CONTROLLING THE DISCONNECTION OF A WHEEL INDIRECTLY COUPLED TO A DIFFERENTIAL COUPLED TO AN ELECTRIC DRIVE MACHINE OF A LAND VEHICLE

Abstract

A control method is implemented in a land vehicle comprising a first half-axle provided with a first wheel, a second half-axle provided with a second wheel and a coupling device capable of being placed in connected and disconnected states, and an electric prime mover coupled to a differential capable of being placed in locked and unlocked states and coupled to the half-axles. This method comprises a step (10-60) in which, in the presence of a request to disconnect the second wheel, it is determined whether the differential is in the unlocked state, and if so, the disconnection is authorized, while if not, a placement of the differential in the unlocked state is ordered and then it is determined again whether the differential is actually in the unlocked state. Figure 3

Description

Title of the invention: CONTROL OF THE DISCONNECTION OF A WHEEL INDIRECTLY COUPLED TO A DIFFERENTIAL COUPLED TO AN ELECTRIC DRIVE MACHINE OF A LAND VEHICLE Technical field of the invention

[0001] The invention relates to land vehicles comprising an electric motor coupled to two half-wheel sets via a differential, and more specifically to the control within such vehicles of the disconnection of a wheel from its half-wheel set. State of the art

[0002] Certain land vehicles, possibly of the automobile type, comprise a transmission chain comprising, for example in a rear part, a first half-train provided with a first wheel, a second half-train provided with a second wheel and a coupling device, and an electric motor coupled to a differential which can be placed in locked and unlocked states and coupled to the first and second half-trains.

[0003] Here, the term "electric motor machine" means an electric machine arranged at least so as to provide engine torque to the first and second half-axles, to which it is coupled via the associated differential, to move its vehicle when it is supplied with electrical energy.

[0004] In the aforementioned vehicles, the coupling device can be selectively placed either in a connected state in which the second wheel is connected (or coupled) to the second half-train (and therefore driven at the same time as the latter), or in a disconnected state in which the second wheel is disconnected (or decoupled) from the second half-train (and therefore cannot be driven at the same time as the latter). This advantageously makes it possible to decouple the electric drive machine from the first and second half-trains.

[0005] When the coupling device is selectively placed in its connected state and the differential is selectively placed in an unlocked state, this allows for different rotational speeds of the first and second wheels, which is useful when cornering. On the other hand, when the coupling device is selectively placed in its connected state and the differential is selectively placed in a locked state, this imposes identical rotational speeds of the first and second wheels.

[0006] In the presence of such an arrangement, when the electric motor is decoupled from the first and second half-trains while the differential is in its state blocked, the torque and speed of the electric motor are entirely directed towards the first wheel which is the only one connected to its first half-train, and therefore the vehicle risks spinning out, which can be dangerous for the safety of the vehicle and its passengers, but also for the safety of objects and people located in the environment of this vehicle. Consequently, before disconnecting (or decoupling) the electric motor from the first and second half-trains (by decoupling the second wheel from its second half-train), it is essential that the differential be placed in its unlocked state.

[0007] Currently, it is the driver of the vehicle who must place the differential in its unlocked state (first action) before ordering the placement of the coupling device in its disconnected state (second action).This requires not only that he understands the reason for these actions, but also that he systematically thinks about doing them. But, even when the driver performs these actions in the correct order and the indicator light associated with the differential signals that the latter is in its unlocked state, it is not certain that the information provided by the indicator light is true because the information indicating the state in which the differential is placed is not 100% reliable. It may indeed happen that this information indicates the unlocked state while in reality the differential is placed in its locked state or in an uncertain state.

[0008] The invention therefore aims in particular to improve the situation by automating the control of the disconnection of the second wheel from its second half-train. Presentation of the invention

[0009] For this purpose, it proposes in particular a control method intended to be implemented in a land vehicle comprising:

[0010] - a first half-train provided with a first wheel,

[0011] - a second half-train provided with a second wheel and a coupling device capable of being placed in connected and disconnected states in which the second wheel is respectively connected and disconnected, and

[0012] - an electric motor coupled to a differential which can be placed in blocked and unblocked states and coupled to the first and second half-trains.

[0013] This control method is characterized by the fact that it comprises a step in which, in the presence of a request to disconnect the second wheel, it is determined whether the differential is in the unlocked state, and if so, disconnection is authorized, while if not, a placement of the differential in the unlocked state is ordered and then it is determined again whether the differential is actually in the unlocked state.

[0014] Thanks to the invention, we are now sure that when we authorize the placement of the coupling device in its disconnected state, the differential is actually in its unlocked state, which ensures that the torque and speed of the prime mover will not be entirely directed to the first wheel of the first half-train.

[0015] The control method according to the invention may include other characteristics which may be taken separately or in combination, and in particular:

[0016] - in its step, it can be ordered that the electric motor provides a engine torque varying according to a predefined variation law in order to determine whether the first and second wheels have identical behaviors, then if not we can consider that the differential is in the unlocked state, while if so we can order a placement of the differential in the unlocked state then we can determine again if the differential is actually in the unlocked state;

[0017] - in the presence of the first option, in its step, when the first and second wheels have identical behaviors, we can determine whether the vehicle is moving substantially in a straight line, and if so (straight line) we can consider that the differential is in an uncertain state, while if not (turning) we can consider that the differential is in a blocked state;

[0018] - in the presence of the last sub-option, in its step, we can determine whether a the vehicle's steering wheel has a current rotation angle greater than a chosen threshold, and if so, the vehicle can be considered to be in a turn and therefore the differential is in the locked state, while if not, the vehicle is considered to be moving substantially in a straight line and therefore the differential is in the uncertain state;

[0019] - as a variant and still in the presence of the last sub-option, in its step, we can determine whether a current geographical position of the vehicle corresponds to the presence of the latter on a portion of traffic lane substantially in a straight line, and if so, the differential can be considered to be in an uncertain state, while if not, the differential can be considered to be in a blocked state;

[0020] - also in the presence of the first option, in its step, the law of variation predefined may consist of a monotonic increase followed by a monotonic decrease to a zero value;

[0021] - in its step, before determining whether the differential is in the unblocked state, we can start by determining whether the differential is in the locked state, and if not, one can determine whether the differential is in the unlocked state, while if so, one can order a placement of the differential in the unlocked state and then one can determine whether the differential is actually in the unlocked state.

[0022] The invention also provides a computer program product comprising a set of instructions which, when executed by processing means, is capable of implementing a control method of the type presented above, in a land vehicle comprising a first half-train provided with a first wheel, a second half-train provided with a second wheel and a coupling device which can be placed in connected and disconnected states in which the second wheel is respectively connected and disconnected, and an electric motor coupled to a differential which can be placed in locked and unlocked states and coupled to the first and second half-trains, to control the disconnection of the second wheel.

[0023] The invention also proposes a control device intended to equip a land vehicle comprising:

[0024] - a first half-train provided with a first wheel,

[0025] - a second half-train provided with a second wheel and a coupling device capable of being placed in connected and disconnected states in which the second wheel is respectively connected and disconnected, and

[0026] - an electric motor coupled to a differential which can be placed in blocked and unblocked states and coupled to the first and second half-trains.

[0027] This control device is characterized by the fact that it comprises at least one processor and at least one memory arranged to carry out the operations consisting, in the presence of a request to disconnect the second wheel, in determining whether the differential is in the unblocked state, and if so, in authorizing the disconnection, or if not, in ordering a placement of the differential in the unblocked state and then in determining again whether the differential is actually in the unblocked state.

[0028] The invention also proposes a land vehicle, possibly of the automobile type, and comprising, on the one hand, a first half-train provided with a first wheel, a second half-train provided with a second wheel and a coupling device which can be placed in connected and disconnected states in which the second wheel is respectively connected and disconnected, and an electric motor coupled to a differential which can be placed in locked and unlocked states and coupled to the first and second half-trains, and, on the other hand, a control device of the type presented above. Brief description of the figures

[0029] Other characteristics and advantages of the invention will appear on examining the detailed description below, and the appended drawings, in which:

[0030] [Fig-1] schematically and functionally illustrates an example of the embodiment of a land vehicle comprising a transmission chain including in particular a control device according to the invention and an electric motor controlled by a machine computer and coupled to a differential, itself coupled to half-wheel sets, one of which comprises a coupling device,

[0031] [Fig.2] schematically and functionally illustrates an exemplary embodiment of a machine calculator comprising an exemplary embodiment of a control device according to the invention, and

[0032] [Fig.3] schematically illustrates an example of an algorithm implementing a control method according to the invention. Detailed description of the invention

[0033] The invention aims in particular to propose a control method, and an associated control device DC4, intended to allow control of the disconnection, by action on a (first) coupling device DC1, of a (second) wheel RR2 of a (second) half-train DT2 coupled, like a (first) half-train DTI (to which a (first) wheel RR1 is connected), to a differential DR which is also coupled to a (first) electric motor MM1 of a land vehicle V.

[0034] In the following, it is considered, by way of non-limiting example, that the land vehicle V is of the automobile type. It is for example a car, as illustrated in [Fig.l]. But the invention is not limited to this type of land vehicle. It in fact relates to any type of land vehicle comprising a transmission chain comprising a differential coupled to a wheel set, provided with a coupling device, and to an electric drive machine. Thus, it relates to utility vehicles, camper vans, minibuses, coaches, trucks, road machinery, construction machinery, and agricultural machinery, for example.

[0035] Furthermore, it is considered in the following, by way of non-limiting example, that the land vehicle V comprises a transmission chain with a hybrid (thermal and electric) powertrain (or GMP). But the GMP could be of the all-electric type (and in this case the drive is provided exclusively by at least one electric motor (here MM1)).

[0036] [Fig.l] schematically shows a (land) vehicle V comprising a transmission chain including in particular a control device DC4 according to the invention, a service battery BS, a main battery BP, a converter CV, and a first electric motor MM1, controlled by a machine computer CM and coupled to a differential DR, itself coupled to first DTI and second DT2 half-wheel sets, one of which (here DT2) comprises a first coupling device DC1 having disconnected and connected states.

[0037] It will be noted that in the example illustrated non-limitingly in [Fig.l] the transmission chain also comprises a second thermal motor MM2 and a possible third electric motor MM3, and a supervision computer CS. But the powertrain (or GMP) of the transmission chain could only comprise the first electric motor MM1, or the first MM1 and third MM3 electric motors, or the first electric motor MM1 and the second thermal motor MM2.

[0038] It is recalled that the term “drive machine” here means a machine arranged at least so as to provide engine torque to move the vehicle V when it is supplied with drive energy.

[0039] The operation of the transmission chain (and therefore of the GMP) is supervised by a CS supervision computer.

[0040] The service battery BS is responsible for supplying electrical energy to the on-board network of the vehicle V, in addition to that supplied by the CV converter powered by the main battery BP via a main electrical circuit, and sometimes instead of this CV converter. For example, this service battery BS may be arranged in the form of a very low voltage type battery (typically 12 V, 24 V or 48 V). It is rechargeable at least by the CV converter. It is considered in the following, by way of non-limiting example, that the service battery BS is of the 12 V Lithium-ion type.

[0041] The on-board network is an electrical power supply network to which electrical (or electronic) equipment (or components) that consume electrical energy are coupled.

[0042] The main electrical circuit (or "high voltage" or "power") is connected, on the one hand, to the main battery BP via an interface device, and, on the other hand, to electronic equipment, such as for example the CV converter and the first MM1 and third MM3 (electric) prime movers. It also allows the main battery BP to be recharged by an external power source and temporarily coupled to a vehicle charging connector V.

[0043] The first electric motor MM1 (here an electric motor) is coupled to the main battery BP via the main electrical circuit, in order to be supplied with electrical energy, as well as possibly to supply this main battery BP with electrical energy during a regenerative braking phase.

[0044] Furthermore, this first electric motor MM1 is coupled to the differential DR via a first transmission shaft ATI. This differential DR is coupled to a first train T1 (of wheels) subdivided into a first half-train DTI provided with a first wheel RR1 and a second half-train DT2 provided with a second wheel RR2 and the first coupling device DC1. In addition, the differential DR can be selectively placed in an unlocked state, allowing different rotational speeds of the first RR1 and second RR2 wheels, or in a locked state, imposing identical rotational speeds of the first RR1 and second RR2 wheels.

[0045] The first coupling device DC1 can be selectively placed in a connected state in which the second wheel RR2 is connected (or coupled) to the second half- DT2 train which can be driven by the DR differential, or in a disconnected state in which the second wheel RR2 is disconnected (or decoupled) from this second half-train DT2.

[0046] For example, the first coupling device DC1 may be a dog clutch device. But this is not mandatory.

[0047] The first train T1 is here located in the rear part PRV of the vehicle V. But in a variant this first train T1 could be the one which is here referenced T2 and which is located in the front part PVV of the vehicle V.

[0048] The operation of the first electric motor machine MM1 (and preferably of the first coupling device DC1) is controlled by a machine computer CM, and supervised by the supervision computer CS.

[0049] It will be noted that in the example illustrated non-limitingly in [Fig.l] the transmission chain also comprises a first gearbox BV1 interposed between the output of the first electric motor MM1 and the first transmission shaft ATI. But this is not an obligation.

[0050] The second driving machine MM2 is thermal and is responsible, when supplied with fuel, for producing a driving torque and supplying the latter to a driving shaft AM which is connected to a second coupling device DC2. The latter (DC2) is capable of coupling the second driving machine MM2 to a primary shaft AP of a second gearbox BV2 to supply it with the driving torque produced by the second driving machine MM2.

[0051] The output shaft of the second gearbox BV2 is coupled to a second transmission shaft AT2 which is itself coupled to the second wheel set T2, preferably via a differential DV.

[0052] For example, the second coupling device DC2 may be a hydraulic circuit clutch. But it could be of another type.

[0053] Also for example, the second gearbox BV2 can be automated. Thus, it can, for example, be double clutch (or DCT (“Dual Clutch Transmission”)). But this is not obligatory.

[0054] It will be noted that in the example illustrated non-limitingly in [Fig.l] the crankshaft of the second prime mover MM2 is also coupled to a belt, itself coupled to an alternator-starter AD which is supplied with electrical energy by the service battery BS (and which can also recharge the latter (BS)). Thus, the alternator-starter AD can supply torque to the belt, which can supply this torque to the crankshaft.

[0055] The third driving machine MM3 is electric and is responsible, when supplied with electrical energy by the main battery BP, for producing engine torque.

[0056] Furthermore, this third driving machine MM3 is, here, suitable for being coupled, downstream of the second coupling device DC2, by a third coupling device DC3, to the second gearbox BV2 to provide it with the engine torque that it produces. But in a variant not illustrated, the third driving machine MM3 could be directly interposed between the output of the second coupling device DC2 and the primary shaft AP.

[0057] The operation of the third electric motor MM3 is controlled by a machine computer (not shown), and supervised by the supervision computer CS.

[0058] The third coupling device DC3 can be placed in coupled and decoupled states, depending on a state instruction generated by the GMP supervision computer CS.

[0059] Furthermore, this third coupling device DC3 may, for example, comprise a cascade of pinions connecting the third driving machine MM3 to the input of the second gearbox BV2 (downstream of the second coupling device DC2).

[0060] The CV converter is also responsible, here, during the driving phases of the vehicle V for converting part of the electric current stored in the main battery BP to supply converted electric current to the on-board network and the service battery BS (to recharge it).

[0061] The main (or "traction" or "power") battery BP supplies here, in particular, the first MM1 and third MM3 electric motors. It may, for example, comprise electrical energy storage cells, possibly electrochemical (for example of the lithium-ion (or Li-ion) or Ni-Mh or Ni-Cd type). Also for example, the main battery BP may be of the low voltage type (typically 450 V for illustration purposes). But it could be of the medium voltage or high voltage type.

[0062] As mentioned above, the invention proposes in particular a control method intended to allow the control of the disconnection of the second wheel RR2 of the land vehicle V. It will be noted that in the example illustrated non-limitingly in [Fig.l], this disconnection of the second wheel RR2 is intended to allow the movements of the vehicle V only by means of the engine torque supplied to its second train T2 (here the front train) and produced by the second driving machine MM2 and / or the third driving machine MM3.

[0063] This (control) method can be implemented at least partially by the control device DC4 (illustrated at least partially in Figures 1 and 2) which comprises for this purpose at least one processor PR1, for example a digital signal processor (or DSP ("Digital Signal Processor")), and at least one memory MD. This control device DC4 can therefore be implemented in the form of a combination of circuits or electrical or electronic components (or "hardware") and software modules (or "software"). For example, this could be a microcontroller.

[0064] The memory MD is RAM in order to store instructions for the implementation by the processor PR1 of at least part of the control method. The processor PR1 may comprise integrated (or printed) circuits, or several integrated (or printed) circuits connected by wired or wireless connections. An integrated (or printed) circuit is understood to mean any type of device capable of carrying out at least one electrical or electronic operation.

[0065] In the example illustrated non-limitingly in Figures 1 and 2, the control device DC4 is part of the machine computer CM. But this is not obligatory. Indeed, the control device DC4 could comprise its own dedicated computer, which is then coupled to the machine computer CM, or could be part of another computer of the vehicle V, such as for example the supervision computer CS.

[0066] As illustrated non-limitingly in [Fig. 3], the (control) method, according to the invention, comprises a step 10-60 which is implemented each time the vehicle V has its GMP in operation and its first electric motor MM1 is coupled to the first train T1 (due to the placement of the first coupling device DC1 in its connected (or coupled) state).

[0067] Step 10-60 of the method comprises a sub-step 40 in which, in the presence of a request to disconnect the second wheel RR2, it is determined (for example the control device DC4) whether the differential DR is in its unblocked state.

[0068] It will be noted that the request to disconnect the second wheel RR2 can come from the driver of the vehicle V or from a computer of the latter (V), such as for example the supervision computer CS.

[0069] If the differential DR is in its unblocked state (and therefore in the affirmative), step 10-60 of the method also comprises a sub-step 50 in which one (for example the control device DC4) authorizes the requested disconnection. On the other hand, if the differential DR is in its blocked state or in an uncertain state (and therefore in the negative), step 10-60 of the method also comprises a sub-step 20 in which one (for example the control device DC4) orders a placement of the differential DR in its unblocked state, then one (for example the control device DC4) performs at least sub-step 40 again in order to determine again whether the differential DR is actually in its unblocked state.

[0070] Thus, it is ensured in an automated manner that the differential DR is indeed in its unblocked state before authorizing the placement of the first coupling device DC1 in its disconnected state (and therefore the disconnection of the second wheel RR2 from its second half-train DT2), which guarantees that the torque and speed of the first machine MM1 drive wheel will not be entirely directed towards the first wheel RR1 of the first DTI half-train. This increases the safety of vehicle V and its passengers, but also the safety of objects and people located in the environment of vehicle V.

[0071] In order to determine (or verify) whether the differential DR is in its unblocked state, one can, for example, proceed as described below (in a non-limiting manner).

[0072] For example, and as illustrated non-limitingly in [Fig. 3], step 10-60 may comprise a sub-step 30 in which one (for example the control device DC4) may order that the first electric motor MM1 provides a motor torque which varies according to a predefined variation law in order to solicit the first train T1, and more precisely its first RR1 and second RR2 wheels. It will be understood that this solicitation is intended to determine whether the first RR1 and second RR2 wheels have identical behaviors. This latter determination is carried out in sub-step 40 of step 10-60.

[0073] It will be noted that the first RR1 and second RR2 wheels can be considered to have identical behaviors if they have substantially identical rotational speeds or if they receive substantially the same engine torque. The rotational speed at a wheel RR1 or RR2 can, for example, be estimated by a sensor coupled to its wheel hub, which can constitute an angular encoder determining a number of teeth passing in front of it per second. The engine torque received at a first RR1 or second RR2 wheel can be estimated from measurements made by at least one sensor coupled to this first RR1 or second RR2 wheel.

[0074] If the first RR1 and second RR2 wheels have different behaviors (and therefore in the negative in substep 40), one (for example the control device DC4) can consider that the differential DR is indeed in its unblocked state. Indeed, as indicated above the first RR1 and second RR2 wheels can only have different behaviors on condition that the differential DR is in its unblocked state. In this situation, one (for example the control device DC4) performs substep 50 to authorize the requested disconnection.

[0075] On the other hand, if the first RR1 and second RR2 wheels have identical behaviors (and therefore in the affirmative in sub-step 40), one (for example the control device DC4) can order the placement of the differential DR in its unblocked state. Indeed, as indicated above the first RR1 and second RR2 wheels can have identical behaviors if the differential DR is in its blocked state or if the differential DR is in its unblocked state and the vehicle V is moving substantially in a straight line. In these situations, one (for example the control device DC4) can again perform sub-step 20. Then, one (for example the control device DC4) can determine (or check) again whether the differential DR is actually in its unblocked state by performing sub-steps 30 and 40 again.

[0076] For example, and as illustrated non-limitingly in [Fig. 3], step 10-60 may comprise a sub-step 60 in which, when the first RR1 and second RR2 wheels have identical behaviors, it may be determined (for example the control device DC4) whether the vehicle V is moving substantially in a straight line. This latter determination is intended to remove ambiguity from the actual state of the differential DR. Indeed, if the vehicle V is in a bend (and therefore in the negative (not in a straight line)), it may be considered (for example the control device DC4) that the differential DR is in a blocked state which requires that the first RR1 and second RR2 wheels have identical behaviors.On the other hand, if the vehicle V moves substantially in a straight line (and therefore in the affirmative), we (for example the control device DC4) can consider that the differential DR is in an uncertain state, since the differential DR is assumed to be in its unblocked state which allows different behaviors of the first RR1 and second RR2 wheels even though these behaviors are identical.

[0077] It will be noted that when the differential DR is in an uncertain state, such as when the differential DR is in its blocked state, one (for example the control device DC4) performs sub-step 20 again, then one (for example the control device DC4) determines (or verifies) again whether the differential DR is actually in its unblocked state by performing sub-steps 30 and 40 again.

[0078] In order to determine whether the vehicle V is moving substantially in a straight line, one can proceed in at least two ways described below.

[0079] In a first way, in sub-step 60 of step 10-60, when the first RR1 and second RR2 wheels have identical behaviors, one (for example the control device DC4) can determine whether the steering wheel of the vehicle V has a current rotation angle arv which is greater than a chosen threshold si (characteristic of a turn). If so (arv > si and identical behaviors), one (for example the control device DC4) can consider that the vehicle V is in a turn and therefore that the differential DR is in its locked state. On the other hand, if not (arv < si and identical behaviors), one (for example the control device DC4) can consider that the vehicle V is moving substantially in a straight line and therefore that the differential DR is in the uncertain state.

[0080] For example, the chosen threshold si can be between 10° and 30°. As an illustrative example, the chosen threshold si can be equal to 20°. But other values ​​of the chosen threshold si can be used. For example, the value of the threshold si can be chosen during the development (or testing) phase of the vehicle V.

[0081] In a second way, in sub-step 60 of step 10-60, when the first RR1 and second RR2 wheels have identical behaviors, one (for example the control device DC4) can determine if the current geographical position of the vehicle V corresponds to the presence of the latter (V) on a portion of traffic lane which is substantially in a straight line. If so, one can consider that the differential DR is in an uncertain state, while if not one can consider that the differential DR is in its blocked state.

[0082] It will be noted that the current geographical position of the vehicle V can, for example, be determined by a satellite guidance device (or GPS) present in the vehicle V. It will also be noted that the characteristics of the portion of traffic lane on which the vehicle V is traveling can be determined in a cartographic database present in the vehicle V or accessible in a server with which a communication module present in the vehicle V can communicate by radio waves.

[0083] Also for example, in sub-step 30 of step 10-60 the predefined variation law may consist of a monotonic increase followed by a monotonic decrease to a zero value.

[0084] For example, the control device DC4 can generate a request requiring the first electric motor MM1 to provide a motor torque, defined by the predefined variation law, to the machine computer CM, and, upon receipt of this request, the machine computer CM controls the first electric motor MM1 so that it provides this motor torque.

[0085] Preferably, the amplitude of the monotonic increase in the engine torque is small so as not to significantly disrupt the operation of the transmission chain and not to consume too much electrical energy stored in the main battery BP. For example, this amplitude of the monotonic increase can be between 3 Nm and 10 Nm. As an illustrative example, the amplitude of the monotonic increase can be equal to 5 Nm. But other values ​​of the amplitude of the monotonic increase can be used. For example, the value of the amplitude of the monotonic increase can be chosen during the development (or testing) phase of the vehicle V.

[0086] Also for example, and as illustrated non-limitingly in [Fig. 3], step 10-60 may comprise a sub-step 10 in which, before determining whether the differential DR is in its unblocked state, one (for example the control device DC4) may begin by determining whether the differential DR is in its blocked state. This latter determination may be made with the machine computer CM, for example. If not (unblocked state), one (for example the control device DC4) performs sub-steps 30 and 40 to determine whether the differential DR is in its unblocked state, because the information having just been obtained from the computer machine CM is not 100% reliable. On the other hand, if so (blocked state) we (for example the control device DC4) carry out sub-step 20 to order a placement of the differential DR in its unblocked state, then we (for example the control device DC4) carry out sub-steps 30 and 40 to determine (or check) whether the differential DR is indeed in its unblocked state.

[0087] It will also be noted, as illustrated non-limitingly in [Fig. 2], that the machine computer CM (or the computer of the control device DC4) can also comprise a mass memory MEM, in particular for storing the possible current rotation angle of the steering wheel or the possible current geographical position of the vehicle V and the possible characteristics of the portion of traffic lane on which the vehicle V is traveling, as well as possible intermediate data involved in all its calculations and processing.Furthermore, this machine calculator CM (or the calculator of the control device DC4) can also comprise an input interface IE for receiving at least the possible current rotation angle of the steering wheel or the possible current geographical position of the vehicle V and the possible characteristics of the portion of traffic lane on which the vehicle V is traveling, to use them in calculations or processing, possibly after having shaped and / or demodulated and / or amplified them, in a manner known per se, by means of a digital signal processor PR2.In addition, this machine calculator CM (or the calculator of the control device DC4) can also include an output interface IS, in particular to deliver a message authorizing disconnection of the second wheel RR2, or a possible message (or order) for placing the differential DR in its unblocked state, or even a possible message (or order) for supply by the first electric motor machine MM1 of a motor torque varying according to the predefined variation law.

[0088] It will also be noted that the invention also proposes a computer program product (or computer program) comprising a set of instructions which, when executed by processing means of the electronic circuit (or hardware) type, such as for example the processor PR1, is capable of implementing the control method described above to control the disconnection of the second wheel RR2 in the land vehicle V.

Claims

Claims

1. Control method for a land vehicle (V) comprising i) a first half-train (DTI) provided with a first wheel (RR1), ii) a second half-train (DT2) provided with a second wheel (RR2) and a coupling device (DC1) capable of being placed in connected and disconnected states in which said second wheel (RR2) is respectively connected and disconnected, and iii) an electric motor (MM1) coupled to a differential (DR) capable of being placed in locked and unlocked states and coupled to said first (DTI) and second (DT2) half-trains, characterized in that it comprises a step (10-60) in which, in the presence of a request to disconnect said second wheel (RR2), it is determined whether said differential (DR) is in said unlocked state, and if so, said disconnection is authorized,whereas in the negative, a placement of said differential (DR) in said unblocked state is ordered and then a new determination is made as to whether said differential (DR) is actually in said unblocked state.

2. Method according to claim 1, characterized in that in said step (10-60) it is ordered that said electric motor (MM1) provides a motor torque varying according to a predefined variation law in order to determine whether said first (RR1) and second (RR2) wheels have identical behaviors, then if not it is considered that said differential (DR) is in said unblocked state, while if so it is ordered that said differential (DR) is placed in said unblocked state and then it is determined again whether said differential (DR) is actually in said unblocked state.

3. Method according to claim 2, characterized in that in said step (10-60), when said first (RR1) and second (RR2) wheels have identical behaviors, it is determined whether said vehicle (V) is moving substantially in a straight line, and if so, it is considered that said differential (DR) is in an uncertain state, while if not, it is considered that said differential (DR) is in said blocked state.

4. Method according to claim 3, characterized in that in said step (10-60) it is determined whether a steering wheel of said vehicle (V) has a current rotation angle greater than a chosen threshold, and if so it is considered that said vehicle (V) is in a bend and therefore that said differential (DR) is in said locked state, while if not it is considers that said vehicle (V) is moving substantially in a straight line and therefore that said differential (DR) is in said uncertain state.

5. Method according to claim 3, characterized in that in said step (10-60) it is determined whether a current geographical position of said vehicle (V) corresponds to a presence of the latter (V) on a portion of traffic lane substantially in a straight line, and if so it is considered that said differential (DR) is in an uncertain state, while if not it is considered that said differential (DR) is in said blocked state.

6. Method according to one of claims 2 to 5, characterized in that in said step (10-60) said predefined variation law consists of a monotonic increase followed by a monotonic decrease to a zero value.

7. Method according to one of claims 1 to 6, characterized in that in said step (10-60), before determining whether said differential (DR) is in said unblocked state, it is first determined whether said differential (DR) is in said blocked state, and if not, it is determined whether said differential (DR) is in said unblocked state, while if so, it is ordered to place said differential (DR) in said unblocked state and then it is determined whether said differential (DR) is actually in said unblocked state.

8. A computer program product comprising a set of instructions which, when executed by processing means, is suitable for implementing the control method according to one of claims 1 to 7, in a land vehicle (V) comprising i) a first half-train (DTI) provided with a first wheel (RR1), ii) a second half-train (DT2) provided with a second wheel (RR2) and a coupling device (DC1) capable of being placed in connected and disconnected states in which said second wheel (RR2) is respectively connected and disconnected, and iii) an electric motor (MM1) coupled to a differential (DR) capable of being placed in locked and unlocked states and coupled to said first (DTI) and second (DT2) half-trains, for controlling the disconnection of said second wheel (RR2).

9. Control device (DC4) for a land vehicle (V) comprising i) a first half-train (DTI) provided with a first wheel (RR1), ii) a second half-train (DT2) provided with a second wheel (RR2) and a coupling device (DC1) capable of being placed in connected and disconnected states in which said second wheel (RR2) is respect- tively connected and disconnected, and iii) an electric motor (MM1) coupled to a differential (DR) which can be placed in locked and unlocked states and coupled to said first (DTI) and second (DT2) half-trains, characterized in that it comprises at least one processor (PR1) and at least one memory (MD) arranged to carry out the operations consisting, in the presence of a request to disconnect said second wheel (RR2), in determining whether said differential (DR) is in said unlocked state, and if so, in authorizing said disconnection, or if not, in ordering a placement of said differential (DR) in said unlocked state and then in determining again whether said differential (DR) is actually in said unlocked state.

10. Land vehicle (V) comprising i) a first half-train (DTI) provided with a first wheel (RR1), ii) a second half-train (DT2) provided with a second wheel (RR2) and a coupling device (DC1) capable of being placed in connected and disconnected states in which said second wheel (RR2) is respectively connected and disconnected, and iii) an electric prime mover (MM1) coupled to a differential (DR) capable of being placed in locked and unlocked states and coupled to said first (DTI) and second (DT2) half-trains, characterized in that it further comprises a control device (DC4) according to claim 9.

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