FR2858674A1 - Double flywheel damper for motor vehicle, has vibration damper that is mounted between coaxial primary and secondary flywheels, where vibration damper has flexible annular sheet plate that damps axial oscillations of primary flywheel - Google Patents

Abstract

The flywheel damper has a vibration damper (12) that is mounted between coaxial primary and secondary flywheels (10, 14), and fixation screw (40) connected to the flywheel (14). The primary flywheel is axially flexible, and has an annular sheet plate (20) carrying an inertial mass. The vibration damper has another annular sheet plate (50) that damps the axial oscillations of the primary flywheel.

Description

i

  The invention relates to a double damping flywheel, in particular for a motor vehicle, of the type comprising two coaxial flywheels, a bearing for centering and guiding in rotation of a second flywheel on the first flywheel, and a torsion damper for elastically deformable elements such as springs, this torsion damper comprising input means connected to the first flywheel and output means connected to the second flywheel.

  In the known art, the torsion damper makes it possible to filter the rotational vibrations and irregularities of torque transmitted by the output shaft of an internal combustion engine of a motor vehicle and is carried by the primary flywheel which is in general relatively massive and rigid.

  It has also been proposed in which the primary flywheel is of the flexible type and comprises a flexible annular plate fixed at its inner periphery on the output shaft of the internal combustion engine of the vehicle, and an annular mass of inertia which is carried by the radially outer circumferential portion of this flexible annular sheet and which carries or constitutes itself the input means of the torsion damper.

  This has the consequence that the axial stiffness of the flexible primary flywheel varies as a function of the transmitted torque, which is detrimental to the filtering of the axial or bending vibrations transmitted by the output shaft of the motor. The object of the invention is in particular to provide a simple, effective and inexpensive solution to this problem.

  To this end, it proposes a double damping flywheel, in particular for a motor vehicle, comprising two coaxial flywheels, a centering and rotational guiding bearing of a second flywheel on a first wheel, and a torsion damper. with elastically deformable elements such as springs, comprising input means connected to the first flywheel and output means connected to the second flywheel, the first flywheel being axially flexible and comprising a first flexible annular plate carrying an annular mass of inertia, characterized in that the torsion damper comprises a second flexible annular sheet 5 which forms on the one hand the input means of the torsion damper and on the other hand means for damping the axial oscillations of the first flywheel.

  Thus, in the double damping flywheel according to the invention, it is the particular structure of the torsion damper which allows damping of the vibrations and axial flexures of the flexible primary flywheel and which decouples the filtering of these vibrations and axial flexions. filtering of rotating vibrations and irregularities of torque.

  According to another characteristic of the invention, said second flexible annular sheet carries the elastically deformable means of the torsion damper.

  In a preferred embodiment of the invention, a third annular sheet is fixed on the radially outer portion of the second annular sheet and cylindrical box hinge means containing the springs of the torsion damper are carried by the second and third annular sheets.

  In an alternative embodiment, the elastically deformable elements of the torsion damper are circumferentially disposed springs housed in windows of the second and third annular plates and cooperating with an annular web integral in rotation with the secondary flywheel.

  According to another characteristic of the invention, the second and third annular sheets are fixed to each other by means such as rivets and one of these fixing means cooperates with an orifice of the first annular sheet to the angular positioning of the torsional damper 30 on the primary flywheel.

  In an alternative embodiment, the fastening means of the second and third annular sheets also form means for fixing the torsion damper on the flexible primary flywheel.

  In another embodiment, the aforementioned second annular plate is fixed to the primary flywheel by fixing means of the primary flywheel on the output shaft of the engine.

  In this case, the fastening means are preferably screws distributed around the bearing support and centering of the secondary flywheel on the primary flywheel.

  In yet another alternative embodiment, the second flexible annular sheet 10 is integral in rotation with the primary flywheel by axial elastic clamping and forms with it a torque limiter.

  According to other features of the invention, the torsion damper comprises a set of friction means which are carried by a thin cylindrical sheet integral with the aforementioned second annular plate 15 and which bear axially on a rim of this sheet. cylindrical thin and include integral washers in rotation of the secondary flywheel.

  These washers are part of an annular element centered on the thin cylindrical sheet and which receives hinge pins on the secondary flywheel of cylindrical rods for guiding and compressing the springs of the torsion damper, when this is of the "radial" type.

  The aforementioned thin cylindrical sheet extends axially between the two flywheels.

  It advantageously comprises at one end an annular flange applied to the second annular sheet and fixed thereto by fixing means such as rivets.

  Alternatively, the thin cylindrical sheet has at one end an annular flange which is applied to the flexible annular sheet of the first wheel and which is fixed thereto by fastening means such as rivets.

  Advantageously, this thin cylindrical sheet is centered on the bearing support and centering of the secondary flywheel.

  According to yet another characteristic of the invention, this bearing is a bearing whose inner and outer rings are welded to the flywheels. At least one inner or outer ring of the bearing is extended axially on one side of this bearing and carries the aforementioned friction means of the torsion damper.

  According to still further features of the invention, the annular mass of the primary flywheel is overmolded on the radially outer periphery of the first flexible annular sheet mentioned above, or is formed by solid washers which are secured by means such as rivets on the radially outer periphery of the first flexible annular sheet.

  The radially outer periphery of the third annular plate may carry ignition targets, as well as means for limiting the angular displacement of the secondary flywheel.

  According to yet another characteristic of the invention, the primary flywheel, the torsion damper and the secondary flywheel are axially juxtaposed subassemblies.

  This facilitates the assembly and assembly of the double damping flywheel according to the invention.

  According to yet another characteristic of the invention, the secondary flywheel is made in one piece, for example sheet metal, and comprises an annular mass of inertia overmolded on its radially outer periphery.

  Conventionally, this annular mass of inertia forms the reaction plate of a clutch connecting the secondary flywheel of the double damping flywheel to an output shaft, such as for example the input shaft of a gearbox. .

  The invention will be better understood and other features, details and advantages thereof will appear more clearly on reading the following description, given by way of example with reference to the accompanying drawings, in which: FIG. 1 is a schematic view in axial section of a double damping flywheel according to the invention, representing the subassemblies of this double damping flywheel axially separated from each other; FIG. 2 is a diagrammatic view in axial section of the double damping flywheel of FIG. 1 showing the three subassemblies in assembled position; - Figure 3 is a schematic axial sectional view corresponding to Figure 1 and showing an alternative embodiment of the invention; - Figure 4 is a schematic axial sectional view of the double damper flywheel of Figure 3 in the assembled state.

  - Figure 5 is a schematic view corresponding to Figure 1 and showing another embodiment of the invention.

  Referring first to Figures 1 and 2 showing a first embodiment of the invention.

  The double damping flywheel shown in these figures essentially comprises a primary flywheel 10, a torsion damper 12 and a secondary flywheel 14 forming three coaxial subassemblies intended to be juxtaposed axially and mounted at the end of a shaft motor 16 such as the crankshaft of an internal combustion engine 20 of a motor vehicle.

  The primary flywheel 10 essentially comprises an axially flexible annular sheet, which carries at its radially outer periphery an annular mass of inertia 22 for example overmolded on the flexible annular sheet 20. A starter ring 24 is mounted and fixed on the part 25 radially. outer ring mass 22.

  The radially inner portion of the flexible sheet 20 comprises a series of orifices 26 distributed over a circumference, which serve to pass the fastening screw of the double damping flywheel on the end of the drive shaft 16. These orifices 26 surround a bearing 28 for centering and guiding in rotation the secondary flywheel 14, this bearing 28 comprising inner and outer rings which are for example made of sheet metal and one of which is fixed by welding on the flexible annular plate 20 of the primary flywheel 10 and the other of which is fixed by welding on an annular plate 30 of the secondary flywheel 14.

  In the example shown, it is the outer ring 32 of the bearing 28 which is welded to the primary flywheel 10 and its inner ring 34 which is welded to the secondary flywheel 14.

  Furthermore, and as can be seen in FIG. 1, the rings 32, 34 of the bearing are each extended axially on one side and the other respectively of the bearing, which makes it possible to move the welding zones away from these bearings. bearing race rings of the bearing balls.

  The secondary flywheel 14 is essentially formed of the aforementioned annular plate 30 and an annular mass of inertia 36 which is fixed, for example overmolded, on the radially outer peripheral portion of the sheet 30.

  This sheet also comprises a series of orifices 38 for the passage of screws 40 for attaching the double damping flywheel to the drive shaft 16 or for access to the heads of these screws, these orifices 38 being distributed over one circumference, and another series of orifices in which are mounted rivets 42 which are output means of the torsion damper 12 12, as will be seen below in more detail.

  Elements 44 forming angular deflection stops, are mounted by rivets on the radially outer circumferential portion of the annular mass 36, on the side facing the torsion damper 12 to cooperate with stops 46 of rubber or the like carried by this 25 torsion damper.

  The torsion damper 12 essentially comprises a flexible annular plate 50, which extends along the flexible annular plate 20 of the primary flywheel in the assembled state of the double damping flywheel and which has in its radially inner peripheral portion a series 30 orifices 52 for passage of the fixing screws 40 on the drive shaft 16, these orifices 52 being distributed along a circumference as the corresponding orifices 26 of the primary flywheel and 38 of the secondary flywheel.

  At its radially outer circumferential part, the annular plate 50 carries axes 54 of articulation of the cylindrical boxes 56 in which are housed the springs 58 of the torsion damper, the axes 54 being parallel to the axis 60 of rotation of the double damper steering wheel.

  In a manner well known to those skilled in the art, the torsion damper shown in Figures 1 and 2 is of the "radial" type, that is to say that the springs 56, 58 housed in the boxes 56 are oriented radially relative to the axis of rotation 60 in the rest position of the torsion damper.

  The end of the boxes 56 located on the side of the axis of rotation 60 is closed by a plate 62 on which the springs 58 rest and which is traversed axially by a rod 64 whose radially outer end carries means for support on the springs 58.

  The radially inner end of each rod 64 is articulated on a rivet 42 of the secondary flywheel 14 and is mounted in a corresponding housing of an annular piece 66 centered on the axis of rotation 60 by means of a cylindrical piece 68 made of sheet metal a thin section extending between the annular plate 50 of the torsion damper and the annular plate 30 of the secondary flywheel 14.

  This cylindrical plate 68 is fixed on the annular plate 50 of the torsion damper, for example by riveting an annular flange 70 formed at its corresponding end and applied to the annular plate 50.

  The annular piece 66 which carries the rod ends 64 is also part of the torsion damper friction means, these friction means comprising a washer formed by a radially internal rib 72 of the piece 66 which is axially clamped in a annular groove 74 of the cylindrical plate 68 by a clamping washer 76 and an applicator washer 78.

  The annular piece 66 comprises another radial annular rib at its outer periphery, this rib 80 forming a washer axially clamped on the annular flange 70 of the cylindrical piece 68 by a clamping washer and an application washer resting on a washer of support 82 secured to the annular plate 50.

  Thus, any angular displacement between the primary flywheel 5 10 and the secondary flywheel 14 results in a rotation of the annular piece 66 relative to the annular plate 50 and by a friction of the washers 72 and 80 on the corresponding parts of the sheet metal. thin cylindrical 68.

  During these angular deflections, the cylindrical boxes 56 pivot about the axes 54 and these pivots are limited by an annular plate 86 whose inner peripheral portion is fixed by means of rivets 88 on a median annular portion of the annular plate 50, this annular plate 86 extending between the torsion damper 12 and the secondary flywheel 14 and supporting at its radially outer peripheral portion 15 the corresponding ends of the hinge pins 54 of the cylindrical boxes 56, the opposite ends of these pins being carried by the annular plate 50 of the torsion damper as already indicated.

  The radially outer peripheral portion of the annular plate 86 comprises a cylindrical rim 90 carrying ignition targets.

  This radially outer peripheral portion also serves as a support for blocks 46 of elastically deformable material, such as a rubber, an elastomer or the like, which cooperate with the stops 44 of the secondary flywheel 14 to damp the end-of-stroke shocks during deflections. angles between the primary flywheel and the secondary flywheel.

  The primary flywheel 10, the torsion damper 12 and the secondary flywheel 14 are subassemblies which are manufactured independently of each other, then which are juxtaposed axially as shown in FIG. 1 for the final assembly of the double flywheel damper.

  At this stage, the outer ring 32 of the bearing 28 is fixed by welding on the annular plate 20 of the primary flywheel 10, radially inside the series of orifices 26 for the passage of the fixing screws 40. The welded end of the outer ring 32 of the bearing bears axially on the annular plate 20.

  To avoid the formation of weld burrs in the immediate vicinity of the orifices 26, which could hinder the application on the periphery of these 5 holes of the annular plate 50 of the torsion damper 12, at the heads of the screws 40, form in the edge of the central orifice of the annular plate 20 notches 92 radially aligned with the orifices 26.

  The subassemblies forming the primary flywheel 10, the torsion damper 12 and the secondary flywheel 14 are pushed axially in abutment with each other and the end of the inner ring 34 of the bearing 28 is welded to the annular plate. 30 of the secondary flywheel 14. A rivet 71 for assembling the annular plate 50 of the torsion damper 12 and the flange 70 of the thin cylindrical sheet 68 is engaged in an orifice 73 of the annular plate 20 of the primary flywheel for the angular positioning of the input means of the torsion damper 12 on the primary flywheel. Similarly, a rivet 88 for fixing the annular plates 50 and 86 is partially engaged in an orifice of the annular plate 20. Next, the fastening screws 40 are introduced into the orifices 38 of the secondary flywheel, the orifices 52 of the shock absorber 12 and the orifices 26 of the primary flywheel 10 to fix the double damping flywheel at the end of the motor shaft 16.

  The screws 40 secure the input means, formed by the annular plate 50, of the damper 12 on the primary flywheel 10 and an elastic axial prestressing of the annular plate 50 of the torsion damper on the flexible sheet. 20 of the primary flywheel, on the side of the axis of rotation 60.

  The radially outer peripheral portions of the annular plate and the annular plate 50 are slightly spaced from each other, as shown in Figure 2, at rest.

  Furthermore, the radial face 94 of the mass of inertia 22 of the primary flywheel 10, located on the side of the torsion damper 12, bears against a radial face 96 of the annular plate 86 of the torsion damper, which makes it possible to damp the axial vibrations and the flexures of the primary flywheel 10 by friction.

  The elongation of the rings 32 and 34 of the bearing 28 makes it possible to center on this bearing the cylindrical plate 68 which carries the friction means of the torsion damper.

  In operation, axial vibrations and friction of the primary flywheel 10 are absorbed by the axial elastic preload of the annular plate 50 of the torsion damper 12 on the flexible annular plate 20 of the primary flywheel 10 and by friction of the annular mass. 22 of the primary flywheel on the annular plate 86 of the torsion damper.

  The rotational vibrations and irregularities of torque result in angular deflections of the primary and secondary flywheels, which cause compressions of the springs 58 of the torsion damper 15 and which are damped by the above-mentioned friction means of this torsion damper. The possible angular displacements between the flywheels are limited by abutment of the cylindrical boxes 56 containing the springs 58 on projecting portions 98 of the annular plate 86 which extend radially towards the axis of rotation 60 between the boxes 56, and by pressing blocks 46 on the stops 44 of the secondary flywheel 14.

  In the positions of maximum angular displacement, there is a slight torsion of the radially outer peripheral portion of the annular plate 86 which carries the pivot pins 54 of the boxes 56, which increases the stiffness and facilitates the damping of the limit switch. .

  Referring now to Figures 3 and 4 which show an alternative embodiment of the invention.

  This embodiment variant differs from the embodiment of FIGS. 1 and 2 essentially in that the annular plate 150 of the torsion damper 12 does not extend radially towards the axis of rotation 60 to the level of the orifices 26. formed in the annular plate 20 of the flexible primary flywheel 10, but stops below these orifices, the diameter of the axial orifice 152 of the annular plate 150 being greater than the diameter of the circumference on which the orifices 26 are distributed.

  In this embodiment, the annular plate 150 is fixed on the primary flywheel not by the screws 40 for fixing the double flywheel 5 damper on the drive shaft 16, but by rivets 188 similar to the rivets 88, a previous embodiment and which serve to fix together the annular plate 20 of the primary flywheel 10, the annular plate 150 of the torsion damper 12 and the annular plate 86 of this torsion damper.

  The annular plate 150 of the torsion damper 12 is thus fixed to the flexible annular plate 20 of the primary flywheel in the vicinity of its outer periphery while its inner peripheral portion is slightly spaced, at rest, from the annular plate 20 as shown schematically. in figure 4.

  The thin cylindrical plate 68 of the torsion damper is fixed by its annular flange 70 directly to the annular plate 20 of the primary flywheel by means of rivets 171, this flange 70 and the annular plate 150 being substantially coplanar and the sheet 150 surrounding externally the annular flange 70.

  In this variant embodiment, the heads of the screws 40 are applied to the flexible annular plate 20 of the primary flywheel when the double damping flywheel is mounted on the motor shaft and it is advantageous that indentations 92 are formed in the edge of the axial orifice of the annular plate 20 in radial alignment with the orifices 26, to prevent the solder burrs of the outer race 32 of the bearing on this annular plate 20 hindering the tightening of the screws 40.

  Furthermore, the mass of inertia 122 of the primary flywheel is formed of massive washers axially superimposed and fixed by rivets 124 on the radially outer peripheral portion of the annular plate 20.

  For the rest, we find the structure already described with reference to Figures 1 and 2.

  In operation, the axial vibrations and the deflections of the primary flywheel are absorbed by elastic deformation of the annular washer 150 of the torsion damper and are frictionally damped between the mass of inertia 122 of the primary flywheel and the annular plate 86 of the 5 twist damper. The rotational vibrations and irregularities of torque are absorbed by the springs 58 of the torsion damper and damped by the friction means thereof.

  The invention is of course applicable to a torsion damper with circumferential springs which are housed in windows of two guide washers 10 formed by the aforementioned annular plates 50, 150 and 86, such a torsion damper comprising, in place of cylindrical rods 60, an annular web integral in rotation with the secondary flywheel and acting on the ends of the circumferential springs.

  In another embodiment shown diagrammatically in FIG. 5, the annular plate 150 of the torsion damper 12 is not secured in rotation with the flexible annular plate 20 of the primary flywheel 10 by fixing screws 40 or by means of rivets, but is axially clamped on this annular plate 20 so as to be rotatable relative thereto around the axis 60 in the event of torque transmitted too large and greater than a predetermined value, to play the role of a torque limiter. In this case, it is also possible for the mass of inertia 22 of the primary flywheel to be clamped axially or pinched between the flexible annular plate 20 of this primary flywheel and the annular plate 86 of the torsion damper 12.

  In a variant and as represented in FIG. 5, the mass of inertia 22 of the primary flywheel is not fixed on the annular plate 20, but on the annular plate 50 of the torsion damper, for example by overmolding.

  An elastic washer, such as a Belleville washer 102, is mounted axially between the annular plate 150 and a washer 104 for supporting the heads of the screws 40 in order to resiliently bias the annular plate 150 onto the annular plate 20. The cylindrical part 68 centering is fixed by welding of its front flange on the washer 104.

  Advantageously, it is also possible to provide on one of the annular plates 20, 50 (or 150) stop means for limiting the axial vibration of the other of these sheets.

  In general, the modular structure of the double damping flywheel according to the invention facilitates its assembly. The flexible primary flywheel is made of sheet metal, with reduced machining costs. The use of bearings formed by bearings comprising rings, advantageously of sheet metal, which are welded to the primary and secondary flywheels also makes it possible to reduce the costs. Overmolding the masses of inertia on the periphery of the sheets forming the primary and secondary flywheels also reduces the machining and therefore the cost. The secondary flywheel is made in one piece and is more easily manipulated and assembled and less expensive than in the prior art.

The torsion damper acts as a damping means for the axial and flexural vibrations of the primary flywheel and can also serve as a torque limiter.

Claims (31)

  1. Double damping flywheel, particularly for a motor vehicle, comprising two coaxial flywheels (10, 14), a bearing (28) for centering and guiding a second flywheel or a second secondary flywheel on a first steering wheel in rotation. or primary flywheel and a torsion damper (12) with elastically deformable elements such as springs (58), comprising input means (50,150) connected to the first flywheel (10) and output means (60,42) connected to the second flywheel (14), the first flywheel (10) being axially flexible and comprising a first annular plate (20) carrying a mass of inertia (22,122), characterized in that the torsion damper (12) comprises a second flexible annular plate (50,150) which forms the input means of the torsion damper and means for damping the axial oscillations of the first flywheel (10).   2. Double damping flywheel according to claim 1, characterized in that the second flexible annular sheet (50,150) carries the elastically deformable elements (58) of the torsion damper.   3. Double damping flywheel according to claim 1 or 2, characterized in that a third annular plate (86) is fixed on the radially outer portion of the second annular plate (50, 150) and means (54) for articulating the cylindrical boxes (56) containing the springs of the torsion damper are carried by the second and third annular sheets (50,150,86).   4. Double damping flywheel according to claim 3, characterized in that the second and third annular sheets (50,150,86) are fixed to each other by means such as rivets (88,188).   5. Double damping flywheel according to claim 4, characterized in that one of these fastening means (88, 188) cooperates with an orifice of the first annular plate (20) for the angular positioning of the torsion damper on the primary flying.   6. Dual damping flywheel according to one of claims 3 to 5, characterized in that the fastening means of the second and third annular sheets (50,150,86) form means for fixing the torsion damper (12) on the primary flywheel (10).   7. Double damping flywheel according to claim 6, characterized in that a radially outer portion of the third annular plate (86) forms a friction surface on a peripheral portion (22,122) of the first wheel (10).   8. Double damping flywheel according to one of claims 1 to 5, characterized in that the second flexible annular plate (50) is fixed to the first wheel (10) by means (40) for fixing the first wheel (10). on a motor shaft (16).   9. Double damping flywheel according to claim 8, characterized in that the means (40) for fixing the first wheel (10) are screws distributed around the bearing (28) for supporting and centering the second wheel (14) on the first steering wheel (10).   10. Dual damping flywheel according to one of claims 1 to 4, characterized in that the second flexible annular plate is integral in rotation with the primary flywheel (10) by axial elastic prestressing and forms therewith a torque limiter.   11. Double damping flywheel according to one of the preceding claims, characterized in that the torsion damper (12) comprises friction means which are carried by a thin cylindrical sheet (68) integral with the primary flywheel 10 and which comprise washers (72,80) 25 integral in rotation with the second flywheel (30) and biased axially on flanges of said thin cylindrical sheet (68).   12. Double damping flywheel according to claim 11, characterized in that said washers (72,80) of the friction means are carried or formed by an annular piece (66) centered on the thin cylindrical sheet (68) and receiving axes. (42) articulation on the second flywheel (14) of cylindrical rods (60) for guiding and compressing the springs of the torsion damper.   13. Double damping flywheel according to claim 11 or 12, characterized in that said thin cylindrical sheet (68) extends axially between the primary flywheel (10) and the secondary flywheel (14).   14. Double damping flywheel according to one of claims 11 to 13, characterized in that said thin cylindrical sheet (68) has at one end an annular flange (70) applied to the second annular plate (50) and fixed to the latter. ci by means such as rivets (71).   15. Double damping flywheel according to claims 11 to 13, characterized in that said thin cylindrical sheet (68) has at one end an annular flange (70) applied to the first annular plate (20) of the first flywheel (10) and fixed thereto by fixing means such as rivets (71).   16. Double damping flywheel according to one of claims 11 to 15, characterized in that the thin cylindrical sheet (68) is centered on the bearing (28) for supporting and centering the second wheel (14).   17. Double damping flywheel according to one of the preceding claims, characterized in that the bearing (28) for supporting and centering the second flywheel is a bearing whose inner and outer rings (34), (32) are welded to first and second wheels (10,14).   18. Double damping flywheel according to claim 17, characterized in that at least one inner or outer ring (34,32) of the bearing is extended axially on one side of the bearing.   19. Double flywheel according to claim 17 or 18, characterized in that a ring (32) of the bearing is extended axially in the opposite direction to the second flywheel (14) and is fixed by welding to the first flywheel (10). its prolonged end.   20. Double damping flywheel according to one of claims 17 to 19, characterized in that a ring of the bearing (28) is extended axially in the opposite direction to the first flywheel and is fixed by welding to the second flywheel at its extended end. .   21. Double damping flywheel according to one of the preceding claims, characterized in that the rings (32,34) of the bearing are welded in axial bearing on the flywheels (10,14).   22. Double damping flywheel according to one of the preceding claims, characterized in that the rings (32,34) of the bearing are sheet metal.   23. Double damping flywheel according to one of the preceding claims, characterized in that the mass of inertia (22) of the first flywheel is overmolded on the radially outer periphery of the first annular sheet (20).   24. Double damping flywheel according to one of claims 1 to 22, characterized in that the washers (122) are axially juxtaposed and fixed by means such as rivets (124) on the radially outer periphery of the first annular sheet. flexible (20).   25. Double damping flywheel according to one of claims 3 to 24, characterized in that the radially outer periphery of the third annular plate (86) carries ignition targets.   26. Double damping flywheel according to one of claims 3 to 25, characterized in that the torsion damper (12) carries means 20 (98,46) for limiting the angular displacement of the second wheel (14).   27. Double damping flywheel according to claim 26, characterized in that said limiting means comprise stops (98) formed on the third annular plate (86) and blocks of elastically compressible material (46) carried by the third annular plate ( 86) 25 and intended to bear against corresponding stops carried by the second wheel (14).   28. Double damping flywheel according to one of the preceding claims, characterized in that the first wheel (10), the torsion damper (12), and the second wheel (14) form subassemblies 30 axially juxtaposed.   29. Double damping flywheel according to one of the preceding claims, characterized in that the second flywheel (14) is a single piece.   30. Double damping flywheel according to one of the preceding claims, characterized in that the second flywheel (14) is sheet metal.   31. Double damping flywheel according to one of the preceding claims, characterized in that a mass of inertia (36) is overmolded on the radially outer periphery of an annular plate (30) of the second wheel (14).