Patent Description:
More specifically, the invention relates to an improvement to the vibration damping device in which an axial misalignment compensation device is positioned between the flywheel of the internal combustion engine and the driven shaft of the gearbox.

In the context of a hybrid motor vehicle, the transmission generally comprises an internal combustion engine, a gearbox, a coupling mechanism connecting the internal combustion engine to the gearbox, and an electric motor coupled to the transmission. The vehicle can thus operate at times with the internal combustion engine and at other times with the electric motor, or sometimes simultaneously with both the electric motor and the internal combustion engine.

A vibration damping device is sometimes necessary to filter the irregularities originating from the internal combustion engine upstream of the gearbox. This vibration damping device is generally installed directly on the flywheel of the internal combustion engine and is connected to an input shaft of the gearbox. This type of installation generally poses a problem of kinematic connection between the device output and the gearbox shaft. Due to the significant number of components used within the transmission, the geometric positioning tolerance of the input and output shafts is large, and even amplified by the use of a rotating electric machine. There are therefore static defects in coaxiality between the motor shaft and the transmission input shaft, these defects being axial and angular. A particular function of the vibration damping device is to compensate for the differences in position between the output shaft connected to the internal combustion engine and the input shaft connected to the gearbox.

Likewise, when the internal combustion engine is in use, the rotation of the crankshaft transmits dynamic axial and/or nutational movements to the vibration damping device by means of the flywheel. The axial displacement measured on the outer periphery of the flywheel can reach peak-to-peak values of the order of several millimetres. Another purpose of the vibration damping device is to compensate for the dynamic axial and/or nutational movements in order to avoid damaging the gearbox.

A damping vibration device is known from the document <CIT>. Further examples can be found in <CIT> and <CIT>.

The invention aims to overcome these technical problems by proposing an improved vibration damping device capable of compensating for the axial and angular tolerances and damping the axial and/or nutational movements of the flywheel significantly better than in the prior art.

Another aim of the invention is to provide a simple, effective and economical solution to these problems.

A further aim of the invention is to supply a vibration damping device capable of reliably transmitting the torque originating from the flywheel to the gearbox input shaft.

To this end, the present invention proposes a vibration damping device for a transmission of a motorized machine, comprising:.

and a device for compensating for axial misalignments between the flywheel and a transmission input shaft, comprising at least one torque output hub which is equipped with an external fluting and radially arranged inside an internal fluting of the intermediate hub, both internal and external fluting splines comprising involute flanks.

Advantageously, the internal and external flutings of the axial misalignment compensation device may be encased one inside the other with a functional play which is substantially uniformly distributed between the inner periphery of the fluting of the intermediate hub and the outer periphery of the fluting of the torque output hub. The functional play, measurable in millimetres, can be measured when the axis of the internal fluting of the intermediate hub and the axis of the external fluting of the torque output hub are coaxial.

Preferably, the functional play may be greater than a threshold value of <NUM>.

The vibration damping device according to the invention has the advantage of compensating for the axial and angular tolerances and also compensating for the nutational movements of the flywheel due to the splined connection between the intermediate hub and the torque output hub. Thanks to the particular geometry of the internal and external flutings, a freedom of movement capacity is available within the vibration damping device, which limits the mechanical stresses within the connection disc.

The torque is also effectively transmitted via splines with involute flanks. In fact, during nutation of the torque output hub relative to the intermediate hub under the effect of rotation of the flywheel, the inner and outer profiles of the splines with involute flanks are coordinated so as to allow the teeth to roll and slide relative to one another. During nutation, the teeth engage and disengage progressively and noiselessly. The torque output hub makes contact with the intermediate hub over several teeth simultaneously thanks to the involute profile, which improves the mechanical fatigue strength of the splines.

Advantageously, the functional play may be equal to the value of the axial eccentricity between the axis of the flywheel and the axis of the transmission input shaft multiplied by a coefficient K, with K between <NUM> and <NUM>. The dimension of the functional play is thus a function of the possible axial and angular eccentricity between the axis of the flywheel and the axis of the input shaft of the transmission, e.g. a gearbox, the overlap length of the internal and external flutings, and the production tolerances of the internal and external flutings. Coefficient K also takes into account the dynamic movements of the flywheel.

Preferably, the internal and external flutings may have a profile allowing mutual contact of several involute flanks at maximal axial eccentricity of the torque output hub relative to the intermediate hub, with minimal spline base play in the direction of eccentricity, such that the minimal play is strictly greater than <NUM>. In this case, the minimal play in the direction of maximal axial eccentricity is between the tooth tip of the external fluting and the spline base of the internal fluting. This has the advantage of not wearing the end of the tooth situated in the direction of the maximal eccentricity.

Advantageously, the internal and external splines of the axial misalignment compensation device may be protected by an anti-wear surface coating, for example a surface treatment or heat treatment.

Preferably, the axial misalignment compensation device may comprise an elastic element for axially preloading the torque output hub along axis X against one of the guide elements.

Advantageously, the axial misalignment compensation device may comprise a friction interface zone provided between a side flank of the torque output hub and a flat face of one of the guide elements.

Preferably, the elastic element may be axially inserted between one of the guide elements and an axial retaining ring, the axial retaining ring being inserted in an annular groove formed on the torque output hub.

Advantageously, two flat load application washers may be arranged on either side of the elastic element and interposed between one of the guide elements and the axial retaining ring. This limits the wear of the elastic element.

Preferably, the elastic element may be a conical washer or a corrugated washer.

As a variant, the elastic element may be axially inserted between the one of the guide elements and an axial rim of the torque output hub.

This axial misalignment compensation device according to the invention has the advantage of constantly pressing the torque output hub against one of the guide elements, and consequently reducing the noise within the vibration-damping device.

Advantageously, the connection disc may be attached to the torque transmission plate or one of the guide elements via fastening zones which are angularly distributed around the axis X and arranged so as to be fastened to a flywheel via anchoring zones angularly distributed around the axis X, each anchoring zone being attached to at least two fastening zones by separate connecting arms.

Preferably, the connection disc may comprise apertures formed by the interleaving of the connecting arms. The connection disc is thus perforated so as to make it flexible without affecting its mechanical strength when subjected to torque.

Advantageously, the connecting arms originating from the same anchoring zone can extend in separate angular directions so that they reach their corresponding fastening zones. The connecting arms are separate from each other and transmit the torque to the torque transmission flange or to one of the guide elements independently.

Preferably, the anchoring zones of the connection disc associated with the flywheel may be positioned on an installation diameter D larger than the installation diameter d of the fastening zones associated with the torque transmission flange or with one of the guide elements.

According to one variant, the connection disc may be fastened to the torque transmission flange by means of a riveted connection comprising a series of rivets positioned in fastening orifices in the disc and in corresponding holes in the torque transmission flange.

Preferably, the connection disc may comprise, in a plane perpendicular to the axis X, two axes of minimal bending stiffness, the axes of minimal bending stiffness being perpendicular to each other and one of the two axes passing through two fastening zones angularly opposite each other relative to the axis of rotation X.

Advantageously, the connection disc may comprise, in a plane perpendicular to the axis of rotation X, two axes of symmetry perpendicular to each other. The two axes of symmetry may correspond to the axes of minimal bending stiffness.

Advantageously, the torque transmission plate can comprise openings for receiving helical compression springs, the fastening zones of the disc being angularly distributed between each receiving opening. The distribution of the mechanical stresses within the connection disc is thus substantially uniform over the perimeter of the torque transmission flange.

Preferably, the guide elements may be rotationally connected to the intermediate hub by means of rivets, or a weld.

For example, the guide elements can be guide washers formed from a stamped metal sheet.

According to one embodiment of the invention, the helical compression springs can bear indirectly on openings in the torque transmission flange and on openings in the guide washers by means of interfacing means positioned on the two coaxial parts, the interfacing means comprising for example spring seats placed at the ends of the helical compression springs.

The invention also relates, according to another of its aspects, to a transmission sub-assembly for a transmission of a motorized machine, comprising:.

The transmission sub-assembly according to this other aspect of the invention has the advantage that it can be pre-assembled in a factory before delivery to the customer.

The invention will be better understood on reading the following description, which is given solely by way of example and with reference to the appended drawings, in which:.

Hereinafter in the description and the claims, by way of non-limiting example and in order to facilitate understanding, the terms "front" and "rear" will be used according to the direction relative to an axial orientation determined by the main axis X of rotation of the transmission of the motor vehicle, and the terms "inner/internal" and "outer/external" will be used relative to the axis X and according to a radial orientation that is orthogonal to said axial orientation.

<FIG> illustrate a transmission <NUM> of a motorized machine of the industrial vehicle type incorporating the vibration damping device <NUM> according to a first embodiment of the invention.

The industrial vehicle comprises in particular an internal combustion engine, a gearbox incorporating a rotating electric machine (not shown) and a transmission sub-assembly <NUM> interposed between the internal combustion engine and the gearbox. The transmission sub-assembly <NUM> comprises:.

The transmission sub-assembly <NUM> has the advantage that it can be pre-assembled in a factory in kit form before delivery to the customer.

The vibration damping device <NUM> comprises a torque transmission flange <NUM> having an annular shape about an axis of rotation X, rotationally connected to the flywheel, guide elements <NUM> and helical compression springs <NUM>. The two guide elements <NUM>, also known as guide washers <NUM>, are positioned on either side of the torque transmission flange <NUM>, trapping the helical compression springs <NUM> in interposed housings. The guide washers <NUM> are fastened together to an intermediate hub <NUM> via rivets <NUM>. This architecture of the vibration damping device <NUM> is said to be "symmetrical" as the engine torque first enters the vibration damping device through the torque transmission flange <NUM>.

As illustrated in <FIG> and <FIG>, the coaxial parts <NUM> and <NUM> are rotationally mounted relative to each other against damping means including, here, helical compression springs <NUM>. The helical compression springs <NUM> bear directly on the openings <NUM> in the torque transmission flange <NUM> and on the openings <NUM> in the guide washers <NUM>.

The ends of the helical compression springs <NUM> are suitable for bearing on the lateral edges of the openings <NUM>, <NUM> in the annular flange <NUM> and the guide washers <NUM>. The helical compression springs <NUM> are distributed circumferentially about the axis X.

When the engine torque passes through the vibration damping device <NUM>, the angular displacement between the guide elements <NUM> and the torque transmission flange <NUM> varies and results in the compression of the helical compression springs <NUM>. The torque transmission flange <NUM> pivots around the intermediate hub <NUM>.

Each guide washer <NUM> is formed from a stamped metal sheet having a generally constant thickness and includes openings <NUM> for receiving springs <NUM> and an outer annular portion <NUM> suitable for guiding the springs <NUM> on the angular displacement of the annular flange <NUM> relative to the guide washers <NUM>.

Friction means <NUM>, <NUM> are further positioned between each of the guide washers <NUM> and the torque transmission flange <NUM>.

The helical compression springs <NUM> and the friction means <NUM>, <NUM> make it possible, as known per se, to absorb and damp the vibrations and rotational irregularities originating from the internal combustion engine.

In one variant (not illustrated), the helical compression springs <NUM> can bear indirectly on the openings <NUM> in the torque transmission flange <NUM> and on the openings <NUM> in the guide washers <NUM> by means of interfacing means positioned on the two coaxial parts <NUM> and <NUM>. More specifically, the interfacing means comprise spring seats placed at the ends of the springs <NUM> and recesses formed in the guide elements <NUM> and in the torque transmission flange <NUM>. The spring seats are suitable for interacting with the recesses formed in the guide elements <NUM> and/or the torque transmission flange <NUM> about a pivot connection.

According to the invention, the vibration damping device <NUM> comprises a connection disc <NUM> attached to the torque transmission flange <NUM> and fastened to the flywheel <NUM>. Fastening screws <NUM> screwed to the flywheel <NUM> apply a clamping force to the connection disc <NUM> so as to transmit the torque produced by the engine towards the gearbox.

As illustrated in <FIG>, the connection disc <NUM> comprises an even number of anchoring zones <NUM> uniformly angularly distributed about the axis X; more specifically, four anchoring zones <NUM> uniformly angularly distributed about the axis X at an angle of <NUM> degrees.

As illustrated in <FIG>, the connection disc <NUM> is fastened to the torque transmission flange <NUM> by means of a riveted connection comprising a series of rivets <NUM> positioned in the fastening orifices <NUM> in the disc and in the corresponding holes <NUM> in the torque transmission plate.

The engine torque enters the vibration damping device <NUM> via the connection disc <NUM> and leaves via a torque output hub <NUM> arranged centrally to the vibration damping device <NUM>. The torque output hub <NUM> is mounted on the driven shaft <NUM> of the gearbox (not shown) with rotational axis Y, and transmits the engine torque via teeth <NUM> formed on the inner bore thereof.

On each rotation of the engine, the crankshaft transmits axial and/or bending vibrations to the vibration damping device <NUM> by means of the flywheel <NUM>. The displacement measured on the outer periphery of the flywheel can then reach peak-to-peak values of the order of several millimetres.

As shown on <FIG>, following the assembly of the transmission of the motorized machine, axial and angular offsets can exist between the internal combustion engine output shaft with rotational axis X and the gearbox input shaft with rotational axis Y. The axial and angular offsets measured between the axes X and Y can in this case reach values of the order of one millimetre and/or one degree.

The main aim of the invention is therefore to provide an improved vibration damping device capable of compensating for the axial and angular tolerances and damping the axial displacement of the flywheel. The addition of an axial misalignment compensation device <NUM> between the flywheel and the transmission input shaft of the motorized machine with the vibration damping device <NUM> allows the torque output hub <NUM> to more easily follow the position of the driven shaft <NUM> of the gearbox.

The arrangement of the axial misalignment compensation device <NUM> according to the first embodiment of the invention will now be described in more detail with reference to <FIG>.

The axial misalignment compensation device <NUM> acting between the flywheel and the transmission input shaft comprises in particular the torque output hub <NUM> which is equipped with an external fluting <NUM> and radially arranged inside an internal fluting <NUM> of the intermediate hub <NUM>, both internal and external fluting splines <NUM>, <NUM> comprising involute flanks. The involute flank geometry ensures a greater mechanical fatigue strength and limits the wear between the internal and external splines. The internal and external splines <NUM>, <NUM> are rectilinear.

In order to ensure an axial misalignment compensation capacity between the flywheel and the transmission input shaft, the internal and external flutings <NUM>, <NUM> of the axial misalignment compensation device are encased one inside the other with a functional play J which is substantially uniformly distributed between the inner periphery of the fluting of the intermediate hub and the outer periphery of the fluting of the torque output hub (see <FIG>). The functional play is greater than a threshold value of <NUM>. The tolerance in the uniform distribution of the functional play is of the order of +/- <NUM>. The functional play applies to the external and internal diameters of the flutings.

More precisely, the functional play J is equal to the value of the maximal axial eccentricity E between the axis of the flywheel and the axis of the transmission input shaft multiplied by a coefficient K, with K between <NUM> and <NUM>. This dimensioning of the functional play is thus a function of the possible axial and angular eccentricity E between the axis of the flywheel and the axis of the input shaft of the transmission, e.g. a gearbox, the overlap length of the internal and external flutings which is generally between <NUM> and <NUM>, and the production tolerances of the internal and external flutings.

On a design basis complying with standard NF E22-<NUM>, the internal and external flutings <NUM>, <NUM> are determined from, inter alia, the following influential parameters: the number of teeth, the modulus corresponding to the pitch p divided by π, the nominal diameter D1, the pitch circle diameter d, the external diameter d2 and the pressure angle α. These parameters are also visible in <FIG>. Relative to standard dimensions, the internal fluting <NUM> or external fluting <NUM> according to the invention is locally thinned. In particular, the internal and external flutings <NUM>, <NUM> have a profile allowing mutual contact of several involute flanks at maximal axial eccentricity E of the torque output hub <NUM> relative to the intermediate hub <NUM>, with minimal spline base play Jmini in the direction of eccentricity, such that the minimal play Jmini is strictly greater than <NUM>. As illustrated in <FIG>, the minimal play Jmini in the direction of maximal axial eccentricity E is between the tooth tip of the external fluting <NUM> and the spline base of the internal fluting <NUM>.

Depending on application, the internal and external splines <NUM>, <NUM> of the axial misalignment compensation device may be protected by an anti-wear surface coating, for example a surface treatment of the nickel-plating type, or a heat treatment of the high-frequency surface hardening type.

In order to damp the dynamic movements coming from the flywheel wheel <NUM>, the axial misalignment compensation device <NUM> comprises an elastic element <NUM> for axially preloading the torque output hub <NUM> along the axis X against one of the guide elements <NUM>.

As illustrated in <FIG> and <FIG>, the elastic element <NUM> is axially inserted between one of the guide elements <NUM> and an axial retaining ring <NUM>, the axial retaining ring <NUM> being inserted in an annular groove 61a formed on the torque output hub <NUM>. Preferably, the elastic element <NUM> is a conical washer. As a variant, the elastic element <NUM> may be a corrugated washer.

To limit the wear on the elastic element, two flat load application washers <NUM> may be arranged on either side of the elastic element <NUM> and interposed between one of the guide elements <NUM> and the axial retaining ring <NUM>. The axial misalignment compensation device <NUM> comprises a friction interface zone <NUM> provided between a side flank 61b of the torque output hub <NUM> and a flat face 30b of one of the guide elements. Thus the torque output hub <NUM> is constantly pressed against one of the guide elements <NUM> and hence reduces the noise within the vibration damping device.

As a variant, the elastic element <NUM> may be axially inserted between one of the guide elements <NUM> and an axial rim of the torque output hub <NUM>.

With reference to <FIG> and <FIG>, a vibration damping device <NUM> according to a second embodiment of the invention will now be described, wherein the connection disc <NUM> is attached to the torque transmission plate via fastening zones which are angularly distributed around the axis X and arranged so as to be fastened to the flywheel via anchoring zones angularly distributed around the axis X, each anchoring zone being attached to at least two fastening zones by separate connecting arms.

As illustrated in <FIG>, the connection disc <NUM> comprises an even number of anchoring zones <NUM> uniformly distributed angularly about the axis X; more specifically, four anchoring zones <NUM> uniformly distributed angularly about the axis X at an angle of <NUM> degrees. The four anchoring zones <NUM> are identified by way of illustration by the dashed lines corresponding substantially to the bearing zone on the flywheel <NUM>.

In this example, each anchoring zone <NUM> of the connection disc <NUM> comprises several anchoring orifices <NUM> angularly offset to one another around the axis X. Each anchoring zone comprises three anchoring orifices <NUM> angularly offset by an angle of <NUM> degrees relative to the axis X.

According to further possible examples, the anchoring orifices in the same anchoring zone can be angularly offset from each other by an angle of between <NUM> and <NUM> degrees about the axis X.

As illustrated in <FIG>, the connection disc <NUM> comprises an even number of fastening zones <NUM> uniformly angularly distributed about the axis X; more specifically, six fastening zones <NUM> uniformly angularly distributed about the axis X at an angle of <NUM> degrees.

The six fastening zones <NUM> bear on the torque transmission flange <NUM> and each of the fastening zones <NUM> of the connection disc <NUM> comprises two fastening orifices <NUM>.

In this example, the number of anchoring zones <NUM> is smaller than the number of fastening zones <NUM>.

The torque transmission flange <NUM> comprises openings <NUM> for receiving helical compression springs <NUM>, the fastening zones <NUM> of the disc being angularly distributed between each receiving opening <NUM>. The distribution of the mechanical stresses within the disc is thus substantially uniform over the perimeter of the torque transmission plate.

In order to make the connection disc <NUM> axially flexible, each anchoring zone <NUM> is connected to at least two fastening zones by separate connecting arms <NUM>. The connecting arms <NUM> are separate from each other and transmit the torque to the torque transmission flange <NUM> independently.

The connecting arms <NUM> originating from different anchoring orifices <NUM> can intersect and be interleaved. The connection disc <NUM> comprises in particular apertures <NUM> formed by the interleaving of the connecting arms, which make the vibration damping device flexible. The anchoring zones <NUM> of the connection disc <NUM> associated with the flywheel <NUM> are positioned on an installation diameter D larger than the installation diameter d of the fastening zones <NUM> associated with the torque transmission plate <NUM>.

In this example, one of the anchoring zones <NUM> of the connection disc <NUM> associated with the flywheel <NUM> is offset by an angle A of <NUM> degrees relative to an axis X3 passing through two fastening zones <NUM> which are angularly opposite each other relative to the axis of rotation X. The effect of this offset of <NUM> degrees of this axis X3 is to increase the number of connecting arms <NUM> and increase the torque transmission capacity of the connection disc <NUM>. This effect also occurs when the angle A is between <NUM> and <NUM> degrees.

The connection disc <NUM> also comprises, in a plane P' perpendicular to the axis X, two axes X1, X2 of minimal bending stiffness, the axes X1, X2 of minimal bending stiffness being perpendicular to each other and one of the two axes X1 passing through two fastening zones <NUM> angularly opposite each other relative to the axis of rotation X. The axis X1 is not congruent with the axis X3. The axes X1, X2 of minimal bending stiffness correspond to preferred axes about which the disc <NUM> can deform in bending more easily. The stiffness can be measured by applying a load in Newtons in a direction perpendicular to the plane P' on the periphery of the disc, for example in the anchoring zones <NUM>. The stiffness is measured on the connection disc <NUM> only, i.e. when it is not assembled on the vibration damping device.

Advantageously, the connection disc <NUM> comprises, in a plane perpendicular to the axis of rotation X, two axes X1, X2 of symmetry perpendicular to each other. The two axes X1, X2 of symmetry perpendicular to each other correspond to the axes of minimal bending stiffness.

The connection disc <NUM> has a homogenous geometry of form, regularly distributed around the axis X. The distribution of mechanical stresses within the connection disc <NUM> is substantially uniform over the periphery of the torque transmission flange <NUM>.

Each connecting arm <NUM> comprises, in a plane P parallel to the axis X, a section of material having a thickness E and a width L such that the ratio L / E is greater than <NUM>.

The connection disc <NUM> is preferably made from a steel sheet, the thickness of which may be variable. According to one variant, the connecting arm <NUM> can comprise a variable thickness E over all or part of the extent of the connecting arm and/or a variable width L over all or part of the extent of the connecting arm.

Claim 1:
Vibration damping device (<NUM>) for a transmission of a motorized machine, comprising:
- a torque transmission flange (<NUM>);
- two guide elements (<NUM>) rotationally connected via an intermediate hub (<NUM>) coaxially along an axis of rotation (X) and positioned on either side of said torque transmission flange (<NUM>);
- helical compression springs (<NUM>) directly or indirectly bearing on the torque transmission flange and the guide elements;
- a connection disc (<NUM>) arranged so as to be fastened to a flywheel and fixedly connected on its internal periphery to the torque transmission flange (<NUM>) or to one of the guide elements (<NUM>);
and, characterized in that the vibration damping device comprises a device for compensating for axial misalignments (<NUM>) between the flywheel and a transmission input shaft, comprising at least one torque output hub (<NUM>) which is equipped with an external fluting (<NUM>) and radially arranged inside an internal fluting (<NUM>) of the intermediate hub (<NUM>), both internal and external fluting splines (<NUM>, <NUM>) comprising involute flanks.