METHOD FOR BRAKING A VEHICLE COMPRISING A HYBRID DRIVE SUB-ASSEMBLY

Abstract

A method of braking a vehicle comprising a hybrid drive subassembly which comprises a transmission box (18) with a multi-disc type shaft braking device (90) engaged with the output shaft (57) and arranged to brake a secondary shaft (16) when the coupling device is in the second coupling position as well as an electromotive group (5) comprising at least one reversible electric machine (56) and a coupling device (58); the braking method having the successive steps of: - positioning the coupling device (58) in the second coupling position; - over a first time interval, generating a first resistive torque to brake the secondary shaft (16) with the reversible electric machine (56) operating as a generator;- over a second time interval, generating a second resistive braking torque via the shaft braking device (90) simultaneously with a third resistive torque with the reversible electric machine (56) operating as a generator. (Abstract figure: Figure 1);

Description

Title of the invention: METHOD FOR BRAKING A VEHICLE COMPRISING A HYBRID DRIVE SUB-ASSEMBLY Technical field of the invention

[0001] The invention relates to a method of braking a vehicle comprising a hybrid drive subassembly.

[0002] The hybrid drive subassembly is positioned between an engine, for example a heat engine, and a set of one or more drive wheels of a vehicle. It relates in particular, although not exclusively, to such a subassembly intended to equip a heavy goods vehicle, i.e. a road vehicle of more than 3.5 tonnes, in particular a road tractor. The vehicle may also be a coach, state of the prior art

[0003] In document WO2011 / 072986A1, a hybrid drive subassembly of a vehicle is described, comprising a primary shaft intended to be driven by a heat engine of the vehicle, a secondary shaft intended to drive a set of one or more drive wheels of the vehicle, and a transmission box comprising one or more primary toothed wheels integral in rotation with the primary shaft or capable of being coupled to the primary shaft, a plurality of secondary toothed wheels integral in rotation with the secondary shaft or capable of being coupled to the secondary shaft, and two intermediate shafts to which intermediate toothed wheels are integral in rotation, the primary toothed wheel(s) and the secondary toothed wheels each meshing with a corresponding toothed wheel among the intermediate toothed wheels.The hybrid drive subassembly further comprises a reversible electric machine kinematically linked to the intermediate shafts via an upstream reduction stage and a dog clutch mechanism, said electric machine being capable of operating as a current generator for braking the intermediate shafts or as a drive motor for the intermediate shafts.Such an electric machine makes it possible to envisage different operating modes, and in particular a transient operation of the electric machine to brake or accelerate the intermediate shafts and promote the synchronization of the transmission box in the transmission ratio change phases, a motor operation to assist the drive of the main engine of the vehicle outside the ratio change phases and an electric generator operation, for the electrical supply of vehicle accessories or a battery, in particular in vehicle braking phases. In this hybrid subassembly, the machine. The reversible electric motor is arranged in line with the heat engine, that is to say that the rotor of the electric machine is concentric with the output of the heat engine.

[0004] In document WO2011 / 072986A1, the reversible electric machine is necessarily kinematically linked to the secondary shaft via the intermediate shaft. This connection with the secondary shaft cannot be direct so that certain operating modes are not optimized in terms of mechanical efficiency, in particular the vehicle braking phases and the battery regeneration phase. In these operating phases, the torque from the vehicle wheels must pass through the entire transmission box to enter the reversible electric machine and allow it to operate in electric generator mode. With this type of vehicle architecture, it will be necessary to increase the size of the reversible electric machine to improve the vehicle's braking capacity.

[0005] It is therefore necessary to envisage a mechanical configuration making it possible to kinematically link the reversible electric machine directly to the secondary shaft with a suitable gear ratio in order to envisage new functionalities such as the vehicle braking assistance mode without intervention of the intermediate shaft and to use a suitable braking method. Statement of the invention

[0006] The invention aims to remedy the drawbacks of the state of the art and to propose a high-performance vehicle braking method without it being necessary to increase the size of the reversible electric machine, in particular thanks to better integration of the electric machine within the intermediate and secondary shafts of the transmission box.

[0007] To do this, according to a first aspect of the invention, a method of braking a vehicle comprising a hybrid drive subassembly which comprises:

[0008] • at least one primary shaft;

[0009] • at least one secondary shaft;

[0010] • a transmission box comprising at least one intermediate shaft separate from the primary shaft and the secondary shaft and gear trains to achieve several transmission ratios between the primary shaft and the secondary shaft via the intermediate shaft;

[0011] • an electromotive group comprising at least one reversible electric machine, and a coupling device which, in a first coupling position, kinematically connects the output shaft of the reversible electric machine to the intermediate shaft and in a second coupling position, kinematically connects the output shaft of the reversible electric machine to the secondary shaft without passing through the shaft intermediate ;

[0012] • a multi-disc type shaft braking device kinematically linked with the output shaft for braking the secondary shaft when the coupling device is in the second coupling position;

[0013] the braking process having the successive stages of:

[0014] - position the coupling device in the second coupling position

[0015] - then, over a first time interval, generate a first resistive torque for braking the secondary shaft with the reversible electric machine operating as a generator in a torque range going beyond the maximum continuous torque value admissible by the electric machine;

[0016] - then, over a second time interval, generate a second resistive torque of braking via the shaft braking device simultaneously with a third resistive torque with the reversible electric machine operating as a generator in a torque range lower than the maximum continuous torque value admissible by the electric machine.

[0017] According to the braking method of the invention, it is advantageous to brake the secondary shaft relative to a fixed part of the transmission box when the coupling device is in the second secondary coupling position. Additional braking capacity is provided to the vehicle in a simple manner.

[0018] In the second coupling position, the coupling device allows direct transmission of power between the reversible electric machine and the secondary shaft without driving the intermediate shaft. This makes it possible to envisage in particular a braking assistance mode of the vehicle in which the shaft braking device is arranged to slow down the secondary shaft. The shaft braking device of the hybrid subassembly makes it possible to ensure the function of slowing down the vehicle when the latter is on a low percentage slope and for which the driver does not want to use his main braking system. In this braking assistance mode, the braking capacity of the multi-disc type shaft braking device can be between 20% and 60% of the braking capacity of the reversible electric machine.The vehicle deceleration function without a shaft braking device would require a high-power reversible electric machine. It is necessary to dissipate a large amount of energy over a short time. The reversible electric machine used alone for this deceleration function should then have specific maximum power characteristics for this application. Thanks to this braking process, the shaft braking device immediately provides significant braking capacity to the vehicle driver. In a second step, the driver has additional braking from the shaft. secondary available over a long period because the use of the electric machine is below the maximum continuous torque value admissible by it. This makes it possible to reduce the dimensioning of the reversible electric machine while ensuring the other operating modes of the vehicle. The cost of the reversible electric machine is thus reduced.

[0019] Preferably, the second time interval is greater than the first time interval.

[0020] According to a variant of this braking method, the second resistive torque can be less than the third resistive torque. This makes it possible to reduce the cost of the electric machine. Thanks to this proportion of resistive torque, the shaft braking device provides the necessary additional braking of the secondary shaft and makes it possible to reduce the size of the reversible electric machine while ensuring the other operating modes.

[0021] According to a variant of this braking method, the second resistive torque may be greater than or equal to the third resistive torque. This makes it possible to reduce the dimensioning of the reversible electrical machine.

[0022] Preferably, the braking method has the following successive step:

[0023] - then, on a third time interval, generate only the second couple braking resistor via the shaft braking device without intervention of the reversible electric machine.

[0024] According to this braking method, the multi-disc type shaft braking device may comprise a rotating disc holder arranged to be connected in rotation with a transmission shaft of the electromotive group, a static disc holder arranged to be connected in rotation with a fixed part of the transmission box and a multi-disc assembly consisting of a first set of discs engaged with splines of the rotating disc holder, and a second set of discs engaged with splines of the static disc holder, the shaft braking device being in indirect engagement with the output shaft of the reversible electric machine by use of a speed reducer, the rotating disc holder being integral in rotation with the output pinion of the speed reducer. Thus, the dimensioning of the shaft braking device takes into account the reduction ratio associated with the speed reducer.The risk of centrifugation of the multi-disc assembly of the shaft braking device is limited due to the reduction in rotation speed.

[0025] According to this braking method, the multi-disc assembly of the shaft braking device can be pressed axially by an annular-shaped actuating piston, the actuating piston being guided axially within a pressure chamber formed directly or indirectly in a protective casing of the electromotive group.

[0026] According to this braking method, the rotating disc carrier of the shaft braking device can be connected in rotation by spline with the transmission shaft of the electromotive group remote from the axis of revolution of the output shaft or rigidly fixed on the transmission shaft of the electromotive group remote from the axis of revolution of the output shaft by means of fixing screws, rivets or by welding.

[0027] According to this braking method, the coupling device may comprise one or more of the following coupling mechanisms:

[0028] - a dog mechanism;

[0029] - a clutch mechanism, preferably a friction clutch mechanism, preferably wet;

[0030] - a double friction clutch, preferably wet.

[0031] According to this braking method, the output shaft of the reversible electric machine may have an axis of revolution parallel to an axis of revolution of the intermediate shaft, one or more of the following characteristics preferably being achieved:

[0032] - the axis of revolution of the output shaft coincides with the axis of revolution of the intermediate shaft;

[0033] - the axis of revolution of the output shaft is distant from the axis of revolution of the shaft intermediate ;

[0034] - the axis of revolution of the output shaft is distant from an axis of revolution of the shaft primary ;

[0035] - the axis of revolution of the output shaft is distant from an axis of revolution of the shaft secondary.

[0036] According to this braking method, the electromotive group may comprise two reversible electrical machines each comprising a rotor with an output shaft rotating around an axis of rotation, the two output shafts meshing simultaneously with a common toothed wheel arranged parallel to the two axes of rotation, the shaft braking device being engaged indirectly with the output shafts by braking the associated common toothed wheel.

[0037] According to another aspect of the invention, it relates to a hybrid subassembly for driving a vehicle, of the type comprising: at least one primary shaft, at least one secondary shaft and a transmission box comprising at least one intermediate shaft separate from the primary shaft and the secondary shaft and toothed wheel sets for producing several transmission ratios between the primary shaft and the secondary shaft via the intermediate shaft. The hybrid subassembly also comprises an electromotive group comprising at least one reversible electric machine, and a coupling device which, in a first coupling position, kinematically connects the output shaft of the reversible electric machine to the intermediate shaft and in a second coupling position, kinematically connects the output shaft of the reversible electric machine to the intermediate shaft and in a second coupling position, kinematically connects the output shaft of the reversible electric machine to the intermediate shaft. nematically the output shaft of the reversible electric machine to the secondary shaft without passing through the intermediate shaft. Remarkably, the hybrid subassembly includes a multi-disc type shaft braking device kinetically linked with the output shaft to brake the secondary shaft when the coupling device is in the secondary coupling position.

[0038] Preferably, the shaft braking device may be engaged indirectly with the output shaft. For the purposes of the invention, when the shaft braking device is engaged indirectly with the output shaft, one of the components of the shaft braking device meshes with a transmission shaft kinematically linked to the output shafts of the electrical machine(s). The kinematic connection may be made using a gear, a belt or a transmission chain. In this case, one of the components of the shaft braking device directly meshes with the associated transmission shaft. Thus, the shaft braking device is engaged indirectly with the output shaft by braking the associated transmission shaft.

[0039] The direct transmission of power between the reversible electric machine and the secondary shaft without driving the intermediate shaft also makes it possible to envisage other operating modes which will be described later, including: a mode of permanent electric drive of the secondary shaft by the reversible electric machine operating as a motor, a transient mode for maintaining traction during gear changes, a pure regenerative braking mode minimizing the resistive mechanical torque.

[0040] Preferably, the shaft braking device comprises a multi-disc assembly.

[0041] Advantageously, the multi-disc type shaft braking device can be interposed in the direction of transmission of the torque between the rotor of the reversible electric machine and the coupling device.

[0042] According to a variant of the invention, the shaft braking device can be in indirect engagement with the output shaft of the reversible electric machine by using a speed reducer, the rotating disc carrier being integral in rotation with the output pinion of the speed reducer.

[0043] According to a variant of the invention, the multi-disc assembly of the shaft braking device can be pressed axially by an annular-shaped actuating piston, coaxial with the output shaft of the reversible electric machine, the actuating piston being guided axially within a pressure chamber formed directly or indirectly in a protective casing of the electromotive group. This shaft braking device structure has the advantage of being radially compact and of being able to be easily integrated within a transmission box.

[0044] According to another variant of the invention, the multi-disc assembly of the shaft braking device can be pressed axially by an actuating piston of shape annular, coaxial with the output shaft of the reversible electric machine, the actuating piston being guided axially within a pressure chamber formed directly or indirectly in the transmission housing.

[0045] The reversible electrical machine may in particular be a permanent magnet synchronous machine, an asynchronous machine, a variable reluctance electrical machine or a variable reluctance synchronous electrical machine, known as synchro-reluctant.

[0046] The reversible electrical machine may preferably be sized so as to be fully operational for wide operating ranges in the various operating modes envisaged. Thus, it is preferentially provided that the reversible electrical machine meets one or more of the following criteria:

[0047] - the reversible electric machine is capable of continuously developing a torque motor greater than 300 Nm, and preferably greater than 350 Nm, in a speed range of more than 1000 rpm, and preferably more than 2000 rpm inclusive having a lower limit which is less than 6000 rpm, and preferably less than 5000 rpm, and an upper limit which is greater than 6000 rpm, preferably greater than 7000 rpm, and preferably greater than 9000 rpm;

[0048] - the reversible electric machine is capable of developing a higher resistive torque at 400 Nm and preferably greater than 450 Nm in a speed range of more than 3000 rpm, and preferably more than 4000 rpm having a lower limit which is less than 6500 rpm, and preferably less than 6000 rpm and an upper limit which is greater than 9000 rpm, and preferably greater than 10000 rpm, for 30 seconds;

[0049] - the reversible electric machine is capable of developing a motor torque greater than 50 Nm and preferably greater than 60Nm in a speed range of more than 5500 rpm, and preferably more than 7000 rpm having a lower limit which is less than 5000 rpm, and preferably less than 4500 rpm and an upper limit which is greater than 10000 rpm, and preferably greater than 11000 rpm, for 5 seconds in gear change transient regime.

[0050] According to a particularly advantageous embodiment, the hybrid subassembly further comprises a power take-off member, capable of being driven at least by the reversible electric machine, preferably the power take-off member is permanently kinematically connected to the intermediate shaft;

[0051] According to this embodiment, the power take-off member can be coaxial with the intermediate shaft.

[0052] According to another particularly advantageous embodiment, the hybrid subassembly comprises a power take-off member, capable of being driven at least by the reversible electric machine, the power take-off member being kinematically linked to permanently to the output shaft of the reversible electric machine.

[0053] According to another particularly advantageous embodiment, the electromotive group may comprise two reversible electric machines each comprising a rotor with an output shaft rotating about an axis of rotation, the two output shafts meshing simultaneously on a common toothed wheel arranged parallel to the two axes of rotation, the shaft braking device being indirectly engaged with the output shafts by braking the associated common toothed wheel. In this way, the use of two reversible electric machines improves the traction capacity of the vehicle operating in the mode of permanent electric drive of the secondary shaft by the reversible electric machine. The association of the shaft braking device with the common toothed wheel makes it possible to distribute the braking assistance mode of the vehicle over the two reversible electric machines.

[0054] It is then possible to envisage driving the power take-off by the reversible electric machine without using the main engine of the vehicle, which makes it possible to achieve rotation speeds significantly higher than 1000 rpm, for example higher than 1500 rpm, and where appropriate up to 5000 rpm.

[0055] In practice, the transmission box can advantageously comprise:

[0056] - one, or preferably several primary gear wheels capable of being coupled to the primary shaft, for example by one or more coupling and uncoupling mechanisms, for example synchronizers or / dog clutches,

[0057] - several secondary gear wheels capable of being coupled to the secondary shaft, by example by one or more coupling and uncoupling mechanisms, for example synchronizers or / dog clutches,

[0058] - intermediate gears permanently secured to the intermediate shaft intermediate, the primary gear wheel(s) and the secondary gear wheels each permanently meshing with a corresponding gear wheel among the intermediate gear wheels to form the gear trains.

[0059] In practice, the transmission box comprises coupling mechanisms for alternately coupling each of the primary gear wheels to the primary shaft, and each of the secondary gear wheels to the secondary shaft. Where appropriate, the hybrid subassembly may further comprise a friction clutch, dry or wet, intended to be arranged between the primary shaft and the main engine.

[0060] Various configurations of the primary gear wheels, the secondary gear wheels, the intermediate shaft and the rotor of the reversible electric machine are conceivable.

[0061] According to one embodiment, the primary shaft and the secondary shaft have axes of revolution which coincide. Alternatively, these axes are parallel and distant.

[0062] According to an exemplary embodiment, the output shaft of the electric machine re- reversible has an axis of revolution parallel to an axis of revolution of the intermediate shaft, one or more of the following characteristics preferably being achieved:

[0063] - the axis of revolution of the output shaft is coincident with the axis of revolution of the intermediate shaft;

[0064] - the axis of revolution of the output shaft is distant from the axis of revolution of the shaft intermediate ;

[0065] - the axis of revolution of the output shaft is distant from an axis of revolution of the shaft primary ;

[0066] - the axis of revolution of the output shaft is distant from an axis of revolution of the shaft secondary.

[0067] According to an exemplary embodiment, the coupling device comprises an epicyclic gear train arranged kinematically between the output shaft and the secondary shaft.

[0068] According to different variants, the coupling device comprises one or more of the following coupling mechanisms:

[0069] - a dog mechanism,

[0070] - a synchronizer mechanism,

[0071] - a clutch mechanism, preferably a friction clutch mechanism, preferably wet,

[0072] - a double friction clutch, preferably wet,

[0073] - a triple friction clutch, preferably wet.

[0074] In particular, a dog clutch mechanism without synchronization may be considered in cases where it is intended that the electric machine itself be used to synchronize the coupling device with the associated toothed wheel.

[0075] According to one embodiment, the hybrid subassembly may be equipped with a control unit for the reversible electric machine and the coupling device, and sensors capable of generating a signal representative of a speed of revolution of the intermediate shaft or of a member kinematically linked to it and a signal representative of a speed of revolution of the reversible electric machine or of a member kinematically linked to it. The control unit may in particular be implemented to synchronize the coupling device.Preferably, the control unit is capable, in a state of uncoupling of the coupling device, of controlling the reversible electric machine so that a relative rotation speed between the coupling member kinematically linked to the reversible electric machine and the coupling member kinematically linked to the intermediate shaft achieves a predetermined condition, and, when the predetermined condition is achieved, of controlling a coupling of the coupling device. The predetermined condition may for example be a zero relative rotation speed or a predetermined relative sliding speed.

[0076] According to another aspect of the invention, the latter comprises a hybrid engine group with a main engine, preferably internal combustion, and a hybrid subassembly as described above. The main engine is equipped with a main drive shaft linked to the primary shaft directly or via a clutch or a torque converter. brief description of the figures

[0077] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures.

[0078] [Fig-1] [Fig.l] illustrates a hybrid drive subassembly of a vehicle according to a first embodiment.

[0079] [Fig.2] [Fig.2] illustrates a detailed view of an electromotive group of the hybrid drive subassembly of [Fig.l].

[0080] [Fig.3] [Fig.3] illustrates the shaft braking device of the hybrid subassembly according to the first embodiment.

[0081] [Fig.4] [Fig.4] illustrates a diagram comparing the resistive torque available within the reversible electric machine with the resistive braking torque of the shaft braking device.

[0082] [Fig.5] [Fig.5] illustrates the evolution of the vehicle speed as a function of time when using the braking process.

[0083] [Fig.6] [Fig.6] illustrates a hybrid drive subassembly of a vehicle according to a second embodiment.

[0084] For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED description of embodiments

[0085] In Figures 1 and 2 is illustrated a hybrid subassembly 10 for driving a vehicle, comprising a primary shaft 12 intended to be driven by a main engine 14 of the vehicle, for example a thermal engine, a secondary shaft 16 intended to drive a set of one or more drive wheels of the vehicle (not illustrated), and a transmission box 18.

[0086] The connection of the main engine 14 to the primary shaft 12 may include a clutch 20 of any suitable type, for example a slip clutch. The connection of the secondary shaft 16 to the wheels of the vehicle may include one or more drive axles.

[0087] The transmission box 18 comprises an intermediate shaft 26 to which intermediate toothed wheels 28, 30, 32, 34, 36 are rotationally secured. Two primary toothed wheels 38, 40 coaxial with the primary shaft 12, each form a gear train with a corresponding toothed wheel 28, respectively 30, among the intermediate toothed wheels. The meshing of the gear trains 38, 28 and 40, 30 between primary gears 38, 40 and the corresponding intermediate gears 28, 30 are permanent. A double synchronizer 41 with three positions allows one or the other of the primary gears 38, 40 to be coupled to the primary shaft 12, and offers a neutral position in which none of the primary gears 38, 40 is coupled to the primary shaft 12. The different gears and primary, secondary and intermediate shafts are housed inside a cavity of a casing 24 of the transmission box 18.

[0088] Secondary gear wheels 42, 44, 46, coaxial with the secondary shaft 16, also each form a gear train with a corresponding gear wheel 32, 34, 36, respectively, among the intermediate gear wheels, one of the gear trains being reversing and comprising an intermediate wheel 48 for producing a reverse gear. The meshing of the gear trains formed by the secondary gear wheels 42, 44, 46 and the corresponding intermediate gear wheels 32, 34, 36 is permanent. A three-position dog clutch without synchronizers 50, positioned between two of the secondary wheels 44, 46, makes it possible either to couple one or the other of the two associated secondary wheels 44, 46 to the secondary shaft 16, or, in an intermediate neutral position, to keep the associated secondary toothed wheels 44, 46 decoupled from the secondary shaft 16.

[0089] In this embodiment, the axis of revolution 100 of the primary shaft 12 is aligned with the axis of revolution 200 with the secondary shaft 16, which makes it possible to use the primary end gear wheel 40 alternately as a primary wheel, associated with the primary shaft 12 by the synchronizer 41, or as a secondary wheel associated with the secondary shaft 16. For this purpose, a three-position dog clutch 52 without synchronizers, positioned between the primary end gear wheel 40 and the secondary wheel 42, makes it possible to couple either the primary end gear wheel 40 or the secondary wheel 42 to the secondary shaft 16, and also makes it possible, in an intermediate neutral position, to keep the primary end gear wheel 40 and the secondary wheel 42 decoupled from the secondary shaft 16.

[0090] A transmission box 18 with six forward gears and potentially two reverse gears is thus established, which can, if necessary, be coupled at the output of the secondary shaft 16 to an epicyclic gear train (not shown) in order to obtain a twelve-speed gearbox.

[0091] Remarkably, the hybrid drive subassembly 10 is equipped with an electromotive group 5 comprising a reversible electric machine 56, the output shaft 57 of which rotates around an axis of revolution XI, and a coupling device 58, comprising in this example a three-position dog clutch mechanism 59 without synchronizer and two reduction gear trains of toothed wheels 60, 62, 64, 66, 68. In a position of connection to the intermediate shaft 26, also called the coupling position intermediate, the coupling device 58 performs a rotational coupling of the output shaft 57 with a so-called intermediate speed reducer 260 comprising here a toothed wheel 60 which meshes permanently with a toothed wheel 62 secured to the intermediate shaft 26. In a position of connection to the secondary shaft, also called secondary coupling position, the coupling device 58 performs a coupling of the output shaft 57 with a so-called secondary speed reducer 264, comprising a toothed wheel 64 which meshes permanently with a reversing toothed wheel 66 which itself meshes permanently with a toothed wheel 68 secured to the secondary shaft 16. Finally, the coupling device 58, in a neutral position, keeps the output shaft 57 decoupled from the toothed wheels 60, 64.Within the coupling device 58, the transition from the intermediate coupling position to the secondary coupling position is carried out via the coupling mechanism 59 controlled by a control unit 76. For example, the coupling mechanism 59 is actuated using an actuating fork which axially moves the dog clutch along the transmission shaft 55.

[0092] Where appropriate, the intermediate shaft 26 is equipped with a power take-off 98, intended to allow coupling of one or more accessories of the vehicle, for example a winch, a pump or a tool. The power take-off 98 may be, for example, a transmission shaft comprising an external connection interface, for example a spline.

[0093] The output shaft 57 illustrated in [Fig.l] is integral with the rotor of the reversible electrical machine 56 and constitutes a motor shaft. Alternatively, the reversible electrical machine can integrate a reducer between the motor shaft and the output shaft 57. The output shaft 57 with axis of rotation XI drives a transmission shaft 55 in rotation via a first speed reducer Zl, Z2. The transmission shaft 55 supports the coupling device 58.

[0094] The reversible electric machine 56 is powered by a battery 70 via a bidirectional current converter, which makes it possible to power the reversible electric machine 56 as a motor, and conversely, to turn the reversible electric machine 56 as a generator to power the battery 70.

[0095] The reversible electrical machine 56 is preferably a high voltage machine, powered for example at a nominal voltage between 300 Volts and 800 Volts, capable of delivering significant torque and power, as will be discussed later. The nominal voltage may be greater than 800 volts.

[0096] The control unit 76 makes it possible to control the reversible electric machine 56 and its coupling device 58. To this control unit are connected sensors 78, 80, 82 to measure the speed of revolution of the output shaft 57, of the intermediate shaft 26 and of the secondary shaft 16 or speeds of revolution of elements permanently driven by these shafts. This control unit 76 can be integrated into a robotic control of the transmission box 18 which controls the opening and closing of the synchronizers 41, the dog mechanisms 50, 52, and where appropriate the main clutch 20, to respond to a torque or speed setpoint.

[0097] The hybrid subassembly 10 also comprises a multi-disc type shaft braking device 90 engaged with the transmission shaft 55 and arranged to brake the secondary shaft 16 when the coupling device 58 is in the secondary coupling position. The shaft braking device 90 comprises a multi-disc assembly 91. The multi-disc type shaft braking device 90 is interposed, in the direction of conveyance of the torque, between the rotor of the reversible electric machine 56 and the coupling device 58.

[0098] As illustrated in Figures 2 and 3, the multi-disc type shaft braking device 90 comprises a rotating disc carrier 92 engaged with the transmission shaft 55, a static disc carrier 93 arranged to be rotationally connected to a fixed part of the transmission box and a multi-disc assembly 91 consisting of a first set of discs engaged with splines of the rotating disc carrier, and a second set of discs engaged with splines of the static disc carrier. For example, the rotating disc carrier 92 of the shaft braking device 90 is rotationally connected by splines to the transmission shaft 55.

[0099] In this example, the shaft braking device 90 is in indirect engagement with the output shaft 57 of the reversible electrical machine by using a speed reducer Z1, Z2, the rotating disc carrier 92 being integral in rotation with the output pinion Z2 of the speed reducer. In this example, the dimensioning of the shaft braking device takes into account the reduction ratio associated with the speed reducer Z1, Z2. The risk of centrifugation of the multi-disc assembly 91 of the shaft braking device 90 is limited due to the reduction in the rotation speed.

[0100] In the example of implementation of the invention of [Fig. 3], the multi-disc assembly of the shaft braking device 90 is pressed axially by an actuating piston 95 of annular shape, coaxial with the transmission shaft 55. The actuating piston 95 is guided axially within a pressure chamber 96 formed directly or indirectly in a protective casing of the electromotive group 5.

[0101] Alternatively, the actuating piston 95 can be guided axially within a pressure chamber 96 formed directly or indirectly in the casing of the transmission box 18.

[0102] The reversible electric machine 56 makes it possible to envisage several operating modes such as pure regenerative braking mode or even braking assistance mode. Each reversible electric machine has what is called a " continuous power”, which is the power it is capable of delivering over a long period of time and a “maximum power” (aka “peak power”), which is the power that cannot be exceeded. Advantageously, the maximum power is only used for a very short time, of the order of a few seconds, in order to avoid excessive overheating and damage to the components of the electric machine. Under normal vehicle driving conditions, the power delivered by the electric machine remains less than or equal to the corresponding nominal power.

[0103] In pure regenerative braking mode or in braking assistance mode, the rotor of the electric machine is braked by an electromagnetic field. This resistive torque is for example obtained by reversing the direction of supply of the stator phases in the case of alternating current machines (synchronous machine with wound rotor, synchronous machine with magnets, asynchronous machine).

[0104] As illustrated in [Fig.4], the reversible electric machine 56 can be braked continuously up to a maximum continuous torque value admitted by the electric machine, corresponding to the curve C3. Below this maximum continuous torque value C3 max, the electric machine can run for hours without reaching the thermal heating limit. However, the electric machine can be braked over a limited time interval beyond the maximum continuous torque value until it reaches a maximum resistive torque corresponding to the curve Cl. Beyond the maximum resistive torque Cl max, the reversible electric machine goes into fault mode due to the risk of overheating.

[0105] [Fig.4] also compares the resistive torque available within the reversible electric machine 56 with the resistive braking torque C2 of the shaft braking device 90. The torque capacity of the braking device 90 generally corresponds to 20%, for example 40%, for example 60% of the maximum continuous torque value C3 max admitted by the reversible electric machine.

[0106] In [Fig.6] is illustrated a second embodiment of the invention, which differs of the first embodiment by the use of two reversible electric machines 56, each electric machine comprising a stator and a rotor having an output shaft movable in rotation around an axis.

[0107] The reversible electrical machines 56 are of the same type and are, for example, permanent magnet synchronous machines. Each electrical machine provides the same nominal mechanical power.

[0108] As can be seen in [Fig.6], the first electrical machine 56 has in the described example a rotor with a first output shaft 57 rotating about a first axis of rotation XI, the second electrical machine 56 has a rotor with a second output shaft 57 rotating about a second axis of rotation X2. In the described example, the axes of rotation of the reversible electrical machines are parallel but not confused, the two electrical machines 56 not having their axes of rotation aligned.

[0109] The output shafts 57 of the two electrical machines mesh simultaneously with a common gear wheel 110 arranged between the axes XI, X2. The common gear wheel 110 is kinematically connected to the two output shafts and receives the motor torque supplied by the two electrical machines, the latter being distributed around the common gear wheel 110 so as to form a first speed reducer Z1, Z2. The common gear wheel 110 is kinematically connected to a transmission shaft 55 specific to the coupling device 58 of this second embodiment of the invention using a second speed reducer Z3, Z4. This second speed reducer Z3, Z4 is optional so that it is possible to secure the common gear wheel directly to the transmission shaft 55.

[0110] In a similar manner to the first embodiment, the coupling device 58 comprises a three-position dog clutch mechanism 59 without synchronizer and two gear reduction trains 60, 62, 64, 66, 68. In a position of connection to the intermediate shaft 26, also called the intermediate coupling position, the coupling device 58 performs a rotational coupling of the transmission shaft 55 with a speed reducer called the intermediate 260 comprising here a gear wheel 60 which meshes permanently with a gear wheel 62 secured to the intermediate shaft 26.In a position of connection to the secondary shaft, also called the secondary coupling position, the coupling device 58 performs a coupling of the transmission shaft 55 with a speed reducer called secondary 264, comprising a toothed wheel 64 which meshes permanently with a reversing toothed wheel 66 which itself meshes permanently with a toothed wheel 68 secured to the secondary shaft 16.

[0111] The hybrid subassembly 10 also comprises a multi-disc type shaft braking device 90 engaged with the output shafts 57 of the two electrical machines via the common toothed wheel 110 and arranged to brake the secondary shaft 16 when the coupling device 58 is in the secondary coupling position. The shaft braking device 90 comprises a multi-disc assembly 91. The multi-disc type shaft braking device 90 is interposed, in the direction of conveyance of the torque, between the rotor of the reversible electrical machine 56 and the coupling device 58.

[0112] As illustrated in [Fig.6], the multi-disc type shaft braking device 90 comprises a rotating disc carrier 92 arranged to be rotationally connected to the common toothed wheel 110 of rotation axis 111, a static disc carrier 93 arranged to be rotationally connected to a fixed part of the transmission box and a multi-disc assembly 91 constituted by a first set of discs engaged with splines of the rotating disc carrier, and a second set of discs engaged with splines of the static disc carrier. For example, the rotating disc carrier 92 of the shaft braking device 90 is rotationally connected by splines with the common toothed wheel 110.

[0113] The various embodiments described have in common a coupling device 58 capable of taking at least a first coupling position in which the reversible electric machine 56 is kinematically connected to the intermediate shaft, and a second coupling position in which the reversible electric machine 56 is kinematically connected to the secondary shaft 16 without passing through the intermediate shaft 26. These various couplings can be used to achieve a wide variety of operating modes, as will now be discussed.

[0114] First, several operating modes can be implemented while the coupling device 58 connects the output shaft 57 to the secondary shaft 16 without the intermediate shaft 26 intervening.

[0115] It is possible to envisage a braking assistance mode without intervention of the intermediate shaft 26, in which the coupling device 58 is positioned in the second coupling position, the secondary shaft 16 is uncoupled from the intermediate shaft 26 by acting on the dog mechanisms 50, 52 and simultaneously electrical energy is generated with the reversible electric machine 56 operating as a generator and the shaft braking device 90 is actuated which then applies a resistant braking torque C2 to the transmission shaft 55 via the pressurized multi-disc assembly 91. This braking assistance mode can be advantageous when the vehicle is on a low percentage slope and for which the driver does not want to use his main braking system.In this braking assistance mode, the braking capacity of the multi-disc type shaft braking device 90 can be between 20% and 60% of the braking capacity of the reversible electric machine 56.

[0116] A braking assistance mode without intervention of the intermediate shaft 26 is particularly effective when the following successive steps are applied:

[0117] - the coupling device 58 is positioned in the second position coupling;

[0118] - then, over a first time interval il, a first resistive torque is generated Cl for braking the secondary shaft 16 with the reversible electric machine 56 operating as a generator in a torque range going beyond the maximum continuous torque value admissible by the electric machine;

[0119] - then, over a second time interval i2, a second pair is generated braking resistor C2 via the shaft braking device 90 simultaneously with a third resisting torque C3 with the reversible electric machine 56 operating as a generator in a torque range lower than the torque value maximum continuous c3 max admissible by the electric machine.

[0120] This braking assistance mode is particularly advantageous for braking the vehicle when the vehicle begins a descent and the driver wants to limit the use of the vehicle's mechanical braking system as much as possible.

[0121] When the battery 70 is completely recharged, it is no longer possible to use the reversible electric machine, the following step is then applied:

[0122] - on a third time interval i3, only the second pair is generated resistant C2 via the shaft braking device 90 without intervention of the reversible electric machine.

[0123] [Fig. 5] illustrates the behavior of the electrical machine(s) 56 and the shaft braking device 90 of the hybrid subassembly and the vehicle as well as the evolution of the speed V of the vehicle as a function of time t during this braking assistance mode without intervention of the intermediate shaft 26. In this figure, curve 5a illustrates the speed V of the vehicle, curve 5b illustrates the level of resistive torque within the electrical machine 56 and curve 5c illustrates the level of resistive braking torque within the braking device 90.

[0124] Furthermore, in this [Fig.5], a first phase illustrates the downhill rolling of the vehicle between the instant t0 and t1 during which the speed of the vehicle increases. Between t1 and t2, the coupling device 58 is positioned in the second coupling position and the reversible electric machine is switched to generator operation.

[0125] Between t2 and t3, which corresponds to the first time interval il, a first resistive torque Cl is generated to brake the secondary shaft 16 with the reversible electric machine 56 operating as a generator in a torque range going beyond the maximum continuous torque value admissible by the electric machine. The speed V of the vehicle drops sharply.

[0126] Beyond a limited time, for example 30 seconds, it is necessary, between t3 and t4, to reduce the resistive torque inside the electric machine at the risk of damaging it.

[0127] Between t4 and t5, the shaft braking device 90 begins to be actuated by increasing the control pressure within the pressure chamber 96.

[0128] Between t5 and t6, which corresponds to the first time interval i2, a second resistive braking torque C2 is generated via the shaft braking device 90 simultaneously with a third resistive torque C3 with the reversible electric machine 56 operating as a generator in a torque range lower than the maximum continuous torque value admissible by the electric machine. During this time interval i2, the cumulative resistive torque corresponds to the sum C2 + C3. The speed V of the vehicle continues to decrease.

[0129] Between t6 and t7, the electric machine is switched off since the battery 70 is fully recharged.

[0130] Between t7 and t8, which corresponds to the first time interval i3, only the second resistive torque C2 is generated on the transmission shaft 55 to brake the secondary shaft 16 via the shaft braking device 90 without intervention of the reversible electric machine.

[0131] Between t8 and t9, the control pressure is released within the pressure chamber 96. The vehicle has reached a low speed V.

[0132] This braking method can also be used when the vehicle is traveling on a level road and the driver wants to stop the vehicle at a traffic light, limiting as much as possible the use of the vehicle's mechanical braking system.

[0133] It is also possible to envisage a pure regenerative braking mode without the intermediate shaft 26, in which the coupling device is positioned in the second secondary coupling position, the secondary shaft 16 is uncoupled from the intermediate shaft 26 by acting on the dog mechanisms 50, 52 and electrical energy is generated with the reversible electrical machine 56 operating as a generator. To optimally achieve this regenerative braking mode without the main motor, it is advantageous for the reversible electric machine to be able to develop a resistive torque greater than 400 Nm and preferably greater than 450 Nm in a speed range of more than 3000 rpm, and preferably more than 4000 rpm having a lower limit which is less than 6500 rpm, and preferably less than 6000 rpm and an upper limit which is greater than 9000 rpm, and preferably greater than 10000 rpm, this for at least 30 seconds.

[0134] Particularly advantageously, other operating modes can be envisaged while the coupling device 58 connects the output shaft 57 to the secondary shaft 16.

[0135] It is thus possible to implement a transient mode for maintaining traction during a gear change, in which the coupling device 58 is positioned in the second coupling position, the main motor 14 is uncoupled from the intermediate shaft 26, and the reversible electric machine 56 is controlled so as to generate a motor torque on the secondary shaft 16 or to minimize a variation in speed of the secondary shaft while a change in ratio of the transmission box 18 is controlled between the main motor 14 and the intermediate shaft 26 and / or between the intermediate shaft 26 and the secondary shaft 16.

[0136] The transient mode of maintaining traction during a gear change and the pure regenerative braking mode without the intermediate shaft 26 are transient operating modes, not intended to last more than around thirty seconds. For information purposes only, with a transmission ratio of the order of 8 between the output shaft 57 and the secondary shaft 16, it is advantageous to size the reversible electric machine to develop a resistive torque greater than 400 Nm and preferably greater than 450 Nm in a speed range of more than 3000 rpm, and preferably more than 4000 rpm having a lower limit which is less than 6500 rpm, and preferably less than 6000 rpm and an upper limit which is greater than 9000 rpm, and preferably greater than 10000 rpm, for 30 seconds.

[0137] A direct electric drive mode can be implemented without the intermediate shaft 26, in which the coupling device 58 is positioned in the second coupling position and the intermediate shaft 26 is uncoupled from the secondary shaft 16 at the dog clutch mechanisms 50, 52, the reversible electric machine acting in a driving or regenerative manner depending on the acceleration or braking needs.

[0138] The reversible electric machine 56 can also be used as a motor to drive the power take-off 98 while the transmission box 18 is in the neutral position to interrupt the connection between the intermediate shaft 26 and the primary shaft 12 on the one hand, and between the intermediate shaft 26 and the secondary shaft 16 on the other hand.

Claims

Claims

1. Method for braking a vehicle comprising a hybrid drive subassembly (10) which comprises: • at least one primary shaft (12); • at least one secondary shaft (16); • a transmission box (18) comprising at least one intermediate shaft (26) separate from the primary shaft (12) and the secondary shaft (16) and sets of toothed wheels (38, 28, 40, 30, 32, 42, 36, 48, 44, 46) for producing several transmission ratios between the primary shaft (12) and the secondary shaft (16) via the intermediate shaft (26); • an electromotive group (5) comprising at least one reversible electric machine (56), and a coupling device (58) which, in a first coupling position, kinematically connects the output shaft (57) of the reversible electric machine (56) to the intermediate shaft (26) and in a second coupling position, kinematically connects the output shaft (57) of the reversible electric machine (56) to the secondary shaft (16) without passing through the intermediate shaft (26); • a multi-disc type shaft braking device (90) kinematically linked with the output shaft (57) for braking the secondary shaft (16) when the coupling device is in the second coupling position; the braking process presenting the successive stages of: - positioning the coupling device (58) in the second coupling position; - then, over a first time interval (il), generate a first resistive torque (Cl) to brake the secondary shaft (16) with the reversible electric machine (56) operating as a generator in a torque range going beyond the maximum continuous torque value (C3 max) admissible by the electric machine; - then, over a second time interval (i2), generate a second resistant braking torque (C2) via the shaft braking device (90) simultaneously with a third resistant torque (C3) with the reversible electric machine (56) operating as a generator in a torque range lower than the maximum continuous torque value (C3 max) admissible by the electric machine.

2. Braking method according to the preceding claim, in which the second time interval (i2) is greater than the first time interval (il).

3. Braking method according to one of the preceding claims, in which the second resistive torque (C2) is less than the third resistive torque (C3).

4. Braking method according to one of the preceding claims, having the following successive step: - then, over a third time interval (i3), generating only the second braking resistive torque (C2) via the shaft braking device (90) without intervention of the reversible electric machine.

5. Braking method according to one of the preceding claims, wherein the multi-disc type shaft braking device (90) comprises a rotating disc carrier (92) arranged to be rotationally connected to a transmission shaft (55) of the electromotive group (5), a static disc carrier (93) arranged to be rotationally connected to a fixed part of the transmission box (18) and a multi-disc assembly (91) consisting of a first set of discs (91a) engaged with splines of the rotating disc carrier, and a second set of discs (91b) engaged with splines of the static disc carrier, the shaft braking device (90) being in indirect engagement with the output shaft (57) of the reversible electric machine by using a speed reducer (Z1, Z2), the rotating disc carrier (92) being rotationally fixed to the output pinion (Z2) of the speed reducer.

6. Braking method according to the preceding claim, in which the multi-disc assembly of the shaft braking device (90) is pressed axially by an annular-shaped actuating piston (95), the actuating piston (95) being guided axially within a pressure chamber (96) formed directly or indirectly in a protective casing of the electromotive group (5).

7. Braking method according to one of claims 5 or 6, wherein the rotating disc carrier (92) of the shaft braking device (90) is rotationally connected by spline (94) with the transmission shaft (55) of the electromotive group (5) distant from the axis of revolution of the shaft of output (57) or rigidly fixed on the transmission shaft (55) of the electromotive group (5) distant from the axis of revolution of the output shaft (57) by means of fixing screws, rivets or by welding.

8. Braking method according to one of the preceding claims, wherein the coupling device (58) comprises one or more of the following coupling mechanisms: - a dog clutch mechanism (59, 159), - a clutch mechanism (259, 359), preferably a friction clutch mechanism, preferably wet, - a double friction clutch (259), preferably wet.

9. Braking method according to one of the preceding claims, wherein the output shaft (57) of the reversible electric machine (56) has an axis of revolution (XI) parallel to an axis of revolution of the intermediate shaft (26), one or more of the following characteristics preferably being achieved: - the axis of revolution of the output shaft (57) coincides with the axis of revolution of the intermediate shaft (26); - the axis of revolution of the output shaft (57) is distant from the axis of revolution of the intermediate shaft (26); - the axis of revolution of the output shaft (57) is distant from an axis of revolution (100) of the primary shaft (12); - the axis of revolution of the output shaft (57) is distant from an axis of revolution of the secondary shaft (16).

10. Braking method according to one of the preceding claims, in which the electromotive group (5) comprises two reversible electric machines (56) each comprising a rotor with an output shaft (57) rotating about an axis of rotation (XI, X2), the two output shafts (57) meshing simultaneously on a common toothed wheel (110) arranged parallel to the two axes of rotation (XI, X2), the shaft braking device (90) being indirectly engaged with the output shafts (57) by braking the associated common toothed wheel (110).