FR3140022A1 - METHOD FOR DISTRIBUTING A TORQUE BETWEEN A FIRST AND A SECOND GEARBOX OF A VEHICLE - Google Patents

Abstract

One aspect of the invention relates to a method 100 for distributing a torque between a first gearbox of a first set of wheels and a second gearbox of a second set of wheels of a four-wheel drive vehicle, the method 100 comprising the steps of: Determining 101 a state of aging of the first gearbox, If the determined state of aging is greater than a predetermined threshold, Decrease 102 a torque transmitted to said first gearbox, and Increase 103 a torque transmitted to said second gearbox. Figure 2

Description

METHOD FOR DISTRIBUTING A TORQUE BETWEEN A FIRST AND A SECOND GEARBOX OF A VEHICLE

One aspect of the invention relates to a method of distributing a torque requested by a driver between a first gearbox of a first set of wheels and a second gearbox of a second set of wheels of a four-wheel drive vehicle.

Another aspect of the invention relates to a four-wheel drive vehicle, in particular an automobile, comprising control means arranged to carry out the method according to the invention.

These aspects of the invention find particularly interesting, but not exclusive, applications in the field of hybrid or electric four-wheel drive vehicles.

Four-wheel drive vehicles usually include a first gearbox mechanically connected to a first set of wheels and a second gearbox mechanically connected to a second set of wheels.

Each gearbox is sized for a specific vehicle and a specific duration of use.

In order to reduce design and manufacturing costs, some manufacturers implement a gearbox initially designed for a passenger vehicle in a utility vehicle.

However, a utility vehicle often has a greater weight than a private vehicle so that the gearbox is subjected to greater average torques. In addition, for a utility vehicle, two-wheel drive use is preferred when the gearbox management is in automatic mode so that only one gearbox is used. This inappropriate use often leads to premature wear of the gearbox.

Conversely, some manufacturers prefer to use an oversized gearbox and therefore applicable to several types of vehicles. This strategy is obviously expensive.

The aim of the invention is to propose a method making it possible to apply the same type of non-oversized gearbox to several types of vehicle.

• Déterminer un état de vieillissement de la première boite de vitesses,
• Si l’état de vieillissement déterminé est supérieur à un seuil prédéterminé,
  • Diminuer un couple transmis à la première boite de vitesses, et
  • Augmenter un couple transmis à la deuxième boite de vitesses.

In this context, the invention thus relates, in its broadest acceptance, to a method of distributing a torque between a first gearbox of a first set of wheels and a second gearbox of a second set of wheels of a four-wheel drive vehicle, the method comprising the steps, executed by vehicle control means, of:

• Determine the aging state of the first gearbox,
• If the determined aging state is greater than a predetermined threshold,
  • Reduce a torque transmitted to the first gearbox, and
  • Increase torque transmitted to the second gearbox.

Thanks to the method according to the invention, when the first gearbox shows premature aging, a percentage of the torque usually supported by the first gearbox is transmitted to the second gearbox. Thus, the stress on the first gearbox is reduced and its lifespan is increased.

Consequently, thanks to this process, the same gearbox designed for a light vehicle can be implemented in a Pickup or SUV type vehicle (for Sport Utility Vehicle in English).

In addition, compared to gearboxes of the prior art, for the same type of vehicle, it is possible to use a gearbox of smaller size.

In addition to the characteristics which have just been mentioned in the previous paragraph, the process according to the invention may present one or more complementary characteristics among the following, considered individually or in all technically possible combinations.

According to a non-limiting aspect of the invention, the state of aging is formed by a capacity of mechanical parts of the first gearbox to resist a torque value depending on use of the first gearbox.

According to a non-limiting aspect of the invention, the mechanical parts are formed by gears and/or bearings.

According to a non-limiting aspect of the invention, the use of the first gearbox is equal to a sum of measurements, each measurement taking into account a torque value applied to a first input shaft of the first gearbox. speeds and a rotational speed of the first input shaft.

According to a non-limiting aspect of the invention, the step of determining an aging state is repeated periodically over a predetermined period.

According to a non-limiting aspect of the invention, the predetermined period is between 5 milliseconds and 1000 milliseconds.

According to a non-limiting aspect of the invention, the method comprises a step of prohibiting the steps of decreasing and increasing if a second actuator transmitting a torque to the second gearbox reaches an operating limitation.

• Une première boite de vitesses d’un premier train de roues,
• Un premier actionneur agencé pour entraîner en rotation un premier arbre d’entrée de la première boite de vitesses,
• Une deuxième boite de vitesses d’un deuxième train de roues, et
• Un deuxième actionneur agencé pour entraîner en rotation un deuxième arbre d’entrée de la deuxième boite de vitesses.

Another aspect of the invention relates to a four-wheel drive vehicle comprising:

• A first gearbox of a first set of wheels,
• A first actuator arranged to rotate a first input shaft of the first gearbox,
• A second gearbox of a second set of wheels, and
• A second actuator arranged to rotate a second input shaft of the second gearbox.

The vehicle according to this aspect of the invention is remarkable in that it comprises control means arranged to execute the steps of the method according to any of the aforementioned aspects.

According to a non-limiting aspect of the invention, the control means are formed by a vehicle control unit or an engine control unit.

The invention and its various applications will be better understood on reading the following description and examining the accompanying figures.

illustrates, schematically, a vehicle according to a non-limiting aspect of the invention.

shows, schematically, the steps of a process according to a non-limiting aspect of the invention.

illustrates a curve representative of predetermined aging states of a first gearbox included in a vehicle conforming to that illustrated in .

Unless otherwise specified, the same element appearing in different figures presents a unique reference.

There schematically illustrates a vehicle 1 conforming to a non-limiting implementation of the invention.

The vehicle 1 can be formed by a four-wheel drive vehicle of electric, hybrid or thermal type. In the example illustrated, vehicle 1 is formed by a hybrid vehicle.

• Une première boite de vitesses 2 d’un premier train de roues 3,
• Un premier actionneur 4 agencé pour entraîner en rotation un premier arbre d’entrée 5 de la première boite de vitesses 2, le premier actionneur 4 étant formé, dans cet exemple non limitatif, par un moteur thermique 6 et un premier moteur électrique 7 pouvant être actionnés simultanément ou indépendamment l’un de l’autre pour transmettre un couple au premier arbre d’entrée 5,
• Une deuxième boite de vitesses 8 d’un deuxième train de roues 9,
• Un deuxième actionneur 10 agencé pour entraîner en rotation un deuxième arbre d’entrée 11 de la deuxième boite de vitesses 8, le deuxième actionneur 10 étant formé dans cet exemple non limitatif par un deuxième moteur électrique,
• Des moyens de contrôle 12 agencés pour exécuter les étapes du procédé de répartition d’un couple entre la première boite de vitesses 2 et la deuxième boite de vitesses 8 du véhicule 1 selon un aspect non limitatif de l’invention illustré à la .

Vehicle 1 includes:

• A first gearbox 2 of a first set of wheels 3,
• A first actuator 4 arranged to rotate a first input shaft 5 of the first gearbox 2, the first actuator 4 being formed, in this non-limiting example, by a heat engine 6 and a first electric motor 7 which can be actuated simultaneously or independently of each other to transmit a torque to the first input shaft 5,
• A second gearbox 8 of a second set of wheels 9,
• A second actuator 10 arranged to rotate a second input shaft 11 of the second gearbox 8, the second actuator 10 being formed in this non-limiting example by a second electric motor,
• Control means 12 arranged to execute the steps of the method of distributing a torque between the first gearbox 2 and the second gearbox 8 of the vehicle 1 according to a non-limiting aspect of the invention illustrated in .

• Une unité de contrôle véhicule (plus connue sous l’acronyme VCU pour Vehicle Control Unit en anglais),
• Une unité de contrôle moteur (plus connue sous l’acronyme MCU pour Motor Control Unit en anglais),

In a non-limiting manner, the control means 12 can be formed by:

• A vehicle control unit (better known by the acronym VCU for Vehicle Control Unit in English),
• A motor control unit (better known by the acronym MCU for Motor Control Unit in English),

There shows a step diagram of one mode of implementation of the method 100 according to the invention.

The steps of the method 100 are executed by control means 12 of a vehicle such as, for example, that illustrated in .

The method 100 includes a step of determining 101 an aging state of the first gearbox 2.

In this non-limiting embodiment, the first gearbox 2 corresponds to the gearbox of the front wheel train. It is understood that in a different embodiment, this first gearbox 2 can be formed by the gearbox of the rear wheel train.

According to a non-limiting aspect of the invention, the state of aging is formed by a capacity of mechanical parts of the first gearbox 2 to resist a torque value depending on use of the first gearbox. speeds 2.

In a non-limiting implementation, the aging state is formed by a capacity of the gears and the rolling bearings (not illustrated) of the first gearbox 2 to resist a value of torque which is applied to them as a function of 'a use of the first gearbox 2.

This capacity can be calculated as follows: resistance of the gears and rolling bearings based on use of the first gearbox 2 determined divided by resistance of the gears and rolling bearings at the start of life.

In a non-limiting implementation, the use of the first gearbox 2 is equal to a sum of measurements, each measurement taking into account a torque value applied to the first input shaft 5 of the first gearbox 2 and a rotation speed of the first input shaft 5. These measurements can be carried out by sensors and/or estimation means included in the vehicle 1,

In fact, an accumulation of rotational speeds and torques transmitted by the first gearbox 2 creates its aging. This aging generates fatigue at the level of the gear teeth as well as the bearings and is likely to lead to breakage of the latter.

There illustrates a curve representative of predetermined aging states of the first gearbox 2.

The ordinate axis represents the capacity of the gears and bearings of the first gearbox 2 to resist a value of torque applied to them in MPa. The abscissa axis illustrates, for its part, the use in Watts of the first gearbox 2 as a function of a sum of measurements, each measurement taking into account a torque value in Nm applied to the first input shaft 5 of the first gearbox 2 and a rotation speed in rd/s of the first input shaft 5.

We can see that the capacity of the gears and bearings of the first gearbox 2 to resist a value of torque applied to them decreases as a function of an increase in the use of the first gearbox 2.

In a different implementation, the aging state can be formed by a capacity of the first input shaft 5 to resist a torque value depending on a use of this first input shaft 5. The use of this first input shaft 5 is equal to a sum of measurements, each measurement taking into account a torque value applied to the first input shaft 5 of the first gearbox 2 and a rotation speed of the first input shaft 5.

In a non-limiting implementation, the step of determining 101 an aging state is repeated periodically according to a predetermined period. This predetermined period can be between 5 milliseconds and 1000 milliseconds. It can for example be of the order of 10 milliseconds or 20 milliseconds.

• Diminuer 102 un couple transmis par le premier actionneur 4 à la première boite de vitesses 2, et
• Augmenter 103 un couple transmis par le deuxième actionneur 10 à la deuxième boite de vitesses 8.

If the state of aging determined by the control means 12 is greater than a predetermined threshold, the method 100 comprises the additional steps of:

• Reduce 102 a torque transmitted by the first actuator 4 to the first gearbox 2, and
• Increase 103 a torque transmitted by the second actuator 10 to the second gearbox 8.

In other words, if the aging of the first gearbox 2 is premature, the method 100 proposes to distribute part or all of the torque requested by the driver on the second gearbox 8.

In the laboratory, it is possible to determine the curve illustrated in which represents predetermined aging states according to predetermined given uses. This curve can be recorded in the control means 12. Thus, the control means 12 are able to determine, for a given use, a theoretical predetermined aging state.

For this same given use, the control means 12 are able to determine a real state of aging based on measurements and/or estimates made by sensors and/or estimation means of the vehicle 1,

Thus, by comparing the determined aging state to the predetermined laboratory aging state, it is possible to determine a difference. If this difference is greater than the predetermined threshold, then the steps of reducing 102 a torque transmitted by the first actuator 4 to the first gearbox 2 and of increasing 103 a torque transmitted by the second actuator 10 to the second gearbox 8 are executed.

The method 100 may also include a step of prohibiting 105 the steps of reducing 103 the torque transmitted to the first gearbox 2 and of increasing 104 the torque transmitted to the second gearbox 8 if the second actuator 10 transmitting a torque at the second gearbox 8 reaches an operating limitation.

In a non-limiting manner, the second actuator 10 reaches its operating limitation, for example when it has reached its maximum rotation speed or when its temperature is too high. In this case, the distribution of the torque between the first set of wheels 3 and the second set of wheels 9 is not carried out.

• Dimensionner une même boite de vitesses pour des véhicules légers et des véhicules dits utilitaires ;
• Réduire les dimensions de la boite de vitesses ;
• Réduire les coûts de développement et de fabrication des boites de vitesses.

The various aspects of the invention mentioned above have numerous advantages. Among these, we can cite:

• Sizing the same gearbox for light vehicles and so-called utility vehicles;
• Reduce the dimensions of the gearbox;
• Reduce gearbox development and manufacturing costs.

Claims (9)

Method (100) for distributing a torque between a first gearbox (2) of a first set of wheels (3) and a second gearbox (8) of a second set of wheels (9) of a four-wheel drive vehicle (1), said method (100) being characterized in that it comprises the steps, executed by control means (12) of said vehicle (1), of:

• Determine (101) an aging state of said first gearbox (2),
• If said determined aging state is greater than a predetermined threshold,
  • Reduce (102) a torque transmitted to said first gearbox (2), and
  • Increase (103) a torque transmitted to said second gearbox (8).

Method (100) according to the preceding claim, characterized in that the aging state is formed by a capacity of mechanical parts of the first gearbox (2) to resist a torque value depending on a use of said first gearbox (2). Method (100) according to the preceding claim, characterized in that the mechanical parts are formed by gears and/or bearings. Method (100) according to any one of the preceding claims, characterized in that the use of the first gearbox (2) is equal to a sum of measurements, each measurement taking into account a torque value applied to a first input shaft (5) of said first gearbox (2) and a rotational speed of said first input shaft (5). Method (100) according to any one of the preceding claims, characterized in that the step of determining (101) a state of aging is repeated periodically according to a predetermined period. Method (100) according to the preceding claim, characterized in that the predetermined period is between 5 milliseconds and 1000 milliseconds. Method (100) according to any one of the preceding claims, characterized in that it comprises a step of prohibiting (105) the steps of decreasing (103) and increasing (104) if a second actuator (10) transmitting a torque at the second gearbox (8) reaches an operating limitation. Four-wheel drive vehicle (1) comprising:

• A first gearbox (2) of a first set of wheels (3),
• A first actuator (4) arranged to rotate a first input shaft (5) of said first gearbox (2),
• A second gearbox (8) of a second set of wheels (9),
• A second actuator (10) arranged to rotate a second input shaft (11) of said second gearbox (8),
• Said vehicle (1) being characterized in that it comprises control means (12) arranged to execute the steps of the method (100) according to any one of the preceding claims.

Vehicle (1) according to the preceding claim, characterized in that the control means (12) are formed by a vehicle control unit or an engine control unit.