Wet clutch for a vehicle transmission

Abstract

Wet clutch for a vehicle transmission Wet clutch (E2) for a vehicle transmission comprising: - a torque input disc carrier (10) arranged to be rotationally linked with a driving shaft along an axis of rotation (X); - a multi-disc assembly driven in rotation by the torque input disc carrier; - a torque output disc carrier (30) arranged radially inside the multi-disc assembly; - a central hub (50) with axis of rotation (X) fixedly connected to the torque input disc carrier, said central hub (50) comprising a cylindrical portion (52) and at least one coolant supply channel (54d) formed in the central hub passing through at least the cylindrical portion (52) and opening axially opposite the torque output disc carrier (30), in which an axial bearing (70) is interposed axially between the central hub (50) and the torque output disc carrier (30). Figure for the abbreviation: Figure 1

Description

Title of the invention: Wet clutch for a vehicle transmission

[0001] The present invention relates to a wet clutch for a vehicle transmission. The invention also relates to a dual wet clutch and a triple wet clutch comprising this wet clutch.

[0002] The present invention relates to the field of torque transmission chains for motor vehicles or industrial vehicles, in particular arranged between a heat engine and / or a rotating electrical machine and a gearbox.

[0003] In the prior art, hybrid motor vehicles are known to comprise a dual wet clutch disposed between an internal combustion engine and a gearbox, a rotating electric machine, and a torque-cutting clutch, also known as a "KO clutch," and an actuation element for this torque-cutting clutch that allows a crankshaft of the internal combustion engine to be rotated and then unrotated by a rotor of the rotating electric machine. Thus, it is possible to shut off the internal combustion engine each time the vehicle stops and to restart it using the rotating electric machine. The rotating electric machine can also act as an electric brake or provide additional power to the internal combustion engine to assist it or prevent it from stalling. When the internal combustion engine is running, the electric machine can act as a generator.The rotating electric machine can also provide vehicle propulsion independently of the internal combustion engine.

[0004] Such a rotating electric machine can be in line with the wet double clutch, i.e. the axis of rotation of the rotor of the rotating electric machine is coincident with the axis of rotation of the clutches as described in document EP2517915. Alternatively, the rotating electric machine can be offset from the wet double clutch, i.e. the axis of rotation of the rotor of the rotating electric machine is offset from the axis of rotation of the wet double clutch.

[0005] In current developments in the hybridization of motor vehicles, there is a requirement for torque transmission systems that integrate an electrical power source without compromising the axial compactness of said transmission system. Therefore, it was necessary to design a triple wet clutch with a radial architecture that supplies cooling fluid and pressurized fluid to the various clutches without altering the overall dimensions of the torque transmission system. This quest for compactness axial is at the basis of the invention.

[0006] To minimize axial space requirements, the clutches of the triple wet clutch are stacked radially one above the other, each comprising an actuating piston controlled by a control chamber supplied with pressurized fluid and a balancing chamber supplied with cooling fluid. In this configuration, taking into account the centrifugal forces applied to the fluids contained in the chambers becomes crucial, particularly for the clutch located on the largest mounting diameter. It is necessary to adapt the geometry of the balancing chamber to achieve the smallest possible force difference on the wall of the actuating piston between the control chamber and the balancing chamber. The geometry is adjusted, in particular, based on the cooling fluid supply channel that feeds the various balancing chambers.Adjusting the geometry of the chambers becomes problematic when there are three clutches stacked radially one above the other and for which there is only one common coolant supply channel.

[0007] Furthermore, the radial architecture of this triple wet clutch sometimes makes it difficult to supply the multi-disc assemblies of the various wet clutches with cooling fluid, such as oil. The fluid supply channels are complex to manufacture and do not always guarantee proper distribution of the cooling oil within the clutches. Inadequate lubrication and cooling can lead to overheating of the friction discs and subsequently impair proper torque transmission.

[0008] The invention aims to improve the existing design by benefiting from a triple wet clutch allowing to reconcile the requirements of axial compactness, to guarantee a dynamic balancing of the radially stacked pressure and balancing chambers, while ensuring a good supply of cooling oil to the clutches.

[0009] To this end, the invention proposes, according to one of its aspects, a wet clutch for a vehicle transmission comprising:

[0010] - a torque input disc holder arranged to be rotationally linked with a shaft leading along an axis of rotation X;

[0011] - a multi-disc assembly comprising friction discs and plates axially stacked pressure plates driven into rotation by the torque input disc carrier;

[0012] - a torque output disc carrier arranged radially inside the assembly multi-disc and arranged to be rotationally linked to a driven shaft;

[0013] - a central hub with an X-axis of rotation fixedly connected to the input disc holder of couple, said central hub comprising a cylindrical portion and at least one channel cooling fluid supply formed in the central hub, passing through at least the cylindrical portion and opening axially opposite the torque output disc carrier,

[0014] the wet clutch being remarkable in that it comprises an axial bearing interposed axially between the central hub and the torque output disc carrier, said axial bearing being fitted into a bore of the central hub and partially obstructing the channel or channels for supplying cooling fluid opening axially opposite the torque output disc carrier.

[0015] Thanks to this architecture, the flow rate of the cooling fluid exiting the central hub is managed according to the needs of the wet clutch, either prioritizing cooling and / or dynamic balancing requirements. It is thus possible to adjust the quantity of fluid contained within the central hub. If the cooling fluid supply channel also feeds the pressure balancing chamber of the wet clutch, it is then possible to adjust the balancing pressure within this chamber.

[0016] Preferably, the axial bearing can be a needle bearing comprising at least one support ring.

[0017] Advantageously, the axial bearing support ring can partially obstruct the cooling fluid supply channel.

[0018] Preferably, the axial bearing can be inserted onto the cylindrical portion of the central hub. The support ring may comprise a cylindrical portion that is fitted inside the cylindrical portion of the central hub.

[0019] Advantageously, the axial bearing can include a first support ring equipped with a centering collar fitted into the bore of the central hub, the centering collar has a cylindrical bore defined by an inner radius, the centering collar obstructing the channel or channels for supplying cooling fluid.

[0020] Preferably, the multi-disc assembly is actuated by an axially movable actuating piston within a control chamber formed at least partially in the central hub, to which a balancing chamber is associated, supplied with fluid by a portion of the cooling fluid supply channel. The control chamber is generally supplied by a dedicated fluid line filled with fluid under high pressure relative to the cooling fluid.

[0021] Advantageously, the control chamber is defined by its outer radius Rp, the balancing chamber is defined by its outer radius Rb, the first support ring is defined by its inner radius Ri, and dynamic balancing of the control chamber with respect to the balancing chamber can be achieved when the The balancing ratio Q = (Rf / Ri) - (Rp / Rb) is between 0.1 and 0.2, taking into account the minimum radius of rotation of the fluid Rf within the clutch.

[0022] In this way, the geometry of the balancing chamber and the axial bearing is adapted to achieve a balance of the pressures applied on either side of the actuating piston. Indeed, during the rotation of the wet clutch, the volume of fluid, for example oil, contained in the control chamber is centrifugally expelled and creates an unwanted additional pressure exerted on the actuating piston. This additional pressure is added to the actuating pressure. By adapting the geometry of the balancing chamber and adjusting the diameter of the coolant leak, it is possible to compensate for this additional pressure. The aim is thus to reproduce the same additional pressure within the balancing chamber so that dynamic balance is achieved on either side of the actuating piston.

[0023] Preferably, the axial bearing is a needle bearing comprising a second support ring in direct contact with the torque output disc carrier, the inner radius of the second support ring being greater than the inner radius of the centering collar of the first support ring.

[0024] Advantageously, the torque output disc carrier may include at least one fluid supply line, one of whose inlet ports is oriented axially towards the cooling fluid supply channel, said channel being arranged to jointly supply fluid to the balancing chamber of the wet clutch and the torque output disc carrier.

[0025] Preferably, the inner radius of the axial bearing centering collar can partially obstruct the cooling fluid supply channel or channels opening axially opposite the fluid supply line(s) of the torque output disc carrier.

[0026] Advantageously, each coolant supply channel can be made by drilling successive axial and radial conduits within the central hub, the conduits opening into each other to form said channel.

[0027] Preferably, each cooling fluid supply channel can open axially opposite a fluid supply line of the torque output disc carrier.

[0028] According to one embodiment of the invention, the torque output disc holder may comprise:

[0029] - a splined hub with an X-axis of rotation provided with an internal spline of torque transmission,

[0030] - a sheet metal disc support in the shape of revolution around the X axis, provided of an external groove arranged to cooperate with the multi-disc assembly, the disc support being axially supported on the splined hub,

[0031] - a fluid retention cavity, annular and concentric to the X axis, formed at less by the association of surfaces from the splined hub and the disc support,

[0032] the splined hub forming partially or totally the fluid supply conduit(s) opening into the fluid retention cavity closed by the internal surface of the disc support.

[0033] Thanks to this torque output disc carrier architecture, the cooling fluid required for the proper functioning of the wet clutch first enters the splined hub via the fluid supply line, then enters the fluid retention cavity before being discharged into the wet clutch multi-disc assembly. Thus, the flow of cooling fluid is efficiently directed within the wet clutch multi-disc assembly.

[0034] The fluid retention cavity is formed at least from the "splined hub" and "disc support" components, specifically from an external surface of the splined hub and an internal surface of the disc support. The internal and external surfaces can be unmachined, unfinished surfaces, the combination of which creates a cavity. The use of components with simple shapes of revolution reduces manufacturing costs. The torque output disc carrier then fulfills the various functions of torque transmission, support for the friction discs, and routing of the cooling fluid within a reduced axial footprint.

[0035] Preferably, the disc carrier may include holes formed on the outer spline and arranged to evacuate the fluid contained in the fluid retention cavity. The holes may be distributed circumferentially around the X-axis and formed on the tooth crests of the outer spline. Thanks to this torque output disc carrier architecture, the flow of cooling fluid collected within the fluid retention cavity is uniformly distributed throughout the wet clutch multi-disc assembly. Thus, the fluid retention cavity does not contain any space where the cooling fluid can become trapped.

[0036] Advantageously, the disc support can be fixed to the splined hub by riveting, crimping, welding or press fitting.

[0037] Preferably, each fluid supply line can form a bend with a portion of the line extending axially and a portion extending radially. The radial orientation of the line allows the flow of cooling fluid to be directed efficiently within the multi-disc assembly of the wet clutch.

[0038] Advantageously, the central hub may comprise:

[0039] - a cylindrical portion,

[0040] - a flange extending radially from the cylindrical portion fixedly attached to the torque input disc holder, and

[0041] - cooling fluid supply channels formed in the hub central passing through the cylindrical portion and opening axially opposite the fluid supply lines of the torque output disc carrier so that the fluid from the central hub can be transferred into the splined hub of the torque output disc carrier and open into the multi-disc assembly.

[0042] Preferably, the cooling fluid supply channels and the fluid supply lines can be distributed angularly around the X axis, the outlets of the cooling fluid supply channels being arranged on a diameter substantially equal to the installation diameter of the inlets of the fluid supply lines.

[0043] According to one embodiment of the invention, the torque output disc carrier may include an annular deflector mounted on the splined hub and having external teeth that cooperate with the profile of the internal surface of the disc support. The fluid retention cavity is formed by the combination of surfaces from the splined hub, the disc support, and the deflector. Advantageously, the fluid retention cavity is formed at least from the components "splined hub," "deflector," and "disc support," in particular from an external surface of the splined hub, a flank of the deflector, and an internal surface of the disc support. The internal and external surfaces may be unmachined, unfinished surfaces, the combination of which creates a cavity.

[0044] Advantageously, the deflector can be made by stamping a sheet of metal or by plastic injection molding of synthetic material, for example, PA66 type polyamide plastic or PEEK type polyetheretherketone. These plastics exhibit high dimensional stability and are resistant to high temperatures.

[0045] The invention may have one or more of the features described below, either combined or taken independently of each other:

[0046] - the fluid retention cavity can be formed in part by a circumferential groove rential made on the outer periphery of the splined hub;

[0047] - the radially extending portion of the conduit can be formed by combining the surfaces of the splined hub and disc support and the axially extending driving part is formed solely by the disc support, for example by means of a hole through the disc support;

[0048] - the radially extending driving portion can be formed by drilling the hub grooved and the axially extending driving portion can be obtained directly from the grooved hub by molding or forging;

[0049] - the radially and axially extending conduit sections can be formed by combining the surfaces of the splined hub and the disc support;

[0050] - the radially extending portion of the conduit can be formed by combining the surfaces of the splined hub and the deflector;

[0051] - the splined hub may include a first machined axial bearing surface;

[0052] - the splined hub may include a second machined axial bearing surface and arranged axially opposite the first axial bearing span;

[0053] - the disc support can press directly on the splined hub;

[0054] - the deflector can press directly on the splined hub;

[0055] - the splined hub may include distributed fluid supply channels angularly around the X axis and opening into the fluid retention cavity;

[0056] - the splined hub may have a general shape of revolution with a base cylindrical;

[0057] - the axial bearing can be fitted into a bore of the central hub concentric to the X-axis;

[0058] - an O-ring can be inserted into an annular groove machined in the hub central to ensure the sealing of the connection between the axial bearing and the central hub, the O-ring being crushed by the centering collar;

[0059] - the axial bearing can be clipped into the bore of the central hub.

[0060] Such a torque output disc carrier, according to one or more of the characteristics described above, whether combined or taken independently, has the advantage, thanks to the use of added annular parts, of reducing manufacturing costs. These added annular parts make it possible to form a fluid retention cavity at a lower cost and can also perform other functions within a wet clutch, such as supporting and centering axial bearings.

[0061] The invention also relates, according to another aspect, to a dual wet clutch for a torque transmission system comprising:

[0062] - a first clutch; and

[0063] - a second wet clutch taking over all or part of the ca characteristics mentioned previously, arranged radially inside the first clutch, the first and second clutches being controlled to selectively couple a driving shaft to a first driven shaft and a second driven shaft, for example first and second gearbox shafts, and the central hub of the second clutch being common with the first clutch.

[0064] Advantageously, the central hub may comprise:

[0065] - a flange extending radially beyond the second clutch,

[0066] - a first control chamber arranged on the side of the flange and configured to receive an actuation piston for the first clutch, and

[0067] - a second control chamber arranged on the same side of the flange as the first annular cavity arranged to receive an actuating piston for the second clutch,

[0068] - at least one fluid channel formed in the central hub passing through the flange and opening into one of the control chambers, said fluid channel being separate from the cooling fluid supply channel of the multi-disc assembly of the second clutch.

[0069] The invention also relates, according to another of its aspects, to a triple wet clutch for a torque transmission system comprising a multi-disc type torque-cutting clutch, controlled to selectively couple a shaft leading to an electric machine, and a double wet clutch incorporating all or part of the characteristics mentioned above, the torque-cutting clutch being arranged radially beyond the double wet clutch.

[0070] Preferably, the inner radius of the centering collar can be defined as a function of the outer radius of the control chamber and the outer radius of the balancing chamber of the torque cut-off clutch.

[0071] Advantageously, the triple wet clutch may comprise the central hub of the double wet clutch which is also common to the torque-cutting clutch, said central hub comprising a third control chamber arranged radially beyond the other two control chambers and arranged to receive an actuating piston for the torque-cutting clutch, said central hub comprising a drive cover attached and arranged to be driven in rotation by an electric machine, the drive cover forming in part the third control chamber.

[0072] Preferably, the three control chambers can be oriented in the same axial direction, in particular in the direction of the driving shaft.

[0073] Advantageously, the drive cover can surround the outer perimeter of the flange. This makes it possible to arrange the control chambers associated with the three clutches radially in the same plane.

[0074] Preferably, the fluid lines supplying the annular cavities can open onto the outer edge of the flange and can be closed by the drive cover. The fluid lines can be arranged angularly around the cylindrical portion of the central hub. In this way, it is possible to seal a portion of the fluid lines without using other expensive components.

[0075] Advantageously, the control chambers of the cut-off clutch, the first clutch and the second clutch can follow each other radially as they approach the X axis.

[0076] Thanks to this triple wet clutch architecture, the clutches are concentric and arranged radially in the same plane. The axial footprint of such a triple wet clutch within a torque transmission system or torque transmission chain is thus reduced.

[0077] Advantageously, the drive cover may include a toothed ring suitable for being rotationally linked with an electrical machine rotating around an axis parallel to the axis of rotation X.

[0078] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent during the following description of a particular embodiment of the invention, given solely by way of illustration and not limitation, with reference to the accompanying figures.

[0079] - Fig. 1 represents an axial cross-sectional view of a wet clutch for a vehicle transmission according to a first embodiment of the invention.

[0080] - [Fig.2] represents an isometric view of the axial bearing according to the first mode of realization of the invention of [Fig.1].

[0081] - Figure 3 shows an axial cross-sectional view of a triple wet clutch for a vehicle transmission according to a second embodiment of the invention.

[0082] In the following description and claims, the terms "front" or "rear" will be used, without limitation and to facilitate understanding, according to the direction with respect to an axial orientation determined by the main X axis of rotation of the transmission of the motor vehicle and the terms "inside / internal" or "outside / external" with respect to the X axis and along a radial orientation, orthogonal to said axial orientation.

[0083] Figures 1 and 2 illustrate a first embodiment of a wet clutch E2 for a motor vehicle transmission. The wet clutch E2 is shown within a motor vehicle torque transmission chain via a gearbox housing 100 equipped with two driven torque output shafts Al, A2.

[0084] In [Fig. 1], a partial wet double clutch E1, E2 comprising is observed: - a first torque output clutch El and a second torque output clutch E2, respectively of the multi-disc type, controlled to couple the driving shaft of a combustion engine to a first driven shaft and a second driven shaft, the first and second clutches El, E2 being arranged radially one above the other, and

[0085] - a central hub 50 supplying fluid, for example oil, to chambers of control of the first clutch E1 and the second clutch E2, and

[0086] - a torque input disc holder 10 having an internal groove which meshes with the multi-disc assembly of the second clutch E2.

[0087] The torque input disc holder 10 is securely fixed to the central hub 50 by means of a weld. The central hub 50 includes, in particular:

[0088] - a cylindrical portion 52,

[0089] - a flange 53 extending radially from the cylindrical portion 52,

[0090] - an annular control chamber 55 disposed on the side of the flange and arranged to receive an actuation piston 25 of the second clutch E2,

[0091] - an actuating piston 25 that is axially movable within the chamber of control 55 to which is associated a balancing chamber 75 supplied with cooling fluid.

[0092] The multi-disc assembly of the second clutch E2 comprises plates 21 rotationally connected to the torque input disc carrier 10 mounted on the central hub 50 and friction discs 22 rotationally connected to a torque output disc carrier 30 according to the first embodiment of the invention. The torque output disc carrier 30 comprises a cylindrical splined hub 31a with an axis of rotation X, provided with an internal torque transmission spline 310, and a disc support 32a of revolution about the axis X. In this first embodiment, the disc support 32a is provided with an external spline 320 arranged to cooperate with a multi-disc assembly and an internal skirt. The internal skirt bears axially on the splined hub 31a. As illustrated in [Fig.1], the disc support 32a is made from a stamped steel sheet.The disc support 32a is notably fixed to the splined hub 31a by welding at the inner skirt. In this example, the weld is continuous over 360°.

[0093] The torque output disc carrier 30 of the second clutch E2 is rotationally linked by the meshing of the external spline 320 with the friction discs 22 and by the internal spline 310 with said second driven shaft A2. The torque output disc carrier 30 is arranged axially between the output disc carrier 13 of the first clutch E1 and the cylindrical portion 52 of the central hub 50. The torque output disc carrier 30 is interposed axially between two axial bearings 60, 70.

[0094] The wet clutch E2 is hydraulically controlled by means of a pressurized fluid, usually oil.

[0095] To selectively control the change of state of the wet clutch E2, a control device manages the pressurized oil supply within the control chamber. The control device is generally integrated into the gearbox housing 100. The control device is connected to the central hub 50, which has a pressurized fluid line that supplies pressurized fluid to the control chamber 55 of the second clutch E2.

[0096] The second clutch E2 has an actuating piston 25 which is movable axially, here from back to front, between a disengaged position and an engaged position which correspond respectively to the open and closed states of the second clutch E2. The multi-disc assembly of the second clutch E2 is actuated directly by the second actuating piston 25 made from a stamped sheet.

[0097] As is known in the operation of a wet clutch, a balancing chamber 75 is associated with the control chamber 55 of the wet clutch E2. The balancing chamber is axially delimited by a balancing cover 40 mounted on the central hub 50. The balancing cover 40 has a general shape of revolution about the X-axis with a radially extending annular wall 41. The balancing cover 40 also includes a central opening to allow its mounting around the central hub.

[0098] The balancing chamber 75 of the wet clutch E2 is axially delimited by the annular wall 41 of the balancing cover 40 and by the internal surface of the actuating piston 25. The sealing of the balancing chamber 75 is ensured radially by sealing means which are carried by the balancing cover 40 and which cooperate with the internal cylindrical wall of the actuating piston 25.

[0099] The cooling fluid is also directed within the multi-disc assemblies of the wet clutches. For this purpose, a cooling fluid supply channel 54d is formed in the central hub 50. This channel 54d passes through the cylindrical portion 52 and opens axially opposite a fluid supply line 34 provided in the torque output disc carrier 30 so that the cooling fluid from the central hub 50 can be transferred into the splined hub 31a of the torque output disc carrier 30 and open into the multi-disc assembly of the second clutch E2.

[0100] The coolant supply channel 54d supplies oil to the torque output disc carrier 30 and to the balancing chamber 75 of the wet clutch E2. The coolant supply channel 54d is formed by drilling successive axial and radial channels within the central hub 50. The channels open into each other and are arranged to supply coolant to the balancing chamber.

[0101] The cooling fluid, for example oil, is injected at the rear of the cylindrical portion 52 of the central hub. Due to the rotation of the wet clutch E2 around the axis of rotation X, sometimes at high speed, a centrifugal phenomenon occurs in the fluid contained in the control and balancing chambers. This creates an unwanted additional pressure exerted on the actuating piston. This additional pressure is added to the actuating pressure. The precision of the actuating piston control is degraded by this centrifugal phenomenon. The invention aims to remedy this problem. To this end, the wet clutch E2 comprises an axial bearing 70 interposed axially between the central hub 50 and the torque output disc carrier 30. The axial bearing 70 is fitted into a bore of the central hub concentric with the X-axis and partially obstructs the coolant supply channels 54d opening axially opposite the torque output disc carrier 30. The axial bearing 70 is specifically inserted on the cylindrical portion 52 of the central hub 50.

[0102] In this way, the geometry of the balancing chamber 75 and the axial bearing 70 is adapted to achieve a balancing of the pressures applied on either side of the actuating piston. By adapting the geometry of the balancing chamber and the diameter of the coolant leakage, it is possible to compensate for the additional pressure. The aim is thus to reproduce the same additional pressure within the balancing chamber so that dynamic balance is achieved on either side of the actuating piston.

[0103] In this first embodiment of the invention, the axial bearing 70 is a needle bearing. Alternatively, the axial bearing may be an angular contact ball bearing.

[0104] As illustrated in [Fig. 2], the axial bearing 70 comprises a first support ring 70a equipped with a centering collar 70c fitted into the bore of the central hub. The axial bearing 70 comprises a second support ring 70b and needles interposed axially between the two support rings.

[0105] To achieve dynamic balancing of the wet clutch E2, the centering flange 70c has a cylindrical bore defined by an inner radius Ri. It is the centering flange 70c that obstructs the coolant supply channels 54d. Remarkably, dynamic balancing of the control chamber relative to the balancing chamber is achieved when the balancing ratio Q = (Rf / Ri) - (Rp / Rb) is between 0.1 and 0.2, taking into account the minimum radius of fluid rotation Rf within the clutch. The minimum radius of fluid rotation Rf is generally located at the fluid inlet within the cylindrical portion 52 of the central hub.

[0106] The first support ring 70a comprises a cylindrical portion 70d which is fitted inside the cylindrical portion 52 of the central hub. The precision of the fitting ensures a seal between the axial bearing and the central hub. The cooling fluid is thus directed inside the centering flange 70c. The second support ring 70b is in direct contact with the torque output disc holder 30, the inner radius of the second support ring being greater than the inner radius Ri of the centering flange 70c of the first support ring.

[0107] To cool the wet clutch E2 more effectively, the central hub 50 includes several coolant supply channels 54d which communicate with several fluid supply lines 34 distributed angularly around the X axis on the splined hub 31a. In the example of the first embodiment, the splined hub 31a includes eight fluid supply lines 34 distributed angularly at 45°.

[0108] Each of the fluid supply lines 34 forms a bend with an axially extending portion of the line 36 and a radially extending portion of the line 35. The radial orientation of the line allows the flow of cooling fluid to be directed efficiently within the multi-disc assembly of the second clutch E2. The cooling fluid supply channels 54d are arranged over a diameter substantially equal to the diameter of the axially extending portions of the line 36.

[0109] To improve the efficiency of the diffusion of the cooling fluid within the second clutch E2, the torque output disc carrier 30 also includes a fluid retention cavity 33, annular and concentric with the X-axis. The disc carrier 32a includes holes 39 formed on the external spline 320 and arranged to evacuate the oil contained in the fluid retention cavity 33. The holes 39 are distributed circumferentially around the X-axis and formed on the tooth crests of the external spline 320.

[0110] To improve the efficiency of the cooling fluid diffusion within the second clutch E2, the torque output disc carrier 30 includes an additional component called a deflector 37, which is annular in shape and attached to the splined hub 31a. The fluid retention cavity 33 is thus formed by the combination of surfaces from the splined hub 31a, the disc support 32a, and the deflector 37. Advantageously, the fluid retention cavity 33 is formed from an external surface of the splined hub 31a, a flank of the deflector 37, and an internal surface 38 of the disc support 32a. Each of the fluid supply lines 34 opens into the fluid retention cavity 33, which is closed by the internal surface 38 of the disc support 32a.

[0111] Each of the fluid supply lines 34 forms a bend with an axially extending line portion 36 and a radially extending line portion 35, the lines 35, 36 are formed by association of the surfaces of the grooved hub 31a and the deflector 37.

[0112] The deflector 37 is made by stamping a sheet of steel. The deflector 37 can be held onto the splined hub 31a by press fitting or welding. Alternatively, the deflector 37 can be made by plastic injection molding of synthetic material, for example, PA66 type polyamide plastic or PEEK type polyetheretherketone.

[0113] We will now present another method of implementing the dynamic balancing of the pressures applied on either side of an actuating piston according to the invention, now applied to a triple wet clutch 1.

[0114] Figure 3 shows a triple wet clutch 1 comprising: - a multi-disc type KO torque-cutting clutch, controlled to selectively couple a shaft leading to an electrical machine,

[0115] - a first torque output clutch E1 and a second clutch E2 torque outputs respectively of the multi-disc type, controlled to selectively couple the electric machine and / or the driving shaft to a first driven shaft and a second driven shaft, the first and second clutches E1, E2 being arranged radially one above the other, and

[0116] - a central hub 50 supplying oil to the clutch control chambers of torque cut-off KO, of the first clutch El and of the second clutch E2.

[0117] The central hub 50 with axis of rotation X is fixedly connected to a torque input disc carrier 10, said central hub 50 comprising a cylindrical portion 52, a flange 53 extending radially from the cylindrical portion 52 and at least one coolant supply channel 54d formed in the central hub passing through at least the cylindrical portion 52.

[0118] The wet triple clutch 1 also includes:

[0119] - a first annular control chamber 56 disposed on the side of the flange and arranged to receive an actuating piston 15 of the first clutch El,

[0120] - a second annular control chamber 55 disposed on the same side of the flange that the first annular cavity is arranged to receive an actuating piston 25 of the second clutch E2,

[0121] - a third annular control chamber 57 arranged radially beyond the two other annular cavities arranged to receive an actuation piston 5 of the KO torque cut-off clutch, and

[0122] - fluid channels 54a, 54b and 54c formed in the central hub 50 passing through the cylindrical portion 52 and the flange 53, and opening separately into the control chambers.

[0123] The control chambers 57, 56, 55 of the torque cut-off clutch KO, of the first clutch El and of the second clutch E2 are oriented in the same direction, for example in the direction of the driving shaft, i.e. in the direction of the internal combustion engine of the torque transmission chain.

[0124] The triple wet clutch 1 comprises, around its axis of rotation X, at least one torque input element 2 which is rotationally linked to a driving shaft (not shown). The input element 2 is generally L-shaped, comprises a radial orientation portion formed by a torque input web 3 and a portion axial orientation formed by a torque input hub 4. The torque input element 2 is guided in rotation inside a housing 101 fixed relative to the torque transmission chain.

[0125] The input element 2 of the torque input is for example linked in rotation by means of splines formed at the output of a damping device (such as a double flywheel damper, etc.) whose input is linked, in particular by means of a flywheel, to the driving shaft formed by a crankshaft which is driven in rotation by a heat engine equipping the motor vehicle.

[0126] The torque input veil 3 has, at its external radial end, a groove arranged to receive the multi-disc assembly of the KO torque cut-off clutch.

[0127] In the example considered, the triple wet clutch 1 further comprises a torque-cutting clutch KO selectively coupling by friction the torque input web 3 and an intermediate disc carrier 81 of the torque-cutting clutch KO rotationally fixed with the splined torque output fluid supply hub 50.

[0128] The KO torque-cutting clutch comprises a multi-disc assembly including several friction discs 7, equipped with friction linings, rotationally fixed to the torque input disc 3, and several plates 6 respectively arranged on either side of each friction disc 7, rotationally fixed to the intermediate disc carrier 81. The KO torque-cutting clutch is actuated by an axially movable actuating piston 5, here from rear to front, between a disengaged position and an engaged position which correspond respectively to the open and closed states of the KO torque-cutting clutch. The actuating piston 5 clamps the friction linings so as to transmit torque between the torque input disc 3 and the intermediate disc carrier 81.

[0129] The plates 6 of the multi-disc assembly of the torque cut-off clutch KO are rotationally linked to the central hub 50 via a spline and the friction discs 7 are rotationally linked to the input element 2.

[0130] The central hub 50 includes a drive cover 80 attached to the outer perimeter of the flange 53. The central hub 50 has the function of transmitting the torque within the triple wet clutch 1. For this purpose, the drive cover 80 is rotationally fixed to the intermediate disc carrier 81, in this case by means of a welded connection.

[0131] The drive cover 80 includes an external groove adapted to be rotationally linked with a rotating electrical machine. In this case, the electrical machine rotates about an axis parallel to the axis of rotation X.

[0132] The central hub 50 is capable of transmitting torque from two sources separate, thermal and electrical. When the torque cut-off clutch KO is closed, the torque from the thermal engine can then be transmitted to the coaxial shafts Al, A2 of the gearbox depending on the closure of one or the other of the first clutch El or the second clutch E2.

[0133] The first driven shaft Al is driven in rotation when said first clutch El is closed and the second driven shaft A2 is driven in rotation when said second clutch E2 is closed.

[0134] The multi-disc assembly of the first clutch El comprises plates 11 rotationally linked to a torque input disc carrier 10 attached to the central hub 50 and friction discs 12 rotationally linked to an output disc carrier 13. The friction discs 12 are, individually, axially interposed between two successive plates 11.

[0135] The output disc carrier 13 of the first clutch El is rotationally linked by meshing with the friction discs 12 and by a splined connection with said first driven shaft Al. The inner radial end of the output disc carrier 13 is fixed to a splined output hub.

[0136] The multi-disc assembly of the second clutch E2 is similar to that described in the first embodiment.

[0137] The triple wet clutch 1 is hydraulically controlled by means of a pressurized fluid, usually oil.

[0138] To selectively control the change of state of the torque-cutting clutch KO, the first clutch E1, and the second clutch E2, a control device for the wet triple clutch manages the pressurized oil supply within separate control chambers. The control device is generally integrated into the gearbox housing 100. The control device is connected to the central hub 50, which has pressurized fluid lines 54a, 54b, and 54c, for example, three of them as shown in [Fig. 3]. The fluid lines 54a, 54b, and 54c are distributed angularly around the cylindrical portion 52 of the central hub 50.

[0139] Each of the fluid channels 54a, 54b and 54c consists of substantially radial and axial bores directed towards the control chambers of the torque cut-off clutch KO, of the first and second clutches El, E2.

[0140] The first clutch El comprises an actuating piston 15 which is axially movable, here from rear to front, between a disengaged position and an engaged position which correspond respectively to the open and closed states of the first clutch EL

[0141] In the first embodiment, the fluid pipes 54a, 54b and 54c open onto the outer perimeter of the flange 53 and are closed by the drive cover 80.

[0142] As is known in the operation of a wet clutch, a balancing chamber is associated with each control chamber. The balancing chambers 75, 76, 77 are supplied with fluid, for example, coolant. The coolant flows through separate channels in the fluid lines 54a, 54b, and 54c. These separate channels are also formed in the central hub 50.

[0143] The balancing chamber 77 of the KO torque-cutting clutch is axially delimited by a balancing cover 42 mounted on the central hub 50. The balancing cover 42 has a general shape of revolution about the X-axis with a radially extending annular wall. The balancing cover 42 also includes a central opening to allow its mounting around the central hub.

[0144] The balancing chamber 75 of the wet clutch E2 is axially delimited by the annular wall of the balancing cover 42 and by the internal surface of the actuating piston 5. The sealing of the balancing chamber 75 is ensured radially by sealing means which are carried by the balancing cover 42 and which cooperate with the internal cylindrical wall of the actuating piston 5.

[0145] The cooling fluid is also directed within the multi-disc assemblies of the wet clutches. For this purpose, a cooling fluid supply channel 54d is formed in the central hub 50. This channel 54d passes through the cylindrical portion 52 and opens axially opposite a fluid supply line 34 provided in the torque output disc carrier 30 so that the cooling oil from the central hub 50 can be transferred into the splined hub 31b of the torque output disc carrier 30 and open into the multi-disc assembly of the second clutch E2.

[0146] The coolant supply channel 54d supplies oil to the torque output disc carrier 30 and to the balancing chambers of the triple wet clutch 1. The coolant supply channel 54d is made by drilling successive axial and radial channels within the central hub 50. The channels open into each other and are arranged to supply coolant to the balancing chambers.

[0147] Due to the rotation of the wet torque-cutting clutch KO around the axis of rotation X, a centrifugal phenomenon occurs in the fluid contained in the control chamber 57 and the balancing chamber 77. This phenomenon is amplified because the wet clutch has a larger diameter. This results in an unwanted additional pressure being exerted on the actuating piston 5. This additional pressure is added to the actuation pressure. The precision of the actuating piston 5 is degraded by this centrifugal phenomenon. The invention aims to remedy this problem. To this end, the triple wet clutch 1 comprises an axial bearing 70 interposed axially between the central hub 50 and the torque output disc carrier 30. The axial bearing 70 is fitted into a bore of the central hub concentric with the X axis and partially obstructs the coolant supply channels 54d opening axially opposite the torque output disc carrier 30.

[0148] In this second embodiment of the invention, the inner radius Ri of the centering flange 70c of the axial bearing 70 is defined as a function of the outer radius Rp of the control chamber 57 and the outer radius Rb of the balancing chamber 77 of the torque-cutting clutch KO. In this way, the geometry of the balancing chamber 77 and the axial bearing 70 is adapted to achieve a balance of the pressures applied on either side of the actuating piston 5. By adapting the geometry of the balancing chamber 77 and the diameter of the coolant leakage, it is possible to compensate for the additional pressure. The aim is thus to reproduce the same additional pressure within the balancing chamber 77 so that dynamic balance is achieved on either side of the actuating piston 5.

[0149] In this second embodiment of the invention, the axial bearing 70 is a needle bearing. As illustrated in [Fig. 3], the axial bearing 70 comprises a first support ring 70a equipped with a centering collar 70c fitted into the bore of the central hub 50. The axial bearing 70 comprises a second support ring and needles interposed axially between the two support rings.

[0150] The first support ring 70a comprises a cylindrical portion 70d which is fitted inside the cylindrical portion 52 of the central hub. An O-ring inserted in an annular groove machined in the central hub seals the connection between the axial bearing and the central hub, the O-ring being compressed by the centering flange. The cooling fluid is thus directed inside the centering flange 70c.

[0151] To achieve dynamic balancing of the wet torque-cutting clutch KO, the centering flange 70c has a cylindrical bore defined by an inner radius Ri. It is the centering flange 70c that obstructs the coolant supply channels 54d. Remarkably, dynamic balancing of the control chamber relative to the balancing chamber is achieved when the balancing ratio Q = (Rf / Ri) - (Rp / Rb) is between 0.1 and 0.2, taking into account the minimum radius of fluid rotation Rf within the clutch. The minimum radius of fluid rotation Rf is generally located at the fluid inlet within the cylindrical portion 52 of the central hub.

[0152] For greater efficiency, the central hub 50 has several feed channels of cooling fluid 54d which communicate with several fluid supply lines 34 distributed angularly around the X-axis on the splined hub 31b. In the example of the first embodiment, the splined hub 31a has eight fluid supply lines 34 distributed angularly at 45°.

[0153] Each of the fluid supply lines 34 forms a bend with an axially extending section 36 and a radially extending section 35. The radial orientation of the line allows the flow of cooling fluid to be directed efficiently within the multi-disc assembly of the second clutch E2. The cooling fluid supply channels 54d are arranged on a diameter substantially equal to the diameter of the axially extending sections 36.

[0154] The torque output disc carrier 30 also includes a fluid retention cavity 33, annular and concentric with the X-axis, formed by the joining of surfaces from the splined hub 31b and the disc support 32b. The fluid retention cavity 33 is formed in particular in part by a circumferential groove made on the outer periphery of the splined hub 31b. Each of the fluid supply lines 34 opens into the fluid retention cavity 33, which is closed by the inner surface of the disc support 32b. The disc support 32b includes holes 39 formed on the outer spline and arranged to evacuate the oil contained in the fluid retention cavity 33.

[0155] The fluid retention cavity 33 is supplied with cooling fluid by a plurality of fluid supply lines 34 distributed angularly around the X-axis. Each of the fluid supply lines 34 forms a bend with an axially extending section 36 formed solely by the splined hub 31d and a radially extending section 35 formed solely by the splined hub 31d. The radially extending sections 35 and the axially extending sections 36 are, in particular, formed by drilling.

[0156] It is understood from the foregoing that the present invention proposes a triple wet clutch in which the clutches are concentric and arranged radially in the same plane. The axial footprint of such a triple wet clutch within a torque transmission chain is reduced.

[0157] The invention is not limited, however, to the means and configurations described and illustrated herein, and also extends to any equivalent means or configuration and to any technical combination operating such means. In particular, the shape of the torque output disc holder can be modified without prejudice to the invention, provided that these components ultimately fulfill the same functionalities as those described in this document.

[0158] In the claims, any reference sign in parentheses may not be in- interpreted as a limitation of claims.

Claims

Claims

1. Wet clutch (KO, El, E2) for a vehicle transmission comprising: - a torque input disc carrier (10) arranged to be rotationally connected to a driving shaft along an axis of rotation (X); - a multi-disc assembly comprising friction discs (7, 12, 22) and pressure plates (6, 11, 21) stacked axially and driven in rotation by the torque input disc carrier; - a torque output disc carrier (30) arranged radially inside the multi-disc assembly and arranged to be rotationally connected to a driven shaft; - a central hub (50) with an axis of rotation (X) fixedly connected to the torque input disc holder, said central hub (50) comprising a cylindrical portion (52) and at least one cooling fluid supply channel (54d) formed in the central hub passing through at least the cylindrical portion (52) and opening axially opposite the torque output disc holder (30),said wet clutch comprising an axial bearing (70) interposed axially between the central hub (50) and the torque output disc carrier (30), said axial bearing being fitted into a bore (58) of the central hub and partially obstructing the coolant supply channel or channels (54d) opening axially opposite the torque output disc carrier, characterized in that the axial bearing (70) comprises a first support ring (70a) equipped with a centering collar (70c) fitted into the bore (58) of the central hub, the centering collar (70c) has a cylindrical bore defined by an internal radius (Ri), the centering collar (70c) obstructing the coolant supply channel or channels (54d).,

2. Wet clutch (KO, El, E2) according to claim 1, in which the multi-disc assembly is actuated by an actuating piston (5, 15, 25) axially movable within a control chamber (55, 56, 57) formed at least in part in the central hub (50) with which is associated a balancing chamber (75, 76, 77) supplied with fluid by a portion of the cooling fluid supply channel (54d).

3. Wet clutch (KO, El, E2) according to the preceding claim, in which the control chamber (55, 56, 57) is defined by its radius outer radius (Rp), the balancing chamber (75, 76, 77) is defined by its outer radius (Rb), the first support ring (70a) is defined by its inner radius (Ri), the dynamic balancing of the control chamber with respect to the balancing chamber being obtained when the balancing ratio Q = (Rf / Ri) - (Rp / Rb) is between 0.1 and 0.2 taking into account the minimum radius of rotation of the fluid (Rf) within the clutch.

4. Wet clutch (KO, El, E2) according to one of the preceding claims, in which the torque output disc carrier (30) comprises at least one fluid supply pipe (34) one of its inlet orifices of which is oriented axially towards the cooling fluid supply channel (54d), said channel being arranged to jointly supply fluid to the balancing chamber of the wet clutch and the torque output disc carrier (30).

5. Wet clutch (KO, El, E2) according to the preceding claim, in which the torque output disc carrier (30) comprises: - a splined hub (31a, 31b) with an axis of rotation (X) provided with an internal torque transmission spline (310), - a disc support (32a, 32b) made of sheet metal with a shape of revolution around the axis (X), provided with an external spline (320) arranged to cooperate with the multi-disc assembly, the disc support (32a, 32b) being axially supported on the splined hub (31a, 31b), - a fluid retention cavity (33), annular and concentric with the axis (X), formed at least by the association of surfaces originating from the splined hub and the disc support, the splined hub (31a, 31b) partially or totally forming the fluid supply conduit(s) (34) opening into the fluid retention cavity (33) closed by the internal surface (38) of the disc support.

6. A wet clutch (KO, El, E2) according to the preceding claim, wherein each fluid supply line (34) forms an elbow with an axially extending line portion (36) and a radially extending line portion (35).

7. Wet clutch (KO, El, E2) according to claim 5 or 6, in which the torque output disc carrier (30) comprises a deflector (37) of annular shape attached to the splined hub (31a) and comprising external teeth cooperating with the profile of the internal surface (38) of the disc carrier (32a), the fluid retention cavity (33) being formed by the association of surfaces from the splined hub (31a), the disc support (32) and the deflector (37).

8. Wet clutch (KO, El, E2) according to one of the preceding claims, in which each cooling fluid supply channel (54d) is produced by drilling successive axial and radial conduits within the central hub (50), the conduits opening into each other to form said channel.

9. Wet clutch (KO, El, E2) according to one of claims 1 to 8, in which the axial bearing (70) is a needle bearing comprising a second support ring (70b) in direct contact with the torque output disc carrier (30), the inner radius of the second support ring being greater than the inner radius (Ri) of the centering collar of the first support ring (70a).

10. Wet clutch (KO, El, E2) according to one of claims 4 to 9, wherein the central hub (50) comprises: - a cylindrical portion (52), - a flange (53) extending radially from the cylindrical portion (52) fixedly connected to the torque input disc carrier (10), and - cooling fluid supply channels (54d) formed in the central hub (50) passing through the cylindrical portion (52) and opening axially opposite the fluid supply lines (34) of the torque output disc carrier (30) so that the fluid from the central hub can be transferred into the splined hub of the torque output disc carrier (30) and open into the multi-disc assembly.

11. Wet clutch (KO, El, E2) according to one of claims 4 to 10, in which the cooling fluid supply channels (54d) and the fluid supply lines (34) are distributed angularly around the axis (X), the outlets of the cooling fluid supply channels (54d) being arranged on a diameter substantially equal to the installation diameter of the inlets of the fluid supply lines (34).

12. Double wet clutch (El, E2) for torque transmission system comprising: - a first clutch (El); and - a second clutch (E2) of the wet clutch type according to claim 1, arranged radially inside the first clutch (El), the first and second clutches (El, E2) being controlled for selectively coupling a driving shaft to a first driven shaft and a second driven shaft, for example first and second gearbox shafts (A1, A2), and the central hub (50) of the second clutch (E2) being common with the first clutch (E1).

13. Triple wet clutch (KO, El, E2) for torque transmission system comprising a multi-disc type torque cut-off clutch (KO), controlled to selectively couple a shaft leading to an electric machine, and a double wet clutch (El, E2) according to the preceding claim, the torque cut-off clutch (KO) being arranged radially beyond the double wet clutch (El, E2).

14. Triple wet clutch (KO, El, E2) according to the preceding claim, wherein the inner radius (Ri) of the centering collar (70c) is defined as a function of the outer radius (Rp) of the control chamber (57) and the outer radius (Rb) of the balancing chamber (77) of the torque cut-off clutch (KO).

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