CN109312816B - Torsional damper - Google Patents

Abstract

A torsional damper for a torque transmission device, in particular for a motor vehicle, in particular for a clutch device, comprising: -a first element (3) which is rotationally movable about an axis of rotation (X), -a second element (2) which is rotationally movable about the axis of rotation (X) and rotationally movable about the axis of rotation (X) relative to the first element, -an arm (81) connected to the second element of the damper by means of an elastic connection (82), the arm comprising a cam surface (20) arranged to cooperate with a cam follower (24) during relative rotation between the first and second elements so as to allow torque to be transmitted between the first and second elements, characterized in that at least a portion of the arm referred to as the transmission portion (83) has at least one region of reduced density (84) along which the cam surface extends.

Description

Torsional damper

Technical Field

The invention relates to a torsional damper intended to be equipped with a torque transmission device. More specifically, the invention relates to the field of transmission devices for motor vehicles, the invention being intended in particular to transmit engine torque between the engine and the wheels of the vehicle. The damper can be applied both to a transmission device of a motor vehicle having a manual transmission, such as a damped friction disc or a dual flywheel damper, and to a transmission device of a motor vehicle having an automatic transmission phase, such as a torque converter or a lock-up clutch, or a dual clutch.

Background

Torsional dampers are known, the input and output elements of which are rotationally coupled by damping means which allow to transmit torque and to damp the rotation non-periodicity. The damping means is typically a helical, curved spring circumferentially disposed in a sealed annular chamber formed between the input and output elements.

Dampers with blades are known to be used in drive chains for transmitting engine torque and damping non-periodic. In patent application FR2938030, the blade mounted on the secondary inertia flywheel comprises a cam surface arranged to cooperate with a cam follower rotatably mounted on the primary inertia flywheel.

However, the large forces transmitted by the vanes and cam followers may cause failure of the damper.

The object of the present invention is to improve the reliability of a damper with vanes of the above-mentioned type, in particular by reducing the risk of damper failure.

Disclosure of Invention

The present invention improves upon the prior art solutions and provides an improved torsional damper with flexible blades.

The invention therefore relates to a torsional damper for a torque transmission device, in particular for a motor vehicle, in particular for a clutch device, comprising:

a first element which is rotationally movable about a rotation axis (X),

-a second element which is rotationally movable about a rotation axis (X) and movable relative to the first element about the rotation axis (X),

an arm connected to the second element of the damper by means of an elastic connection, the arm comprising a cam surface arranged to cooperate with the cam follower during relative rotation between the first and second elements so as to allow torque to be transmitted between the first and second elements,

characterized in that at least a portion of the arm called the transmission portion, along which the cam surface extends, has at least one zone of reduced density.

For the sake of clarity, said part of the arm will be referred to later as "transmission part", along which the cam surface extends.

In the description and claims, the terms "outer (outside)" and "inner (inside)" and the orientations "axial" and "radial" will be used to refer to the elements of the torsional damper, according to the definitions given in the description.

Conventionally, the "axial" orientation is defined by the axis of rotation (X) of the elements of the torsional damper.

The "radial" orientation is orthogonal to the axis of rotation (X) of the elements of the torsional damper.

The "circumferential" orientation is orthogonal to the rotational axial direction of the damper and directed orthogonal to the radial direction. Thus, an element described as developing in the circumferential direction is an element whose constituent parts develop in the circumferential direction (i.e., about the axis of rotation).

Similarly, the indication of an angle or angular sector is to be interpreted as being defined by two straight lines perpendicular to the plane of the rotation axis X and a secant at said rotation axis X.

The terms "outer (outboard)" and "inner (inboard)" are used to define the relative position of one element with respect to the other, with reference to the rotational axis of the torsional damper, whereby the element proximate the axis is said to be inner (inboard) with respect to the outer element located radially at the periphery.

Cut in any plane including the axis of rotation X, the transmission portion has a width extending parallel to the axis X along the axial direction, and a height extending in the radial direction.

Due to the area of reduced density, the mass of the transmission part is reduced, thus reducing the risk of damper failure, especially in the high speed range when the centrifugal forces are at their maximum.

Whereas in the previous solutions the transmission part was formed of a single material steel and had a solid rectangular section in all the sections cut along a plane comprising the rotation axis (X), the transmission part of the arm of the invention is improved in that it has at least one region of reduced density.

Thus, when the cam follower is arranged radially outside the transmission portion, the reduction of the mass of the transmission portion allows to reduce the centrifugal force and to actuate the cam follower more moderately, in particular in the high speed range. Further, the weight reduction of the arm contributes to the overall weight reduction of the damper.

Furthermore, it is also suitable to reduce the mass of the transmission part and thus its eccentricity if the choice is to position the cam follower radially inside the transmission part. In effect, this will reduce the failure associated with the loss of contact between the cam follower and the cam surface.

According to other advantageous embodiments, such a torsional damper may have one or more of the following features:

at least one of the first and second elements is adapted to be driven in rotation about a rotation axis X.

The region of reduced density is located at a distance from the cam surface. Thus, the lightness of the transmission portion does not impair the rigidity of the cam surface and the displacement of the cam follower on the cam surface, particularly when the cam follower includes a roller that rolls on the cam surface.

-the transmission part is multi-material.

The transmission part is of a bi-material.

When the transmission portion is of bi-material, the area of reduced density is formed at least partially in the material of the transmission portion of the arm having the lowest density.

The or one of the regions of reduced density of the transmission part is a recess provided in the transmission part. The region of reduced density is formed at least in part by the recess.

The recess is located at a distance from the cam surface in a plane intersecting the cam surface and comprising the axis of rotation of the damper, inside a rectangular space in which the transmission part is located.

The first and second elements are adapted to be driven in rotation about an axis X.

In the absence of torque transmission, the first and second elements occupy relative angular positions of rest.

The elasticity of the elastic connection allows to keep the cam follower in contact with the cam surface.

The drive portion of the arm and the cam follower are arranged so that, in operation, the cam follower exerts a bending force on the drive portion, generating, as a reaction, a reaction force transmitted by the drive portion to the elastic connection of the cam follower, which reaction force is able to reset the first and second elements to the angular position of rest.

The relative rotation between the first and second elements is accompanied by a displacement of the cam follower on the cam surface.

The cam surface is arranged such that, for at least some angular travel region between the first and second elements, displacement of the cam follower on the cam surface is accompanied by elastic deformation of the elastic connection.

The cam follower comprises a roller arranged to be rollingly displaced on the cam surface during relative rotation of the first and second elements. Thus, excessive friction between the cam follower and the cam surface is avoided.

The roller is mounted on the first element so as to be rotationally movable.

The roller is mounted on the first element so as to be rotationally movable by means of a rolling bearing.

According to another embodiment, not shown, the roller is rotationally movable with respect to the first and second elements. The rolling bodies are displaced on the one hand on the cam surface of the transmission part of the arm and on the other hand on the first element. Preferably, the rolling body performs a curvilinear path on the first element over at least one predetermined angular sector, in particular by rolling, by rolling on a cam surface carried by the transmission portion.

-the arm is formed on a transmission member comprising:

o a fixed part fixed to the second element,

-at least one flexible blade comprising:

the arm, on which the transmission part is formed,

an elastic connection connecting the fixed part to the arm.

The resilient connection is a curved portion which is able to flex to absorb aperiodicity during relative rotation of the first and second elements or when the cam follower moves over the cam surface.

The blade is arranged to flex in a plane perpendicular to the axis of rotation X.

The reaction force is an elastic return force exerted by the flexible blade on the cam follower in response to the elastic deformation of the flexible blade.

The reaction force is an elastic return force exerted on the cam follower by the flexible blade only in response to the elastic deformation of the flexible blade.

The flexible blade comprises a free end region and the damper is arranged such that when the cam follower flexes the blade, the free end region is displaced with a radial component relative to the rotational axis of the damper. In other words, the radial distance separating the axis of rotation from the free distal end region varies as a function of the angular travel between the first and second elements.

-a free end area circumferentially extending cam surface.

The transmission part extends circumferentially between the elastic connection part and the free end area.

The transmission member comprises two blades arranged symmetrically with respect to the rotation axis.

The transmission member comprises a plurality of blades regularly arranged around the rotation axis.

The blades are arranged around the annular body, if necessary.

Alternatively, the damper comprises at least two transmission members, which are arranged, for example, symmetrically with respect to the axis of rotation.

-where appropriate, the transmission members are regularly arranged around the rotation axis.

-where appropriate, each transmission member comprises a single blade.

Preferably, the fixation portion is fixed such that it does not flex when the first and second elements are rotated relative to each other.

Each blade is connected to the second element only by its fixed part.

The damper comprises two flexible blades carried by the second element, and the damper comprises two cam followers carried by the first element, the cam followers being arranged to cooperate with one and the other of the two flexible blades, respectively.

The cam surface extends circumferentially around the rotation axis X.

The cam surface comprises a neutral position occupied by the cam follower when the damper is not transmitting torque.

The cam follower is in a neutral position of the cam surface when the first and second elements are in the angular position of rest.

The damper is intended to be placed in the drive train, i.e. between the engine and the wheels of the motor vehicle.

The damper is arranged to transfer engine torque transferred from the engine to the wheels. In other words, it is intended to be placed in the torque transmission path between the engine and the wheels.

The damper is capable of transmitting a torque in the range of 10n.m to 500n.m

The damper is capable of transmitting a torque in the range of 100n.m to 300n.m, such as 150n.m or 200n.m.

The transmission part comprises a plane of symmetry perpendicular to the axis of rotation of the damper.

The transmission part comprises regions of reduced density over at least two angular sectors spaced at least 10 degrees around the rotation axis X, in particular at least two angular sectors spaced at least 30 degrees apart, in particular at least 45 degrees, for example at least 60 degrees.

The transmission part comprises regions of reduced density on at least two angular sectors located on either side of a neutral position of the transmission part.

The at least one region of reduced density extends around the rotation axis X over an angular sector of at least 20 degrees, in particular over an angular sector of at least 30 degrees, for example at least 45 degrees, preferably at least 60 degrees, in particular over the same angular sector as the cam surface.

The transmission portion of the arm comprises a body at least partially covered with a skin on which the cam surface is at least partially formed and on which the area of reduced density is at least partially formed.

The body and the skin are formed of two different materials.

The body is less dense than the skin.

Thus, the displacement of the cam follower is improved due to the material dedicated to the displacement of the cam follower on the cam surface.

In one embodiment of the invention, the skin has a stiffness greater than the stiffness of the body with respect to the bending forces exerted by the cam follower on the transmission portion. The skin thus allows to limit deformations in the transmission part of the arm.

The skin thus also allows to limit or even prevent any deformation of the transmission part when the torque is transmitted through the damper.

-the cam surface extends completely over the skin.

The skin is metallic.

At least a portion of the region of reduced density is directly covered by the epidermis.

The skin is formed from sheet material, such as steel sheet material.

-the epidermis has a thickness in the range of 1 to 3 mm.

The region of reduced density is at least partially formed by a fibre-reinforced polymer material, known as composite material.

-the body is made of a composite material.

The fibers of the composite material are, for example, aramid fibers, carbon fibers or glass fibers.

The fibers are predominantly unidirectional fibers.

For example, the unidirectional fibers represent more than 60% of the mass of the fibers.

The unidirectional fibres extend along the driving portion of the arm.

The fibers extend parallel to the cam surface.

The polymeric material preferably belongs to the family of thermosetting materials.

The polymer material is for example an epoxy resin.

According to one variant, the polymeric material belongs to the family of thermoplastic materials.

The body and the skin are connected to each other, in particular by a layer of adhesive substance. According to one variant, the skin is overmoulded directly on the body.

The elastic connection of the transmission member is a bend arranged such that, for a predetermined angular sector, the transmission member comprises two regions radially offset from each other according to a radial direction, the free space radially separating the two regions radially offset.

If desired, each blade comprises two regions radially offset from each other according to a radial direction, the free space radially separating the two regions radially offset.

These two areas are remote from the transmission section, if necessary.

The bend is made of composite material.

The anchoring portion is at least partially made of a composite material.

The reduced density region of the transmission portion, the bend and the fixed portion are integrally moulded from a composite material.

-manufacturing the skin by cutting a sheet and then bending.

The skin is fixed to the body of the transmission part, in particular by means of an adhesive.

The skin and the body can be connected to each other by a form interlock, if desired.

The width of the skin is smaller than the width of the transmission portion in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

The region of reduced density comprises two edges bordering the epidermis axially.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the skin comprises two sides facing the edge, and at least one of its sides comprises an undercut. The body includes an edge having a shape complementary to the undercut to retain the skin to the body surface.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the skin comprises two undercuts and the body comprises two edges having a shape complementary to these undercuts for mutual retention of the body and the skin to each other.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the cam surface is crowned in order to reduce edge effects and avoid excessive stress concentrations (Hertz pressure) during displacement of the cam follower (in particular the roller) on the transmission part.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the skin comprises a raised upper surface on which the cam surface is formed.

The body is made entirely of composite material.

The transmission portion comprises a reinforcement allowing to reinforce the transmission portion with respect to the bending forces exerted on the transmission portion by the cam follower. Therefore, when torque is transmitted through the damper, the reinforcing member increases the rigidity of the power transmission portion and restricts deformation of the power transmission portion.

-if necessary, arranging a reinforcement on the skin.

The skin has a protrusion extending inside the body, which forms a reinforcement of the skin.

The reinforcement has, in a plane intersecting the cam surface and comprising the axis of rotation of the damper, a geometric pattern extending circumferentially, continuously or discontinuously, about the axis X along the transmission portion.

-the reinforcement is metallic.

The reinforcement extends circumferentially along at least a part of the transmission portion.

The reinforcement extends completely along the transmission portion.

The skin and the stiffener extend circumferentially along the same angular sector.

The reinforcement comprises a plane of symmetry perpendicular to the axis of rotation of the damper.

The reinforcement and the transmission part comprise the same plane of symmetry.

The reduced density zone and the reinforcing element are connected to each other by a layer of adhesive substance.

The reinforcement extends from the skin over at least half the height of the transmission portion.

The bend is not provided with a reinforcement.

The skin and the reinforcement are integrally formed, in particular with an extruded profile. Therefore, the number of parts to be assembled is limited and manufacturing is simplified. For example, the extruded profile may have a T-shape in a plane intersecting the cam surface and including the axis of rotation of the damper.

The reinforcement comprises a frame at least partially embedded in the region of reduced density (e.g. in the composite material). According to one embodiment, the reinforcement is a frame at least partially embedded in the region of reduced density (e.g. in the composite material).

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the height of the frame extends over at least one fifth, in particular at least one quarter, for example at least one third, in particular at least half the height of the transmission portion.

The frame extends perpendicular to the cam surface.

The frame extends perpendicular to the axis of rotation of the damper.

The frame extends completely along the transmission portion.

The epidermis is connected to the frame.

The skin and the frame are integrally formed, in particular from extruded profiles. For example, the extruded profile has a T-shape in a plane intersecting the cam surface and including the axis of rotation of the damper.

The frame extends to the half-width of the transmission part in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

The frame comprises a grip portion arranged to retain the frame, in particular in composite material, in particular radially in the region of reduced density.

-the grip portion extends completely along the frame.

The frame has a T-shape in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

The frame is connected to the skin and the grip is arranged on the frame on an edge of the frame diametrically opposite the skin. The skin, the frame and the grip may be integrally formed, in particular by an extruded profile. For example, the extruded profile has an I-shape in a plane intersecting the cam surface and including the axis of rotation of the damper.

The frame comprises a plane of symmetry perpendicular to the axis of rotation of the damper. The frame and the transmission part comprise the same plane of symmetry.

The height of the frame is lower than the height of the body in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

The grip portion of the frame is completely embedded in the area of reduced density, for example in a composite material.

The reinforcement comprises a base extending circumferentially along at least a portion of the surface of the body opposite the skin.

The seat increases the stiffness of the transmission part and limits the deformation, in particular the elastic deformation, of the transmission part when the damper transmits a torque. The chassis also allows for the absorption of compressive stresses, which is particularly advantageous when the region of reduced density is comprised of unidirectional fiber composite material, the unidirectional fibers being weak with respect to compressive loads.

The base is metallic.

The base extends completely along the transmission portion.

The base extends substantially parallel to the epidermis.

The skin and the base extend circumferentially along the same angular sector.

-the base is formed from a sheet material.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the base and the skin are separated by a region of reduced density.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the transmission portion comprises a base and a frame.

-the base and the frame are connected to each other.

The base and the frame are formed as one and the same part.

-a frame connecting the base and the skin.

The base, the frame and the skin are formed as one and the same part, in particular from extruded profiles, in particular I-shaped.

The reinforcement comprises at least one wing at least partially covering the transmission portion in a plane perpendicular to the axis of rotation of the damper.

The reinforcement comprises two wings between which the area of reduced density is arranged. If necessary, a skin connects the two wings.

The wings and the skin are formed as one and the same part, in particular as an extruded profile in an L-shape when having a single wing, or as an extruded profile in a U-shape when having two wings.

The skin and the wings extend along the same angular sector.

The wing extends over the entire height of the transmission portion in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

According to another embodiment or in combination with the use of the reduced density areas made of composite material, at least one of the reduced density areas of the transmission portion, in a plane intersecting the cam surface and comprising the axis of rotation of the damper, is a recess located at a distance from the cam surface, the recess being located within a rectangular space in which the transmission portion is located.

At least one of these recesses is formed at least partially to half the height of the transmission part. In other words, at least a portion of the recess is remote from the corners of the rectangular space.

According to one embodiment, the width of the recess is smaller than the width of the transmission portion in a plane intersecting the cam surface and comprising the axis of rotation of the damper. In particular, the recess need not be a through hole running through the width of the blade.

The transmission part is formed by an extruded profile along which the cam surface extends, the profile being curved around the axis of rotation of the damper.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the transmission portion comprises a reinforcement and has a U-shaped, I-shaped, T-shaped or L-shaped shape. Preferably, the transmission part is formed by a U-shaped, I-shaped, T-shaped or L-shaped extruded profile.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the transmission portion has an I-shape with a head, on which the cam surface is formed, a base and a core connecting the base and the head.

The base and the core form a reinforcement of the transmission part, if necessary.

The transmission portion comprises two recesses extending circumferentially around the axis X, the two recesses being axially disposed on either side of the core.

-if desired, the base has a width smaller than the width of the head.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the base may have a circular shape, for example in the shape of a drop.

If desired, in this plane, the core of the transmission part comprises a half-height thinned portion in the width direction.

In this plane, the side wall of the core adjacent to the recess is curved. Thus, the gradual change in the width of the core makes it possible to avoid the occurrence of stress accumulation regions that may weaken the transmission portion. Furthermore, the implementation of the curved wall allows to facilitate the manufacturing process of the I-shaped transmission part when manufacturing the transmission part by forging.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, when the transmission portion has a U-shape, the transmission portion comprises a single recess extending circumferentially about the axis X.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the U-shaped transmission portion comprises a head on which the cam surface is formed and two lateral wings connected by the head, between which the recess is arranged.

The two wings form a reinforcement of the transmission part.

The transmission portion has a U, I, T or L shape in a plane intersecting the cam surface and comprising the axis of rotation of the damper, the cam surface being formed on a first portion of the profile and a second portion of the profile forming a reinforcement of the transmission portion.

As a variant, the transmission portion comprises a plurality of regions of reduced density formed by recesses that extend in width through the transmission portion. The recess is, for example, a through-hole provided in the width of the transmission part. In order to significantly reduce the mass of the transmission part, these through-going holes preferably do not partially or completely fill their extra parts.

The transmission part comprises at least two holes spaced at least 10 degrees around the rotation axis X, in particular at least 30 degrees, in particular at least 45 degrees, for example at least 60 degrees.

The transmission part comprises at least two holes located on either side of a neutral position of the transmission part.

The through recess extends around the rotation axis X over an angular sector of at least 20 degrees, in particular over an angular sector of at least 30 degrees, for example at least 45 degrees, preferably at least 60 degrees, if desired over the same angular sector as the cam surface.

The frame has a V-shape in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

The frame is separated from the epidermis by a zone of reduced density.

In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the recess may be a chamfer provided on a corner of the transmission portion opposite the cam surface.

These chamfers may extend at least up to half the height of the transmission part.

The transmission part may comprise: a first reduced density region, for example made of a composite material; and a second reduced density region comprising, for example, at least one recess, in particular a chamfer.

The invention also relates to:

a method of manufacturing a transmission part of an arm of a torsional damper for a torque-transmitting device, in particular for a motor vehicle, in particular for a clutch device, the damper comprising:

a first element which is rotationally movable about a rotation axis (X),

-a second element which is rotationally movable about a rotation axis (X) and rotationally movable about the rotation axis (X) relative to the first element, an arm connected to the second element of the damper by means of an elastic connection, the arm comprising a cam surface arranged to cooperate with a cam follower during relative rotation between the first and second elements to allow torque transmission between the first and second elements, the transmission portion being such portion of the arm: along which the surface of the cam surface extends, the method comprising the steps of:

providing an extruded profile or skin comprising a cam surface,

bending the skin or the profile in order to bend the cam surface of the damper.

According to other advantageous embodiments, the method may have one or more of the following features:

the manufacturing method further comprises the step of machining the cam surface.

The transmission portion comprises a main body at least partially covered by a skin, the main body being at least partially formed of a fibre-reinforced polymer material, called composite material, and the method comprises the steps of:

-moulding a composite body with a fibre-reinforced polymer material,

omicron connects the body and the curved epidermis.

-performing a step of connecting the skin and at least a portion of the body during moulding of the composite body, the skin being present in the mould, the body being overmoulded on the skin, the body being connected to the skin by shape locking.

The transmission part comprises a reinforcement, for example formed by a bent metal extruded profile, on which the body is overmoulded.

The skin and the body comprise structures interconnected by shape locking.

The arm is formed on a transmission member comprising a fixed portion, an elastic connection portion connecting the arm to the fixed portion, characterized in that the regions of reduced density of the fixed portion, the elastic connection portion and the transmission portion are integrally formed during the molding step from a fiber-reinforced polymer material, known as composite material.

The arm is formed on a transmission member comprising a fixed part, an elastic connection connecting the arm to the fixed part, and a transmission part, characterized in that the fixed part, the elastic connection and the transmission part are integrally formed by a curved extruded profile.

Drawings

The invention will be better understood and other objects, details, characteristics and advantages thereof will appear more clearly in the following description of a number of specific embodiments thereof, given by way of example only and not in limitation thereof, with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a front view of a dual flywheel damper illustrating the general operation of a torsional damper with the drive member and cam follower shown in phantom;

FIG. 2 is a cross-sectional view of the dual flywheel damper of FIG. 1 according to II-II;

FIG. 3 is a perspective view of the dual flywheel damper of FIG. 1;

FIG. 4 is a perspective view of the dual flywheel damper of FIGS. 1-3, with the secondary inertial flywheel shown disassembled and separated from the primary inertial flywheel to illustrate a first embodiment of the present invention;

FIG. 5 is a cross-sectional view showing a dual flywheel damper of a second embodiment of the present invention;

FIGS. 6, 7, 8 and 9 show different views of the drive member of FIG. 5;

fig. 10, 11 and 12 show different variants of the second embodiment.

Fig. 13, 14 and 15 show a third embodiment of the invention in perspective, front and cross-sectional views, respectively.

Fig. 16, 17 and 18 show a fourth embodiment of the invention in perspective, front and cross-sectional views, respectively.

Fig. 19, 20 and 21 show a fifth embodiment of the invention in perspective, front and cross-sectional views, respectively.

Fig. 22, 23 and 24 show a sixth embodiment of the invention in perspective, front and cross-sectional views, respectively.

Fig. 25, 26 and 27 show a seventh embodiment of the invention in perspective, front and cross-sectional views, respectively.

Fig. 28 and 29 show an eighth embodiment of the invention in two views, a perspective view and a sectional view, respectively.

Fig. 30 and 31 show a ninth embodiment of the invention in two views, a perspective view and a cross-sectional view, respectively.

Fig. 32 and 33 show a tenth embodiment of the invention in two views, a perspective view and a cross-sectional view, respectively.

Fig. 34, 35 and 36 show an eleventh embodiment of the invention in perspective, front and cross-sectional views, respectively.

Detailed Description

Note that the "axial" orientation is defined by the axis of rotation (X) of the elements of the torsional damper. The "radial" orientation is orthogonal to the axis of rotation (X) of the elements of the torsional damper. The orientation "circumferential" is directed orthogonal to the rotational axial direction of the damper and orthogonal to the radial direction. Thus, an element described as developing in the circumferential direction is an element whose components develop in the circumferential direction (i.e. about the axis of rotation).

Similarly, the indication of an angle or angular sector is to be interpreted as being defined by two straight lines perpendicular to the plane of the rotation axis X and a secant at said rotation axis X.

The terms "outer (outboard)" and "inner (inboard)" are used to define the relative position of one element with respect to the other, with reference to the rotational axis of the torsional damper, whereby the element proximate the axis is said to be inner (inboard) with respect to the outer element located radially at the periphery.

Furthermore, intersecting any plane including the axis of rotation X, the transmission portion has a width L extending in the axial direction parallel to the axis X, and a height h extending in the radial direction.

In an embodiment of the invention, the damper is intended to be placed in a drive train, i.e. between the engine and the wheels of the motor vehicle, for transmitting the engine torque from the engine to the wheels. In one variation, the damper may be placed by-pass with respect to the path through which the engine torque passes, particularly in the case of a damper.

Reference is first made to fig. 1 to 4, which show a first embodiment of the invention in the context of a dual flywheel damper 1. The first and second elements are formed by a secondary inertial flywheel and a primary inertial flywheel, respectively. The dual flywheel damper 1 includes: a primary inertia flywheel 2 for fixing to an end of a crankshaft of an internal combustion engine, not shown; and a secondary inertial flywheel 3 centered and guided on the primary flywheel 2 by means of ball bearings 4. The secondary flywheel 3 serves to form a reaction plate of a clutch, not shown, connected to the input shaft of the gearbox. The primary inertial flywheel 2 and the secondary inertial flywheel 3 are intended to be mounted movably about an axis of rotation X and, moreover, to be movable in rotation relative to each other about said axis X.

The primary flywheel 2 includes a radially inner hub 5 that supports the rolling bearing 4, an annular portion 6 that extends radially from the hub 5, and a cylindrical portion 7 that extends axially from the outer periphery of the annular portion 6 on the side opposite the engine. The annular portion 6 is provided, on the one hand, with holes for the passage of fixing screws 8 for fixing the primary flywheel 2 to the crankshaft of the engine, and, on the other hand, with holes for the passage of rivets 9 for fixing the transmission member to the primary flywheel 2. The primary flywheel 2 carries on its outer periphery a gear ring 10 for driving the primary flywheel 2 in rotation by means of a starter.

The hub 5 of the primary flywheel comprises a shoulder 11, the shoulder 11 being intended to support the inner ring of the rolling bearing 4 and to retain said inner ring in the direction of the engine. Similarly, the secondary flywheel 3 includes, on its inner periphery, a shoulder portion 12, the shoulder portion 12 serving to support the outer ring of the rolling bearing 4 and to hold the outer ring in the direction opposite to the engine.

The secondary flywheel 3 comprises a flat annular surface 13, facing the side opposite to the primary flywheel 2, forming a bearing surface for the friction linings of the clutch disc, not shown. The secondary flywheel 3 comprises, near its outer edge, a post portion 14 and a hole 15 for mounting a clutch cover. The secondary flywheel 3 also comprises a hole 16, the hole 16 being arranged opposite the hole formed in the primary flywheel 2 during the mounting of the dual flywheel damper 1 on the crankshaft and being intended for the passage of the screw 8.

The primary flywheel 2 and the secondary flywheel 3 are rotationally coupled by a transmission member 30. In the embodiment shown in fig. 1 to 4, the damping means comprises two flexible blades 17a, 17b mounted to rotate integrally with the primary flywheel 2. To this end, the flexible blades 17a, 17b are carried by a fixed part, here an annular body 18 hole provided with a hole allowing the passage of a fixing rivet 9 for fixing to the primary flywheel 2. The annular body 18 also comprises holes 19 for the passage of fixing screws 8 for fixing the twin flywheel damper 1 to the front end of the crankshaft. The fixing body remains fixed, in other words, it does not flex when the wheels are rotated relative to each other. These transmission members may be cut from sheet material or cast, for example.

The two flexible blades 17a and 17b are symmetrical with respect to the axis of rotation X of the damper.

Fig. 4 shows that the flexible blades 17a, 17b each comprise, on the one hand, an arm 81, the arm 81 extending substantially circumferentially about the axis X and comprising the cam surface 20, and that the flexible blades 17a, 17b each comprise, on the other hand, an elastic connection 82. The portion of the arm 81 along which the cam surface 20 extends is referred to as the "drive portion". The arm 81 is connected to the fixed part 18 of the transmission member 30 by means of a resilient connection 82, which is curved here. The elastic connection 82 and the arm 81 thus form here a flexible blade 17a and a flexible blade 17 b. The flexure 82 is capable of flexing during relative rotation of the primary and secondary flywheels.

The secondary flywheel 3 comprises two cam followers 24 arranged each to cooperate with a cam surface 20. The bending motion of the blades 17a and 17b is accompanied by a relative rotation between the primary and secondary flywheels to damp the non-periodic rotation between the primary and secondary flywheels. The cam follower 24 is displaced on the cam surface 20 during this relative rotation. The cam surface 20 is arranged on an arm 81 to cooperate with the cam follower 24 during relative rotation between the primary and secondary flywheels to allow torque to be transferred between the flywheels.

The cam follower 24 comprises a roller 21 carried by a cylindrical bar 22 fixed to the secondary flywheel 3. The roller 21 is mounted on a mast 22 so as to be rotationally movable about an axis of rotation parallel to the axis of rotation X. Due to the resilient connection 82, the roller 21 is held bearing against its cam surface 20 and is arranged to roll against said cam surface 20 during relative movement between the primary flywheel 2 and the secondary flywheel 3. The rollers 21 are arranged radially outside their respective cam surfaces 20 to radially retain the flexible blades 17a, 17b when the flexible blades 17a, 17b are subjected to centrifugal forces. In order to reduce the parasitic friction that may affect the damping function, the roller 21 is advantageously mounted rotatably on the cylindrical rod by means of a rolling bearing. For example, the rolling bearing may be a ball bearing or a roller bearing. In one embodiment, the roller 21 has an anti-friction coating.

Without torque transmission, the primary flywheel 2 and the secondary flywheel 3 occupy relative angular positions of rest. When the damper is not transmitting torque, the cam surface 20 includes a neutral position N occupied by the cam follower 24. When the primary and secondary flywheels 2, 3 are in the angular position of rest, the cam follower is in the neutral position of the cam surface 20.

Each cam surface 20 is arranged so that, for an angular stroke between the primary flywheel 2 and the secondary flywheel 3 relative to the relative angular rest position, the displacement of the roller 21 on the cam surface exerts a bending force on the flexible blade. By reaction, each flexible blade 17a, 17b exerts a return force on each roller 21, which tends to return the primary flywheel 2 and the secondary 3 to their relative angular positions of rest. The reaction force is an elastic restoring force exerted on the roller 21 by the flexible blade in response to the bending of the blades 17a and 17 b. The reaction force is an elastic restoring force exerted on the roller 21 only by each flexible blade 17a, 17b in response to the elastic deformation of the blade.

In other words, the cam surface 20 is arranged such that displacement of the cam follower 24 on the cam surface 20 is accompanied by elastic deformation of the elastic connection 82 for at least some angular travel region between the first and second elements.

Thus, the flexible blades 17, 17b are able to transfer the driving torque from the primary flywheel 2 to the secondary flywheel 3 (positive direction) and the drag torque from the secondary flywheel 3 to the primary flywheel 2 (negative direction). Thereby, the damper is capable of transmitting a torque in the range of 10N.m to 500N.m

Each flexible blade includes a free end region 80 and the damper is arranged such that when the cam follower 24 flexes the blade, the free end region 80 is close to the axis of rotation of the damper. In other words, the radial distance separating the axis of rotation X from said free distal end region 80 varies as a function of the angular travel between the first and second elements. The free end region 80 extends circumferentially the cam surface 20.

In fig. 4, it can be seen that the portion of the arm 81 along which the cam surface extends, i.e. the transmission portion 83, has a region 84 of reduced density. The region of reduced density is formed by a recess 84 provided in the transmission part. The recess is here a hole 84 which runs through the transmission part 83 parallel to the axis of rotation X in width. These holes lighten the transmission part 83. Thus, the arm 81 more moderately actuates the cam follower 24 when centrifugal force is greatest, particularly in the high speed range. Further, the weight reduction of the arm contributes to the overall weight reduction of the damper.

Here, each transmission portion 83 includes five holes 84, and each hole 84 is spaced apart from an adjacent hole by about 10 degrees. Thus, the holes 84 are arranged on an angular sector of about 45 degrees around the rotation axis X.

Some of the apertures 84 are located on the drive portion on which the cam follower rolls in the forward direction, while other apertures are located on the drive portion on which the cam follower rolls in the reverse direction. In other words, the holes are located on both sides of the neutral position N of the cam surface.

These holes 84 are made by passing the driving part of the blade in the width direction, where the blade may be made entirely of metal, such as steel. These perforations 84 are large enough to significantly lighten the transmission portion and should not be excessive to avoid weakening the blade. Their diameter may for example be in the range of 5mm to 10 mm.

Referring now to fig. 5 to 9, a second embodiment of the present invention is shown, still in the context of a dual flywheel damper. Elements that are the same or similar to elements of fig. 1-4, that is, elements that perform the same function, have the same reference numeral increased by 100

In this embodiment, each drive member 130 includes a single flexible blade 117. The damper here comprises two transmission members 130, which are arranged symmetrically with respect to the axis X, at a distance from each other.

The cam follower 124 includes a roller 121, and the roller 121 is mounted to be rotatably movable on the primary flywheel 102 about a rod 122 fixed to the primary flywheel 102.

As seen in the cross-sectional view of fig. 5, which includes the axis of rotation X and intersects the cam surface of the transmission portion, the transmission portion of the arm may be multi-material, here bi-material.

Here, the reduced density region 184 is formed in the material of the power transmitting portion having the lowest density. Here a composite material

As can be seen in fig. 7, the regions of reduced density extend on either side of the neutral position N of the drive section 183. A region 184 of reduced density made of composite material extends along the drive section 183 about the axis of rotation X, here over an angular sector of about 90 degrees.

As can be seen in fig. 9, which shows a part of the transmission portion according to section CC of fig. 8, the region 184 of reduced density is located at a distance from the cam surface 120. Therefore, the lightness of the transmission portion 183 does not impair the rigidity of the cam surface 120 and the displacement of the cam follower 124 on the cam surface, particularly when the cam follower includes the roller 121 that rolls on the cam surface 120.

The driving portion 183 of the arm comprises a main body 185 covered with a skin 186, the cam surface 120 being at least partially formed on the skin 186, and the region 184 of reduced density being integrally formed here by the main body 185.

The body 185 and the skin 186 are formed of two different materials. The average density of the body is lower than the average density of the skin 186.

Similarly, the material of the skin 186, particularly in terms of its stiffness characteristics, may be selected to facilitate displacement of the cam follower on the cam surface, particularly when the cam follower is a rolling roller.

Here the skin 186 completely covers the body 185 over its width. The curvature of the cam profile may be obtained during the bending operation of the skin. Additional machining may allow for increased accuracy of the curvature of the cam surface, if desired.

Similarly, with respect to the bending force exerted on the transmission portion 183 by the cam follower, the skin has a rigidity greater than that of the main body. Thus, the skin also allows for limiting deformation in the drive portions 183 of the arms, if desired. Depending on its dimensions, the skin allows to limit or even prevent any deformation of the transmission portion 183 when the torque is transmitted through the damper.

In the illustrated embodiment, the camming surface 120 extends entirely over the skin 186. To ensure good displacement of the cam follower 124 and to limit wear of the cam surface, the skin 186 is formed of a metallic material. The skin is formed, for example, of a steel plate having a thickness of 1 to 3 mm.

In the circumferential direction, the skin here has a constant thickness (height). In one variation, the thickness of the skin may be varied to refine the definition of the cam profile. Such operation may be performed, for example, by machining before or after assembling the skin 186 and the body 185.

The body 185 is formed of a fiber reinforced polymer material known as a composite. The fibers of the composite material are here carbon fibers. These fibers are unidirectional fibers that extend along the drive portion 183 of the arm. The fibers extend, for example, parallel to the cam surface. Polymeric materials belong to the family of thermosets. The polymer material is here an epoxy resin. As can be seen in fig. 7, the body of the transmission part is made entirely of composite material.

If desired, the body 185 and the skin 186 are attached to one another by a layer of adhesive substance 187.

The resilient connection 182 of the transmission member is a bend 182 arranged such that for a predetermined angular sector the blade comprises two regions radially offset from each other in the radial direction, the free space E radially separating the two regions radially offset.

Preferably, the flexures, whether made as described above or as in the first embodiment, are also made of composite material. Embodiments of the flexures made of composite material allow for greater flexibility, accept higher levels of stress, and store more energy in the blade 117 than flexures made of metal, particularly steel.

To manufacture this type of transmission member, a skin may be manufactured by cutting a plate material and then bending. The reduced density region 184 of the transmission portion 183, the bend 182 and the fixed portion 118 are integrally molded from a composite material. The skin may then be secured to the body of the transmission section 183, particularly by adhesive substance 187.

Reference is now made to fig. 10, 11 and 12, which show a variation of the second embodiment. The differences relate to the shape of the skin 186 and its assembly with the body 185.

In a cross section of the transmission portion intersecting the cam surface and including the rotation axis X, as shown in fig. 10, it can be seen that the width of the skin is smaller than the width of the transmission portion 183. The reduced density region 184 includes two edges 188a and 188b that axially border the skin 186. The reduced density region 184 is formed from a composite material, for example, as previously described.

In a section of the transmission portion intersecting the cam surface and comprising the rotation axis X, as shown in fig. 11, it can be seen that the skin 186 and the body 184 can be assembled to each other by shape locking. In a plane intersecting the cam surface and comprising the axis of rotation of the damper, the skin 186 actually comprises undercuts on each of its lateral faces 189a and 189b, and the main body comprises two edges 188a and 188b having a shape complementary to these undercuts, so that the main body 185 and the skin 186 mutually hold one another.

For both variants shown in fig. 11 and 12, the composite material may be overmolded onto the skin after the skin bending operation. The skin and the body are then held to each other by shape locking.

In a section of the transmission section intersecting the cam surface and comprising the rotation axis X, as shown in fig. 12, it can be seen that the skin 186 comprises a raised upper surface from which the cam surface 120 is formed in order to reduce edge effects and avoid excessive stress concentrations (hertzian stress) during moving the cam follower 124, in particular the roller 121, over the transmission section 183.

Fig. 13 to 15 depict another embodiment of the invention wherein the transmission portion further comprises a reinforcement 190. This addition applies to any of the embodiments shown in fig. 5 to 12.

The skin 186 of the drive section 183 includes a stiffening member 190, the stiffening member 190 allowing stiffening of the drive section with respect to bending forces exerted on the drive section 183 by the cam follower. The skin 186 has protrusions 190, the protrusions 190 extending within the body 185. Therefore, the reinforcing member increases the rigidity of the power transmission portion 183 and restricts the deformation of the power transmission portion 183 when the torque is transmitted through the damper.

The reinforcement is metallic. The reinforcement extends completely along the drive portion 183. The skin 186 and the stiffeners 183 extend along the same angular sector. In this example, the body is again integrally constructed of a composite material.

The body 185 and the stiffener 190 may be connected to each other by a layer 191 of adhesive substance.

Here, the skin 186 and the stiffener 190 are integrally formed of an extruded profile having a T-shape.

The reinforcement 190 is a frame 193 embedded in the reduced density region 184, that is, embedded in the composite material.

In a section CC of the transmission portion intersecting the cam surface and comprising the axis of rotation X, as shown in fig. 15, it can be seen that the height of the frame extends from the skin over at least half the height of the transmission portion 183, here about four fifths of the height of the transmission portion 183. The frame 193 extends substantially perpendicular to the cam surface 120 and the rotational axis of the damper. The frame extends about the axis X over the same angular sector as the cam surface.

In fig. 13, it can be seen that the flexures are also formed of composite material. The use of composite materials to fabricate the curved resilient connection 182 allows higher levels of stress to be accepted and more energy to be stored in the blade. Without the reinforcement, the bend provides a greater possibility of deformation than the transmission part, which allows more energy to be stored.

The reinforcement arranged on the transmission portion makes it possible to limit the deformation only at the transmission portion. By limiting the deformation on the transmission portion, the damping characteristics of the damper can be set more accurately, and the size of the cam profile 120 can be determined more accurately.

Fig. 16 to 18 depict another embodiment of the invention in which the reinforcement 190 of the transmission portion is a frame 193 that includes a grip 192.

The grip 192 is fully embedded in the composite material to radially retain, among other things, the frame 193 in the composite material. Therefore, the frame 193 and the region of reduced density are held to each other by shape locking.

The grip 192 extends completely circumferentially along the frame 193.

In a section C-C of the transmission portion intersecting the cam surface and including the rotation axis X, as shown in fig. 18, it can be seen that the frame 193 is T-shaped. The frame 193 and the skin 186 are connected to each other, and the grip 192 is arranged on an edge of the frame diametrically opposite the skin. In the cross section shown in fig. 18, it can be seen that the skin 186 and the frame 193 are here integrally formed from an extruded profile having a substantially I-shape, where the width of the grip 192 is shorter than the width of the skin 186.

Fig. 19 to 21 depict a fifth embodiment of the invention, wherein the reinforcing member 190 comprises a base 194.

Here, the reinforcement 190 includes a frame 193 and a base 194. In a cross section of the transmission portion intersecting the cam surface and including the axis of rotation X, as shown in fig. 21, it can be seen that the base 194 and the frame 193 are connected to each other. The frame 193 connects the base 194 and the skin 186. The base 194, frame 193 and skin 186 are formed from the same piece as an extruded profile in an I-shape. Thus, here, on the transmission part 183, there is a two-part body 185, i.e. two regions 184a and 184b of reduced density made of composite material arranged axially on either side of the frame 183. The two regions of reduced density made of composite material extend circumferentially around the axis X along the transmission portion. The two regions 184a and 184b then meet beyond the transmission portion in a direction towards the bend.

The seat 194 increases the rigidity of the transmission portion 183 and restricts the deformation, particularly the elastic deformation, of the transmission portion 183 when the damper transmits the torque. The base 194 also allows for the ability to withstand compressive stresses that can degrade the composite 184.

In the embodiment shown in fig. 22-24, the stiffener 190 is formed only by the base 194. Here the stiffeners are not embedded in the frame in the region of reduced density 184. In a cross-section of the transmission portion intersecting the cam surface and including the axis of rotation X, as shown in fig. 24, it can be seen that the base 194 and the skin 186 are completely separated by the region of reduced density 184 (i.e., the composite material).

As previously described, the mount 184 increases the stiffness of the transmission portion 183 and limits the deformation, particularly the elastic deformation, of the transmission portion 183 when the damper transmits torque. The base 194 also allows for the ability to withstand compressive stresses that can degrade the composite material.

The base 194 is metal. It is formed, for example, in sheet material. The base extends completely along the drive portion 183. In the example shown in fig. 22, it can be seen that the base extends substantially parallel to the skin 186. The skin 186 and the stiffeners 194 extend along the same angular sector. The assembly between the skin and the body by form locking shown in fig. 11 and 12 can be applied to the assembly of the bottom plate 194 and the body 185, if desired. The body may thus be over-molded onto the base.

With respect to the bending forces exerted by the cam follower on the transmission portion, the mount has a greater stiffness than the region of reduced density, which thereby allows the body 185 of the transmission portion to be reinforced.

In a section of the transmission portion intersecting the cam surface and comprising the rotation axis X, as shown in fig. 24, it can also be seen that the width of the seat 194 is equal to the width of the body 185 supported by the composite material.

Fig. 25 to 27 depict another embodiment of the bi-material transmission part. The body 185 is again formed from a composite material and the stiffener 190 here comprises two wings 196a and 196b arranged on each side of the transmission portion 183.

The reduced density region 184 is disposed axially between the two wings 196a and 196 b. The wings 196a and 196b and the skin 186 are formed from the same component, i.e., a U-shaped extruded profile. The skin and the wings extend along the same angular sector. Note that in fig. 25, the wings extend over the entire height of the transmission section 183.

It can be seen that in the third, fourth, fifth, sixth and seventh embodiments shown in figures 13, 16, 19, 22 and 25, the stiffeners have a geometric pattern extending continuously circumferentially about the axis X along the transmission portion 183 in a plane intersecting the cam surface and including the axis of rotation of the damper. The stiffener 190 comprises a plane of symmetry perpendicular to the axis of rotation of the damper. The stiffener and drive section 183 include a common plane of symmetry.

In the third, fourth, fifth and seventh embodiments of fig. 13, 16, 19 and 25, the stiffener is connected to the skin. The skin 186 and the stiffeners 190 are manufactured as a single component to simplify the construction and manufacture of the transmission portion (fig. 13, 16, 19, 25).

Referring now to fig. 28 to 33, there are shown further embodiments of the invention in which the region of reduced density is a recess. Elements that are the same or similar to elements of fig. 5 to 27, that is, elements that perform the same function, have the same reference numerals increased by 100 for ease of understanding, and only the transmission portion is shown.

In a plane intersecting the cam surface and including the rotational axis of the damper, the region of reduced density corresponds to the recesses 284, 284a, 284b located at a distance from the cam surface within a rectangular space 298 in which the drive portion 283 is located. These recesses extend circumferentially around the rotation axis X along the transmission part, here over an angular sector of about 90 degrees.

According to the eighth and ninth embodiments shown in fig. 28 to 31, the transmission part 283 is formed by an I-shaped, preferably extruded profile having a head 286, a base 294 and a core 299 connecting the base 294 and the head 286, a cam surface 220 being formed on the head 286. The profile can be extruded and bent around the axis of rotation X of the damper. The base 294 of I and the core 299 form the stiffener 290 of the drive portion 283.

The transmission portion 283 includes two recesses 284a and 284b extending circumferentially about the axis X, the two recesses 284a and 284b being axially disposed on either side of the core 299.

In the height direction, each recess is bounded by a base 294 and a head 286. The core 299 extends perpendicular to the rotational axis of the damper and has a plane of symmetry for the drive portion 283.

If desired, and as seen in a cross-section intersecting the cam surface and including the axis of rotation of the damper of FIG. 31, the base portion 294 has a width less than the width of the head portion 286. Similarly, the base 294 has a circular shape, in the shape of a droplet.

The core 299 of the transmitting portion 283 includes a thinned portion of half height in the width direction. The side walls of the core 299 adjacent the recesses 284a and 284b are curved.

The drive portion 283 may be made from a bent extruded profile or by casting or forging. Regardless of the method by which the drive portion 283 is obtained, the machining of the cam surface 220 may be carried out to refine the precision of its profile and its curvature about the axis X.

According to the embodiment shown in fig. 32 and 33, the drive portion 283 is formed by an extruded U-shaped profile along which the cam surface 220 extends, which profile is curved around the rotational axis X of the damper.

The transmission portion comprises a single recess 284 extending circumferentially about the axis X. According to the section shown in fig. 33, which intersects the cam surface and comprises the axis of rotation of the damper, the U-shaped transmission part comprises a head 286 and two flanks 296a, 296b connected by the head 286, on which head 286 the cam surface 220 is formed, and a recess is arranged between these flanks 296a and 296 b. These two wings form a reinforcement of the drive portion 283.

In general, the transmission portion has a U-shape (fig. 33), I-shape (fig. 29 and 31) or T-or L-shape (not shown) when in a plane intersecting the cam surface and including the rotational axis of the damper, the cam surface 220 is formed on a first portion of the profile, and a second portion of the profile forms the stiffener 290 of the transmission portion 283.

Referring now to fig. 34 to 36, there is shown an eleventh embodiment of the invention which combines two types of reduced density regions, namely a composite region 384 and recessed regions 384a and 384 b. Elements that are the same or similar to elements of fig. 1-4, that is, elements that perform the same function, have the same reference number incremented by 300. Elements that are the same or similar to elements of fig. 28 to 33, that is, elements that perform the same function, have the same reference numeral increased by 100

The reinforcement 390 is here arranged in the body 385 of the transmission part 383. The stiffener 390 is a frame 393 separated from the skin 386 by a reduced density region 384 made of a composite material. Thus, the skin 386 and the frame 393 form two separate pieces here. The frame 383 is embedded in a composite material 384 that has been overmolded onto the frame.

The frame has a V-shape in a plane intersecting the cam surface and including the rotational axis of the damper. The recesses are chamfers 384a 'and 384b' disposed at corners of the drive portion opposite the cam surface 320. These chamfers may extend at least half way up to the drive portion 383.

Thus, the transmission part includes: a first reduced density region 38 made of a composite material; 4 and a second reduced density region, i.e. a recess, in particular chamfers 384a 'and 384 b'.

Although the invention has been described in connection with several specific embodiments, it is obvious that the invention is by no means limited to these and comprises all technical equivalents of the means described and their combinations if these are within the scope of the invention.

Furthermore, the figures show the torsional damper in the context of a dual flywheel damper, but such a torsional damper may be mounted on any suitable device. Such a torsional damper can thus be equipped with a clutch disk in the case of a manual or automatic transmission, or with a lock-up clutch (also referred to as a "lock-up clutch for equipping a hydraulic coupling device) in the case of an automatic transmission.

Use of the verbs "comprise", "include", "consist" and their variants do not exclude the presence of other elements or steps than those stated in the claims. The use of the indefinite article "a" or "an" does not exclude the presence of a plurality of such elements or steps, unless stated to the contrary.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims (27)

1. A torsional damper for a torque transmitting device for a motor vehicle, the damper comprising:

a first element (3; 102) which is movable in rotation about a rotation axis (X),

a second element (2; 103) which is movable in rotation about a rotation axis (X) and is movable in rotation about the rotation axis (X) relative to the first element,

an arm (81, 181, 281, 381) connected to the second element of the damper by a resilient connection (82, 182, 382), the arm comprising a cam surface (20, 120, 220, 320) arranged to cooperate with a cam follower (24, 124, 224) during relative rotation between the first and second elements so as to allow torque to be transmitted between the first and second elements,

characterized in that at least a part of the portion of the arm called the transmission portion (83, 183, 283, 383) has at least one region of reduced density (84, 184, 184a, 184b, 284, 284a, 284b, 384, 384a ', 384b') to lighten the transmission portion and thus the torsional damper, the cam surface extending along the transmission portion.

2. The torsional damper of claim 1, wherein said reduced density region (84, 184, 184a, 184b, 284, 284a, 284b, 384, 384a ', 384b') is positioned away from said cam surface (20, 120, 220, 320).

3. The torsional damper according to claim 1 or 2, wherein the cam follower (24, 124, 224) comprises a roller (21, 121, 221) arranged to be rollingly displaced on the cam surface (20, 120, 220, 320) during relative rotation of the first and second elements.

4. The torsional damper of claim 1, wherein the arm (81, 181, 281, 381) is formed on a transmission member (30, 130, 330) comprising:

a fixing portion (18, 118, 318) fixed to the second element,

at least one flexible blade (17a, 17b, 117, 317) comprising:

the arm (81, 181, 281, 381) on which the transmission portion (83, 183, 283, 383) is formed,

the resilient connecting portion (82, 182, 382) connecting the fixed portion to the arm.

5. The torsional damper of claim 1, wherein the at least one region of reduced density (184, 184a, 184b, 284, 284a, 284b, 384, 384a ', 384b') extends over an angular sector of at least 20 degrees about the axis of rotation (X).

6. The torsional damper of claim 1, wherein the transmission portion of the arm includes a main body (185, 385) at least partially covered with a skin (186, 386), the cam surface (120, 320) is at least partially formed on the skin (186, 386), and the reduced density region (184, 184a, 184b, 384) is at least formed on a portion of the main body.

7. The torsional damper of claim 6, wherein the skin (186, 386) is formed from sheet material.

8. The torsional damper of claim 1, wherein said reduced density regions (184, 184a, 184b, 384) are formed at least in part from a fiber reinforced polymer material known as a composite material.

9. The torsional damper of claim 6, wherein said body (185, 385) and said skin (186, 386) are connected to each other by a shape lock.

10. The torsional damper of claim 6, wherein the body (185) is made entirely of a composite material.

11. The torsional damper of claim 6, wherein said transmission portion includes a reinforcement (190, 290, 390) that allows said transmission portion (183, 283, 383) to be reinforced with respect to bending forces exerted on said transmission portion by said cam follower (124, 224).

12. The torsional damper of claim 11, wherein the skin (186) and the stiffener (190) are integrally formed.

13. The torsional damper of claim 11, wherein the stiffener comprises a frame (193) at least partially embedded in the reduced density region (184).

14. The torsional damper of claim 13, wherein the height of the frame (193) extends over at least one fifth of the height of the transmission portion (183) in a plane intersecting the cam surface and comprising the axis of rotation of the damper.

15. The torsional damper of claim 11, wherein the stiffener includes a base (194) extending circumferentially along at least a portion of a surface of the body (185) opposite the skin (186).

16. The torsional damper of claim 11, wherein the stiffener (190, 290) includes at least one wing (196a, 196b, 296a, 296b) at least partially covering the drive portion (183, 283) in a plane perpendicular to the rotational axis of the damper.

17. The torsional damper of claim 1, wherein in a plane intersecting the cam surface and including the axis of rotation of the damper, at least one of said regions of reduced density of the drive portion (283) is a recess (284, 284a, 284b, 384a ', 384b') located away from the cam surface, said recess being located within a rectangular space (298) in which the drive portion (283) is inscribed.

18. The torsional damper of claim 1, wherein the drive portion (283) is formed from a U-shaped, I-shaped, T-shaped or L-shaped extruded profile.

19. The torsional damper of claim 12, wherein the skin (186) and the stiffener (190) are formed from extruded profiles.

20. A method of manufacturing a transmitting portion (183, 283, 383) of an arm (181, 281, 381) of a torsional damper for a torque transmitting device for a motor vehicle, the damper comprising:

a first element (3; 102) which is movable in rotation about a rotation axis (X),

a second element (2; 103) which is movable in rotation about an axis of rotation (X) and in rotation about the axis of rotation (X) with respect to the first element, an arm (81) connected to the second element of the damper by means of an elastic connection (82), the arm comprising a cam surface (20) arranged to cooperate with a cam follower (24) during the relative rotation between the first and second elements to allow the transmission of torque between the first and second elements, the transmission portion being that part of the arm: the cam surface extending along the portion and the drive portion having at least one region of reduced density to reduce the mass of the drive portion and hence the torsional damper, the method comprising the steps of:

providing a skin (186, 386) or extruded profile (283) comprising a cam surface (120, 220, 320),

-bending the skin (186, 386) or the profile (283) in order to bend the cam surface of the damper.

21. The method of manufacturing of claim 20, further comprising the step of machining the cam surface.

22. Manufacturing method according to any one of claims 20 to 21, wherein the transmission portion (183, 383) comprises a body (185, 385) at least partially covered by the skin (186, 386), said body being at least partially formed of a fibre-reinforced polymer material, called composite material, and the method comprises the steps of:

moulding a composite body (185, 385) from a fibre reinforced polymer material,

connecting the body and the curved skin (186, 386).

23. Manufacturing method according to claim 22, wherein the step of connecting a skin (186, 386) present in the mould and at least a portion of a body (185, 385) over-moulded on the skin, the body (185, 385) being connected to the skin by shape locking, is carried out during moulding of the composite body.

24. A manufacturing method according to claim 23, wherein the transmission part comprises a reinforcement, for example formed by a bent metal extruded profile, on which the body is overmoulded.

25. A method of manufacturing according to claim 24, wherein the skin and the body comprise structures interconnected by shape locking.

26. A manufacturing method according to claim 20, wherein the arms are formed on a transmission member comprising a fixed portion, an elastic connection connecting the arms to the fixed portion, characterized in that the fixed portion, the elastic connection and the area of reduced density of the transmission portion are integrally formed during the moulding step by a fibre-reinforced polymer material, called composite material.

27. The manufacturing method according to claim 20, wherein the arm is formed on a transmission member comprising a fixed portion, an elastic connection portion connecting the arm to the fixed portion, and a transmission portion, characterized in that the fixed portion, the elastic connection portion, and the transmission portion are integrally formed by a curved extruded profile.

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