Transmission assembly in a motor vehicle, the assembly comprising a locking device

Abstract

The invention relates to a device for locking a drivetrain transmission in a vehicle, comprising: an electric motor (6), with a rotor (60) having an axis (A1); a first pinion (21) constrained to rotate with the rotor; a secondary shaft (2) mounted rotatably about a second axis (A2) and provided with a second pinion (22) and a third pinion (23), the second pinion being engaged with the first pinion; an output ring (3) engaged with the third pinion and in kinematic relation with a wheel of the vehicle; a locking sleeve (1) centred on the first axis and axially movable between an unlocking position (P1) and a locking position (P2); and a fork (4) for moving the locking sleeve axially between the unlocking position and the locking position, wherein, in the locking position, the locking sleeve rotationally couples the first pinion directly to the output ring.

Description

DESCRIPTION TITLE OF THE INVENTION: Transmission assembly in a motor vehicle and comprising a locking device

[0001] The invention relates to a transmission assembly comprising a locking device intended to lock an axle or wheel drive train in a motor vehicle. The invention relates in particular to vehicle axles equipped with electric motors, for the front or rear axles. A local electric motor system specific to a wheel is also targeted.

[0002] The locking device of interest here, by mechanical engagement of a locking member, commonly called a "parking brake", is conventionally used in particular on vehicles with automatic transmission. This type of locking device is also used in electric or hybrid vehicles. The transmission locking device is activated when the driver positions the transmission selection lever in the "P" position, generally when the vehicle is stationary.

[0003] The locking device in question here is distinct from and complementary to another braking system called a parking brake, also present on motor vehicles, and acting directly on the vehicle's wheels. Said parking brake also acts as an emergency brake to slow down and immobilize the vehicle. Conversely, the parking brake which is the subject of the present invention is intended and designed to be engaged only at zero or near-zero speed.

[0004] Parking brake solutions are known where a pivoting toothed element (latch or 'pawl') selectively interferes with a toothed wheel forming part of the transmission. However, it turns out that the known solutions take up a significant amount of space, with a specific parking brake wheel, and furthermore they are not free of play. An example of such a solution is known from document US2016223082.

[0005] The inventors sought to improve the situation and propose a new configuration to achieve the parking brake function, in particular more compact, especially for an electric motor assembly.

[0006] To this end, a transmission assembly for a motor vehicle is thus proposed, the assembly comprising a locking device by mechanical engagement of at least one locking member, the assembly comprising at least: - a primary shaft configured to rotate around a first axis and configured to be driven by a motor, - a first pinion rotating with the primary shaft, - a secondary shaft mounted to rotate around a second axis, equipped with a second pinion and a third pinion, with a different number of teeth, the second pinion being engaged with the first pinion, - an output crown, engaged with the third pinion, the output crown being in kinematic relation with at least one wheel of the vehicle, - a locking sleeve centered on the first axis, axially movable between an unlocking position and a locking position, - a fork configured to move the locking sleeve along the first axis between the unlocking position and the locking position, characterized in that in the locking position, the locking sleeve directly connects the output ring gear to the first pinion or the primary shaft in rotation, which blocks the rotation of the output ring gear due to the engagement between the first pinion and the output ring gear via a mutual reduction ratio other than 1.

[0007] The characteristic "the output crown being in kinematic relation with at least one wheel of the vehicle" includes in particular either a direct engagement for the case of an electric motorization of a single wheel (the term 'E-wheel' is sometimes used) or an indirect engagement relating to two 2 wheels via a differential (the term 'E-axle' is then used).

[0008] The term “engaged” in this document refers to a permanent mechanical meshing by complementary teeth.

[0009] The term "locking sleeve" can also be called "coupling sleeve", "dog clutch", or "sliding clutch". It is an annular member comprising internal grooves, as will be seen in more detail below. The locking sleeve forms the aforementioned locking member.

[0010] Thanks to the arrangements presented above, the parking brake function is arranged on the main axis, and the need for a specific parking brake wheel, in particular one offset from the main axis, is avoided. The number of parts required to implement the function is lower in the proposed solution than in the known prior art. Advantageously, the proposed system is therefore devoid of a specific parking brake wheel and any other related component.

[0011] The proposed configuration is compact and simple to manufacture and assemble. Advantageously, the proposed configuration is lighter than configurations known in the art.

[0012] It should be noted that in the unlocked position, the mechanical connection, provided by the locking sleeve, between the output crown and the primary shaft or the first pinion, is no longer established. According to one embodiment, the locking sleeve is then located on the side of the output crown and rotates with it.

[0013] Alternatively, the rest position could be on the other side, namely on the primary shaft side.

[0014] It should be noted that in the present disclosure, the motor driving the primary shaft may be an electric motor having a rotor rotatably connected to the primary shaft. However, it is not excluded that the motor is a motor internal combustion, the primary shaft then being driven directly or indirectly, or via a clutch by the crankshaft of this engine.

[0015] In one aspect, the output ring gear is connected to a single wheel of the vehicle directly or via a permanent gear (e.g. a reduction gear). This provides an elegant solution for a wheel-specific local electric drive system. In a vehicle with multiple local wheel drive systems, one may choose to equip one or more systems with such a parking brake function.

[0016] In one aspect, the output ring gear is connected to two wheels of the vehicle via a differential comprising a ring gear and two satellites, the output ring gear being formed by the differential ring gear. As a result, the transmission can be locked upstream of the differential and the parking brake function is provided with a single locking sleeve for two wheels of the vehicle axle. This configuration is ideal for electrically powered axles, whether arranged at the front or rear of the vehicle.

[0017] In this context, it should be noted that the parking brake function is compatible with a differential lock function, both functions can be implemented on the axle in question.

[0018] In one aspect, the primary shaft is hollow and includes an axial through bore.

[0019] This bore allows the passage of a wheel shaft (also called a half-axle shaft) which extends from a differential output to one of the wheels. As a result, the arrangement is completely coaxial, except for the secondary shaft.

[0020] According to one aspect, there is provided on the differential a first axial end portion (71) equipped with first external splines, complementary to internal splines of the locking sleeve and forming a location for the rest / unlocking position of the locking sleeve, the first axial end portion being rigid in rotation with the part carrying the differential crown or the axial end portion forming an integral part of the differential crown.

[0021] Thanks to the above-mentioned splines, it is possible to transfer torque between the locking sleeve and the output crown. Generally, the splines preferably extend parallel to the first axis. The locking sleeve remains at least partly straddling the first axial end portion, in particular when the locking sleeve is in the locking position. In the unlocked position, the entire locking sleeve surrounds the first axial end portion, which is its rest position.

[0022] In one aspect, the primary shaft may include a second axial end portion with second outer splines adapted to receive inner splines of the locking sleeve.

[0023] Thanks to the above-mentioned splines, it is possible to pass torque between the locking sleeve and the primary shaft when the sleeve is in the locking position.

[0024] According to one aspect, entry chamfers are provided on the outer grooves of the second axial end portion, on the sleeve docking side.

[0025] This facilitates the engagement of the sleeve on the primary shaft. Entry chamfers can also be provided on the radially inner splines of the locking sleeve on the side of its front face, the one that advances for coupling.

[0026] According to one aspect, the first axial end portion (71) and the second axial end portion (52) are opposite each other, face each other axially and are separated by a gap (E1) of less than 5 millimeters.

[0027] The gap that needs to be crossed for the locking sleeve to reach and cover its target on the input shaft side is sufficiently small.

[0028] In one aspect, the first axial end portion and the second axial end portion have substantially the same outer diameters.

[0029] The longitudinal grooves of the locking sleeve can thus easily slide from the first axial end portion to cover the second axial end portion.

[0030] In one aspect, the number of splines may be between 20 and 40. This number makes it possible to minimize the probability of difficulty in tooth-to-tooth engagement and still have a sufficiently large size of the spline profiles to absorb torque.

[0031] According to one aspect, the locking sleeve has an outer diameter (D1) and an axial dimension (L1), the outer diameter being less than 12 cm, preferably less than 10 cm, and the axial dimension preferably less than 4 cm.

[0032] The proposed solution is therefore compact. The locking sleeve only absorbs torque at zero speed, so it can be dimensioned as precisely as possible. This distinguishes it from a differential or gearbox locking dog clutch, which must operate over a wide range of rotation speeds.

[0033] In one aspect, the first pinion comprises external splines adapted to receive internal splines of the locking sleeve. This is an alternative to the solution presented above where the receiving splines are arranged on the primary shaft. Here the splines are arranged on the primary pinion.

[0034] According to one aspect, there are provided inlet chamfers on the outer splines of the first pinion, on the sleeve docking side.

[0035] The invention also relates to a powertrain for a vehicle comprising an electric motor and a transmission assembly as described previously.

[0036] In one aspect, the motor is an axial flux motor. In one aspect, the motor is a radial flux motor.

[0037] The invention also relates to an electrically powered axle for a vehicle comprising a motor, two wheels, two wheel shafts connected to a differential, and a transmission assembly as described previously comprising said differential.

[0038] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates in section an example of a transmission assembly according to the present invention, with the locking sleeve in the unlocked position; - [Fig.2] schematically illustrates in section the transmission assembly of figure 1, with the locking sleeve in the locking position; - [Fig.3] schematically illustrates in section another example of a transmission assembly according to the present invention; - [Fig.4] schematically illustrates in section yet another example of a transmission assembly according to the present invention; - [Fig.5] schematically illustrates in section the area of ​​the locking sleeve; - [Fig.6] illustrates in perspective an example of a locking sleeve; - [Fig.7] illustrates in sectional view a detail of the engagement of the grooves.

[0039] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale.

[0040] Figures 1 and 2 show an example of an electrically powered axle. This axle can be part of the front axle of a vehicle or the rear axle of a motor vehicle. It can be a steered or non-steered axle. Generally, an electrically powered axle comprises a drive unit, a transmission including a differential, two axle shafts and two wheels. The transmission can include a reducer, if necessary with several selectable reduction ratios (gearbox) and optionally, as will be seen below, devices for connecting two rotating elements together.

[0041] More precisely, such an axle comprises a left wheel and a right wheel, not shown in the figures. As known per se, in a middle portion of the axle, a differential 7 is arranged. A first output of the differential is connected in rotation to a left wheel shaft ARG which is itself connected in rotation to the left wheel. The other output of the differential is connected in rotation to a right wheel shaft ARD which is itself connected in rotation to the right wheel.

[0042] The differential 7 allows for differentiated wheel speeds, particularly for example when the vehicle takes a turn or also when one of the wheels slips or skids. A differential locking device, not shown in the figures, may be provided which allows for certain phases of the vehicle's life, to secure in rotation one of the output shafts with the differential body.

[0043] The two rear and rear wheel shafts rotate around a first axis marked A1. The body 70 of the differential also rotates around the axis A1.

[0044] The axle is motorized, in the example illustrated by an electric motor marked 6. The axis of the electric motor coincides with the first axis A1.

[0045] In the illustrated example, the rotor 60 is flat and the magnetic flux is axial. In an alternative example, the motor may be a radial magnetic flux motor. It is not excluded that the electric motor has an axis different from the first axis.

[0046] It should be noted that the gearbox / axle housing is not shown in the figures and the bearing assembly and guidance is only shown symbolically.

[0047] The rotor 60 is mounted on a shaft called the primary shaft 5. The primary shaft is hollow and includes a through axial bore, marked 50. The left wheel shaft ARG is housed inside the bore 50 of the primary shaft 5. The left wheel shaft ARG and the primary shaft 5 are coaxial. A small functional clearance is provided to allow the wheel shaft to rotate inside the bore 50 of the primary shaft. The left wheel shaft ARG is connected to an output bevel gear 77 of the differential 7.

[0048] On the primary shaft 5 is arranged a first pinion marked 21. The first pinion may be integrally manufactured from the primary shaft or may be an added part mounted integrally in rotation on the primary shaft 5. The primary shaft 5 may include shoulders, bearing surfaces, annular grooves for circlips, keyway grooves and any other device or function known per se.

[0049] The torque produced by the electric motor 6 is delivered downstream through the first pinion 21 and in particular its external teeth.

[0050] The primary shaft has one end on the differential side, the purpose of which will be seen later.

[0051] In addition to the differential, the transmission assembly includes a secondary shaft 2. The secondary shaft is mounted to rotate around a second axis denoted A2. The second axis A2 is separated from the first axis A1 by a distance typically between 10 cm and 20 cm.

[0052] The secondary shaft 2 is equipped with a second pinion 22 and a third pinion 23. The second pinion 22 and the third pinion 23 have a different number of teeth. The second pinion 22 is engaged with the first pinion 21.

[0053] The secondary shaft can be manufactured in one piece with the second and third pinions included. Alternatively, one of the two pinions can be an insert mounted on splines or by means of keying or pinning or by means of smooth shrink fitting. The two pinions 22, 23 can be inserts rigidly mounted on the shaft.

[0054] The secondary shaft 2 can be hollow or solid. As with the primary shaft, the secondary shaft can include shoulders, bearing surfaces, annular grooves for circlips, keyways and any other device or function known per se.

[0055] The differential 7 comprises an outer ring gear with teeth. In this document, this outer ring gear is also called the “output ring gear” marked 3. The output ring gear 3 is centered on the axis A1 and coaxial with the primary shaft 5.

[0056] The third pinion 23 is engaged with the output crown 3. The output crown rotates more slowly than the primary shaft due to the cascade of two reductions, namely a first reduction obtained by the engagement of the second pinion on the first pinion, then that which couples the output crown with the third pinion.

[0057] In the configuration with differential presented according to figures 1 and 2, the crown of the differential 3 drives the axes 75 of satellites, the bevel satellites 76 in turn drive the bevel gears 77 linked to the respective wheel shafts. The differential is not described further because it is assumed to be known per se.

[0058] Advantageously according to the present invention, a locking sleeve 1 is provided.

[0059] The differential body 70 comprises a splined bearing surface 71 for receiving said locking sleeve 1 around this splined bearing surface. This splined bearing surface 71 is herein referred to as the first axial end portion. The splined bearing surface 71 comprises splines herein referred to as first outer splines 73, which receive radially inner splines of the locking sleeve.

[0060] The locking sleeve 1 can also be called a coupling sleeve, dog clutch, dog clutch, or even a sliding sleeve. It is an annular member comprising internal shapes comprising grooves 12, oriented longitudinally with respect to the first axis, and visible in Figures 6 and 7.

[0061] Furthermore, the locking sleeve 1 comprises an annular groove 10 open towards the outside. The annular groove is framed by two rims 16.

[0062] At least one free end of a fork 4 is engaged in the annular groove 10. Preferably, the fork 4 has a semicircular shape which engages in the groove over an angular range of approximately 180°. Alternatively, there may be two diametrically opposed fingers in the fork.

[0063] The locking sleeve 1 is centered on the first axis A1. The locking sleeve 1 is axially movable between an unlocking position denoted P1 and a locking position denoted P2.

[0064] The fork 4 is movable along the axis A1 to cause the locking sleeve to move along the first axis A1 between the unlocking position P1 shown in Figure 1 and the locking position P2 shown in Figure 2.

[0065] The fork 4 can be moved in translation along the first axis. Alternatively, the fork 4 can be rotatably mounted and be rotated relative to an auxiliary axis distant from the first axis and perpendicular to the latter.

[0066] The fork 4 does not rotate around the first axis A1 whereas in the general case when the vehicle is moving, the locking sleeve 1 rotates around the axis A1. It can be provided that in the unlocked position, at rest, the locking sleeve is in an indexed position and that the end of the fork slides without contact in the annular groove 10.

[0067] In the locking position, the locking sleeve 1 directly connects the output ring gear 3 to the primary shaft 5 in rotation. In other words, the locking sleeve 1 directly connects the output ring gear 3 and the primary shaft 5 in rotation and thus the locking sleeve imposes Q5 = Q3. Q5 is the rotational speed of the primary shaft, Q3 is the rotational speed of the differential body.

[0068] Furthermore, due to the meshing of the pinions, we have the engagement relationship Q3 = K x Q5 with K different from 1, due to the cascade of difference in the number of teeth between the first pinion 21 and the second pinion 22 then between the third pinion 23 and the output crown 3. K is much lower than 1 in practice (reduction at a fairly high rate).

[0069] The only solution of this hyperstatic system is Q5 = 0 and Q3 = 0, this is blocking.

[0070] Thus, the engagement of the locking sleeve leads to the blocking of the rotation of the differential crown due to the meshing of pinions with a cascade gear ratio other than 1.

[0071] Preferably, the command to move the fork 4 to the left, i.e. towards the coupling position, is only authorized if the speed of the vehicle is zero or even optionally almost zero, i.e. less than 3 km / h.

[0072] A control unit, not shown in the figures, is responsible for the logic of controlling the position of the locking sleeve, depending on the position of the transmission lever 'P' or Non-'P' and the current speed of the vehicle.

[0073] We note that the locking sleeve only works in torque at zero speed, i.e. it is never subjected to a torque while it rotates, which allows its diameter D1 and its splines 12 to be dimensioned as precisely as possible. It is also possible to relax the choice of material or to do without certain heat treatments, if we compare this locking sleeve with a gearbox sliding sleeve or a differential locking sleeve.

[0074] The grooves 12 of the locking sleeve are provided with inlet chamfers 14 of pronounced shape, the end of the groove being in the form of a point. The inlet chamfers 14 are provided in particular on the side of the front face 17 of the sleeve which advances during translation towards the locking position. Thus, at the moment when the coupling movement occurs, the pointed shapes of the grooves 12 engage on the grooves 54 on the side primary shaft, with a small rotation if necessary, in an unfavorable case where the splines are opposite each other.

[0075] The primary shaft 5 comprises a second axial end portion 52 with the splines 54 capable of receiving the radially internal splines 12 of the locking sleeve.

[0076] The splines 54 on the primary shaft 5 side also have entry chamfers 55.

[0077] The number of grooves 12 can be between 20 and 40. Of course, the number of grooves chosen is the same for the locking sleeve which forms the female part as well as the two male parts arranged end to end which are covered at least in part by the locking sleeve.

[0078] The inner diameter D3 of the locking sleeve is slightly larger than the diameter of the primary shaft excluding the splines.

[0079] The wheel shafts have an outside diameter D5 smaller than the diameter D4 of the bore 50 provided in the primary shaft.

[0080] The locking sleeve 1 has an axial dimension L1, preferably less than 4 cm. The outer diameter D1 is less than 12 cm, and preferably less than 10 cm. Depending on the torque specifications, the diameter D1 can even be smaller. In an exemplary embodiment, L1 + D1 can be chosen to be less than 14 cm.

[0081] As seen in Figure 5, the first axial end portion 71 and the second axial end portion 52 are opposite each other, i.e. they face each other and are separated by a gap E1 of less than 5 millimeters. In some embodiments, the gap E1 is less than 4 mm, or even less than 3 mm.

[0082] The first axial end portion 71 and the second axial end portion 52 have outer diameters D2 of substantially the same dimension.

[0083] It is noted that the elements involved, including the locking sleeve 1, are lubricated by the splashing of oil from the transmission.

[0084] According to a second embodiment shown in Figure 3, the coupling sleeve 1 covers a part 25 of the first pinion instead of directly the primary shaft. However, given that the first pinion 21 is coaxial and connected in rotation with the primary shaft 5, the functionality is identical to what was explained above for the first embodiment.

[0085] The so-called second axial end portion is then located on the first pinion 21.

[0086] It is thus possible to have a primary shaft 5 of smaller diameter knowing that the external diameter of the second axial end portion of the first pinion is substantially identical to the external diameter D2 of the first axial end portion 71.

[0087] According to a third embodiment shown in Figure 4, there is no differential because the system only concerns one wheel and there is a single rear output shaft to one wheel. The crown 3 engaged by the third pinion 23 is a crown of a classic gear, which can be called here fourth pinion 44, connected in rotation with the rear wheel shaft.

[0088] Like the arrangement set out above for the case of the differential body, this fourth pinion 44 of the third embodiment comprises a splined bearing surface for receiving the locking sleeve, which forms the first axial end portion 71.

[0089] It is therefore understood that the term output crown designates either the crown of a differential body or a peripheral portion of a conventional gear pinion.

[0090] In other words, the output crown 3 is configured to be in kinematic relationship with at least one wheel of the vehicle. In the third embodiment, the characteristic “the kinematic relationship with at least one wheel of the vehicle” means a direct engagement for the case of an electric motorization of a single wheel. In the first embodiment, the characteristic “the kinematic relationship with at least one wheel of the vehicle” means an indirect engagement with respect to the two wheels via the differential 7.

[0091] All parts of the transmission assembly are made of metal, such as steel or cast iron. The parts of the transmission assembly are lubricated by splashing oil into the bottom of the crankcase or by force via an oil pump.

[0092] It is noted that in the configuration promoted here the following parts are mounted coaxially with respect to the first axis A1: the primary shaft 5, the first pinion 21, the output crown 3, the locking sleeve 1, and the rear wheel shaft or the rear, rear wheel shafts.

[0093] It is noted that there are no friction elements necessary for the parking brake function promoted here; nor is there a synchronizer associated with the locking sleeve.

Claims

CLAIMS 1. Transmission assembly for a motor vehicle, the assembly comprising a locking device by mechanical engagement of at least one locking member, the assembly comprising at least: - a primary shaft (5) configured to rotate around a first axis (A1) and configured to be driven by a motor, - a first pinion (21) integral in rotation with the primary shaft, - a secondary shaft (2) mounted to rotate around a second axis (A2), equipped with a second pinion (22) and a third pinion (23), with a different number of teeth, the second pinion (22) being engaged with the first pinion (21), - an output crown (3), engaged with the third pinion (23), the output crown being configured to be in kinematic relation with at least one wheel of the vehicle, - a locking sleeve (1) centered on the first axis, axially movable, between an unlocking position (P1) and a locking position (P2), - a fork (4) configured to move the locking sleeve along the first axis between the unlocking position (P1) and the locking position (P2), characterized in that in the locking position, the locking sleeve directly connects the output ring gear (3) in rotation with the first pinion (21) or the primary shaft (5), which blocks the rotation of the output ring gear due to the engagement between the first pinion and the output ring gear via a mutual reduction ratio other than 1.

2. Transmission assembly according to claim 1, in which the output crown is connected to a single wheel of the vehicle directly or via a permanent gear.

3. Transmission assembly according to claim 1, in which the output crown is connected to two wheels of the vehicle via a differential (7) comprising a crown and two satellites, the output crown being formed by the differential crown (3).

4. Transmission assembly according to claim 3, in which the primary shaft (5) is hollow and comprises an axial through bore (50).

5. Transmission assembly according to any one of claims 3 to 4, in which there is provided on the differential a first axial end portion (71) equipped with first external splines (73), complementary to internal splines (12) of the locking sleeve and forming a location for the unlocking position of the locking sleeve, the first axial end portion being rigid in rotation with the differential crown wheel or the axial end portion forming an integral part of the differential crown.

6. Transmission assembly according to any one of claims 1 to 5, in which the primary shaft (5) comprises a second axial end portion (52) with first external splines capable of receiving internal splines of the locking sleeve.

7. Transmission assembly according to claims 5 and 6, in which the first axial end portion (71) and the second axial end portion (52) are opposite each other, face each other axially and are separated by a gap (E1) of less than 5 millimeters.

8. Transmission assembly according to any one of claims 1 to 5, in which the locking sleeve has an outer diameter (D1) and an axial dimension (L1), the outer diameter being less than 12 cm.

9. Transmission assembly according to any one of claims 1 to 5, in which the first pinion (21) comprises external splines capable of receiving internal splines (12) of the locking sleeve.

10. Powertrain for a vehicle comprising an electric motor and a transmission assembly according to any one of claims 1 to 9.

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