Patent ID: 12227068

For greater clarity, identical or similar elements are identified using identical reference signs in all of the figures.

DETAILED DESCRIPTION OF EMBODIMENTS

FIGS.1and2show a propulsion system1for an electric vehicle V according to a first implementation example of the invention.

Here, this propulsion system1is purely electric, that is to say it does not use a combustion engine to drive the vehicle, which is an industrial vehicle in this case, for example a heavy goods vehicle. This propulsion system1comprises an assembly of n electric propulsion machines2, n being an integer greater than or equal to 3, each electric machine comprising a stator and a rotor having an output shaft that is movable in rotation about an axis. In the first implementation example of the invention shown inFIGS.1and2, the assembly comprises four electric propulsion machines2a,2b,2cand2d.

The rotary electric machines2a,2b,2c,2dare of the same type and are, for example, permanent-magnet synchronous machines. Each electric machine provides the same mechanical nominal power, this power being, for example, of the order of 100 kW. In a variant, they may be asynchronous machines, for example.

As can be seen inFIG.2, in the example described, the first electric machine2ahas a rotor with a first output shaft rotating about a first axis of rotation X1, the second electric machine2bhas a rotor with a second output shaft rotating about a second axis of rotation X2, the third electric machine2chas a rotor with a third output shaft rotating about a third axis of rotation X3, and the fourth electric machine2dhas a rotor having a fourth output shaft rotating about a fourth axis of rotation X4. In the example described, the axes of rotation of the rotary electric machines are parallel but not coincident, the axes of rotation of the four electric machines2a,2b,2c,2dnot being aligned.

The four electric machines are regularly distributed about the axis of rotation of the common gearwheel at an angle Δ equal to 90°.

The output shafts of the four electric machines simultaneously mesh with a common gearwheel11disposed within the axes X1, X2, X3and X4. The common gearwheel11is kinematically connected to the four output shafts and receives the drive torque C0 provided by the four electric machines, the four electric machines being angularly distributed around the common gearwheel so as to form a first speed reducer Z1, Z2.

A transmission casing3supports the four electric machines and the common gearwheel11with the aid of a guide bearing15. The guide bearing may be a roller bearing or a ball bearing. The transmission casing3notably comprises a central core3asituated in the centre of the electric machines. The central core3acomprises a fluid circulation circuit4passing between the four electric machines in order to discharge heat energy emitted during the transmission of torque within the propulsion system. The fluid may be cooling oil or an aqueous solution.

The propulsion system1comprises primary gearwheels Z3, Z5able to be driven by the common gearwheel by means of a first selective coupling system10. The first selective coupling system10disposed between the common gearwheel11and the primary gearwheels Z3, Z5makes it possible to select a first pair of gears Z3, Z4or a second pair of gears Z5, Z6from an uncoupling neutral position. This first selective coupling system10with three positions takes the form of a dog clutch. In a variant, the first coupling system may comprise two coupling sub-assemblies, the first being associated solely with the first pair of gears Z3, Z4and the second being associated solely with the second pair of gears Z5, Z6. In a variant, the coupling system may take the form of a synchronizer.

The propulsion system1comprises an intermediate shaft12able to be driven by intermediate gearwheels Z4, Z6and Z7, each primary gearwheel Z3, Z5being kinematically connected to a corresponding intermediate gearwheel Z4, Z6so as to form a pair of gears with which a second speed reducer is associated. The intermediate shaft12is supported in rotation by a housing attached to the transmission casing3with the aid of guide bearings14.

The propulsion system1also comprises a secondary shaft13able to drive an assembly of one or more driving wheels of the vehicle. The secondary shaft13has a secondary gearwheel Z8kinematically connected to the intermediate shaft12by the intermediate gearwheel Z7, so as to form a third speed reducer Z7, Z8.

In this first implementation example of the invention, the axis of rotation110of the common gearwheel11, the axis of rotation120of the intermediate shaft12and the axis of rotation130of the secondary shaft13are parallel.

As a function of the configuration of the first selective coupling system10for selecting either a first pair of gears Z3, Z4or a second pair of gears Z5, Z6, the secondary shaft13receives different torque values. On the basis of a drive torque C0 transmitted by the four electric machines, the secondary shaft selectively receives: the torque C1 that has passed via the first pair of gears, or the torque C2 that has passed via the second pair of gears such that C1>C2.

Advantageously, the first ratio between the drive torque C0 and the torque C1 that has passed via the first pair of gears Z3, Z4may be between 10 and 15, such that 10<C0/C1<15, and the second ratio between the drive torque C0 and the torque C2 that has passed via the second pair of gears Z5, Z6may be between 5 and 10, such that 5<C0/C2<10.

By way of indication, in the context of an industrial vehicle, the first ratio may be equal to 10.5 and the second ratio may be equal to 6.

As illustrated inFIG.1, a transmission shaft6equipped with universal joints connects the secondary shaft13to a differential7. This differential7may be a mechanical differential or an electronic differential controlling the output torque fed to each driving wheel of the vehicle. Notably, the differential may be disposed so as to selectively receive: the torque C1 that has passed via the first pair of gears Z3, Z4, or the torque C2 that has passed via the second pair of gears Z5, Z6.

The transitional phase of changing to a higher speed reduction ratio for the propulsion system1will now be described.

During the running phase of the electric vehicle V between a time t0 and t1, the first speed reduction ratio is considered to be engaged and the first selective coupling system10is considered to be in a first coupling position in which the first pair of gears Z3, Z4is selected.

Between a time t1 and t2, the propulsion system passes from the engaged position to the neutral position, with the dog clutch10being disengaged. The first selective coupling system10is now in an uncoupling neutral position. In order to prepare for the engagement of the dog clutch10in a second coupling position, the relative speed of rotation between the common gearwheel11and the primary gearwheel Z5is measured by using various speed sensors present in the propulsion system1. In this phase, the electric machines no longer provide torque.

Between a time t2 and t3, the reversible electric machines2are activated in order to slow the common gearwheel11so as to synchronize the speeds of rotation of the common gearwheel11and of the primary gearwheel Z5.

Between a time t3 and t4, the dog clutch10is engaged to couple the common gearwheel11to the associated primary gearwheel Z5when their speeds of rotation are synchronized. The second speed reduction ratio is engaged when the first selective coupling system10is in a second coupling position in which the second pair of gears Z5, Z6is selected.

After the time t4, the electric machines provide torque again.

By virtue of the use of reversible electric machines2, it is possible to reduce the jaw clutching times, without resorting to a gearbox brake.

The transitional phase of changing to a lower speed reduction ratio for the propulsion system1will now be described.

During the running phase of the electric vehicle V between a time t0 and t1, the second speed reduction ratio is considered to be engaged and the first selective coupling system10is considered to be in a second coupling position in which the second pair of gears Z5, Z6is selected.

Between a time t1 and t2, the propulsion system passes from the engaged position to the neutral position, with the dog clutch10being disengaged. The first selective coupling system10is now in an uncoupling neutral position. In order to prepare for the engagement of the dog clutch10in a first coupling position, the relative speed of rotation between the common gearwheel11and the primary gearwheel Z3is measured by using various speed sensors present in the propulsion system. In this phase, the electric machines no longer provide torque.

Between a time t2 and t3, the reversible electric machines2are activated in order to accelerate the common gearwheel11so as to synchronize the speeds of rotation of the common gearwheel11and of the primary gearwheel Z3.

Between a time t3 and t4, the dog clutch10is engaged to couple the common gearwheel11to the associated primary gearwheel Z3when their speeds of rotation are synchronized. The first speed reduction ratio is engaged when the first selective coupling system10is in a first coupling position in which the first pair of gears Z3, Z4is selected.

After the time t4, the electric machines provide torque again.

By virtue of the use of reversible electric machines2, it is possible to reduce the jaw clutching times, without resorting to a gearbox brake.

In this first embodiment of the invention, the secondary shaft13may be driven by the secondary gearwheel Z8by way of a second selective coupling system. In this way, it is possible to disconnect the propulsion system from the wheels of the vehicle. This second selective coupling means may take the form of a dog clutch or a synchronizer.

FIG.3illustrates a second embodiment of the invention, which differs from the preceding embodiment by the positioning of the first selective coupling system10between the intermediate shaft12and the intermediate gearwheels Z4, Z6. This arrangement has the advantage of being able to offset the selective coupling system and of facilitating the integration of its control device within the propulsion system.

The operation of this second embodiment is similar to the first embodiment of the invention since the structure of the propulsion system1is unchanged. The common gearwheel11is still kinematically connected to the four output shafts and receives the drive torque C0 provided by the four electric machines, the four electric machines being angularly distributed around the common gearwheel so as to form a first speed reducer Z1, Z2.

During the transitional phases of changing to a lower or higher speed reduction ratio, the speeds of rotation of the intermediate gearwheels Z4, Z6and of the intermediate shaft12are still synchronized by acceleration or slowing of the common gearwheel11, but taking account of the speed reduction ratio of the first pair of gears or of the second pair of gears.

In this second embodiment of the invention, the secondary shaft13is driven by the secondary gearwheel Z8by way of a second selective coupling system20. In this way, it is possible to disconnect the propulsion system from the wheels of the vehicle. This second selective coupling means takes the form of a dog clutch.

The propulsion system also comprises a control member 50 for controlling the first and second selective coupling systems10,20when these two coupling systems are present. The control member 50 is programmed so that the propulsion system can adopt the following configurations:a configuration (i) according to which the secondary shaft13receives the torque C1 passing via the first pair of gears, the first selective coupling system10being in a first coupling position and the second selective coupling system20being in a coupling position,a configuration (ii) according to which the secondary shaft13receives the torque C2 passing via the second pair of gears, the first selective coupling system being in a second coupling position that is different from the first position and the second selective coupling system being in the coupling position, anda maintenance configuration (iii) in which the first and second coupling systems are in an uncoupling neutral position.

The control of the coupling systems that is effected by the control member 50 in order to obtain the configurations (i) to (iii) above is indicated in the table below.

First couplingSecond couplingConfigurationsystem 10system 20(i)Coupling accordingCouplingto a first position(ii)Coupling accordingCouplingto a second position(iii)UncouplingUncoupling

Configuration (i) is for example suited to low vehicle speeds with high torque demands.

Configuration (ii) is for example suited to high vehicle speeds with low torque demands.

Configuration (iii) is for example suited to operation as a maintenance mode for which the wheels of the vehicle can rotate without driving the propulsion system.

FIG.4illustrates a third embodiment of the invention, which differs from the first embodiment by a first selective coupling system10that is disposed between the common gearwheel and the primary gearwheels and that takes the form of a dual clutch, notably a dual wet clutch. This dual wet clutch10has the advantage of being able to dispense with the synchronization of the speeds of rotation of the common gearwheel11and of the primary gearwheels Z3, Z5.

The dual wet clutch10has a radial-type architecture in which first and second multi-disc clutches E1, E2are disposed radially one above the other. More specifically, in this example, the first multi-disc clutch E1is disposed radially around the second multi-disc clutch E2. A torque transmission housing40common to the first and second multi-disc clutches E1, E2is secured to rotate as one with the common gearwheel11.

The first multi-disc clutch E1is associated with the first pair of gears Z3, Z4whereas the second multi-disc clutch E2is associated with the second pair of gears Z5, Z6. The uncoupling neutral position is obtained by simultaneously opening both clutches.

Advantageously, the first multi-disc clutch E1disposed radially around the second multi-disc clutch E2is associated with the first ratio between the drive torque C0 and the torque C1 that has passed via the first pair of gears Z3, Z4. The second multi-disc clutch E2is associated with the second ratio between the drive torque C0 and the torque C2 that has passed via the second pair of gears Z5, Z6.

FIG.5illustrates a fourth embodiment of the invention, which differs from the third embodiment by the fact that the common gearwheel11circumferentially surrounds the torque transmission housing40. In this fourth embodiment, the torque transmission housing40common to the first and second multi-disc clutches is secured to rotate as one with the common gearwheel11. For example, the common gearwheel11is attached to the torque transmission housing40or machined directly on the housing40.

Advantageously, the transmission casing3supports the torque transmission housing40directly and supplies fluid to the first and second multi-disc clutches, notably to the control chambers of the clutches E1, E2. Pressurized-fluid supply ducts41that open out into the transmission casing3pass through the torque transmission housing40and extend axially through the guide bearing15.

In a variant, the dual wet clutch may have an axial-type architecture in which first and second multi-disc clutches E1, E2are disposed axially one next to the other and in which a torque transmission housing common to the first and second multi-disc clutches is secured to rotate as one with the common gearwheel. In this variant, the common gearwheel circumferentially surrounds the torque transmission housing.

The invention is not limited to the examples that have just been described.