine on the primary shaft of so as to generate a resistive torque on the primary shaft;

[0019] - a step of generating electrical energy following the resistive torque produced on the primary shaft;

[0020] - a step of supplying electricity to a starter-alternator with energy electricity produced by the electric machine;

[0021] - a step of controlling the starter-alternator in order to generate an engine torque on the motor shaft.

[0022] In the context of the present invention, the powertrain is a hybrid powertrain comprising the heat engine and an electric machine which are capable of setting the motor vehicle in motion, either alternately or with each other.

[0023] In the context of the present invention, the starter-alternator is for example of the belt-driven type and makes it possible to start the thermal engine by driving the motor shaft. The starter-alternator then generates a motor torque on the motor shaft, so as to rotate said motor shaft and allow the thermal engine to start. The starter-alternator is commonly arranged on the accessory front of the powertrain.

[0024] In the context of the present invention, the heat engine is a combustion engine providing mechanical work from an overpressure gas obtained by combustion of a fuel.

[0025] In the context of the present invention, the drive shaft is an output shaft of the heat engine. It is the shaft onto which - first - the engine torque generated by the heat engine is transferred.

[0026] In the context of the present invention, the primary shaft is a shaft located at the gearbox and the clutch. The primary shaft is intended to be coupled in rotation to the drive shaft by means of the clutch. The primary shaft is an input shaft for the gearbox.

[0027] In the context of the present invention, the gearbox comprises at least one input shaft intended to receive the engine torque supplied by the heat engine via coupling means, and an output shaft intended to receive this engine torque via the input shaft in order to communicate it to a transmission shaft to which it is coupled. These coupling means comprise gears, pinions, teeth or the like capable of undergoing acyclisms caused by the heat engine, these acyclisms generating noise, in particular during driving modes in which the heat engine is not used much, such as creeping or take-off modes, during which the electric machine is not recharged.

[0028] In the context of the present invention, the clutch comprises for example a flywheel fixedly secured to the drive shaft and a clutch disc fixedly secured to the primary shaft which is coupled to the input shaft of the gearbox.

[0029] In the context of the present invention, the electric machine is a non-thermal machine arranged so as to provide torque to move the motor vehicle, either alone or in addition to the thermal engine.

[0030] These arrangements are such that the control method of the present invention makes it possible to generate a positive engine torque at the level of the thermal engine and the starter-alternator and a negative engine torque at the level of the electric machine, without the problem of a full battery. This results in an advantageous use of the starter-alternator to continuously provide a positive torque on the teeth of the electric machine and put the latter under stress.

[0031] Thus, it is possible to minimize, or even eliminate, any noise affecting the gears of the gearbox, by using the starter-alternator of the powertrain to stress the gears of the gearbox, and more particularly those connected to the electric machine, in particular using electrical energy produced by the electric machine.

[0032] In addition, a supply of positive torque by the starter-alternator makes it possible to minimize fuel consumption by the thermal engine, from which less torque is required, particularly at low speeds.

[0033] The control method according to the first aspect of the invention advantageously comprises at least one of the improvements below, the technical characteristics forming these improvements being able to be taken alone or in combination:

[0034] - the method comprises a step of storing the electrical energy produced by the electric machine in an electric traction battery of the powertrain, the storage stage being intermediate between the generation stage and the supply stage;

[0035] - the storage step is carried out as long as a state of charge of the electric battery of traction is different from a full load state;

[0036] - when the state of charge of the electric traction battery corresponds to a state at full load, the electrical energy generated by the resistive torque of the electric machine is sent directly to the starter-alternator, the storage step being ignored;

[0037] - the resistive torque generated by the electric machine is between 1 Nm and 30 Nm, preferably between 5 Nm and 15 Nm, preferably equal to 10 Nm.

[0038] According to a second aspect of the invention, there is provided a powertrain for a motor vehicle, the powertrain comprising:

[0039] - a heat engine configured to generate a motor torque on a motor shaft;

[0040] - a gearbox coupled in rotation to a primary shaft;

[0041] - a clutch configured to selectively assume a closed configuration or an open configuration in which the input shaft and the drive shaft are respectively coupled or uncoupled;

[0042] - an electric machine configured to generate a motor torque on the shaft primary ;

[0043] - an electric traction battery configured to store electrical energy;

[0044] - a control unit configured to implement the control method in accordance with the first aspect of the invention or according to any of its improvements.

[0045] In the context of the present invention, the control unit is for example integrated into a supervision computer which is capable of operating the motor vehicle according to different driving modes.

[0046] In the context of the present invention, the electric traction battery is an electric battery making it possible to generate a direct voltage of at least 48V, which can go up to 400V or 800V. Generally speaking, the electric traction battery is configured to supply electrical energy to an electric machine generating engine torque on the powertrain of the motor vehicle.

[0047] According to a third aspect of the invention, there is provided a motor vehicle comprising a powertrain in accordance with the second aspect of the invention.

[0048] The motor vehicle is advantageously of the electrified motor vehicle type, and more particularly of the hybrid type. Generally speaking, the powertrain of such a hybrid motor vehicle is rotated by the thermal engine and / or by the electric machine, electrically powered by the electric traction battery, in order to generate an engine torque used to set the motor vehicle in motion. According to the invention, the electric machine is also configured to recover mechanical energy from the powertrain and convert it into electrical energy, thus producing a braking torque - called resistive torque - on said powertrain and making it possible to power the starter-alternator so that it in turn generates an engine torque on the powertrain and / or to recharge the electric traction battery.

[0049] Various embodiments of the invention are provided, integrating according to all of their possible combinations the different optional characteristics set out here.

[0050] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several exemplary embodiments given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0051] [Fig. 1] illustrates a powertrain capable of implementing a control method of the present invention;

[0052] [Fig.2] schematically illustrates the control method of the present invention implemented by the powertrain illustrated in [Fig.l].

[0053] Of course, the features, variants and different embodiments of the invention may be combined with each other, in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0054] In particular, all the variants and all the embodiments described can be combined with each other if nothing prevents this combination from a technical point of view.

[0055] In the figures, the elements common to several figures retain the same reference.

[0056] In [Fig.l], a powertrain 1 equipping a motor vehicle is illustrated. The powertrain 1 comprises a heat engine 2 which is configured to generate engine torque on a drive shaft 3. The powertrain 1 also comprises a gearbox 4 rotatably coupled to a primary shaft 5. The powertrain 1 also comprises a clutch 6 configured to selectively assume a closed configuration in which the primary shaft 5 and the drive shaft 3 are coupled or an open configuration in which the primary shaft 5 and the drive shaft 3 are uncoupled. The powertrain 1 also comprises an electric machine 7 configured to generate engine torque on the primary shaft 5 and an electric traction battery 8 configured to store electrical energy.The powertrain 1 also comprises a control unit 9 configured to implement a control method 100 of the present invention and a control device 10 of the gearbox 4.

[0057] The power unit 1 also comprises a starter-alternator 11, positioned on the accessory front of the power unit 1 which is designed to start the thermal engine 2 and which notably comprises a starter belt 12.

[0058] The powertrain 1 also comprises a differential 13, such as a front differential, capable of rotating wheels of a wheel set 14, such as a front axle, of the motor vehicle.

[0059] In [Fig.2], the control method 100 is illustrated, which comprises the following successive steps, when the heat engine 2 is started and the engine thermal 2 drives the motor shaft 3 and the primary shaft 5 in rotation, the clutch 6 being configured in its closed configuration.

[0060] The control method 100 comprises a step of generating torque 101 of the electric machine 7 on the primary shaft 5 so as to generate a resistive torque on the primary shaft 5.

[0061] The control method 100 comprises a step 102 of generating electrical energy following the resistive torque produced on the primary shaft 5.

[0062] the control method 100 comprises a step 103 of storing the electrical energy produced by the electric machine 7 in the electric traction battery 8 of the powertrain 1.

[0063] The control method 100 comprises a step 104 of supplying electricity to the starter-alternator 11 with the electrical energy produced by the electrical machine 7.

[0064] The control method 100 comprises a step 105 of controlling the starter-alternator 11 in order to generate a motor torque on the motor shaft 3.

[0065] It is understood that the storage step 103 is carried out as long as a state of charge E of the electric traction battery 8 is different from a full charge state Ep.

[0066] It is also understood that when the state of charge E of the electric traction battery 8 corresponds to the full charge state Ep, the electrical energy generated by the resistive torque of the electric machine 7 is directly sent to the starter-alternator 11, the storage step 103 being ignored in this case.

[0067] It is noted that the resistive torque generated by the electrical machine 7 is between 1 Nm and 30 Nm, preferably between 5 Nm and 15 Nm, preferably equal to 10 Nm.

[0068] In summary, the invention relates to a method 100 for controlling a powertrain 1 of a motor vehicle making it possible in all circumstances to minimize, or even eliminate, the noise caused by acyclisms generated by the powertrain on teeth of the gearbox 6, from a stressing of these teeth by the electric machine 7, such a method of control not requiring any structural modification of the powertrain 1.

[0069] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the different characteristics, forms, variants and embodiments of the invention can be associated with each other in various combinations insofar as they are not incompatible or mutually exclusive. In particular, all the variants and embodiments described above can be combined with each other.

Claims

Claims

1. Method for controlling (100) a powertrain (1) of a motor vehicle, the powertrain (1) comprising: - a heat engine (2) configured to generate an engine torque on a drive shaft (3); - a gearbox (4) coupled in rotation to a primary shaft (5); - a clutch (6) configured to selectively take a closed configuration or an open configuration in which the primary shaft (5) and the drive shaft (3) are respectively coupled or uncoupled; - an electrical machine (7) configured to generate an engine torque on the primary shaft (5);the control method (100) comprising the following steps when the heat engine (2) is started and it rotates the motor shaft (3) and the primary shaft (5), the clutch (6) being configured in its closed configuration: - a step of generating torque (101) of the electric machine (7) on the primary shaft (5) so as to generate a resistive torque on the primary shaft (5); - a step of generating (102) electrical energy following the resistive torque produced on the primary shaft (5); - a step of storing (103) the electrical energy produced by the electric machine (7) in an electric traction battery (8) of the powertrain (1), this storage step (103) being carried out as long as a state of charge (E) of the electric traction battery (8) is different from a full charge state (Ep), - a step of supplying (104) electrical power to a starter-alternator (11) with the electrical energy produced by the electric machine (7);- a control step (105) of the starter-alternator (11) in order to generate a motor torque on the motor shaft (3).;

2. Control method (100) according to the preceding claim, wherein when the state of charge (E) of the electric traction battery (8) corresponds to a full charge state (Ep), the electrical energy generated by the resistive torque of the electric machine (7) is directly sent to the starter-alternator (11), the storage step (103) being ignored.

3. Control method (100) according to any one of the preceding claims, in which the resistive torque generated by the electrical machine (7) is between 1 Nm and 30 Nm, preferably between 5 Nm and 15 Nm, preferably equal to 10 Nm.

4. Powertrain (1) for a motor vehicle, the powertrain (1) comprising: - a heat engine (2) configured to generate engine torque on a drive shaft (3); - a gearbox (4) rotatably coupled to a primary shaft (5); - a clutch (6) configured to selectively assume a closed configuration or an open configuration in which the primary shaft (5) and the drive shaft (3) are respectively coupled or uncoupled; - an electric machine (7) configured to generate engine torque on the primary shaft (5); - an electric traction battery (8) configured to store electrical energy; - a control unit (9) configured to implement the control method (100) according to any one of the preceding claims.

5. Motor vehicle comprising a powertrain (1) according to the preceding claim.

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