FR3014775A1 - SYSTEM FOR CONTROLLING A COUPLER BETWEEN FRONT AXLE AND REAR AXLE OF A MOTOR VEHICLE AND METHOD OF CONTROLLING THE SAME - Google Patents

Abstract

The engine torque distribution device (1) comprises a controlled coupler (4) configured to distribute a driving torque between the front axle and the rear axle of a vehicle. The device comprises an electronic control unit (10) configured to develop a coupling setpoint (CCons) imposing a torque transmitted by the coupler (4). For at least one mode of operation of the coupler (4), and for at least one gearbox position, the electronic control unit (10) is configured to develop a coupling setpoint (CCons) whose value tends towards a first value resulting from a first mapping (18) depending on the speed (V) of the vehicle if the pedal signal (Acc) is less than a signal threshold, and tends towards a second value resulting from a second mapping (19). ) function of the vehicle speed (V) if the pedal signal (Acc) is greater than the signal threshold.

Description

The invention relates to systems for transferring torque between a front axle and a rear axle of a motor vehicle of the above-mentioned type. 4x4. The vehicle may be equipped with a manual gearbox or an automatic gearbox. In such a vehicle, a motor is typically connected by a gearbox with the wheels of a first axle of the vehicle, and can be connected or decoupled from a second axle by a coupler which is capable of transmitting, in a controllable manner. , a part of the torque available at the output of the gearbox at the second axle. The coupler can be regulated according to different strategies, or "modes", for example a so-called "4x2" mode where only the first axle receives the torque available at the output of the box, a so-called "automatic" mode in which a torque distribution is controlled. available between the front axle and the rear axle, taking account of wheel slippage, ie taking into account differences in rotation speeds between the wheels of the front axle and the wheels of the axle. rear axle of the vehicle, and an off-road mode often called "lock" mode, in which the torque transferred to the second axle of the vehicle is independent of differences in wheel speeds between the two axles of the vehicle.

When the vehicle is operating in off-road mode, it is desired to manage the transfer of torque so as to both provide sufficient torque to the low speed crossing maneuvers, so as to guarantee the stability of the vehicle at higher speed, and it is also desired to optimize the acoustic comfort of the occupants of the vehicle by avoiding generating noise related to a sudden reversal of the direction of rotation of the coupler.

Patent Application FR 2 949 212 proposes a strategy for distributing torque between the front and rear axles of a vehicle according to different signals including wheel speeds, the position of an accelerator pedal and the gear ratio. engaged.

The torque transfer setpoint from the front axle to the rear axle notably takes into account the speed of the vehicle and a detection of a phenomenon of front wheel slip. The patent application FR 2 958 589 also proposes a strategy for distributing torque between a front axle and a rear axle of a motor vehicle.

This request proposes in particular to memorize the torque transfer setpoint which was current just before a motor stall. This patent application proposes to impose a specific torque value transferred when the vehicle is in reverse or forward in off-road mode.

The object of the invention is to improve torque transfer strategies in off-road mode so that these strategies can be used in particular for a vehicle with an automatic gearbox, over the entire speed range of the gearbox. The object of the invention is also to improve overall the torque transfer strategy in off-road mode so as to optimize both the maneuvering noise limitation linked to the rotational inversions of the coupler and so as to always ensure times enough torque for the required maneuvers, and good stability when driving on roads or highways.

To this end, the invention proposes a device for distributing a motor torque between a front axle and a rear axle of a motor vehicle configured to be able to pass from two to four driving wheels, comprising a controlled coupler configured to distribute the torque engine between the front end and the rear end of the vehicle, comprising a coupler mode selector, and comprising an electronic control unit connected to a means for estimating the speed of the vehicle, to a gearbox configured to transmit the position current of the box, and a throttle pedal emitting a pedal signal. It is considered that the vehicle can go from two to four driving wheels when two wheels of a train are always connected to the engine except when the gearbox is in neutral position, and that a variable proportion of the engine torque can be transmitted through two-wheel coupler on the other wheel set of the vehicle. The electronic control unit is configured to develop a coupling setpoint imposing a torque transmitted by the coupler. The engine torque distributed is typically a motor torque available at the output of the gearbox. For at least one selected mode of operation of the coupler, and for at least one gearbox position, the electronic control unit is configured to develop a coupling instruction whose value tends to a first value resulting from a first mapping a function of the vehicle speed if the pedal signal is less than a signal threshold, and tends to a second value derived from a second map based on the speed of the vehicle if the pedal signal is greater than the signal threshold. The values of the first map are preferably strictly less than the values of the second map. The first and the second mapping can for example be represented by a plateau of constant value of the coupling setpoint until the speed reaches a speed threshold. The speed threshold is preferably lower for the first mapping. The value of the mapped coupling setpoint can then decrease, for example linearly, to reach zero. It reaches zero for two limit values which are also different for the first and for the second mapping. The reading in maps can be replaced in an equivalent way by calculating the values corresponding to those mapped by carrying out tests on the value of the speed of the vehicle. The value "mapped" is then calculated as a function of the position of the speed with respect to two speed thresholds, in the form of a piecewise linear function. By at least one position of the box means for example at least one forward position of the box, or at least one reverse position of the box. According to an alternative embodiment, at least one position of the box means both a forward position of the box, and a reverse position of the box. By "the coupling setpoint tends towards the mapped value", it is meant that, starting from the value of the coupling setpoint at a given instant, the control unit determines a coupling setpoint value for the next instant which takes into account the current value of the coupling setpoint and which takes into account the mapped value corresponding to the current speed. The consideration is preferably made in such a way that, if the mapped value taken into account becomes constant, the coupling instruction converges towards this mapped value. It can also be considered, equivalently, that two levels of coupling setpoint are developed successively, the first level of the coupling setpoint being equal to a first value resulting from a first mapping function of the speed of the vehicle if the signal of pedal is less than a signal threshold, and equal to a second value derived from a second map based on the speed of the vehicle if the pedal signal is greater than the signal threshold. The second setpoint level is then obtained by digital filtering taking into account the history of the first setpoint level. Known filtering methods can be used to calculate the coupling setpoint at each instant, as a function of the value of the coupling setpoint at the previous instant -or of the value of the coupling setpoint over a period of time. previous instants-, and the mapped value taken as objective at the current time. Preferably, the coupling setpoint value is a total torque value, rather than a value proportional to the torque available at the output of the gearbox. Preferably, the maximum value of the first mapping corresponds to a value between 35% and 55% of the maximum torque value usually available at the output of the gearbox when the vehicle is traveling at 10km / h. Preferably, the maximum value of the second map corresponds to a value between 35% and 55% of the maximum torque value usually available at the gearbox output when the vehicle is traveling at a speed greater than that defined for the first time. mapping, for example 40km / h.

According to alternative embodiments, it is possible to envisage a coupling setpoint which defines a value of a fraction of torque to be transmitted to one of the wheel trains of the vehicle, as a function of the total torque available at the output of the gearbox. The gearbox may in particular be an automatic gearbox, for example transmitting four different signals depending on whether it is in forward mode, reverse mode, neutral mode or parking mode. According to another variant embodiment, the gearbox is a manual gearbox or a robotized gearbox, configured to transmit at least three different signals, instrumented or estimated, representing its state, depending on whether it is in forward gear configuration, reverse, or neutral position of freewheels. The coupler can for example be configured to be placed in at least two different coupling configurations, including a configuration without transfer of torque between the front axle and the rear axle of the vehicle, and a configuration with transfer of a torque whose value is determined. by the electronic control unit. The coupler can then be configured to transmit at least two different values to the control unit corresponding to the coupling modes. Preferably, the coupler may be placed in at least three different configurations, including a configuration without transfer of torque, a second configuration with transfer of a torque determined by the electronic control unit depending in particular on a difference in speed. of rotation between the front wheels and the rear wheels of the vehicle, and a third configuration with transfer of a torque determined by the electronic control unit without taking into account the difference in speed of rotation between the front wheels and the rear wheels of the vehicle, depending other operating parameters of the vehicle. This third configuration, which may for example be designated as the "lock" mode, is preferably that for which the electronic control unit elaborates the torque transfer setpoint to tend alternately to the two aforementioned maps. Advantageously, in said at least one selected mode of operation of the coupler, and for said at least one box position, the electronic control unit takes into account in the calculation of the coupling setpoint, only the overall speed of the vehicle, without taking into account differences in rotation speeds between different wheels of the vehicle, in particular without taking into account differences in rotation speeds between the front wheels and rear wheels of the vehicle. According to an advantageous embodiment, the control unit is furthermore configured to periodically check whether a combination of particular conditions on the vehicle speed, the gearbox position, and the pedal signal is verified and to put in this case to zero the coupling setpoint. This coupling setpoint is maintained at zero during a timeout interval if the combination of particular conditions is satisfied during the timeout interval.

Preferably, the control unit is furthermore configured, in at least one combination of particular conditions on the speed of the vehicle, the gearbox position, and the pedal signal, to periodically check during maintenance to zero of the coupling setpoint, if the pedal signal becomes greater than the signal threshold, and when the pedal signal becomes greater than the signal threshold, the control unit is configured to again develop a coupling setpoint whose value tends towards a value resulting from the second mapping. According to an advantageous embodiment, the engine torque distribution device comprises a gearbox with at least one forward position, at least one reverse position, and at least one neutral position uncoupling the wheels of the vehicle from a vehicle engine. In particular, the control unit is configured to zero the coupling setpoint if the coupling setpoint is other than zero, and if the gearbox is in the forward direction for a duration less than a threshold duration or is in reverse for a period of less than the threshold duration. According to an alternative embodiment, this zeroing of the torque setpoint can be further subject to an additional condition, such as for example the fact that the current state of the gearbox results from a forward-neutral passage -marche back or a passage back-neutral forward. The control unit may be further configured to then maintain this coupling setpoint at zero during the delay interval, unless the pedal signal becomes greater than the signal threshold before the timeout interval has elapsed ( timer interval elapsed since the zeroing of the coupling setpoint).

The dispensing device may further comprise an estimator of an operating temperature of the coupler, and the control unit may be configured to deliver a constant value coupling setpoint greater than all the values of the first and second mappings. , when the temperature value exceeds a threshold value. This "superlock" mode makes it possible to improve the crossing of obstacles when the torque delivered from the first and second maps is insufficient. The temperature estimator may for example be configured to estimate, for example by means of mappings, a value varying with the temperature of the coupler and with the slips between the input and the output of the coupler, for example from the value of the coupling setpoint, the value of a rotational speed of a coupler input shaft, a rotational speed of an output shaft of the coupler.

The invention also proposes a device for distributing a motor torque between a front axle and a rear axle of a motor vehicle configured to be able to pass from two to four driving wheels, comprising a controlled coupler configured to distribute the engine torque, comprising a mode selector of the coupler, the device being configured to be connected to a vehicle speed estimation means, to a gear position detector, and to an accelerator pedal. The device comprises an electronic control unit configured to develop a coupling setpoint imposing a torque transmitted by the coupler. The device further comprises a switch which can be placed either in a first state, wherein first state the device operates as the device described above, or in a second state, wherein second state the control unit is configured to output a coupling instruction without using a box position value. The switch may be a physical switch or a logical switch, for example a command in an initial vehicle configuration software at the factory outlet.

Advantageously, when the switch is in the second state, the control unit is configured to zero the coupling setpoint if the pedal signal becomes lower than the signal threshold, and is configured to maintain this coupling setpoint at zero during a delay interval, unless the pedal signal becomes greater than the signal threshold before the delay time has elapsed (timer interval elapsed since the coupling setpoint was reset). If the pedal signal becomes greater than the signal threshold before the delay time has elapsed, the control unit is configured to develop from this moment a coupling instruction whose value tends to a value derived from the second mapping. If the pedal signal remains below the signal threshold after the delay interval has elapsed, the control unit is configured to develop after the delay interval a coupling setpoint whose value tends towards a value derived from the first mapping. More generally, when the switch is in the second state, the control unit can be configured to, when the pedal signal is greater than the signal threshold, develop a coupling instruction whose value tends to a value derived from the second mapping. The invention also proposes a method of distributing a motor torque between a front axle and a rear axle of a motor vehicle configured to be able to pass from two to four driving wheels, using a vehicle speed value, a position value. of the vehicle's gearbox, a set value from an accelerator pedal. In this method, a coupling setpoint value is imposed on a coupler capable of distributing the engine torque between a front axle and a rear axle of the vehicle. For at least one mode of operation of the coupler, and for at least one gearbox position, a coupling setpoint is calculated whose value tends to a first value derived from a first mapping function of the vehicle speed if the signal pedal is less than a signal threshold, and tends to a second value derived from a second map based on the speed of the vehicle if the pedal signal is greater than the signal threshold. Preferably, for this mode of operation of the coupler and for this gearbox position, the coupling setpoint is determined without taking into account the differences in rotation speeds of the wheels between the front and rear axle of the vehicle. Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example, and with reference to the appended drawings, in which: FIG. 1 is a diagrammatic representation of A vehicle equipped with a dispensing device according to the invention, FIG. 2 is a simplified algorithm of a first part of an operating strategy of a dispensing device according to the invention, FIG. a simplified algorithm of a second strategy portion implemented in a distribution device according to the invention together with the strategy illustrated in FIG. 2; FIG. 4 is a simplified algorithm of a third strategy portion that can be set implemented in a dispensing device according to the invention. As illustrated in FIG. 1, a vehicle 2 equipped with a torque distribution device 1 according to the invention comprises - a front axle 3 carrying front wheels 11 and 12 of the vehicle, - a rear axle 5 carrying wheels rear 13 and 14 of the vehicle - a coupler 4 adapted to transmit, in variable proportions, a torque between the front axle 3 and the rear axle 5 of the vehicle. The torque distribution device 1 comprises an electronic control unit 10, which sends a coupling setpoint Ccons to the coupler 4, the setpoint Ccons representing a desired torque value at the second axle of the vehicle. This coupling setpoint is typically a total torque value (positive or negative) that it is desired to recover at the second axle of the vehicle.

In the example illustrated, the front axle 3 is connected to a gearbox 15 receiving a motor torque of a motor (not shown). Part of the torque available at the output of the gearbox can be transmitted to the rear axle 5 by means of the coupler 4. Each of the wheels 11, 12, 13, 14 is equipped with a wheel speed sensor respectively 21 , 22, 23, 24. These wheel speed sensors 21, 22, 23, 24 respectively transmit a value n1, n2, n3, n4 to a wheel speed calculator 6 which in turn transmits to the control unit electronics 10 four values which can be either the values ni, n2, n3, n4 of wheel rotation speed is values V1, V2, V3, V4 of linear speed of wheels and which also transmits to the electronic control unit 10 , a speed V representing the linear speed of advance of the vehicle, calculated according to known methods. The electronic control unit 10 is connected to maps 18 and 19 each connecting a value comparable to a speed V of linear advance of the vehicle, and a value comparable to a torque. The gearbox 15 comprises an instrumented gear lever 16, which transmits to the electronic control unit 10 a position value BV of the gearbox. The value BV represents the current mode in which the gearbox 15 is located and can typically take, for an automatic gearbox, values commonly referred to as "parking", "neutral", "drive" and "reverse". The invention can also be applied to robotic boxes, the value BV can then take values corresponding to the neutral position, the reverse, and different forward speeds. The dispensing device 1 comprises a mode selector 9 of the coupler 4, for example in the form of a man-machine interface allowing the driver of the vehicle to select an operating mode of the coupler 4 from at least two, and preferably from minus three different modes of operation of the coupler 4. The mode selector transmits a value "mode" to the electronic control unit 10. Typically, the value "mode" can take three values often referred to as "4x2" for a mode to only two driving wheels, the coupler being open, an "auto" mode for a torque transfer mode taking into account slippage between the front wheels 11, 12 and the rear wheels 13, 14 of the vehicle, for example from a calculation difference in speed of rotation between front wheel speed and rear wheel speed, and a "lock" mode for an off-road mode calculated without taking into account such differences in speed wheel rotation between the front wheels and the rear wheels of the vehicle. The dispensing device 1 also comprises an accelerator pedal 8 which transmits to the control unit 10 an Acc value conveying a desired acceleration instruction by the driver of the vehicle. This Acc acceleration setpoint can be obtained for example directly from a map connecting the position of the pedal 8 and the pedal setpoint Acc, or can be calculated by integrating more complex strategies taking into account other vehicle operating parameters such as for example the speed of the vehicle. In some embodiments, the dispensing device may include an estimator 7 configured to send to the electronic control unit 10 a value T comparable to an operating temperature of the coupler 4. This estimator may be absent in some embodiments of FIG. the invention. The temperature estimator 7 may be typically configured to estimate an operating temperature of the coupler 4 from parameters such as a rotational speed of an input shaft of the coupler 4, a rotational speed of an output shaft of the coupler 4, a coupling setpoint Ccons received by the coupler 4 and emanating for example from the electronic control unit 10.

To estimate the temperature of the coupler 4 which in fact translates a level of friction at the coupler 4, the estimator 7 can use different maps integrated in the estimator. The manner in which the electronic control unit 10 elaborates the coupling setpoint Ccons depends on various parameters and, in particular, follows different strategies according to the "mode" mode selected at the mode selector 9. The object of the invention is to particular on a strategy of elaboration of the setpoint of torque Ccons in a mode called "all terrain" of the coupler corresponding to a mode here called "lock" delivered by the selector of modes 9. In order to always ensure a relevant torque at the level of the rear axle of the vehicle, while limiting the occurrences of impact noise during reversals of rotation of the coupler 4, the electronic control unit is configured to go back and forth between several strategy components, two of which are illustrated in Figures 2 and 3, a first component to ensure sufficient torque as soon as the driver wants to move the vehicle forward or backward, and the second component providing a timed "opening" of the coupler when the history of the operating parameters of the vehicle indicates a probability of changing the direction of rotation of the coupler and the absence of urgency to immediately deliver a consequent torque at the second axle of the vehicle. FIG. 2 illustrates a simplified algorithm illustrating a part of the strategy for developing the coupling setpoint Cons by the electronic control unit 10 of FIG. 1. FIG. 2 shows some of the notations common to FIG. the same elements and the same variables being designated by the same references.

At a step 31, the electronic control unit 10 tests whether the mode selector 9 is in the "lock" position, and if it is not the case, successively performs tests 32 and 34 to check whether the selector is found in one of the other two possible modes "4x2" or "auto". The electronic control unit 10 then switches if necessary respectively, in step 33 to a strategy dedicated to "4x2" mode or step 35 to a strategy dedicated to the "auto" mode. The strategies corresponding to steps 33, 35 are not developed here. If, in step 31, the mode selector is indeed in "lock" mode, then in a step 36 the electronic control unit 10 performs a test to know if the transmission position value BV is equal to one of the values "park" (parking) or "N" (neutral). If the gearbox, after the test 36, is neither in the "park" position nor in the "N" position, it may be considered that the gearbox is in the "drive" position or in the "reverse" position; that it may possibly be reverified by a test 37. The test 37 may possibly be omitted according to the embodiments. A test 38 is then carried out to determine whether the value delivered by the accelerator pedal 8 is lower than a threshold threshold Acc, and whether, at the same time, a recent passage of the variable BV by the value N has been recorded. By "recent passage", it is possible for example to hear a passage going back to an earlier date of less than one second from the current moment. If one of the two conditions of the test 38 is not verified, then in a step 39 we switch to a calculation strategy of the variable C '' which is here designated as motricity strategy "Motr", this strategy is detailed in FIG. 3. If both conditions of the test 38 are satisfied, a test 40 is then carried out to check whether the gearbox is in the "drive" position and if at the same time the vehicle speed V is less than a first threshold speed 'liml'. If these two conditions are satisfied, the electronic control unit goes to step 43 of the algorithm 30. If one of the conditions of the test 40 is not satisfied, the electronic control unit 10 performs a test 41 to see if the position of the gearbox corresponds to the "reverse" position and if at the same time the speed in absolute value of the vehicle is less than a second speed threshold "lim2". If these two conditions are verified, the electronic control unit also goes to step 43. If none of the tests 40 or 41 is checked, then the electronic control unit switches, in a step 42, to the "Motr" motricity strategy, illustrated in FIG. 3. In steps 33, 35, 39, and 42, the electronic control unit 10 resets a timer counter "t" to zero. If one of the tests 40, 41 or 36 is verified, the electronic control unit therefore starts a portion of an algorithm corresponding to a step 43. In this step 43, the electronic control unit 10 performs a test for check if the coupling setpoint Cco 'is already zero, and if the delay variable t is strictly greater than zero, which would mean that an opening of the coupler has already been started. If the two conditions of the test 43 are verified, this means that the coupling setpoint Cco 'has already been set to zero and the timer countdown has been started. In this case, in a step 44, the coupling setpoint C '' is kept at zero and it is checked whether the "opening" time of the coupler has not already reached the desired minimum duration of the desired delay time. If the result of this test 45 is positive, the electronic control unit 10 returns to step 31. If the result of the test 45 is negative, the electronic control unit 10 maintains the service coupling set point zero. and increments the timer counter t by one increment S. It then returns to step 31. If the result of the test 43 is negative, it means that the coupling instruction has not yet been set to zero, and in In this case, in step 44, the electronic control unit 10 sets the coupling setpoint Ccons to zero, resets the timer counter t, and returns to step 31. Thus, as can be seen generally on FIG. 30, in order to avoid the noise related to the reversal of the direction of rotation of the coupler 4, the setpoint Cons is set to zero for a minimum duration of 1 minute, ie if the transmission lever is placed in parking mode or in "neutral" mode, ie if, following a recent passage by the neutral position, it is found that the vehicle is in maneuver at low speed, the low speed threshold having different values depending on whether the vehicle is in forward or reverse. However, if in step 38, despite a recent passage by the neutral point, the support on the accelerator pedal is greater than the threshold thresholdAcc, it is considered that the driver wants a quick reaction of the vehicle and we favor the traction of the vehicle on acoustic comfort, by switching to the so-called motor strategy described in FIG. 3. FIG. 3 illustrates an algorithm 50 of a strategy portion of elaboration of a coupling setpoint Cons, complementary to the portion The strategy of FIG. 2. FIG. 3 shows notations common to FIGS. 1 and 2, the same elements and the same variables being designated by the same references. The portion of the algorithm 50 represents a portion intended to improve the traction of the vehicle 2. It comprises test steps 51, 52 and 54 which, like the tests 31, 32 and 34 of FIG. 2, make it possible to switch over to other strategies than the strategy dedicated to off-road mode if the value "mode" delivered by the mode selector 9 is different from the value "lock". If necessary, at a step 53 or 55, the electronic control unit 10 switches respectively to a strategy type 4x2 or a strategy of auto type. If the result of the test 51 is positive, that is to say if the mode of the coupler actually corresponds to the off-road mode, the electronic control unit 10 performs a test 56 to check if the position of the gearbox corresponds to the values "park" or "N". If this is the case, the electronic control unit 10 then switches to a step 57, on step 31 of the algorithm portion of FIG. 2, designated here as the "noise canceling" strategy. Similarly, when in Figure 2 the electronic control unit 10 is found in steps 39 or 42, it resumes in step 51 the algorithm portion 50, or motricity strategy. If the result of the test 56 is negative, then it is possible to consider that the gearbox is in the "drive" or "reverse" position, and then a test 58 is made to determine whether the accelerator pedal is raised and whether a recent passage through the neutral point N of the gearbox 15 has been detected. If so, the electronic control unit 10 also switches to step 57 and the noise strategy. If the passage through the neutral position is already older, or if the accelerator pedal is pressed, the electronic control unit 10 goes to step 59 and tests whether the accelerator pedal is pressed, ie if the value of the pedal signal variable Acc is greater than the threshold threshold Acc. If the value of the pedal signal is below the threshold, then the electronic control unit proceeds to a step 60 using a reference map 18. If the pedal signal is greater than the threshold, then the electronic control unit 10 passes. in a step 61 using a reference map 19. The maps 18 and 19 are typically torque values as a function of the speed of the vehicle, which begin with a constant plateau value from the zero speed, to a first threshold speed which is different for the two maps, then the torque value decreases linearly until reaching zero at a second threshold speed which is also different for the two maps.

In ordinates, the torque values of the map 18 are typically all smaller than the values of pairs of the same abscissa of the map 19. The threshold speed values of the map 18 may for example be respectively between 20 and 30 km for the first, respectively. hour and for the second between 30 and 40 km / hour. The value of the plateau of the first map can be for example between 200 and 400 Newton.meter. The threshold speed values of the second map 19 may be for the first for example between 30 and 50 km / hour and for the second between 60 and 100 km / hour or better between 70 and 90 km / hour. The value of the plateau of the first map can be for example between 800 and 1000 Newton.meter. Other values may be considered in the context of the present invention. In step 60 as in step 61, the electronic control unit 10 reads, as a function of the speed V of the vehicle, in the associated map, a value Cobj which is a first-level coupling setpoint. We then go to a step 62, which develops a Cc.nsecond level coupling setpoint which is obtained by digital filtering of the torque setpoint values of the first level Cobj. The filtering can be done on one or more values of the first-level torque setpoint determined at the previous instants. The second-level coupling setpoint Ccons (t) is then sent as a reference value to the coupler 4 of FIG. 1. The electronic control unit 10 then returns to step 51. Thus, thanks to the portion of strategy so-called "traction" illustrated in Figure 3, as tests 56 or 58 do not detect the need to switch back on the noise strategy, the driver has, depending on whether it is pedal configuration raised or pedals supported respectively, a minimum torque allowing the crossing of obstacles at low speed (mapping 18) or a higher minimum torque (mapping 19). The torque is reduced in both cases as the vehicle speed increases to ensure sufficient vehicle stability.

If the result of the test 58 is positive, that is to say if the control unit 10 detects that it has just made a recent passage by the neutral position and detects that the accelerator pedal is raised, then the electronic control unit 10 switches to step 57 and applies the noise strategy of FIG. 2. In addition to the complementary operating diagrams of the electronic control unit described in FIGS. 2 and 3, which are applied when the coupler is in off-road mode, the electronic control unit 10 can also be configured to switch to a mode of operation called "superlock" which corresponds to a substitution of the maps 18 or 19 by a third map whose plateau is higher as the map plate 19, when certain particular operating conditions are detected, for example when the temperature estimator 7 detects a "temperature" T d e operation above a threshold. The level of torque imposed at low speed for this "superlock" mode may for example be at least 10% greater than the maximum torque level of the map 19. Thus in the mode of operation of the coupler in off-road mode according to the the invention, the driver always has a sufficient wheel torque for the crossing of obstacles encountered, while maintaining a mode of operation independent of slips possibly found between the front and rear train of the vehicle.

The driver thus has a vehicle reaction mode and adaptation to obstacles encountered, which is different from the automatic mode, and which is better suited for example in terrain where the sliding between the front and rear axle is very variable. The dispensing device according to the invention may also be equipped with a switch which makes it possible to activate in a first position of the switch the strategy described above in FIGS. 2 and 3, this strategy being typically activated during the commissioning the vehicle at the factory if the vehicle has an automatic transmission or a box to know, at the electronic control unit 10, the current position of the box. The second position of the switch makes it possible to place the dispensing device 1 in a configuration where the strategy used during the off-road mode is independent of the position of the gearbox. This configuration, an embodiment of which is illustrated by the simplified algorithm 63 of FIG. 4, can typically be activated when the vehicle is put into service at the time of delivery if the vehicle is equipped with a manual transmission. . Part of this strategy for manual gearbox can take steps of the algorithm of FIG. 2 which are independent of the position BV of the gearbox, and part of the steps of FIG. 3 also independent of the position of the gearbox. gearbox. An example of a corresponding algorithm 63 is illustrated in FIG. 4. FIG. 4 shows notations common to FIGS. 1 to 3, the same variables and the same elements being designated by the same references. The algorithm 63 takes up the upper part of the algorithm 30 of FIG. 2, in particular steps 31 to 35 and then steps 43 to 46, except that step 43 is triggered by the passage of the pedal signal Acc. below a threshold value in a step 66 provided that this passage under the pedal signal threshold provided that this crossing of the threshold is recent (date distant from the current moment of a value below a duration threshold A -seull) - If the result of the test 66 is negative, the control unit resets in a step 64 the timer counter "t" to zero. It then goes on to a step 59 corresponding to step 59 of FIG. 3, then by steps 60 to 62 similar to those of FIG. 3 and using mappings 18 and 19, and loops back on test 31 to verify that the Off-road mode is always on. This provides a global coupler management strategy that optimizes both vehicle traction and acoustic comfort while being easily adaptable to both an automatic transmission configuration and a manual transmission configuration.

The invention is not limited to the embodiments described and can be declined in many variants. The maps used may be different from those described here. The dispensing device may or may not have a switch to switch from the automatic transmission configuration to the manual transmission configuration. The algorithms of FIGS. 2, 3 and 4 may be replaced by other algorithms making it possible to obtain an equivalent distribution torque control mode.

Claims (10)

REVENDICATIONS1. Device (1) for distributing a driving torque between a front axle (3) and a rear axle (5) of a motor vehicle (2) configured to be able to pass from two to four driving wheels (11, 12, 13, 14), comprising a controlled coupler (4) configured to distribute a driving torque between the front end and the rear end of the vehicle, comprising a mode selector (9) of the coupler (4), and comprising a control unit electronics (10) connected to an estimation means (6) of the speed (V) of the vehicle, to a gearbox (15) configured to transmit the current position of the gearbox (BV), and to a pedal of acceleration (8) emitting a pedal signal (Acc), the electronic control unit being configured to develop a coupling setpoint (Ccons) imposing a torque transmitted by the coupler (4), characterized in that, for at least one selected mode of operation of the coupler (4), and for at least one position (drive , reverse) of the gearbox, the electronic control unit (10) is configured to develop a coupling setpoint (Ccons) whose value tends to a first value (Cobj) resulting from a first mapping (18) depending on the speed (V) of the vehicle if the pedal signal (Acc) is less than a signal threshold (thresholdAcc), and tends to a second value (Cobj) resulting from a second mapping (19) depending on the speed (V ) of the vehicle if the pedal signal (Acc) is greater than the signal threshold (thresholdAcc). The engine torque distribution device according to claim 1, wherein the control unit (10) is further configured to periodically check whether a combination of particular conditions on the vehicle speed (V), the position of gearbox (BV), and the pedal signal (Acc) are met, is configured to zero the coupling setpoint (Ccons) if the combination of particular conditions is verified, and is configured to maintain this coupling setpoint at zero during a delay interval (to ',) if the combination of particular conditions is maintained during the delay time (all). Motor torque distribution device according to claim 2, wherein the control unit (10) is furthermore configured, in at least one combination of particular conditions on the speed of the vehicle (V), the position of gearbox (BV), and the pedal signal (Acc), to periodically check during zeroing of the coupling setpoint, if the pedal signal (Acc) becomes greater than the signal threshold (thresholdAcc), and when the pedal signal becomes greater than the signal threshold, the control unit is configured to again develop a coupling setpoint (Ccons) whose value tends to a value from the second mapping (19). 4. Device for distributing a motor torque according to one of claims 2 or 3, comprising a gearbox with at least one forward position (drive), at least one reverse position (reverse), and at at least one neutral position (N) decoupling the wheels of the vehicle from a motor of the vehicle, wherein the control unit (10) is in particular configured to zero the coupling setpoint (Ccons) if the coupling setpoint is different from zero and if the gearbox is in forward motion (drive) for a duration less than a threshold duration or is in reverse gear (reverse) for a duration less than the threshold duration. 5. Device for distributing a motor torque according to claim 4, wherein the control unit (10) is configured to then maintain this coupling setpoint (Ccons) to zero during the delay time (ton,), unless the pedal signal (Acc) becomes greater than the signal threshold (thresholdAcc) before the delay time (tone,) has elapsed. Motor torque distribution device according to any one of the preceding claims, further comprising an estimator (7) of an operating temperature (T) of the coupler, wherein the control unit (10) is further configured to provide a constant-value coupling setpoint (Ccons) greater than all values of the first (18) and the second mapping (19), when the temperature value exceeds a threshold value. 7. Device for distributing a driving torque between a front axle (3) and a rear axle (5) of a motor vehicle (2) configured to be able to pass from two to four driving wheels (11, 12, 13, 14 ), comprising a controlled coupler (4) configured to distribute the motor torque, comprising a mode selector (9) (mode) of the coupler (4), the device (1) being configured to be connected to an estimation means (6) the speed (V) of the vehicle (2), a transmission position detector, an accelerator pedal, and comprising an electronic control unit (10) configured to develop a coupling setpoint ( Ccons) imposing a torque transmitted by the coupler (4), the device further comprising a switch which can be placed in a first state, wherein the first state the device functions as a device according to any one of the preceding claims, or in a second state, in which second state the control unit (10) is configured to deliver a coupling setpoint (Ccons) without using a box position value. Motor torque distribution device according to claim 7, wherein, when the switch is in the second state, the control unit is configured to reset the coupling setpoint (C, ..) if the pedal signal becomes less than the signal threshold (thresholdAcc), and is configured to maintain this coupling setpoint at zero during a delay interval, unless the pedal signal (Acc) becomes greater than the signal threshold (thresholdAcc) before the delay time (ton,) has elapsed. The engine torque distributing device according to claim 8, wherein, when the switch is in the second state, the control unit (10) is configured for, when the pedal signal (Acc) is greater than threshold signal (thresholdAcc), develop a coupling setpoint (Ccons) whose value tends to a value from the second mapping (19). 10. A method of distributing a driving torque between a front axle (3) and a rear axle (5) of a motor vehicle configured to be able to pass from two to four driving wheels (11, 12, 13, 14), using a vehicle speed value (V), a vehicle gearbox position value (BV), a setpoint value (Acc) derived from an acceleration pedal, in which a coupling setpoint value is imposed (Ccons) to a coupler adapted to distribute the engine torque between a front axle and a rear axle of the vehicle, characterized in that, for at least one operating mode (lock) of the coupler, and for at least one position (BV) of a gearbox, a coupling setpoint (Ccons) whose value tends to a first value derived from a first cartography (18) which is a function of the speed of the vehicle is calculated if the pedal signal is below a signal threshold, and tends to a second value from a second mapping (19) depending on the speed (V) of the vehicle if the pedal signal (Acc) is greater than the signal threshold (thresholdAcc).