EP1581752A2

EP1581752A2 - Flexible flywheel for torque transmission device

Info

Publication number: EP1581752A2
Application number: EP04700270A
Authority: EP
Inventors: Roel Verhoog
Original assignee: Valeo Embrayages SAS
Current assignee: Valeo Embrayages SAS
Priority date: 2003-01-06
Filing date: 2004-01-06
Publication date: 2005-10-05
Also published as: WO2004065807A3; KR20050086957A; FR2849683A1; JP4724110B2; KR101087884B1; BRPI0406461A; FR2849683B1; WO2004065807A2; DE112004000107T5; JP2006515048A

Abstract

The invention concerns a flexible flywheel for torque transmission device, in particular for a motor vehicle, comprising a radially internal annular element (26) including means for being fixed on an input shaft and linked through at least two diametrically opposite radial arms (28) to an annular mass (30), the radial arms (28) defining an oscillation axis (34) for the flywheel perpendicular to the axis of rotation and which has a predetermined angular position relative to the input shaft.

Description

FLEXIBLE FLYWHEEL FOR TORQUE TRANSMISSION DEVICE

The invention relates to a flexible flywheel for a torque transmission device, in particular for a motor vehicle, this flexible flywheel being intended to be driven in rotation about an axis by a driving shaft and comprising an annular mass carried by a flexible element intended to be fixed to the driving shaft.

In the case of a torque transmission device for a motor vehicle, the driving shaft is the crankshaft of an internal combustion engine, and the torque is transmitted to a driven element such as the input shaft of a gearbox for example, generally by means of at least one clutch and a torsional damper.

In certain embodiments, the flywheel is the primary flywheel of a double damper flywheel, which also includes a secondary flywheel centered and guided in rotation on the primary flywheel by means of a bearing, and a damper. torsional mounted generally between the two flywheels, the secondary flywheel forming the clutch reaction plate for transmitting a torque to the input shaft of a transmission.

In the current technique, the annular mass of a flexible flywheel is generally formed by a cast iron ring fixed by screws or rivets on the radially external periphery of a flexible annular sheet, the radially internal peripheral part of which comprises fixing screw passage holes on the driving shaft, that is to say on the crankshaft of an internal combustion engine in the case of a torque transmission device for a motor vehicle.

The flexible annular sheet has a relatively small thickness (of the order of 2 to 3 mm for example) and its radially internal peripheral part for fixing to the driving shaft is reinforced by a stiffening washer having a greater thickness and on which heads fixing screws can be supported. This thin annular sheet must be checked after cutting, possibly straightened and carefully assembled with the annular mass in cast iron. These operations are relatively long and delicate and are therefore expensive. It has been found that in operation, a flywheel of this type deforms in "pumping" bending (bending deformation in which the flexible flywheel remains substantially parallel to itself) and in oscillation around an axis which is perpendicular to the axis of rotation of the flywheel and which has a determined angular position relative to the crankshaft, this oscillation being linked to a bending of the last crankpin of the crankshaft. Known flexible flywheels are characterized by a structure with symmetry of revolution and are therefore not designed to take this oscillation phenomenon into account.

The invention particularly relates to a flexible steering wheel which meets this need and which does not have the drawbacks of the flexible steering wheels of the prior art.

To this end, it provides a flexible flywheel for a torque transmission device, in particular for a motor vehicle, intended to be driven around an axis of rotation by a drive shaft and comprising an annular mass carried by a flexible element intended to be fixed to the driving shaft, characterized in that this flexible element comprises radial arms defining a preferred axis of oscillation perpendicular to the axis of rotation of the flywheel.

The flexible flywheel according to the invention is therefore particularly designed to respond to the aforementioned oscillation phenomenon and to absorb it, at least in part, by decoupling from the shaft driving the flywheel oscillating around the preferred axis.

In practice, the radial arms of the flexible element can advantageously be formed by a local excess thickness of this flexible element. In other words, the flexible element has a greater thickness in its parts which form the radial arms, and it has a greater thickness. low in its other parts, this smaller thickness can be reduced and even canceled as soon as the radial arms have a thickness and a rigidity sufficient to ensure the transmission of the torque between the driving shaft and the driven shaft. The flexible element of the flexible steering wheel according to the invention can then be formed from a thicker sheet than in the prior art, which can be of a lower quality and which does not need pretreatment, which is more easy to work, which deforms less and which does not need to be straightened, so that the steering wheel according to the invention is less expensive than in the prior art.

This also makes it possible to manufacture the flexible element in a single piece with the annular mass, in particular of cast iron of a quality resistant to the flexural and torsional stresses, which avoids all the problems and drawbacks associated with the separate manufacture of the annular mass and the flexible element and their assembly.

According to other characteristics of the invention, the axis of oscillation is formed by two radial arms which extend in line with one another substantially between the axis of rotation and the annular mass of inertia or else three radial arms, two of which are symmetrical to each other with respect to the extension of the third, these three radial arms each extending between the axis of rotation and the annular mass.

In a first embodiment, the flexible element is formed of a disc having symmetrical recesses formed on either side of the axis of oscillation. These recesses can be through or not.

When the flexible element is not formed in one piece with the annular mass, it is fixed to the latter by screws, rivets or the like, at the ends of the above-mentioned radial arms.

The flexible element can be formed either of a single sheet metal element of a desired thickness, or of several flat elements superimposed and fixed together on the annular mass. According to another characteristic of the invention, the flexible flywheel comprising hysteresis means carried by the flexible element and cooperating by friction with the annular mass.

In one embodiment, these hysteresis means comprise two radial arms extending perpendicular to the axis of oscillation and having radially internal ends integral with the flexible element and radially external ends in contact with the annular mass.

The radial arms of the hysteresis means are formed in one piece with the flexible element or, as a variant, are part of a washer attached to the flexible element, this washer being intended to be fixed with the flexible element. on the leading tree.

In another embodiment, the hysteresis means comprise elastic pins mounted in semi-cylindrical housings with two lugs secured to the flexible element and two lugs secured to the annular mass, these lugs extending in one direction perpendicular to the above-mentioned axis of oscillation.

According to yet another characteristic of the invention, the radial arms which define the axis of oscillation comprise, between their radially internal and radially external ends, cutouts or notches for locating maximum stresses.

This removes the maximum stresses from the areas of attachment or connection of the radial arms to the annular mass.

The aforementioned radial arms may extend perpendicular to the axis of rotation or may be slightly inclined obliquely relative to a perpendicular to the axis of rotation, for example in a direction opposite to the shaft leading from their ends radially internal.

According to yet another characteristic of the invention, the flexible element comprises means defining a second axis of oscillation which is perpendicular to the axis of rotation and to the first axis of oscillation mentioned. The two axes of oscillation are defined by radial arms of the flexible element. In a particular embodiment of the invention, these radial arms are connected to the annular mass by tongues which have different stiffnesses depending on whether they connect to the annular mass the radial arms defining the first axis of oscillation or those defining the second axis of oscillation.

The flexible flywheel according to the invention can in particular form the primary flywheel of a double damper flywheel which also comprises a secondary flywheel intended to be connected to the input shaft of a transmission by a clutch and a shock absorber of torsion mounted between the two flywheels.

In one embodiment of the invention, the torsion damper is of the type comprising springs oriented radially with respect to the axis of rotation, in the rest position of the double damping flywheel.

The hysteresis means associated with the flexible primary flywheel advantageously comprise an elastic washer which is carried by the flexible element of the primary flywheel and which comes to bear on the latter, or else which is mounted between the flexible element of the primary flywheel and the annular mass carried by this flexible element.

The invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, given by way of example with reference to the appended drawings in which: FIG. 1 is a schematic front view of a flexible steering wheel according to the invention; - Figure 2 is a schematic view in axial section of the steering wheel of Figure 1; Figures 3 and 4 are views similar to Figures 1 and 2, for an alternative embodiment of the flexible steering wheel; Figures 5 and 6 are views similar to Figures 1 and 2 for another alternative embodiment; Figure 7 is a schematic view in axial section of another alternative embodiment of the flexible flywheel; Figure 8 is a schematic perspective view of the steering wheel of Figure 7; - Figures 9 and 10 are views similar to Figures 1 and 2 for another alternative embodiment of the invention;

FIG. 11 schematically represents an arrangement of consecutive flexible elements in a sheet metal strip before cutting;

Figure 12 is a schematic elevational view of another alternative embodiment of the flexible flywheel;

Figure 13 is a schematic perspective view of the steering wheel of Figure 12;

Figure 14 is a schematic front view of another alternative embodiment of the flexible steering wheel; - Figures 15 and 16 are schematic sectional views along lines XV-XV and XVI-XVI respectively of Figure 14;

Figure 17 is a schematic front view of yet another alternative embodiment of the flexible steering wheel;

Figures 18 and 19 are schematic views in axial section in two perpendicular planes of the steering wheel of Figure 17;

Figure 20 is a schematic front view of yet another alternative embodiment of the flexible steering wheel;

Figure 21 is a partial schematic view in axial section, on a larger scale, of the steering wheel of Figure 20; - Figure 22 is a schematic front view of another alternative embodiment of the flexible steering wheel on the invention;

Figure 23 is a schematic view in axial section of a double damping flywheel according to the invention;

Figure 24 is a schematic half-view in axial section of an alternative embodiment of the double damping flywheel; Figures 25 and 26 are schematic views in axial section of two other alternative embodiments of the double damping flywheel according to the invention;

Figure 27 is a schematic view of the steering wheel of Figure 1 describing its positioning relative to the drive shaft.

Reference is first made to FIGS. 1 and 2 in which a first embodiment of a flexible flywheel according to the invention is shown diagrammatically. This flexible flywheel, generally designated by the reference 10, is intended for the transmission of a torque between a driving shaft 12 which is the crankshaft of an internal combustion engine of a motor vehicle, and a driven shaft (not shown) which is the input shaft of a gearbox for example, and which is intended to be mounted integral in rotation with a hub 14 of a torsional damper coaxial with the flywheel 10 and the driving shaft 12 .

The hub 14 of the torsion damper is, in known manner, connected by a clutch E to the flywheel 10, a radial face 16 oriented on the side opposite to the drive shaft 12 forms a friction surface cooperating with the disc clutch 18 of clutch E.

The flywheel 10 according to the invention is fixed at the end of the driving shaft 12 by screws 20, oriented parallel to the axis 22 of rotation of the shaft 12 and of the flywheel 10, and distributed evenly in circle around this axis 22. The screws 20 are received in orifices 24 of a radially internal annular part 26 of the flywheel 10, this annular part 26 being connected by two radial arms 28 diametrically opposite to an annular mass 30 which surrounds the annular part 26 and whose external cylindrical periphery carries ignition targets 32. In this embodiment, the annular part 26, the radial arms

28 and the annular mass 30 are formed in a single piece of cast steel of a quality resistant to bending stresses, for example in spheroidal graphite cast iron.

The arms 28 are not exactly perpendicular to the axis of rotation 22, but are inclined slightly obliquely and extend towards the clutch from the annular part 26. This makes it possible to increase the axial stiffness of the flywheel which resists better with declutching efforts, and increase the pumping frequency.

The radial arms 28 have dimensions in width and in thickness which make it possible to transmit the maximum torque generated by the internal combustion engine of the motor vehicle.

They also define an axis of oscillation 34 which is perpendicular to the axis of rotation 22 and whose angular position around this axis is determined relative to the drive shaft 12 and is known by measurement or by calculation (the position angular of the flywheel 10 relative to the driving shaft 12 being itself fixed and determined for mounting by appropriate means).

The annular part 26 and the radial arms 28 of the flywheel define a flexible element, similar to the flexible annular sheet of a flexible flywheel of the prior art, allowing deformations of the flywheel in bending (the annular mass 30 then moving parallel to itself).

The radial arms 28 of the flywheel 10 also allow an oscillation of this flywheel about the axis 34, this oscillation being linked to a bending of the last crankpin of the crankshaft forming the driving shaft 12. The section of the radial arms 28 is determined for example to allow this oscillation phenomenon at a vibration frequency of the crankshaft which corresponds to a rotation speed of approximately 2700 to 4500 revolutions per minute.

In one embodiment of the invention, the diameter of the friction is 220 mm, the radial arms 28 have a cross section of oblong or substantially rectangular shape with rounded ends, the flywheel of inertia is made of spheroidal graphite cast iron having a breaking strength of the order of 500 MPa and the radial arms 28 have a thickness of 6 to 10 mm for a width of 30 to 40 mm. The radii of the connections 36 of the radial arms to the annular mass 30 are determined to reduce the stress concentrations and are for example approximately 8 mm.

The damping in spheroidal graphite cast iron is approximately three or four times greater than the damping in steel.

In the embodiment shown in Figures 3 and 4, the axis of oscillation 34 of the flywheel 10 is defined by a radial arm 28 identical to those already described and by two other radial arms 40 which are symmetrical one on the other relative to the axis 34 and which extend in directions substantially opposite to that of the radial arm 28 relative to the axis of rotation 22, these radial arms 40 making an angle of about 140 degrees with the radial arm 28 in the example shown.

These two radial arms 40 are a little easier to foundry than a single radial arm 28 and can also reduce the problems of molding shrinkage.

For the rest, the structure of the flywheel 10 shown in FIGS. 3 and 4 is identical to that of the flywheel in FIGS. 1 and 2.

In the embodiment of FIGS. 5 and 6, the flywheel 10 is of the type shown in FIGS. 1 and 2 and is associated with hysteresis means making it possible to dampen the oscillations of the flywheel around the defined axis 34 by the radial arms 28. These hysteresis means comprise an elastic washer 42 of annular shape, made for example of spring steel and intended to be fixed on the end of the aforementioned driving shaft at the same time as the annular part radially internal 26 of the flywheel. For this purpose, the elastic washer 42 has orifices 44 coinciding with the orifices 24 formed in the annular part 26 for the passage of the fixing screws 20, and its internal diameter is substantially equal to that of the annular part 26 of the flywheel.

This elastic washer 42 comprises two diametrically opposite radial arms 46, which extend in a direction perpendicular to the axis of oscillation 34 and whose radially external ends 48 are bent parallel to the axis to come to apply pressure on the internal cylindrical surface 50 of the annular mass 30.

Under these conditions, in operation, any oscillation of the annular mass 30 around the axis 34 results in friction on the folded ends 48 of the arms of the elastic washer 42 secured to the radially internal annular part 26 of the flywheel .

In an alternative embodiment, the ends 48 of the arms 46 extend through small orifices formed in a veil connecting the annular part 26 to the annular mass 30. In the embodiment of FIGS. 7 and 8, the flywheel inertia 10 according to the invention is formed of two independent elements which are fixed to each other, namely a flexible element 52 made of sheet steel and an annular mass of inertia 30 made of cast iron, the element flexible 52 being of generally annular shape and being fixed at its radially outer periphery to the mass of inertia 30 by screws 54, rivets or the like.

The flexible element 52 comprises a radially internal annular part 56, formed with holes 58 for the passage of the fixing screws on the end of the driving shaft, a radially external annular part 60 comprising holes for the passage of the fixing screws 54 on the annular mass 30, and two radially opposite radial arms 62, which connect the annular parts 56 and 60 together.

Preferably, the flexible element 52 is formed of an annular washer in which two diametrically opposed cutouts 64 are formed, substantially in the shape of a bean, which define between them the radial arms 62. Typically, the flexible element 52 is formed from a steel sheet which has a thickness considerably greater than that of the steel sheets forming the flexible elements of the flexible flywheels of the prior art, this thickness being for example of around 5 mm. This thickness reduces the risks of deformation of the sheet during its machining and facilitates and simplifies the manufacture of the flexible element 52.

As before, the axis of oscillation of the flywheel is defined by the diametrical axis of symmetry of the radial arms 62.

In the alternative embodiment of FIGS. 9 and 10, the flexible element 72 of the flywheel 10 according to the invention is essentially formed by an internal annular part 74 which includes the orifices 76 for the passage of the fixing screws on the end of the driving shaft, of two radial arms 78 of the aforementioned type which define the axis of oscillation of the flywheel and which have radial extensions 80 towards the outside, these extensions 80 forming fixing zones on the annular mass 30 and comprising for this purpose holes for fixing screw 82, rivets or the like.

Notches or cutouts 84 are formed in the sides of the radial arms 78, in order to constitute zones for locating maximum stresses and to separate these maximum stresses from the orifices for the passage of screws 82.

FIG. 11 schematically represents a succession of flexible elements such as the element 52 of FIGS. 7 and 8, and the outer peripheral edge 86 of which has a notch 88 and a point 90 diametrically opposite, this point and this notch making it possible to nest partially in each other the flexible elements 52 during their formation in a sheet metal strip.

As shown in FIG. 11, the tip 90 of an element 52 extends inside the notch 88 of the next element 52 and so on. To save space and therefore material, the tip 90 of each flexible element 52 is itself formed by two curved notches 92 formed in the radially external annular part 60 of the flexible element. In the embodiment of Figures 12 and 13, the flexible element of the flywheel 10 according to the invention is of the same type as the flexible element 72 of Figures 9 and 10 and is associated with hysteresis means formed by an elastic element 96 in the shape of a cross, which extends in a plane perpendicular to the axis of rotation and which is applied to the element 72. This elastic element 96 comprises two radially opposite radial arms 98, which have the same forms that the radial arms 78 of the flexible element 72 and which are superimposed on the latter and two other radial arms 100 perpendicular to the radial arms 98 and having a radially external end 102 supported on a radial face of the inertia mass 30 for generate a damping by radial friction during the oscillations of the flywheel around the axis defined by the radial arms 78 and 98.

The elastic element 96 is fixed at the ends of its radial arms 98 to the annular mass 30 by the screws 82 for fixing the flexible element 72, and its radially internal annular part includes orifices 104 for passage of the steering wheel fixing screws. of inertia on the leading tree.

In this embodiment, the flexible element 72 can be formed by a stack of elongated flat elements made of thin sheet, and the elastic element 96 is part of the stack.

In the embodiment of FIGS. 14, 15 and 16, the flywheel 10 is made in one piece, for example of cast iron, and its radially internal annular part 26 is connected to the annular mass 30 by two radial arms 28 diametrically opposite, similar to those of the embodiment of FIGS. 1 and 2, and by an annular web 108 of relatively small thickness, which occupies the entire space between the annular part 26, the annular mass 30 and the radial arms 28. The flexible element of the steering wheel is then a ring comprising local excess thicknesses forming the radial arms 28.

For the rest, this flywheel has the same structure as that of FIGS. 1 and 2. In the embodiment of FIGS. 17 and 19, the flexible flywheel 10 comprises an annular mass 30 in cast iron and a flexible element of the type shown. Figures 9 and 10, this flexible element being formed of a stack of identical elements 72 made of thin sheet.

As in the embodiment of Figures 9 and 10, this flexible element is fixed to the annular mass 30 by screws 82, rivets or the like at the ends 80 of its radial arms 78 defining the axis of oscillation.

As best seen in FIG. 19, the stack of identical elements 72 is applied to a thin annular sheet 110 fixed to the annular mass 30 by the screws 82 for fixing the flexible elements 72, the periphery of this thin annular sheet 110 being supported on a radial face of the annular mass 30 and thus constituting hysteresis means for damping the flexions and oscillations of the flywheel. The stacked elements 72 can have different thicknesses, greater in the middle of the stack than at its ends, to equalize the bending stresses. The hardnesses of the stacked elements can also be different.

In the embodiment of Figures 20 and 21, the flexible flywheel 10 is made in one piece and comprises a radially internal annular part 26 connected by two radial arms 28 diametrically opposite an annular mass 30, as in the modes of embodiment already described, and further comprises two radial lugs 112 which are oriented perpendicular to the axis of oscillation 34 defined by the radial arms 28, and which extend from the annular part 26 towards the annular mass 30. This this also includes two radial lugs 114, oriented towards the annular part 26 from the internal cylindrical surface of the annular mass 30, the radial lugs 112 and 114 being aligned in pairs and ending in semi-cylindrical housings oriented towards each other and in which are housed means such as elastic pins 116 forming hysteresis means for damping the oscillations of the flywheel around the axis 34. More generally, the hysteresis means comprise intermediate elements mounted between the part annular 26 and the annular mass 30, in a direction perpendicular to the axis 34. In the embodiment of FIG. 22, the flexible flywheel 10 comprises a radially internal annular part formed with orifices 24 for passage of the fixing means on the driving shaft and with four radial arms 28 of the aforementioned type, which are oriented 90 degrees from each other and which are connected at their ends radially ex dull to the annular mass 30 by elastically deformable tongues 120, 122 which extend in a plane perpendicular to the axis of rotation and which are fixed at their ends to the radial arms 28 and to the annular mass 30 by screws, rivets or the like.

In the embodiment shown, each tongue 120, 122 is of elongated shape and extends in a direction substantially perpendicular to the radial arm 28 on which it is fixed.

Two axes 34, 124 of oscillation of the flexible flywheel are thus defined which are perpendicular to the axis of rotation and perpendicular to each other, one of these axes of oscillation corresponding to the above-mentioned axis 34 and the other 124 itself. being perpendicular.

The tongues 120 fixed to the radial arms 28 defining the axis of oscillation 124 have a stiffness less than that of the tongues 122 fixed to the radial arms 28 defining the axis of oscillation 34. This makes it possible to have two frequencies of oscillation around of two perpendicular axes which are each in a determined angular position relative to the driving shaft. The oscillation around the axis 34 is characterized by a low stiffness and therefore by a low frequency, while the oscillation around the axis 124 is characterized by a greater stiffness and therefore by a higher frequency. The same result can be achieved by having different masses generating different inertias on the two oscillation axes 34 and 124. When the masses placed on an oscillation axis are larger, the oscillation frequency is lower around the axis perpendicular to this axis of oscillation. It is of course possible to combine these two means, that is to say to differentiate the stiffnesses of the tongues 120 and 122 and the masses disposed on the axes of oscillation.

One can also, as a variant, connect the arms 28 on the axis 124 by two tongues 120 to the annular mass 30 and not have tongues 122, the tongues 120 helping to transmit the torque.

In the embodiments of FIGS. 23 to 26, the flexible flywheel according to the invention forms part of a double damping flywheel and forms the primary flywheel thereof.

In FIG. 23, the flexible primary flywheel 10 comprises a radially internal annular part 26 forming a hub, to which is fixed by rivets 130 the radially internal part of a flexible annular sheet 132 whose radially external periphery is fixed by axial clamping on a annular mass 30 formed of two cylindrical rings 134, 136, welded one inside the other, the external periphery of the annular sheet 132 being clamped between an axial end of the internal ring 134 and an end flange of the outer ring 136.

Hysteresis means are associated with this flexible annular sheet and are formed by an elastic washer 138 whose radially outer periphery is clamped with the radially outer periphery of the annular sheet 132 between the rings 134 and 136 as indicated, and whose radially internal annular part comprises radial lugs 140 which are applied elastically to the flexible annular sheet 132.

The flexible primary flywheel 10 is associated with a secondary flywheel 142 which is centered and guided in rotation on the hub 26 by means of a plain bearing 144 and which forms the reaction plate of a clutch of a conventional type.

A torsional damper 146 with circumferential springs is mounted between the two flywheels and connects them in rotation with a possibility of angular movement between them, for the absorption of vibrations and torque irregularities.

This torsional damper conventionally comprises an input element which is integral in rotation with the primary flywheel 10 and an output element which is integral in rotation with the secondary flywheel 142, the input element here being fixed by rivets 148 on the elastic washer 138 while the outlet element is fixed by rivets 150 on the secondary flywheel.

A torque limiter is formed by the axially clamped mounting of the external periphery of the annular sheet 132 between the rings 134 and 136 of the annular mass 30, this axial clamping allowing relative rotation of the annular sheet 132 relative to the washer. elastic 138 when the transmitted torque is greater than a predetermined maximum value.

In the variant embodiment shown in FIG. 24, which is a half-view in axial section of a flexible primary flywheel for a double shock-absorbing flywheel, the primary flywheel 10 comprises a flexible annular sheet 152 whose radially internal part is fixed by means of screw 154 on the end of the shaft leading at the same time as a cylindrical hub forming the internal annular part 26 of the flexible flywheel, and the radially external annular part of this sheet 152 is fixed by rivets 156 on an annular mass 30 cast. This annular mass 30 carries a starter ring as well as a closing plate 158 on the side opposite to the driving shaft, this plate 158 being fixed to the annular mass 30 by rivets 160 and comprising an internal peripheral rim 162 oriented radially and disposed in the vicinity of the flexible annular sheet 152.

An elastic washer 164 is mounted between the flexible annular sheet 152 and the flange 162 of the closure sheet 158 and forms hysteresis means for damping the bending vibrations of the primary flywheel 10.

In the variant embodiments of FIGS. 25 and 26, the double damping flywheel shown in axial section comprises a flexible primary flywheel 10 according to the invention, a secondary flywheel 170 formed by two annular parts 172 and 174 connected together by a torque limiter 176, a bearing 178 for centering and guiding in rotation the secondary flywheel 170 on a cylindrical hub formed by the radially internal annular part 26 of the primary flywheel 10, and a torsion damper 180 which is mounted between the two flywheels and which is of the radial or radial spring type.

In known manner, the springs 182 of this torsion damper are guided on cylindrical rods 184 housed in cylindrical boxes 186, which are pivotally mounted at their radially external ends on the annular mass 30 of the primary flywheel around a parallel axis 188 to the axis of rotation, while the radially internal ends of the cylindrical rods 184 are pivotally mounted on the internal annular part 174 of the secondary flywheel 170 by means of axes 190 parallel to the axis of rotation. The annular mass 30 of the primary flywheel comprises blocks 192 of cast iron, housed between the cylindrical boxes 186 of the springs of the torsion damper and having a substantially triangular shape with apex oriented towards the axis of rotation to allow angular movement of the boxes. cylindrical around their axes 188 of articulation on the annular mass 30. The masses of the blocks 192 can be distributed on the two perpendicular axes of oscillation 34 and 124, as described with reference to FIG. 22.

The blocks 192 are fixed by rivets 194 to a sheet 196 of the annular mass 30 of the primary flywheel, at the same time as the radially external part of the flexible annular sheet 132 of the primary flywheel.

An elastic washer 198 is mounted between the annular sheet 132 and a radial flange 200 of the aforementioned sheet 196, on the side of the primary flywheel facing the driving shaft. This elastic washer forms means for damping the flexural vibrations of the primary flywheel.

The embodiment shown in FIG. 26 differs from that of FIG. 25 only by the constitution of the blocks 192 carried by the primary flywheel, which here consist of an axial stack of sheets 202 fixed by the aforesaid rivets 194 on the sheet. 196 of the primary flywheel, at the same time as the radially external peripheral part of the flexible annular sheet 132.

For the rest, the structure is identical to that already described with reference to FIG. 25.

Referring to Figure 27, we will now describe in more detail the positioning of a flexible flywheel according to the invention on the drive shaft.

The driving shaft 12 is generally a crankshaft comprising at least one crankpin 1200,1201 capable of being connected to at least one connecting rod (not shown) associated with a piston of a heat engine. The crank pin called first crank pin 1200 is adjacent to the flexible flywheel 10 according to the invention. The crankpin 1200 defines in association with the axis of rotation 22 of the driving shaft and the flexible flywheel 10 a plane P. As we have seen previously, the axis of oscillation 34 of the flexible flywheel 10 according to the invention is substantially perpendicular to the axis of rotation 22 and it is positioned angularly with respect to the driving shaft 12. This angular position is determined between the plane P previously described and the axis of oscillation 34 which then have a positioning angle α between them.

The value of the positioning angle α is optimized in order to allow a reduction of the stresses in the driving shaft and / or of the noises generated by the motor. The value of the positioning angle α is determined by measurement or by calculation. This value is a function of the number of cylinders of the thermal engine considered as well as of the arrangement of said cylinders. This value is also a function of the phenomenon or phenomena for which a reduction is sought (essentially the constraints and the noises). On the other hand, the value of the positioning angle α is measured in a direction of rotation R of the shaft leading from the plane P to the axis of oscillation 34 of the flexible flywheel 10 along the invention.

For example, when the axis of oscillation 34 is close to a perpendicular to the plane P (that is to say the value of the positioning angle α is equal to approximately 90 °), this position then allows a reduction of stresses in the crankshaft mainly.

It has been observed that, in a heat engine, the maximum pressure exerted on a piston head is situated while the crank pin carrying said piston makes an angle with the vertical of the order of approximately 15 ° to 20 ° in the direction of rotation, that is to say an angle appreciably greater than the so-called explosion angle (angle with the vertical that the crank pin takes at the time of the explosion). An offset in the direction of rotation of the shaft leading on the order of approximately 15 ° to 20 ° of the flexible flywheel 10 according to the invention makes it possible to reduce noise.

Thus, the value of the positioning angle α can be between approximately 80 ° and approximately 120 °. This makes it possible to weight the reduction in noise generated compared to the reduction in stresses and vice versa. Advantageously, the value of the positioning angle α can be between approximately 90 ° and around 110 °.

Advantageously, for a value of the positioning angle α of around 90 °, the stresses are reduced, while for a value of the positioning angle α of around 110 °, the noise generated is reduced.

The intermediate values of the positioning angle α make it possible to adapt the stress and noise reductions generated as a function of what is sought in this material.

Claims

1) Flexible flywheel for torque transmission device, in particular for a motor vehicle, intended to be driven around an axis of rotation (22), by a driving shaft (12) and comprising an annular mass (30) carried by a flexible element intended to be fixed to the driving shaft, characterized in that the flexible element comprises radial arms (28) defining a privileged axis of oscillation (34) perpendicular to the axis of rotation (22) of the steering wheel.

2) Steering wheel according to claim 1, characterized in that the oscillation axis (34) has a predetermined angular position relative to the driving shaft (22).

3) Steering wheel according to claim 1 or 2, characterized in that the radial arms (28) extend between the axis of rotation (22) and the annular mass (30).

4) Steering wheel according to one of the preceding claims, characterized in that the oscillation axis (34) is formed by two radial arms extending in extension of one another, between the axis of rotation and the annular mass (30).

5) Steering wheel according to one of claims 1 to 3, characterized in that the oscillation axis (34) is formed by three radial arms (28, 40), two of which are symmetrical with respect to one another to the extension of the third radial arm (28). 6) Steering wheel according to one of the preceding claims, characterized in that said flexible element is of annular shape and has recesses (64) on either side of the axis of oscillation.

7) Steering wheel according to claim 6, characterized in that the recesses (64) are through. 8) Steering wheel according to one of the preceding claims, characterized in that said flexible element is formed in one piece with the annular mass (30).

9) Steering wheel according to one of the preceding claims, characterized in that said flexible element is made of cast iron.

10) Steering wheel according to one of claims 1 to 8, characterized in that said flexible element is made of steel.

11) Steering wheel according to claim 10, characterized in that said flexible element is a separate piece and is fixed to the annular mass (30) by screws (54, 82), rivets or the like at the ends of the above-mentioned radial arms.

12) Steering wheel according to claim 10 or 11, characterized in that said flexible element is formed of several flat elements (72) superimposed and fixed together on the annular mass (30). 13) Steering wheel according to one of the preceding claims, characterized in that the radial arms (38) defining the oscillation axis (34) are connected at their radially internal ends to a central ring (26), comprising orifices ( 24) passage of fixing means on the driving shaft. 14) Steering wheel according to one of the preceding claims, characterized in that it comprises hysteresis means (42, 100, 102, 110) carried by the flexible element and cooperating by friction with the annular mass (30).

15) Steering wheel according to claim 14, characterized in that the hysteresis means comprise two radial arms (42) extending perpendicular to the axis of oscillation (34) and having radially internal ends integral with the flexible element and radially outer ends (48) in contact with the annular mass (30).

16) Steering wheel according to claim 15, characterized in that the radial arms of the hysteresis means are part of the flexible element. 17) Steering wheel according to claim 16, characterized in that the flexible element (72) comprises a stack of flat elements and the radial arms (100) of the hysteresis means are formed on an element (96) of this stack. 18) Steering wheel according to claim 15, characterized in that the radial arms of the hysteresis means are part of a washer (42) attached to the flexible element.

19) Steering wheel according to claim 18, characterized in that said washer (42) is intended to be fixed with the flexible element on the driving shaft.

20) Steering wheel according to claim 14, characterized in that the hysteresis means comprise intermediate elements mounted between the annular mass (30) and an internal annular part (26) of the flexible element, in a direction perpendicular to the privileged axis (34). 21) Steering wheel according to claim 14, characterized in that the hysteresis means comprise elastic pins (116) mounted in semi-cylindrical housings of two legs (112) integral with the flexible element and two legs (144) integral with the annular mass (30), said tabs extending in a direction perpendicular to the axis of oscillation (34).

22) Steering wheel according to one of the preceding claims, characterized in that the radial arms (78) defining the axis of oscillation comprise, between their radially internal and radially external ends, cutouts or notches (84) for locating stresses maximum.

23) Steering wheel according to one of the preceding claims, characterized in that the radial arms (28) defining the axis of oscillation (34) are slightly inclined obliquely relative to a perpendicular to the axis of rotation in a direction opposite the shaft leading from their radially inner end. 24) Steering wheel according to one of the preceding claims, characterized in that said flexible element comprises means (28) defining a second axis of oscillation (124) perpendicular to the axis of rotation (22) and to the preferred axis of oscillation (34), the second axis of oscillation (124) having a stiffness greater than that of the preferred axis (34).

25) Steering wheel according to claim 24, characterized in that the two axes of oscillation (34, 124) are defined by radial arms (28) of the flexible element. 26) Steering wheel according to claim 25, characterized in that said radial arms (28) are connected to the annular mass (30) by tongues (120, 122).

27) Steering wheel according to claim 26, characterized in that the tongues (120) connecting two radial arms aligned with the annular mass (30) have a stiffness different from that of the tongues (122) connecting the other two radial arms 28 to the mass annular (30).

28) Steering wheel according to one of the preceding claims, characterized in that it forms the primary flywheel of a double damping flywheel also comprising a secondary flywheel (142, 170) intended to be connected to the input shaft of a transmission and a torsional damper (146, 180) mounted between the two flywheels.

29) Steering wheel according to claim 28, characterized in that the torsion damper (180) is of the type comprising springs (182) oriented radially at rest.