Differential drive device

Abstract

The invention relates to a differential drive (2) for a transmission system (1) of a motor vehicle, having an axis of rotation (X) and comprising:-a planet carrier (12) having, in particular, axial dog clutch teeth (20); -an output ring gear (16) which is rotatable about an axis of rotation (X) and in particular has radial dog clutch teeth (21); -a blocking slide gear (24), which is axially displaceable and is in particular provided with radial dog clutch teeth; and a connecting slide gear (27) which is axially movable and in particular provided with axial dog clutch teeth, the connecting slide gear (27) and the blocking slide gear (24) being movable so as to be in three axial positions: a disconnected position, a connected position, a blocking position.

Description

Technical Field

[0001] The present invention relates to the field of powertrains for motor vehicles.

[0002] More specifically, the invention relates to a transmission system comprising a differential drive device intended to transmit and distribute the torque from an electric machine to two wheel axles of an axle of a vehicle. The differential drive device comprises a first element intended to be driven by the electric machine and a second element intended to drive one and / or the other of the two wheel axles of the axle of the vehicle, and a coupling device suitable for selectively coupling the first element to the second element. Background Art

[0003] Patent application US2006 / 0270510 describes a differential assembly comprising a differential case and a pinion case. The pinion case comprises a first pinion and a second pinion. The first side gear and the second side gear are operatively coupled to the first pinion and the second pinion. A sliding belt selectively engages the pinion case and at least one of the first side gear and the second side gear. Thus, the sliding belt provides three engagement modes, namely a disconnect mode, an open mode, and a locked mode. The differential assembly comprises a spring assembly disposed between the case and the sliding belt so as to urge the belt in a direction opposite to the direction provided by the actuator. Summary of the invention

[0004] The present invention aims to improve arrangements of this type.

[0005] The object of the invention is therefore a differential drive for a driveline of a motor vehicle, the differential drive having an axis of rotation and comprising:

[0006] a planet carrier which supports a toothing, in particular an axial toothing;

[0007] an output ring gear which is rotatable about an axis of rotation and which supports a toothing, in particular a radial toothing;

[0008] - an axially displaceable blocking sliding gear, which is provided with an engaging toothing, in particular a radial engaging toothing;

[0009] - an axially displaceable connecting sliding gear, which is provided with an engaging toothing, in particular an axial engaging toothing;

[0010] Among them, the connecting sliding gear and the blocking sliding gear can be moved so as to be in three axial positions:

[0011] o a disconnected position in which the engaging tooth portion of the connecting sliding gear is disconnected from the engaging tooth portion of the planet carrier, and the engaging tooth portion of the blocking sliding gear is disconnected from the engaging tooth portion of the output ring gear;

[0012] o a connecting position, in which the engaging tooth portion of the connecting sliding gear is connected to the engaging tooth portion of the planet carrier, and the engaging tooth portion of the blocking sliding gear is disconnected from the engaging tooth portion of the output ring gear;

[0013] o a blocking position, in which the engaging tooth portion of the connecting sliding gear is connected to the engaging tooth portion of the planet carrier, and the engaging tooth portion of the blocking sliding gear is connected to the engaging tooth portion of the output ring gear;

[0014] - a spring arranged to exert a force on the connecting sliding gear towards the planet carrier in order to promote the engagement of the engaging toothing of the connecting sliding gear in the engaging toothing of the planet carrier when changing from the disconnected position to the connected position.

[0015] The axial engagement toothing comprises teeth which protrude axially toward the rotation axis.

[0016] The radial toothing comprises teeth which project radially and therefore perpendicularly to the axis of rotation.

[0017] According to the invention, "promoting the engagement of the engagement toothing of the connecting sliding gear in the engagement toothing of the planet carrier" is understood to mean that when the conjugate toothing has a relative angular offset so that they cannot immediately engage when changing from the disconnected position to the connected position, the compressed spring can act on the connecting sliding gear as soon as the relative rotation of the toothing puts the toothing in the mutual engagement position. The spring thus helps to accelerate the mutual engagement of the conjugate toothing, thereby improving the dynamic performance of the differential drive. In fact, the spring can move the connecting sliding gear faster than the actuator can act alone because the inertia of the spring is lower.

[0018] In the disconnected position, torque transmission between the electric motor and the wheels is disconnected.

[0019] In the connected position, torque can be transferred between the electric machine and the wheel axle by applying a differential function, thereby allowing the two wheel axles to have different rotation speeds.

[0020] However, when two opposing wheels encounter friction differences on the road (sticking, etc.), it may be necessary to block operation of the differential in order to allow both wheel axles to rotate at the same speed while transmitting different torques.

[0021] In the blocked position, relative movement between the output ring gears is blocked and both wheels are forced to rotate at the same speed as the differential case.

[0022] According to one aspect of the invention, the spring is an axial spring.

[0023] According to one of the aspects of the present invention, the spring is a prestressed spring. In this case, the spring permanently stores elastic energy, and no matter how its position is.

[0024] According to one aspect of the invention, the sliding blocking gear is rotationally fixed relative to the planet carrier in the connected position.

[0025] According to one aspect of the invention, the connecting sliding gear is axially movable and rotationally fixed relative to the planet carrier in the connected position.

[0026] According to one aspect of the present invention, the connecting sliding gear and the blocking sliding gear are arranged to be moved by the same actuator.

[0027] According to one aspect of the invention, a spring is arranged between the actuator and the connecting sliding gear.

[0028] According to one of the aspects of the invention, the blocking sliding gear and the connecting sliding gear are connected rigidly in translation along the axis of rotation, for example, they are manufactured on the same part.

[0029] In another embodiment of the present invention, the blocking sliding gear and the connecting sliding gear are axially movable relative to each other, and a spring is interposed between the blocking sliding gear and the connecting sliding gear so that the connecting sliding gear can be axially moved through the blocking sliding gear by means of the spring.

[0030] In this case, the spring is in particular arranged between the connecting sliding gear and the blocking sliding gear.

[0031] In this case, the stiffness of the spring is in particular such that the blocking sliding gear and the connecting sliding gear are axially fixed when there are no obstacles hindering the axial movement of the connecting sliding gear and / or the blocking sliding gear.

[0032] According to one aspect of the invention, the connecting sliding gear is arranged to be axially movable relative to the blocking sliding gear between a stop position on a stopper of the blocking sliding gear and an axially retreated position retreated from the stopper, in which the spring is compressed.

[0033] According to one aspect of the invention, the spring is prestressed when the connecting sliding gear is in a stop position abutting against a stopper of the blocking sliding gear.

[0034] The prestressed spring tends to push the connecting sliding gear against the stop.

[0035] According to one aspect of the present invention, the stopper on the sliding blocking gear is formed by an elastic retaining ring fixed to the sliding blocking gear.

[0036] Thus, when in the disconnected position, the connecting sliding gear abuts against the circlip.

[0037] In the disconnected position, the engagement teeth of the connecting sliding gear do not overlap with the engagement teeth of the planet carrier, and the engagement teeth of the blocking sliding gear do not overlap with the engagement teeth of the output ring gear. The spring can then be in a less stressed state, in particular in its initial prestressed state.

[0038] In the connected position, the meshing toothing of the connecting sliding gear axially overlaps the meshing toothing of the planet carrier and the spring can still be in a less stressed state, in particular in its initial prestressed state.

[0039] According to one aspect of the present invention, the engaging tooth portion connecting the sliding gear and the engaging tooth portion of the planet carrier extends axially.

[0040] Therefore, the spring is not only used to promote the engagement of the connecting sliding gear by storing energy when interference occurs, but it also promotes the use of axial toothing instead of radial toothing. The use of axial toothing is advantageous because it particularly allows the provision of a tooth profile with anti-disengagement. In the absence of a spring, with such an axial toothing, the connected position / unblocked position would involve the use of long axial teeth, which have a partial axial overlap of the teeth of such a toothing, so as to allow additional axial movement, so as to reach another connected position / blocked position, which is not optimal for torque transmission. In fact, it is preferred that the axial toothing engages as far as the bottom of the toothing in order to transmit torque. With the help of a spring, teeth that are fully engaged with each other in the connected position / unblocked position can be used.

[0041] According to one of the aspects of the invention, the device comprises a friction device arranged to generate a torque deviation between two wheels connected to the differential drive, in particular in the connected mode.

[0042] A perfect (ie without internal friction) differential will distribute the input torque between the two wheels to which it is associated in a perfectly symmetrical manner in a 50 / 50 ratio. In the event that a wheel loses its adhesion (for example in the presence of ice or muddy terrain), the torque on the other wheel is also offset and the vehicle loses its drivability. By voluntarily adding a friction device that produces a constant and / or proportional friction between the moving parts of the differential, a torque deviation between the two wheels that is constant or proportional to the input torque can be created and the off-road capabilities of the vehicle can be improved. Without additional devices, the torque deviation between the two wheels is in particular about 3% to 5%. With additional, passive or active friction devices, deviations of about 30% can be achieved.

[0043] According to one aspect of the present invention, a friction device comprises a stack of friction discs.

[0044] According to one of the aspects of the invention, the device further comprises an output ring gear opposite to the above-mentioned output ring gear, and the friction device is placed between the opposite output ring gear and the planet carrier. The first set of friction discs is rotatably fixed to the opposite output ring gear, in particular by means of teeth and splines. The second set of friction discs is rotatably fixed to the planet carrier, in particular by means of teeth and splines. The discs of the first and second sets are arranged alternately to obtain a plurality of friction surfaces. The conical toothing of the opposite output ring gear allows the friction discs to be pressed against each other during rotation of the ring gear in order to generate a friction torque.

[0045] In another way, the first set of friction discs can be driven by the differential case. Thus, the manufacture of the planet carrier is simplified.

[0046] In the blocking position, the axial toothing of the connecting sliding gear and the axial toothing of the planet carrier particularly overlap axially, the connecting sliding gear abuts axially against the differential case or the planet carrier, the spring is compressed, and the radial engagement toothing of the blocking sliding gear radially overlaps the radial engagement toothing of the output ring gear. The connecting sliding gear is in an axially retracted position retracted from the stopper of the blocking sliding gear.

[0047] According to one aspect of the present invention, the teeth of the planet carrier and the teeth of the output ring gear are arranged inside the differential case.

[0048] The teeth of the blocking sliding gear and of the output ring gear are of radial type, thus allowing a greater overlap length to be provided, which is not detrimental since the dynamics for blocking the differential drive when the vehicle is stopped are not as critical as the dynamics for connecting / disconnecting.

[0049] According to one aspect of the invention, the device comprises a differential case, and the planet carrier can rotate freely in the differential case when the connecting sliding gear is in the disconnected position.

[0050] The device includes a differential case, and the blocking slip gear is prismatically connected to the differential case.

[0051] According to one of the aspects of the invention, this prismatic connection is implemented by blocking corresponding axial splines of the sliding gear and of the differential case, these splines meshing to allow relative translational movement while blocking relative rotational movement.

[0052] According to one aspect of the present invention, the blocking sliding gear is provided with radial engagement teeth.

[0053] According to one aspect of the present invention, the engaging toothing connecting the sliding gear and the engaging toothing of the planet carrier has an axial engaging toothing, in particular of the anti-disengagement type.

[0054] In a manner known in the prior art, the anti-disengagement engagement teeth have undercuts and counter-undercuts having angles selected to ensure that the teeth do not spontaneously disengage when they transmit torque, thereby avoiding untimely disconnection.

[0055] In general, pairs of conjugate teeth may be axial or radial, with or without anti-disengagement angles.

[0056] Another object of the present invention is a transmission system comprising the above-mentioned differential drive device and an actuator, wherein the actuator is arranged to move the blocking sliding gear and the connecting sliding gear to three positions, namely a disconnecting position, a connecting position and a blocking position and in the reverse order.

[0057] Therefore, the actuator is arranged to return the sliding gear to the disconnected position.

[0058] The blocking sliding gear transmits the force from the actuator to the connecting sliding gear via the spring.

[0059] According to one aspect of the present invention, the blocking slide gear comprises a groove arranged to engage with the actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The invention will be more clearly understood, and further objects, details, features and advantages of the invention will become more apparent, from the following description of several specific embodiments of the invention, provided by way of non-limiting illustration only, with reference to the accompanying drawings.

[0061] Figure 1 is a cross-sectional view of a transmission system including a differential drive device according to an embodiment of the present invention.

[0062] Figure 2 yes Figure 1 A perspective cross-sectional view of a differential drive device in a disconnected position.

[0063] Figure 3 yes Figure 1 A perspective cross-sectional view of a differential drive device in a connected position.

[0064] Figure 4 yes Figure 1 A three-dimensional cross-sectional view of a differential drive device in a blocked position.

[0065] Figure 5 yes Figure 1 A perspective cross-sectional view of a blocking sliding gear of a differential drive device.

[0066] Figure 6 yes Figure 1 Detailed perspective view of the differential case and sliding gear.

[0067] Figure 7 is a schematic diagram of the second embodiment. DETAILED DESCRIPTION

[0068] In the specification and claims, by convention, the axis of rotation of the differential case, ie, the X-axis, defines an "axial" orientation. A "radial" orientation is directed orthogonally to the X-axis.

[0069] Figure 1 A transmission system 1 according to one embodiment is shown. The transmission system 1 comprises a differential drive 2. The differential drive 2 is intended to rotate two wheel axles 3, 4 of an axle of a vehicle and is configured to distribute torque from an electric machine (not shown) to the two wheel axles 3, 4, thereby allowing the two wheel axles to rotate at different speeds.

[0070] For example, such a transmission system 1 is intended for a hybrid vehicle. Thus, the transmission system 1 is capable of transmitting torque from an electric motor to the rear axle or the front axle of the vehicle, for example, while another transmission system coupled to another electric motor, such as an internal combustion engine, is capable of generating and transmitting torque between this other electric motor and two wheel axles of another axle of the vehicle. The vehicle may also be fully electric.

[0071] The differential drive 2 comprises a first assembly 5 rotatable about the X axis, intended to be kinematically coupled to the motor by means of a reducer device (not shown). The differential drive 2 also comprises a second assembly 6 rotatable about the X axis and intended to drive the wheel axles 3 , 4 .

[0072] The first assembly 5 of the differential drive 2 comprises a differential case 8. The differential case 8 comprises two parts 10, 11 which are fixed to each other.

[0073] The second assembly 6 of the differential drive 2 comprises a planet carrier 12 of annular shape which is rotatably guided about the X axis inside the differential case 8. The second assembly 6 further comprises a geared planetary gear 14 and two geared ring gears 15,16.

[0074] The planetary gears 14 are rotatably mounted on the planet carrier 12 about a Y axis perpendicular to the X axis. In a manner known per se, the planetary gears 14 each comprise a conical toothing which meshes with a complementary conical toothing of two ring gears 15, 16. The two ring gears 15, 16 are rotatable about the X axis and are each rotatably fixed to one of the two wheel axles 3, 4, respectively. The planetary carrier 12, the planetary gears 14 and the ring gears 15, 16 thus form a differential, thereby allowing the two wheel axles 3, 4 to rotate at different speeds, if appropriate.

[0075] The differential drive device 2 comprises:

[0076] - a planet carrier 12 which supports an axially engaging toothing 20;

[0077] an output ring gear 16 which rotates about the axis of rotation X and supports a radial toothing 21 ;

[0078] - an axially movable blocking gear 24, which is provided with a Figure 5 The radial engagement teeth 25 are more clearly shown in FIG.

[0079] An axially displaceable connecting sliding gear 27 provided with an axial engagement toothing 28 .

[0080] The connecting sliding gear 27 and the blocking sliding gear 24 are movable so as to be in three axial positions:

[0081] - a disconnected position in which the engaging tooth portion 28 of the connecting sliding gear 27 is disconnected from the engaging tooth portion 20 of the planet carrier 12, and the engaging tooth portion 25 of the blocking sliding gear 24 is disconnected from the engaging tooth portion 21 of the output ring gear 16 (in Figure 1 and Figure 2 )

[0082] - a connected position, in which the engaging tooth portion 28 of the connecting sliding gear 27 is connected to the engaging tooth portion 20 of the planet carrier 12, and the engaging tooth portion 25 of the blocking sliding gear 24 is disconnected from the engaging tooth portion 21 of the output ring gear 16 (in Figure 3 )

[0083] - a blocking position, in which the engaging toothing 28 of the connecting sliding gear 27 is connected to the engaging toothing 20 of the planet carrier 12, and the engaging toothing 25 of the blocking sliding gear 24 is connected to the engaging toothing 21 of the output ring gear 16 (in Figure 4 ).

[0084] The device 2 further comprises a prestressed axial spring 30 which is arranged to exert a force on the connecting sliding gear 27 towards the planet carrier 12 in order to promote the engagement of the engagement toothing 28 of the connecting sliding gear 27 in the engagement toothing 20 of the planet carrier 12 when changing from the disconnected position to the connected position.

[0085] In the example described, the spring 30 is a helical spring.

[0086] The axial engagement toothing 20 and 28 comprises teeth which protrude axially towards the axis of rotation.

[0087] The radial toothings 21 and 25 comprise teeth which project radially and therefore perpendicularly to the axis of rotation.

[0088] In the disconnected position, torque transmission between the electric motor and the wheels is disconnected.

[0089] In the connected position, torque can be transmitted between the electric machine and the wheel axles 2 , 3 by applying a differential function, thereby allowing different rotational speeds to be provided for the two wheel axles.

[0090] In the blocked position, relative movement between the output ring gears is blocked and both wheels are forced to rotate at the same speed as the differential case, regardless of any differences in traction between the wheels.

[0091] The blocking sliding gear 24 is rotationally fixed relative to the differential case 8. The blocking sliding gear 24 is rotationally fixed relative to the planet carrier 12 in the connected position.

[0092] The connecting sliding gear 27 is rotationally fixed relative to the differential case 8. The connecting sliding gear 27 is axially movable in the connecting position and rotationally fixed relative to the planet carrier 12.

[0093] The connecting sliding gear 27 and the blocking sliding gear 24 are arranged to be moved by the same actuator 32 .

[0094] In the described example, the blocking sliding gear 24 and the connecting sliding gear 27 are axially movable relative to each other, and a spring 30 is interposed between the blocking sliding gear 24 and the connecting sliding gear 27 so that the connecting sliding gear 27 can be axially moved through the blocking sliding gear 24 by means of the spring 30 .

[0095] In this case, the spring 30 is arranged between the connecting sliding gear 27 and the blocking sliding gear 24 .

[0096] The stiffness of the spring 30 is selected such that the blocking sliding gear 24 and the connecting sliding gear 27 are axially fixed when there are no obstacles hindering the axial movement of the connecting sliding gear 27 and / or the blocking sliding gear 24 .

[0097] The connecting sliding gear 27 is arranged to be axially movable relative to the blocking sliding gear 24 between a stop position on a stopper 33 of the blocking sliding gear 24 and an axially retreated position retreated from the stopper 33 in which the spring 30 is compressed.

[0098] When the connecting sliding gear 27 is in the stop position against the stop 33 of the blocking sliding gear 24 , the spring 30 is prestressed.

[0099] The prestressed spring 30 tends to push the connecting sliding gear 27 against the stop 33 formed by a circlip fixed to the blocking sliding gear 24 .

[0100] Therefore, when in the disconnected position, the connection sliding gear 27 abuts against the circlip 33 .

[0101] The spring 30 is supported at its end opposite to the connecting sliding gear 27 on a stop formed by a circlip 34 .

[0102] In the disconnecting position, the engaging teeth 28 of the connecting sliding gear 27 do not overlap with the engaging teeth 20 of the planet carrier 12 , and the engaging teeth 25 of the blocking sliding gear 24 do not overlap with the engaging teeth 21 of the output ring gear 16 .

[0103] In the connected position, the engagement toothing 28 of the connecting sliding gear 27 axially overlaps the engagement toothing 20 of the planet carrier 12 and the spring 30 is in a less stressed state, in its initial prestressed state.

[0104] The toothing 28 connecting the sliding gear 27 and the toothing 20 of the planet carrier 12 extend axially.

[0105] The device 2 comprises a friction device 40 arranged to generate, in connected mode, a torque deviation between the axles 3 , 4 of the two wheels connected to the differential drive 2 .

[0106] By voluntarily adding a friction device 40 that generates a constant and / or proportional friction between the moving parts of the differential, a torque deviation between the two wheels that is constant or proportional to the input torque can be generated and the off-road capability of the vehicle can be improved. Without additional devices, the torque deviation between the two wheels is in particular about 3% to 5%. With additional, passive or active friction devices, deviations of about 30% can be achieved.

[0107] The friction device 40 comprises a stack of friction discs 41 .

[0108] The friction device 40 is placed between the opposing output ring gear 15 and the planet carrier 12 .

[0109] The first set of friction discs 60 is rotatably fixed to the opposite output ring gear 15, in particular by means of teeth and splines. The second set of friction discs 61 is rotatably fixed to the planet carrier 12, in particular by means of teeth and splines. The discs of the first set 60 and the second set 61 are arranged alternately to obtain a plurality of friction surfaces. The conical toothing of the opposite output ring gear 15 allows the friction discs 41 to be pressed against each other during rotation of the said ring gear so as to generate a friction torque.

[0110] exist Figure 3 In the blocking position shown, the axial tooth portion of the connecting sliding gear 27 axially overlaps with the axial tooth portion of the planet carrier 12, the connecting sliding gear 27 axially abuts against the planet carrier 12, the spring 30 is compressed, and the radial engagement tooth portion of the blocking sliding gear 24 radially overlaps with the radial engagement tooth portion of the output ring gear 16.

[0111] The toothing 20 of the planet carrier 12 and the toothing 21 of the output ring gear 16 are arranged inside the differential case 8 and inside the gearbox housing. Therefore, the movable connecting sliding gear 27 and the blocking sliding gear 24 benefit from the lubrication of the gearbox.

[0112] When the connection sliding gear 27 is in the disconnection position ( Figure 1 ), the planet carrier 12 can rotate freely in the differential case 8.

[0113] The blocking gear 24 is connected to the differential case 8 in a prismatic manner.

[0114] This prismatic connection is implemented by means of corresponding axial splines 47 of the blocking sliding gear 24 and corresponding axial splines 48 of the differential case 8 , these splines meshing to allow relative translational movement while blocking relative rotational movement.

[0115] The splines 48 are manufactured on a sleeve 49 of the differential case 8 .

[0116] This sleeve 49 supports a circlip 50 which forms a stop for the sliding gear 24 .

[0117] The engaging tooth portion 28 connecting the sliding gear 27 and the engaging tooth portion 20 of the planet carrier 12 has an axial engaging tooth portion of a disengagement prevention type.

[0118] In a manner known in the prior art, the anti-disengagement engagement teeth have undercuts and counter-undercuts having angles selected to ensure that the teeth do not spontaneously disengage when they transmit torque, thereby avoiding untimely disconnection.

[0119] The actuator 32 is arranged to move the blocking sliding gear 24 and the connecting sliding gear 27 between three positions (i.e., the disconnecting position ( Figure 1 and Figure 2 ), Connection Location( Figure 3 ) and blocking position ( Figure 4 ))Move in sequence and in reverse order.

[0120] The blocking sliding gear 24 transmits the force from the actuator 32 to the connecting sliding gear via the spring.

[0121] The blocking slide gear 24 comprises a groove 55 arranged to engage with the actuator 32 which in this position presents a fork shape.

[0122] In this case, the actuator 32 is an actuator of the electromagnetic type.

[0123] Figure 6 Some details of the blocking sliding gear 24 and the connecting sliding gear 27 are shown. For example, it can be seen that the complementary axial splines 35, 36 provided on the blocking sliding gear 24 and the connecting sliding gear 27 respectively allow blocking of the relative rotation between these two sliding gears 24 and the sliding gear 27. The connecting sliding gear 27 is thus rotatably fixed to the differential case 8, on the one hand via the complementary splines 35, 36 rotatably fixing it to the blocking sliding gear 24, and on the other hand via the axial splines 47 of the blocking sliding gear 24 and the axial splines 48 of the differential case 8.

[0124] According to an alternative embodiment not shown, the blocking sliding gear 24 and the connecting sliding gear 27 are rotatably fixed to the differential case 8 by virtue of the corresponding shapes between the connecting sliding gear 27 and the blocking sliding gear 24 and the opening 51 of the differential case 8 .

[0125] Figure 7 A second embodiment is schematically shown in which the connecting sliding gear 27 and the blocking sliding gear 24 are axially fixed. For example, they can be made of the same part. Together, they form a double sliding gear 65.

[0126] The spring 30 is kinematically arranged between the actuator 32 and the double sliding gear 65. Thus, the same spring can be used to manage both any engagement interference of the connecting sliding gear 27 and any engagement interference of the blocking sliding gear 24.

Claims

1. A differential drive (2) for a drive train (1) of a motor vehicle, the differential drive having an axis of rotation (X) and comprising: - a planet carrier (12) which supports a toothing (20), in particular an axial toothing; an output ring gear (16) which is rotatable about the axis of rotation (X) and which supports a toothing (21), in particular a radial toothing; - an axially movable blocking sliding gear (24), which is provided with an engaging toothing, in particular a radial engaging toothing; - an axially movable connecting sliding gear (27), which is provided with an engaging toothing, in particular an axial engaging toothing; Wherein, the connecting sliding gear (27) and the blocking sliding gear (24) are movable so as to be in three axial positions: o a disconnected position, in which the engaging tooth portion (28) of the connecting sliding gear (27) is disconnected from the engaging tooth portion (20) of the planet carrier (12), and the engaging tooth portion (25) of the blocking sliding gear (24) is disconnected from the engaging tooth portion (21) of the output ring gear (16); o a connection position, in which the engaging tooth portion (28) of the connecting sliding gear (27) is connected to the engaging tooth portion (20) of the planet carrier (12), and the engaging tooth portion (25) of the blocking sliding gear (24) is disconnected from the engaging tooth portion (21) of the output ring gear (16); o a blocking position, in which the engaging tooth portion (28) of the connecting sliding gear (27) is connected to the engaging tooth portion (20) of the planet carrier (12), and the engaging tooth portion (25) of the blocking sliding gear (24) is connected to the engaging tooth portion (21) of the output ring gear (16); - a spring (30) arranged to exert a force on the connecting sliding gear (27) towards the planet carrier so as to promote the engagement of the engaging toothing (28) of the connecting sliding gear (27) in the engaging toothing (20) of the planet carrier (12) when changing from the disconnected position to the connected position.

2. A differential drive according to the preceding claim, wherein: The spring (30) is an axial spring, in particular a prestressed spring.

3. A differential drive as claimed in any one of the preceding claims, wherein: The blocking sliding gear (24) is rotatably fixed relative to the planet carrier (12) in the connected position.

4. A differential drive as claimed in any one of the preceding claims, wherein: The connecting sliding gear (27) is axially movable in the connecting position and is rotationally fixed relative to the planet carrier (12).

5. A differential drive as claimed in any one of the preceding claims, wherein: The spring (30) is arranged between the connecting sliding gear and the blocking sliding gear (27, 24).

6. A differential drive according to the preceding claim, wherein: The blocking sliding gear (24) and the connecting sliding gear (27) are axially movable relative to each other, and the spring (30) is interposed between the blocking sliding gear and the connecting sliding gear so that the connecting sliding gear can be axially movable through the blocking sliding gear by means of the spring.

7. A differential drive as claimed in any one of the preceding claims, wherein: The connecting sliding gear (27) is arranged to be able to move axially relative to the blocking sliding gear (24) between a stop position on a stopper (33) of the blocking sliding gear and an axially retreated position retreated from the stopper, in which the spring is compressed.

8. A differential drive as claimed in any one of the preceding claims, wherein: The engaging tooth portion (28) of the connecting sliding gear and the engaging tooth portion (20) of the planet carrier extend axially.

9. A differential drive as claimed in any preceding claim, comprising a friction device (40) arranged to generate a torque deviation between two wheels connected to the differential drive.

10. A differential drive according to the preceding claim, wherein: The friction device comprises a stack of friction discs (41).

11. A differential drive as claimed in any one of the preceding claims, wherein: The engaging tooth portion (28) of the connecting sliding gear and the engaging tooth portion (20) of the planet carrier have an axial engaging tooth portion of an anti-disengagement type.

12. A transmission system comprising a differential drive device (2) as claimed in any one of the preceding claims and an actuator (32), wherein: The actuator is arranged to move the blocking sliding gear and the connecting sliding gear to three positions, namely a disconnecting position, a connecting position and a blocking position and in reverse order.

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