System and method for controlling a propulsion system of a hybrid vehicle

Abstract

The invention relates to a method for controlling a propulsion system comprising the following successive steps: - detecting a movement of a control member of a gearbox towards a neutral position; - moving a connection clutch into a slipping position in which said connection clutch allows relative rotation between a heat engine and an intermediate shaft coupled to an electric machine in response to the detection of the movement of the control member towards the neutral position; - detecting an event representative of a synchronization of the speed of the intermediate shaft and the speed of the input shaft of a gearbox; and - moving the connection clutch from said slipping position towards the engaged position in response to the detection of said event representative of a synchronization of the speed of the intermediate shaft and the speed of the input shaft.

Description

Title of the invention: System and method for controlling a propulsion system of a hybrid vehicle Technical field

[0001] The invention relates to the field of propulsion systems for hybrid vehicles.

[0002] The invention relates more particularly to a method and a system for controlling such propulsion systems. Technological background

[0003] In the state of the art, numerous hybrid vehicle architectures are known that combine an electric machine and a heat engine. In particular, there is an architecture in which the electric machine is coupled to the transmission chain, between the heat engine and the gearbox. The transmission chain then comprises a connecting clutch that is interposed between the heat engine and the electric machine. This connecting clutch is controlled by means of a control unit and is in particular intended to be kept open in order to decouple the heat engine and the electric machine when only the electric machine generates torque for the wheels of the vehicle, which avoids friction losses in the heat engine.

[0004] A main clutch is also interposed between the electric machine and the gearbox in order to decouple the electric machine and the thermal engine from the gearbox, during gear changes. The simplest and least expensive architecture comprises a manual gearbox. The main clutch is thus actuated by the driver by means of a clutch pedal. However, depending on the driver's skills, gear changes are likely to generate oscillations in the vehicle speed causing discomfort for the driver and the vehicle's passengers. Such oscillations in the vehicle speed are observed, after the new gear is engaged, when the clutch pedal is released, at the moment when the speeds upstream and downstream of the main clutch are synchronized. Summary of the invention

[0005] An idea underlying the invention is to propose a method and a control system for a propulsion system of the aforementioned type making it possible to improve driving comfort during gear changes.

[0006] According to a first aspect, the invention provides a control method for a propulsion system, said propulsion system comprising: - a heat engine; - an intermediate shaft coupled to an electric machine; - a connecting clutch movable between an engaged position in which said connecting clutch couples the heat engine, and in particular its crankshaft, to the intermediate shaft and a disengaged position in which the heat engine and the intermediate shaft are uncoupled from each other; - a gearbox which has an input shaft and which is controlled by a control member; - a main clutch which is movable between an engaged position in which said main clutch couples the intermediate shaft to the input shaft and a disengaged position in which the intermediate shaft and the input shaft are disengaged; said main clutch being controlled by a clutch pedal movable between a released position in which the main clutch is in the engaged position and a depressed position in which the main clutch is in the disengaged position; the control process comprising the following successive steps: - detect a movement of the control member towards a neutral position; - moving the connecting clutch into a slipping position in which said connecting clutch ensures relative rotation between the heat engine and the intermediate shaft in response to the detection of the movement of the control member towards the neutral position; - detect an event representative of a synchronization of the intermediate shaft and the input shaft; and - moving the connecting clutch from said slipping position towards the engaged position in response to the detection of said event representative of a synchronization of the speed of the intermediate shaft and the speed of the input shaft.

[0007] Thus, when the main clutch returns towards its engaged position after engaging a new gear ratio, the connecting clutch is in a slipping position. This allows for faster synchronization of the speed of the intermediate shaft with that of the gearbox input shaft. The variation in the torque transmitted by the main clutch at the time of synchronization of the intermediate shaft and the gearbox input shaft is therefore smaller, which allows for reduced oscillations in the vehicle speed.

[0008] Furthermore, since the connecting clutch is controlled by the control system, after the synchronization of the intermediate shaft and the input shaft, the synchronization of the crankshaft of the thermal engine and the intermediate shaft can be done in such a way as to limit the variations of the torque transmitted by the connecting clutch.

[0009] According to embodiments, such a control method may comprise one or several of the following characteristics.

[0010] According to one embodiment, the speed of the intermediate shaft and the speed of the input shaft are compared and the event representative of a synchronization of the intermediate shaft and the input shaft is detected when said speeds are equal.

[0011] According to one embodiment, the control method comprises, prior to detecting the movement of the control member towards the neutral position, the following steps: - detect an event representative of a movement of the main clutch from the engaged position towards the disengaged position; and - moving the connecting clutch from the engaged position towards the disengaged position to a set position in which the connecting clutch does not slip, in response to the detection of the event representative of a movement of the main clutch from the engaged position towards the disengaged position.

[0012] This makes it possible to reach the slipping position of the connecting clutch more quickly when a movement of the control member towards the neutral position is detected.

[0013] According to one embodiment, in response to the detection of the movement of the control member towards the neutral position, the thermal engine and / or the connection clutch are controlled so as to control a speed difference between a speed of the thermal engine and a speed of the intermediate shaft to a set value.

[0014] According to one embodiment, an event representative of a movement of the main clutch from the engaged position towards the disengaged position beyond a threshold is detected and the electric machine is controlled as a function of a variable representative of the speed of the input shaft so as to maintain rotation of said heat engine until the event representative of synchronization of the intermediate shaft and the input shaft is detected.

[0015] Thus, the speed of the intermediate shaft can be kept close to the speed of the input shaft. The difference between the acceleration of the intermediate shaft and that of the input shaft of the gearbox at the time they synchronize is therefore small. This makes it possible to reduce the torque transmitted by the main clutch before synchronization and, consequently, to further limit the variation of the torque transmitted by the main clutch during synchronization of the intermediate shaft and the input shaft. The oscillations of the vehicle speed are therefore further limited.

[0016] According to one embodiment, a movement of the gearbox control member representative of a change in gear ratio is detected; and - when the movement corresponds to a new gear engaged which is higher than the previous one, the electric machine is controlled so that the rotation speed of the intermediate shaft is controlled by a set value Varbrejnter = VO + Cl; with: - VO: the speed of the input shaft 9 of the gearbox 10 (curve 59); and - Cl: a constant, for example between 1 and 50 revolutions per minute; and - when the movement corresponds to a new gear engaged which is lower than the previous one, the electric machine is controlled so that the rotation speed of the intermediate shaft is controlled by Varbrejnter = VO - C2; with: - C2: a constant, for example between 1 and 50 revolutions per minute.

[0017] According to one embodiment, in response to the detection of the event representative of a synchronization of the intermediate shaft and the input shaft, the electric machine is controlled in torque as a function of a decreasing torque setpoint and the thermal engine is controlled as a function of said decreasing torque setpoint of the electric machine in order to compensate for the reduction in the torque of the electric machine and a signal representative of a position of an accelerator pedal.

[0018] According to another embodiment, an event representative of a movement of the main clutch from the engaged position towards the disengaged position beyond a threshold is detected and the thermal engine is controlled as a function of a speed of the input shaft until the event representative of a synchronization of the intermediate shaft and the input shaft is detected. This also makes it possible to limit oscillations in the speed of the vehicle.

[0019] According to one embodiment, a movement of the gearbox control member representative of a change in gear ratio is detected; and - when the movement corresponds to a new gear engaged which is higher than the previous one, the thermal engine is controlled so that its speed is controlled by Vmotor = V0 + Cl; with: - V0: the speed of the gearbox input shaft; and - Cl: a constant, for example between 1 and 50 revolutions per minute; and - when the movement corresponds to a new gear engaged which is lower than the previous one, the thermal engine is controlled so that its speed is controlled by V motor = V0 - C2; with: - C2: a constant, for example between 1 and 50 revolutions per minute.

[0020] According to a second aspect, the invention also provides a control system for a propulsion system, said propulsion system comprising: - a heat engine; - an intermediate shaft coupled to an electric machine; - a connecting clutch movable between an engaged position in which said connecting clutch couples the heat engine, and in particular its crankshaft, to the intermediate shaft and a disengaged position in which the heat engine and the intermediate shaft are uncoupled from each other; - a gearbox which has an input shaft and which is controlled by a control member; - a main clutch which is movable between an engaged position in which said main clutch couples the intermediate shaft to the input shaft and a disengaged position in which the intermediate shaft and the input shaft are disengaged; said main clutch being controlled by a clutch pedal movable between a released position in which the main clutch is in the engaged position and a depressed position in which the main clutch is in the disengaged position; said control system being configured to: - detect a movement of the control member towards a neutral position; - moving the connecting clutch into a slipping position in which said connecting clutch ensures relative rotation between the heat engine and the intermediate shaft in response to the detection of the movement of the control member towards the neutral position; - detect an event representative of a synchronization of the intermediate shaft and the input shaft; and - moving the connecting clutch from said slipping position towards the engaged position in response to the detection of said event representative of a synchronization of the intermediate shaft and the input shaft.

[0021] According to embodiments, such a control system may comprise one or more of the following features.

[0022] According to one embodiment, the control system is configured to: - detect an event representative of a movement of the main clutch from the engaged position towards the disengaged position; and - moving the connecting clutch from the engaged position towards the disengaged position to a set position in which the connecting clutch does not slip, in response to the detection of the event representative of a movement of the main clutch from the engaged position towards the disengaged position.

[0023] According to one embodiment, the control system is configured to control the heat engine and / or the connecting clutch so as to control a speed difference between a speed of the heat engine and a speed of the intermediate shaft to a set value in response to the detection of the movement of the control member towards the neutral position.

[0024] According to one embodiment, the control system is configured to: - detect an event representative of a movement of the main clutch of the engaged position towards the disengaged position beyond a threshold; and - controlling the electric machine as a function of a variable representative of a speed of the input shaft until the event representative of a synchronization of the intermediate shaft and the input shaft is detected.

[0025] According to one embodiment, the control system is configured to: - controlling the electric machine in torque according to a decreasing torque setpoint in response to the detection of the event representative of a synchronization of the intermediate shaft and the input shaft, and - control the thermal engine according to said decreasing torque setpoint of the electric machine in order to compensate for the decrease in the torque of the electric machine and a signal representative of a position of an accelerator pedal.

[0026] According to another embodiment, the control system is configured to: - detect an event representative of a movement of the main clutch from the engaged position towards the disengaged position beyond a threshold; and - control the thermal engine according to a variable representative of a speed of the input shaft until the event representative of a synchronization of the intermediate shaft and the input shaft is detected.

[0027] According to a third aspect, the invention relates to a motor vehicle comprising: - a heat engine; - an intermediate shaft coupled to an electric machine; - a connecting clutch movable between an engaged position in which said connecting clutch couples the heat engine, and in particular its crankshaft, to the intermediate shaft and a disengaged position in which the heat engine and the intermediate shaft are uncoupled from each other; - a gearbox which has an input shaft and which is controlled by a control member; - a main clutch which is movable between an engaged position in which said main clutch couples the intermediate shaft to the input shaft and a disengaged position in which the intermediate shaft and the input shaft are uncoupled; said main clutch being controlled by a clutch pedal movable between a released position in which the main clutch is in the engaged position and a depressed position in which the main clutch is in the disengaged position; and - a aforementioned control system.

[0028] According to one embodiment, the electric machine is coupled to the intermediate shaft, directly or indirectly in particular by a reducer. The reducer has, for example, a reduction ratio of between 1 and 4, and preferably of the order of 2.2. Brief description of the figures

[0029] The invention will be better understood, and other aims, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the appended drawings.

[0030] [Fig.l] is a schematic representation of a hybrid vehicle according to one embodiment.

[0031] [Fig.2] is a graph illustrating the evolution of the state of the equipment of the propulsion system according to the state of the art during a change of speed ratio to a higher speed ratio.

[0032] [Fig. 3] is a graph illustrating the evolution of the state of the equipment of the propulsion system according to the state of the art during a change of speed ratio to a lower speed ratio.

[0033] [Fig.4] is a diagram illustrating the steps of a method for controlling the propulsion system according to a first embodiment, during a gear change.

[0034] [Fig.5] is a graph similar to that of [Fig.2] when implementing the control method according to the first embodiment, for a gear change to a higher gear.

[0035] [Fig.6] is a graph similar to that of [Fig.5] when implementing the control method according to the first embodiment, for a gear ratio change to a lower gear ratio.

[0036] [Fig.7] is a graph similar to that of [Fig.2] when implementing a control method according to a second embodiment, for a gear ratio change to a higher gear ratio.

[0037] [Fig.8] is a graph similar to that of [Fig.7] when implementing the control method according to the second embodiment, for a gear ratio change to a lower gear ratio.

[0038] [Fig.9] is a graph similar to that of [Fig.2] when implementing a control method according to a third embodiment, for a gear change to a higher gear.

[0039] [Fig. 10] is a graph similar to that of [Fig. 9] when implementing the control method according to the third embodiment, for a gear ratio change to a lower gear ratio.

[0040] [Fig. 11] is a graph similar to that of [Fig. 2] when implementing a control method according to a fourth embodiment, for a gear change to a higher gear. Description of the embodiments

[0041] In relation to [Fig.l], a propulsion system of a hybrid vehicle according to an exemplary embodiment is described below.

[0042] The hybrid vehicle comprises at least two axles 1, 2 of which at least one, here the front axle 1, is coupled to the propulsion system.

[0043] The propulsion system comprises a heat engine 3 whose crankshaft is coupled to a flywheel 4, for example a double flywheel equipped with a torsion damper. The propulsion system also comprises an electric machine 5 as well as a connecting clutch 6 which is arranged along the torque transmission path between the heat engine 3 and the electric machine 5.

[0044] The connecting clutch 6 is capable of coupling the thermal engine 3 to an intermediate shaft 7, said intermediate shaft 7 being coupled to the electric machine 5. In the embodiment shown, the intermediate shaft 7 is indirectly coupled to the electric machine 5 by a reduction gear 8. However, in other embodiments not shown, the electric machine 5 is directly coupled to the intermediate shaft 7. Thus, the intermediate shaft 7 may for example be coaxial with the axis of rotation of the rotor of the electric machine 5 and consequently be constituted at least partially by the rotor shaft of the electric machine 5.

[0045] The intermediate shaft 7 is further coupled to an input shaft 9 of the gearbox 10 by a main clutch 11. The output shaft of the gearbox 10 is coupled by a differential device 12 to the left 13 and right 14 transmission shafts of the front axle 1.

[0046] The thermal engine 3 is controlled by an engine control unit 15. To do this, the engine control unit 15 receives in particular the following signals: - a signal representative of the speed of the thermal engine 3, this signal being for example delivered by a speed sensor 16 measuring the rotation speed of the flywheel 4; - a signal representative of the position of the accelerator pedal 17 measured by a position sensor 18; and - various information available on the communication bus 19 which is connected to the other vehicle control equipment.

[0047] The electrical machine 5 is supplied with electrical energy and controlled by an inverter 20 which is connected by the communication bus 19 to a hybrid control unit 21. The inverter 20 is connected to the High Voltage electrical network 24 and in particular to the High Voltage battery 22. The inverter 20 is also connected to a DC / DC voltage converter 23 which is connected to a Low Voltage electrical network Voltage 25 and in particular to the Low Voltage battery 26 and which is configured to convert the voltage level delivered by the Low Voltage battery 26 to the voltage level required by the High Voltage electrical network 24. The low voltage network has a voltage of between 9V and 30V, and preferably 12V for a passenger vehicle or a light vehicle for transporting goods or people and 24V for a heavy vehicle intended for transporting goods or people or for construction sites. The high voltage network corresponds to a voltage of between 40V and 1000V depending on the level of hybridization of the vehicle and the power of the electric machine 5, and preferably 48V.

[0048] The connecting clutch 6 is actuated by a clutch actuator 39 which thus allows it to be moved between an engaged position in which the heat engine 3 and the electric machine 5 are coupled to each other and a disengaged position in which the heat engine 3 and the electric machine 5 are uncoupled. The clutch actuator 39 is connected to the hybrid control unit 21 and powered by the low voltage battery 26 by means of the low voltage network 25.

[0049] The main clutch 11 is actuated by the driver by means of a clutch control member, such as a clutch pedal 27. If the clutch pedal 27 is not pressed, the main clutch 11 is in the engaged position in which it couples the intermediate shaft 7 to the input shaft 9 of the gearbox 10. When the driver presses the clutch pedal 27, the main clutch 11 is moved towards the disengaged position in which the intermediate shaft 7 and the input shaft 9 of the gearbox 10 are uncoupled.

[0050] According to one embodiment, the main clutch 11 is controlled by the clutch pedal 27 by means of a hydraulic control system. Such a hydraulic control system comprises a transmitter 28 which is associated with the clutch pedal 27, a receiver 29 which is associated with the main clutch 11 and a hydraulic connection 30 which connects the transmitter 28 to the receiver 29. The clutch pedal 27 is associated with a position sensor 31 which delivers information representative of the position of the clutch pedal 27 between a released position corresponding to the engaged position of the main clutch 11 and a depressed position corresponding to the disengaged position. The position sensor 31 is connected to the engine control unit 15 and optionally to the hybrid control unit 21.

[0051] The gearbox 10 is controlled by the driver by means of a control member 32 of the gearbox 10, such as a gear lever. The control member 32 of the gearbox 10 is associated with a position sensor 33 which delivers, to the hybrid control unit 21, information representative of the position of said control member 32. This information makes it possible to determine the ratio of the gearbox 10 which is engaged and to estimate the driver's gear change intention.

[0052] The hybrid vehicle comprises other sensors which are connected to the hybrid control unit 21 and to the engine control unit 15, such as a sensor delivering information representative of the angle of the steering wheel 34, a sensor 35 delivering information representative of the position of the brake pedal 36 or of the pressure exerted on it, a sensor 37 delivering information representative of the speed of the wheels and a sensor 38 delivering information representative of the speed of the input shaft 9 of the gearbox 10.

[0053] Hereinafter, the term "control system" will be used to designate the element(s) making it possible to control the equipment of the propulsion system and in particular the connection clutch 6, the electric machine 5 and the thermal engine 3. In the embodiment shown, the control system comprises in particular the hybrid control unit 21 and the engine control unit 15. However, the control system can be implemented in different forms, in a unitary or distributed manner, by means of hardware and / or software components. Usable hardware components are specific ASIC integrated circuits, FPGA programmable logic networks or microprocessors. Software components can be written in different programming languages, for example C, C++, Java or VHDL. This list is not exhaustive.

[0054] In particular, according to one embodiment, the functionalities of the control system which will be described below are partially or fully integrated into a control unit which is incorporated into the hydraulic control system of the main clutch 11.

[0055] [Fig.2] is a graph illustrating the evolution of the state of the equipment of the propulsion system according to the state of the art during a change of speed ratio to a higher speed ratio.

[0056] In [Fig.2] (as in the following figures 3 and 5 to 11), curves 50 to 60 have the following meanings: - the first curve 50 illustrates the position of the accelerator pedal 17; - the second curve 51 illustrates the position of the clutch pedal 27; - the third curve 52 illustrates the position of the control member 32; - the fourth curve 53 illustrates the torque delivered by the thermal engine 3; - the fifth curve 54 illustrates the maximum torque capable of being transmitted by the main clutch 11; - the sixth curve 55 illustrates the torque delivered by the electric machine 5; - the seventh curve 56 illustrates the maximum torque capable of being transmitted by the connecting clutch 6; - the eighth curve 57 illustrates the speed of the vehicle; - the ninth curve 58 illustrates the speed of the thermal engine 3; - the tenth curve 59 illustrates the speed of the input shaft 9 of the gearbox 10; and - the eleventh curve 60 illustrates the speed of the intermediate shaft 7, this being where appropriate correlated to the speed of the electric machine 5 by the reduction ratio of the reducer 8.

[0057] The operation of changing a gear ratio can be broken down into four successive phases respectively, designated PHASE I, PHASE II, PHASE III and PHASE IV in the figures.

[0058] In a phase preliminary to the operation of changing a gear ratio, the speed of the input shaft 9 of the gearbox 10 (tenth curve 59) is correlated to the speed of the vehicle (eighth curve 57) by the reduction ratio corresponding to the gear ratio of the gearbox 10 which is engaged.

[0059] The speed of the thermal engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) are equal as long as the connecting clutch 6 is in the engaged state, which is the case during a gear ratio change operation according to the state of the art, as shown in [Fig.2].

[0060] The first phase (PHASE I) corresponds to the release of the accelerator pedal 17, visible on the first curve 50.

[0061] The second phase (PHASE II) corresponds to the movement of the clutch pedal 27 towards the depressed position (second curve 51). This movement results in a movement of the main clutch 11 towards the disengaged position and, consequently, in a reduction of the maximum torque transmissible by the main clutch 11 (fifth curve 54) until it becomes zero. The speed of the heat engine 3 (ninth curve 58) as well as the speed of the intermediate shaft 7 (eleventh curve 60) then decrease due to the internal residual friction and thus become lower than the speed of the input shaft 9 of the gearbox 10 (tenth curve 59).

[0062] Depending on the driver's speed of execution, phases I and II are likely to overlap.

[0063] The third phase (PHASE III) corresponds to the actuation of the control member 32 of the gearbox 10 (third curve 52) in two stages. In a first stage, the control member 32 of the gearbox 10 is moved in order to disengage the previous gear ratio. In a second stage, the control member 32 of the gearbox 10 is moved in order to engage a higher gear ratio, i.e. one having a lower reduction ratio than that of the previous gear ratio. Thus, the speed of the input shaft 9 of the gearbox 10th gear (tenth curve 59) is lower when the higher gear is engaged.

[0064] Depending on the driver's speed of execution, phases II and III are also likely to overlap.

[0065] Phase IV corresponds to the movement of the clutch pedal 27 towards the released position (second curve 51) and to the pressing of the accelerator pedal 17 (first curve 50). During this phase IV, as soon as the torque transmissible by the main clutch 11 becomes greater than 0 (fifth curve 54), the speed of the thermal engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) increase until they are synchronized with the speed of the input shaft 9 of the gearbox 10 (tenth curve 59).

[0066] During this phase IV, oscillations in the vehicle speed are observed in the zone referenced A in [Fig.2] (eighth curve 57). These oscillations are due to the sudden variation in the torque transmitted by the main clutch 11 during the synchronization of the speed of the intermediate shaft 7 (eleventh curve 60) with that of the input shaft 9 of the gearbox 10 (tenth curve 59).

[0067] When the main clutch 11 slips, as long as the intermediate shaft 7 (eleventh curve 60) is not synchronized with the input shaft 9 of the gearbox 10 (tenth curve 59), the torque transmitted by the main clutch 11 depends firstly on the maximum torque capable of being transmitted by the main clutch and, consequently, on the pressure exerted by the receiver of the hydraulic system on the clutch. The transmitted torque thus depends on the position of the clutch pedal 27. The more the clutch pedal 27 is pressed, the lower the pressing force exerted by the pressure plate on the friction disc, which limits the transmitted torque. Conversely, if the clutch pedal 27 is partially released, the pressing force increases, allowing a greater torque transfer.

[0068] Thus, the torque transmitted by the main clutch 11 depends in particular on the difference between the speed of the intermediate shaft 7 (eleventh curve 60) and that of the input shaft 9 of the gearbox 10 (tenth curve 59) during the synchronization of the intermediate shaft 7 and the input shaft 9 of the gearbox 10. The greater this speed difference, the longer the synchronization. Thus, for the same clutch pedal release speed, the torque transmissible by the main clutch 11 will be greater when the difference between the speed of the intermediate shaft 7 and the speed of the input shaft 9 of the gearbox 10 is greater.

[0069] Therefore, depending on the position of the clutch pedal 27 and consequently the value of the maximum torque transmissible by the main clutch 11, the torque transmitted by the main clutch 11 is likely to be much greater than that which it transmits when synchronization is achieved. This sudden variation in the torque transmitted in the main clutch 11 excites the rigidity of the transmission shafts, which produces the undesirable undulations in the vehicle speed, as illustrated in the area referenced A.

[0070] As soon as synchronization is obtained, the torque Csynch which is transmitted by the main clutch 11 corresponds to the following equation: Csynch = (13+14) / (11+I2+I3+I4) * Cword + (11+12) / (I1+I2+I3+I4) * Cload ; with It: the moment of inertia of the engine group, i.e. of the elements of the propulsion system upstream of the connecting clutch 6 (including the crankshaft, the flywheel, the input of the connecting clutch 6 and all the inertia connected by the accessory belt); 12: the moment of inertia of the elements of the propulsion system arranged between the connecting clutch 6 and the main clutch 11 (output of the connecting clutch 6, electric machine 5, reducer 8, intermediate shaft 7 and input of the main clutch 11); 13: the moment of inertia of the elements of the propulsion system downstream of the main clutch 11 (output of the main clutch 11, engaged shafts and gears of the gearbox, transmission shafts, differential); 14: the inertia of the vehicle (including the mass of the vehicle, wheels and axles) Cmot: the engine torque (fourth curve 53); and Load: The vehicle load torque corresponding to rolling resistance, aerodynamic forces and the weight of the vehicle due to the road gradient.

[0071] The sum of the moments of inertia 13+14 being largely greater than the sum of the moments of inertia 11+12, the torque Csynch transmitted by the main clutch 11 when synchronization is obtained depends mainly on the engine torque Cmot, which is likely to be relatively low during synchronization, which explains the sudden drop in the torque transmitted in the main clutch 11 as soon as synchronization is obtained.

[0072] [Fig.3] is a graph similar to that of [Fig.2] but during a change of gear ratio to a lower gear ratio. We also observe during phase IV, in the zone referenced A, the same phenomenon of oscillations of the speed of the vehicle (eighth curve 57) which is also explained by a sudden reduction in the torque transmitted by the clutch.

[0073] A first embodiment of the invention is described below in relation to Figures 4, 5 and 6, making it possible to limit, or even eliminate, the aforementioned ripples during a gear change. [Fig. 4] is a diagram illustrating the control steps implemented by the control system while Figures 5 and 6 illustrate the state of the equipment of the propulsion system respec tively when changing gears to a higher gear and to a lower gear.

[0074] The preliminary phase to the operation of changing a gear ratio is identical to that described above in relation to [Fig.2]: a gear of the gearbox 10 is engaged and the accelerator pedal 17 is at least partially depressed (first curve 50 - figures 5 and 6).

[0075] During phase I, the control system detects that the accelerator pedal 17 moves towards the released position (step 100, [Fig.4]). This movement of the accelerator pedal 17 is visible in Figures 5 and 6 (first curve 50).

[0076] During phase II, the control system detects a movement of the clutch pedal 27 towards the depressed position (step 101, [Fig.4]). This movement of the clutch pedal 27 is also visible in Figures 5 and 6 (second curve 51).

[0077] As soon as a movement of the clutch pedal 27 has been detected, the control system implements two processes in parallel until the new gear ratio is engaged (step 130, [Fig.4]), one aimed at controlling the connecting clutch 6 and the thermal engine 3 (steps 102 to 109, [Fig.4]) and the other aimed at controlling the electric machine 5 (steps 120 to 124, [Fig.4]).

[0078] Thus, as soon as a movement of the clutch pedal 27 towards the disengaged position has been detected, the control system moves the connection clutch 6 (steps 102 and 103, [Fig.4]), towards its fully disengaged position, to a set position ensuring that said connection clutch 6 does not slip. This set position corresponds to a torque transmission capacity greater than Csynch, as defined above. The movement of the connection clutch 6 during phase II is observed in Figures 5 and 6 (seventh curve 56).

[0079] These steps are optional and only aim to reach the slipping position of the connecting clutch as quickly as possible during the following steps (steps 105 and 106, [Fig.4]) which will be described below.

[0080] The control system is configured to detect phase III, i.e. the position of the control member 32 of the gearbox 10 corresponds to the neutral position of the gearbox 10 (step 104, [Fig. 6]). The movement of the position of the control member 32 of the gearbox to the neutral position is visible in Figures 5 and 6 (third curve 52). In response to the detection of such a position of the control member 32, the control system moves the connecting clutch 6 again towards the disengaged position so that it reaches a slipping position, in which said connecting clutch 6 ensures a relative rotation between the crankshaft of the heat engine 3 and the intermediate shaft 7 (steps 105, 106 and 107, [Fig.4]). In other words, in this slipping position, the connecting clutch 6 ensures a speed difference between the speed of the heat engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60). According to one embodiment, the control system detects that said slipping position is reached as soon as a difference between the speed of the heat engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) is detected.

[0081] Subsequently, during phase IV, the control system compares the position of the clutch or clutch pedal 27 to a position threshold which corresponds to a position of the main clutch 11 located, on its travel towards the engaged position, before the slipping point (step 108, [Fig. 4]), i.e. the point from which said main clutch 11 begins to slip. As soon as the control system has detected a position of the clutch or clutch pedal 27 beyond said position threshold during the clutch travel, the heat engine 3 and / or the connecting clutch 6 are controlled so that the connecting clutch 6 slips, i.e. there is a relative rotation between the crankshaft of the heat engine 3 and the intermediate shaft 7 (step 109, [Fig. 4]).To do this, the heat engine 3 and / or the connecting clutch 6 are controlled so as to control the speed difference between the speed of the heat engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) to a setpoint value. This setpoint value is for example between 1 and 50 revolutions per minute. Thus, in Figures 5 and 6, a speed difference between the speed of the heat engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) is observed.

[0082] As indicated previously, as soon as a movement of the clutch pedal 27 has been detected (PHASE II), the control system implements, in parallel with the aforementioned steps 102 to 109 aimed at controlling the connection clutch 6 and the thermal engine 3, a second process aimed at controlling the electric machine 5 (steps 120 to 123, [Fig.4]).

[0083] The control system compares the position of the clutch or clutch pedal 27 to a position threshold which corresponds to a position of the main clutch 11, during a disengagement stroke, before the slipping point, i.e. the aforementioned point from which said main clutch 11 begins to slip.

[0084] As soon as the control system has detected a position of the clutch or the clutch pedal 27 beyond said position threshold during the disengagement stroke, the control system controls the electric machine 5 as a function of the speed of the input shaft 9 of the gearbox 10 (step 120, [Fig.4]).

[0085] More particularly, the control system controls the electric machine 5 of so that the rotation speed of the intermediate shaft 7 (eleventh curve 60) is controlled by a set value Varbæjnter = V0 + Cl (step 121, [Fig.4]); with: - V0: the speed of the input shaft 9 of the gearbox 10 (tenth curve 59); and - Cl: a constant, for example between 1 and 50 revolutions per minute.

[0086] During phase III, the control system detects a movement of the control member 32 of the gearbox 10 (third curve 52) representative of a change in gear ratio (step 122, [Fig.4]).

[0087] If the new gear engaged is a lower speed gear than the previous one, the control system controls the electric machine 5 so that the rotation speed of the intermediate shaft 7 (eleventh curve 60) is controlled by Varbrejnter = V0 - C2 (step 123, [Fig.4]); with: - V0: the speed of the input shaft 9 of the gearbox 10 (tenth curve 59); and - C2: a constant, for example between 1 and 50 revolutions per minute.

[0088] Thus, as shown in [Fig.5], as soon as a new gear ratio higher than the previous one is engaged, the speed of the intermediate shaft 7 (eleventh curve 60) decreases while remaining slightly higher than the new speed of the input shaft 9 of the gearbox 10 (tenth curve 59) corresponding to the new gear ratio engaged.

[0089] On the other hand, as visible in [Fig.6], as soon as the new gear ratio which is engaged is lower than the previous one, the speed of the intermediate shaft 7 (eleventh curve 60) increases to approach the new speed of the input shaft 9 of the gearbox 10 (tenth curve 59) corresponding to the new gear ratio engaged.

[0090] During phase IV, the control system compares the rotation speed of the input shaft 9 of the gearbox 10 (tenth curve 59) with that of the intermediate shaft 7 (eleventh curve 60) and detects a press on the accelerator pedal 17. As soon as the speeds are synchronized (step 130, [Fig.4]), the control system controls the electric machine 5 with a torque setpoint decreasing over time so that the torque it generates (sixth curve 55) gradually decreases until reaching zero torque (step 140, [Fig.4]).

[0091] Furthermore, when the accelerator pedal 17 is depressed, which is likely to correspond to the case of [Fig. 5] in which the gear change is made to a higher gear, the control system further controls the torque of the thermal machine (fourth curve 53) as a function of the decreasing torque setpoint of the electric machine 5 and the position of the accelerator pedal 17 so that the torque delivered by the electric machine 5 (sixth curve 55) is progressively transferred to the thermal engine 3 and the torque delivered by the thermal engine 3 (fourth curve 53) corresponds to a torque setpoint cor corresponding to the position of the accelerator pedal 17 (first curve 50) (step 140, [Fig.4]).

[0092] On the other hand, in the case of [Fig.6], in which the gear change is made to a lower gear, the user does not press the accelerator pedal 17 in phase IV and the torque delivered by the thermal engine 3 (fourth curve 53) remains zero.

[0093] The connecting clutch 6 is then torque controlled so as to reduce the speed difference between the speed of the thermal engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) until it becomes zero (steps 150 and 151, [Fig.4]).

[0094] As soon as the speed of the thermal engine 3 (ninth curve 58) and that of the intermediate shaft 7 (eleventh curve 60) are synchronized, the connection clutch 6 is moved to its maximum transmissible torque capacity (step 160, [Fig.4]).

[0095] The advantages arising from the method described above are as follows.

[0096] Firstly, during phase IV corresponding to the movement of the clutch pedal 27 towards the released position (second curve 51), the connecting clutch 6 being in a slipping position (seventh curve 56), only the speed of the elements of the propulsion system arranged between the connecting clutch 6 and the main clutch 11 will have to be synchronized with the speed of the input shaft 9 of the gearbox 10. The inertia of the elements to be synchronized being lower, the synchronization of the speed of the intermediate shaft 7 with that of the input shaft 9 of the gearbox 10 is done more quickly. The value of the torque transmissible by the main clutch 11 just before the synchronization of the speeds of the intermediate shaft 7 and the input shaft 9 of the gearbox 10 is therefore lower. This makes it possible to reduce the excitations of the transmission when synchronization is obtained.

[0097] Secondly, since during the synchronization phase the electric machine 5 is controlled so that the speed of the intermediate shaft 7 is kept close to the speed of the input shaft 9 of the gearbox 10, the difference between the acceleration of the intermediate shaft 7 (eleventh curve 60) and that of the input shaft 9 of the gearbox 10 (tenth curve 59) at the time they synchronize is small. The torque transmitted by the main clutch 11 before synchronization is therefore small.

[0098] Furthermore, since the connecting clutch 6 is kept sliding, the torque transmitted by the main clutch 11 just after the synchronization of the intermediate shaft 7 with the input shaft 9 of the gearbox 10 is obtained is equal to: CSynch (13+14) / (I2+I3+I4) Cemb-connex-!- (12) / (I2+I3+I4) Ccharg J with Cemb_connex of torque transmitted by the connecting clutch 6.

[0099] Thus, as the sum of the inertias 13+14 is much greater than the inertia 12, the torque Csynch transmitted by the main clutch 11 when synchronization is obtained is substantially equal to the torque transmitted by the connecting clutch 6 Cemb_COnnex which is low. The variation in the torque transmitted by the main clutch 11 during synchronization of the intermediate shaft 7 with the input shaft 9 of the gearbox 10 is therefore low.

[0100] Finally, as the connecting clutch 6 is controlled by the control system, the difference between the acceleration of the engine speed and that of the intermediate shaft 7 is small, which also makes it possible to avoid a sudden change in the torque transmitted by the connecting clutch 6 when the synchronization of the thermal engine 3 and the intermediate shaft 7 is obtained.

[0101] Figures 7 and 8 represent the implementation of a control method according to a second embodiment respectively during a change of speed towards a higher speed ratio and towards a lower speed ratio.

[0102] In this second embodiment, the control method is simplified in that it only acts on the connecting clutch 6 to limit unwanted undulations in the vehicle speed.

[0103] In this embodiment, as soon as a movement of the clutch pedal 27 towards the disengaged position has been detected, the control system moves the connecting clutch 6 towards its fully disengaged position to a slipping position, in which said connecting clutch 6 transmits a drag torque between the crankshaft of the heat engine 3 and the intermediate shaft 7.

[0104] Subsequently, the control system compares the rotational speed of the input shaft 9 of the gearbox 10 (tenth curve 59) with that of the intermediate shaft 7 (eleventh curve 60). As soon as the input shaft 9 of the gearbox 10 and the intermediate shaft 7 are synchronized, the connecting clutch 6 is then torque controlled so as to reduce the speed difference between the speed of the heat engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60) until it becomes zero.

[0105] Thus, only the elements of the propulsion system arranged between the connecting clutch 6 and the main clutch 11 are synchronized with the input shaft 9 of the gearbox 10, which makes it possible to obtain this synchronization more quickly. The value of the torque transmissible by the main clutch 11 just before the synchronization of the intermediate shaft 7 and the input shaft 9 of the gearbox 10 is lower, which makes it possible to reduce the excitations of the transmission when synchronization is obtained.

[0106] Figures 9 and 10 represent the implementation of a control method according to a third embodiment respectively when changing gear to a higher gear ratio and to a lower gear ratio.

[0107] In this third simplified embodiment, the control method is simplified in that it only acts on the connecting clutch 6 and the thermal engine 3 to limit undesirable ripples in the vehicle speed.

[0108] As in the first and second embodiments, as soon as a movement of the clutch pedal 27 towards the disengaged position has been detected, the control system moves the connecting clutch 6 towards its fully disengaged position to a slipping position, in which said connecting clutch 6 transmits a drag torque between the crankshaft of the heat engine 3 and the intermediate shaft 7.

[0109] Subsequently, the control system detects a movement of the control member 32 of the gearbox 10 (third curve 52) representative of a change in gear ratio, during phase III. If the new gear engaged is a gear ratio higher than the previous one, as illustrated in [Fig.8], the control system controls the heat engine 3 so that its speed (ninth curve 58) is controlled by Vmotor = V0 + Cl; with: - V0: the speed of the input shaft 9 of the gearbox 10 (tenth curve 59); and - Cl: a constant, for example between 1 and 50 revolutions per minute.

[0110] On the other hand, if the new gear engaged is a lower speed ratio than the previous one, as illustrated in [Fig.9], the control system controls the thermal engine 3 so that its speed (tenth curve 59) is controlled by Vmotor = V0 - C2; with: - V0: the speed of the input shaft 9 of the gearbox 10 (tenth curve 59); and - C2: a constant, for example between 1 and 50 revolutions per minute.

[0111] The connecting clutch 6 being in a slipping position, it also ensures the increase or decrease of the speed of the intermediate shaft 7.

[0112] During phase IV, the control system compares the rotational speed of the input shaft 9 of the gearbox 10 (tenth curve 59) with that of the intermediate shaft 7 (eleventh curve 60). As soon as the crankshaft of the heat engine 3 and the input shaft 9 of the gearbox 10 are synchronized, the connection clutch 6 is controlled so as to synchronize the crankshaft of the heat engine 3 (ninth curve 58) with the intermediate shaft 7 (eleventh curve 60) and then moved to its maximum transmissible torque capacity (seventh curve 56).

[0113] [Fig. 11] represents the implementation of a control method according to a fourth embodiment during a gear change to a ratio of higher speed.

[0114] In this fourth embodiment, the control method is simplified in that it only acts on the connecting clutch 6 and the electrical machine 5 to limit undesirable ripples in the vehicle speed.

[0115] The method implemented differs from that described above in relation to figures 4 and 5 only in that, during phase IV, the torque of the heat engine 3 (fourth curve 53) is not controlled as a function of a speed difference setpoint between the speed of the heat engine 3 (ninth curve 58) and the speed of the intermediate shaft 7 (eleventh curve 60).

[0116] Although the invention has been described in connection with several particular embodiments, it is quite obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0117] The use of the verb “comprise”, “comprise” or “include” and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0118] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

Claims

1. Method for controlling a propulsion system, said propulsion system comprising: - a heat engine (3); - an intermediate shaft (7) coupled to an electric machine (5); - a connecting clutch (6) movable between an engaged position in which said connecting clutch (6) couples the heat engine (3) to the intermediate shaft (7) and a disengaged position in which the heat engine (3) and the intermediate shaft (7) are uncoupled from each other; - a gearbox (10) which comprises an input shaft (9) and which is controlled by a control member (32); - a main clutch (11) which is movable between an engaged position in which said main clutch (11) couples the intermediate shaft (7) to the input shaft (9) and a disengaged position in which the intermediate shaft (7) and the input shaft (9) are uncoupled; said main clutch (11) being controlled by a clutch pedal (27) movable between a released position in which the main clutch (11) is in the engaged position and a depressed position in which the main clutch (11) is in the disengaged position; the control method comprising the following successive steps: - detecting a movement of the control member (32) towards a neutral position; - moving the connecting clutch (6) into a slipping position in which said connecting clutch (6) ensures relative rotation between the heat engine (3) and the intermediate shaft (7) in response to the detection of the movement of the control member (32) towards the neutral position; - detect an event representative of a synchronization of the intermediate shaft (7) and the input shaft (9); and - moving the connecting clutch (6) from said slipping position towards the engaged position in response to the detection of said event representative of a synchronization of the intermediate shaft (7) and the input shaft (9).

2. Control method according to claim 1, comprising prior to the detection of the movement of the control member (32) towards the neutral position, the following steps: - detecting an event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position; and - moving the connecting clutch (6) from the engaged position towards the disengaged position to a set position in which the connecting clutch (6) does not slip, in response to the detection of the event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position.

3. Control method according to claim 1 or 2, wherein, in response to the detection of the movement of the control member (32) towards the neutral position, the heat engine (3) and / or the connecting clutch (6) are controlled so as to control a speed difference between a speed of the heat engine (3) and a speed of the intermediate shaft (7) to a set value.

4. Control method according to any one of claims 1 to 3, in which an event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position beyond a threshold is detected and the electric machine (5) is controlled as a function of a speed of the input shaft (9) until the event representative of a synchronization of the intermediate shaft (7) and the input shaft (9) is detected.

5. Control method according to claim 4, in which in response to the detection of the event representative of a synchronization of the intermediate shaft (7) and the input shaft (9), the electric machine (5) is controlled in torque as a function of a decreasing torque setpoint and the thermal engine (3) is controlled as a function of said decreasing torque setpoint of the electric machine in order to compensate for the reduction in the torque of the electric machine and a signal representative of a position of an accelerator pedal (17).

6. Control method according to any one of claims 1 to 3, in which an event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position beyond a threshold is detected and the heat engine (3) is controlled as a function of a variable representative of the speed of the input shaft (9) so as to maintain a rotation of said heat engine (3) until an event representative of a synchronization of the intermediate shaft (7) and the input shaft (9).

7. Control system of a propulsion system, said propulsion system comprising: - a heat engine (3); - an intermediate shaft (7) coupled to an electric machine (5); - a connecting clutch (6) movable between an engaged position in which said connecting clutch (6) couples the heat engine (3) to the intermediate shaft (7) and a disengaged position in which the heat engine (3) and the intermediate shaft (7) are uncoupled from each other; - a gearbox (10) which comprises an input shaft (9) and which is controlled by a control member (32); - a main clutch (11) which is movable between an engaged position in which said main clutch (11) couples the intermediate shaft (7) to the input shaft (9) and a disengaged position in which the intermediate shaft (7) and the input shaft (9) are uncoupled; said main clutch (11) being controlled by a clutch pedal (27) movable between a released position in which the main clutch (11) is in the engaged position and a depressed position in which the main clutch (11) is in the disengaged position; said control system being configured to: - detect a movement of the control member (32) towards a neutral position; - moving the connecting clutch (6) into a slipping position in which said connecting clutch (6) ensures relative rotation between the heat engine (3) and the intermediate shaft (7) in response to the detection of the movement of the control member (32) towards the neutral position; - detect an event representative of a synchronization of the intermediate shaft (7) and the input shaft (9); and - moving the connecting clutch (6) from said slipping position towards the engaged position in response to the detection of said event representative of a synchronization of the intermediate shaft (7) and the input shaft (9).

8. A control system according to claim 7, configured to - detect an event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position; and - moving the connecting clutch (6) from the engaged position towards the disengaged position to a set position in which the connecting clutch (6) does not slip, in response to the detection of the event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position.

9. Control system according to claim 7 or 8, configured to control the heat engine (3) and / or the connecting clutch (6) so as to control a speed difference between a speed of the heat engine (3) and a speed of the intermediate shaft (7) to a set value in response to the detection of the movement of the control member (32) towards the neutral position.

10. Control system according to any one of claims 7 to 9, configured to: - detect an event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position beyond a threshold; and - control the electric machine (5) as a function of a variable representative of a speed of the input shaft (9) until the event representative of a synchronization of the intermediate shaft (7) and the input shaft (9) is detected.

11. Control system according to claim 10, configured to: - control the electric machine (5) in torque according to a decreasing torque setpoint in response to the detection of the event representative of a synchronization of the intermediate shaft (7) and the input shaft (9), and - control the thermal engine (3) according to said decreasing torque setpoint of the electric machine in order to compensate for the decrease in the torque of the electric machine and a signal representative of a position of an accelerator pedal (17).

12. Control system according to any one of claims 7 to 9, configured to: - detect an event representative of a movement of the main clutch (11) from the engaged position towards the disengaged position beyond a threshold; and - control the heat engine (3) as a function of a variable representative of a speed of the input shaft (9) until the event representative of a synchronization of the intermediate shaft (7) and input shaft (9) is detected.

13. Motor vehicle comprising: - a heat engine (3); - an intermediate shaft (7) coupled to an electric machine (5); - a connecting clutch (6) movable between an engaged position in which said connecting clutch (6) couples the heat engine (3) to the intermediate shaft (7) and a disengaged position in which the heat engine (3) and the intermediate shaft (7) are uncoupled from each other; - a gearbox (10) which comprises an input shaft (9) and which is controlled by a control member (32); - a main clutch (11) which is movable between an engaged position in which said main clutch (11) couples the intermediate shaft (7) to the input shaft (9) and a disengaged position in which the intermediate shaft (7) and the input shaft (9) are uncoupled; said main clutch (11) being controlled by a clutch pedal (27) movable between a released position in which the main clutch (11) is in the engaged position and a depressed position in which the main clutch (11) is in the disengaged position; and - a control system according to any one of claims 7 to 12.

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