FR2885193A1 - Dual mass damping flywheel for internal combustion engine of motor vehicle, has damper with non pre-curved springs including non-grinded ends that are applied on bosses which cooperate with ends to prevent rotation of springs - Google Patents

Abstract

The flywheel has a damper with two helical springs (30) having a rectilinear shape and mounted circumferentially in an annular chamber, where the springs are not pre-curved prior to the mounting. The springs have non-grinded ends (54) applied on bosses which cooperate with the ends to prevent a rotation of the springs around their axis of rotation. The ends of the springs have spires and are spaced radially from a chute (32). A radial clearance (50) is formed between the ends and the chute.

Description

The present invention relates to a double damping flywheel for an engine

  internal combustion linked to a transmission, in particular for a motor vehicle.

  To filter the rotational vibrations of an internal combustion engine due to the succession of combustion in the engine cylinders, it is known to use a double damping flywheel having a first flywheel integral with the crankshaft of the engine, a second flywheel connected to the transmission by a clutch and a damping device mounted between these flywheels and connecting them in rotation. This damping device comprises energy storage springs and friction energy dissipation means which brake the relative oscillations of the steering wheels.

  In a known embodiment, helical springs are arranged circumferentially around the axis of rotation and are generally pre-bent in an arc to facilitate their mounting in an annular chamber of one of the flywheels. During an oscillation in one direction of a steering wheel relative to the other, ends of the springs rest on bosses connected to the first steering wheel and the other ends of the springs rest on radial tabs connected to the second steering wheel. . For an oscillation in the other direction, the ends of the springs change support, passing from the first wheel to the second wheel for some and vice versa for others.

  Document FR-A-2676789 describes a double damping flywheel of this type. An annular chamber of the primary flywheel contains circumferential springs which are radially supported on a radially outer guide surface formed by or on the bottom of the annular chamber.

  This surface comprises cavities or clearances, leaving unsupported spring portions and allowing a freer movement of the turns of the springs which are opposite these cavities and which do not rub on the guide surface.

  These springs usually have ground ends to have flat end faces and perpendicular to their axis, so that the rotation of the springs about their axis do not change the bearing conditions of their ends. The grinding operation, however, has a significant cost compared to the cost of the spring.

  When the springs have unmolded ends, their end faces are not flat but inclined at a helix angle, and it is necessary to provide on the steering wheel supports having shapes corresponding to those of the end faces of the springs. This poses problems, however, when changes of support of the ends of the springs from one steering wheel to another. The springs can indeed rotate around their axis under the effect of different stresses and their last turns then arise in a defective manner on the supports, which can cause high stresses in the springs.

  The present invention also aims to avoid these disadvantages and to provide a simple, effective and economical solution to the aforementioned problems.

  It aims in particular to achieve simply, reliably and economically double damping flywheels with circumferential springs not preclinated and unmolished end faces.

  It proposes for this purpose a double damping flywheel comprising a primary flywheel, a secondary flywheel centered on the primary flywheel, and a damping device mounted between the two flywheels and connecting them in rotation, comprising springs mounted circumferentially in an annular chamber of one of the flywheels and applying at their ends on the bearing means of both flywheels, wherein the springs being helical springs not preclinated before mounting in the annular chamber and non-ends ground, the support means of the ends of the springs cooperate with these ends of the springs to prevent the rotation of the springs about their axis.

  It has been found that when helicoidal springs which are not preclinated, ie whose axis is rectilinear in the free state, are mounted in the annular chamber, their median part is curved substantially in an arc of a circle and rests on the radially outer guide surface of the annular chamber while their end portions are less curved and extend substantially rectilinearly along the radially outer guide surface of the annular chamber. The turns of these end portions therefore do not rub on this guide surface and are able to effectively absorb the small vibrations and oscillations of the flywheels, which avoids providing a set of additional springs usually mounted for this purpose in the device. depreciation and reduces its cost. The invention by preventing rotations of these springs about their axis ensures a good support of the ends of the springs on both flywheels and a long life of the springs and their smooth operation, without friction or jerks. In addition, the use of non-pre-bent springs before mounting and unmolded ends results in a significant saving.

  The invention thus makes it possible to combine a very economical embodiment of the springs, a very effective damping of the vibrations and a long service life of the damping device.

  In a first embodiment of the invention, the ends of the springs extend beyond the outer diameter of the springs, substantially tangentially or obliquely, to cooperate with stop means formed on the first flywheel and immobilize the springs. rotation around their axis.

  Thus, as soon as a spring begins to rotate about its axis in one direction or the other, one of its ends abuts on a lateral face or on the other side face of the annular chamber which contains the springs, and opposes the rotation of the spring.

  In order to prevent the cut ends of the springs from damaging the lateral faces of the annular chamber, bosses may be formed on these lateral faces on which parts of the springs close to their ends will be applied, leaving the cut ends of the springs at a short distance. side faces of the annular chamber.

  In a variant, the cut end of this spring can be bent towards the inside of the spring. It is then a convex curved portion of the end branch of the spring which will be applied on a side wall of the annular chamber, without risk of damaging it.

  According to another characteristic of the invention, the support means of the ends of the springs on the other wheels comprise radial tabs which extend substantially diametrically with respect to the ends of the springs and whose faces bearing on the ends springs each comprise two incurved arcuate notches receiving two diametrically opposite portions of the end turn of the corresponding spring and forming means for radial retention of this turn.

  It is thus possible to center and position radially the end of the spring on a radial tab of the other flywheel, which helps to maintain the corresponding end portion of the spring radially spaced from the guide surface formed by or on the bottom of the annular chamber and ensures a better operation of the springs and therefore better absorption of vibrations and operating jolts of the internal combustion engine.

  Advantageously, the faces of the aforementioned notches which bear on the spring wire are oriented obliquely, on one side and the other respectively relative to the axis of the spring, to follow the helical winding of the wire around the axis of the spring.

  Thus, when the end turn of the spring engages and rests in the notches of the radial lug of the other flywheel, the resulting bearing force of this radial lug on the end of the spring is well oriented in the axis of the spring, which improves the operation of the spring and the absorption of vibrations.

  In an alternative embodiment, annular cups are interposed between the ends of the springs and the support means on the flywheels and comprise a peripheral annular portion which extends helically around a central axis and which is intended to receive a turn end of a spring, this peripheral annular portion having an axial end flange forming a stop for the end of the spring and thus preventing the rotation of the spring about its axis in the direction applying the end of the spring on the said radial face of the annular peripheral portion of the cup.

  The other end of the spring is likewise supported on another cup of the same type, which has a peripheral annular portion with an axial end flange cooperating with said other end of the spring to prevent rotation thereof around its axis. in the opposite direction to the above meaning.

  In this way, each spring is immobilized in rotation about its axis by the cups, in the two possible directions of rotation.

  Advantageously, each cup comprises a central cylindrical or frustoconical centering portion of the end of the spring, this cylindrical or frustoconical portion having an annular boss or projections formed for example by punctured, the cup being thus retained by the spring in order to avoid it escaping.

  Thus, the end of each spring is not only immobilized in rotation on the cup, but also holds the cup axially. In this way, during relative oscillations of the flywheels, the cup moves with the end of the spring being applied correctly either on the support means provided on the first wheel, or on the support means provided on the second steering wheel.

  In a preferred embodiment of the invention, each spring extends to rest on about a half circle. Its end portions, which are at rest spaced radially inwardly from the guide surface which is formed by the bottom of the annular chamber or which is attached to the bottom of the annular chamber, comprise from eight to twelve turns approximately , which guarantees a very good absorption of relative oscillations of low amplitude of the two flywheels, especially in neutral and at high speeds of rotation.

  Advantageously and economically, especially in embodiments without an annular cup, each spring has a constant winding pitch over its entire length and does not include a dead coil at its ends.

  The invention will be better understood and other features and advantages will emerge more clearly on reading the following detailed description given by way of example and with reference to the appended drawings, in which: FIG. 1 is a front view in partial section of a double damping flywheel according to the invention; - Figure 2 is an axial sectional view of the double damping flywheel according to the line II-II of Figure 1; - Figure 3 is a partial view in axial section of a double flywheel 20 damper according to an alternative embodiment of the invention; - Figure 4 is a partial schematic view on a larger scale showing the supports of the ends of the springs on a radial tab of the second wheel; - Figures 5 and 6 are schematic sectional views along the lines V-25 V and VI-VI of Figure 4, respectively; - Figure 7 is a schematic sectional view along the line VII-VII of Figure 8, showing an alternative embodiment of the invention; - Figure 8 is a partial axial sectional view of the embodiment of Figure 7; - Figure 9 is a side view of a support cup used in the embodiment of Figures 7 and 8; - Figure 10 is a schematic sectional view of the cup along the line X-X of Figure 9; - Figure 11 is a perspective view of this cup.

  The double damping flywheel 1 shown in Figures 1 and 2 comprises a primary flywheel 2 centered and fixed on a crankshaft not shown and a secondary flywheel 4 carried and centered on the primary flywheel by means of a bearing 6. The secondary flywheel 4 has a planar radial face on which a clutch disc 8 is clamped by a mechanism (not shown) having a cover fixed on the secondary flywheel 4, and an annular spring or diaphragm which bears on this cover and which applies a axial load on a pressure plate rotatably connected to the cover and sliding axially. The clutch disc 8 rotates a coaxial shaft 10 input of a transmission.

  The primary flywheel 2 is formed of a stamped sheet 12 having a central bore 16 and fixed by a series of screws 18 on the crankshaft. Its outer peripheral portion carries a starter ring gear 14.

  The bearing 6 is a plain bearing comprising two annular plates 20 and 22 whose internal parts are superimposed and fixed on the face of the primary flywheel 2 opposite the secondary flywheel 4 by rivets 24 made by extrusion of the sheet 12 and by the screws 18. The first sheet 20 extends over the primary flywheel and has a flat portion radially external to the screws 18 and serving for the axial support of the secondary flywheel 4. The second sheet 22 comprises a cylindrical portion for centering and supporting the flywheel secondary 4, the axial retention is provided by a radial flange turned outwardly of the end clutch side of this cylindrical portion. A sliding ring 26 is interposed between the bearing 6 and the secondary flywheel and is mounted tightly in the central bore of the secondary flywheel. This ring has two end flanges facing outward and covering the radial faces of the secondary flywheel at the ends of the bore.

  The radially outer portion of the first sheet 20 also comprises a flange for axially clamping a friction means 28 for damping the relative oscillations of the flywheels.

  Both flywheels are connected in rotation by a damper comprising helical springs 30 arranged circumferentially and radially guided on the outer side by troughs 32 formed of sheet metal strips bent in the width along the outer diameter of the springs, and bent in the length along a arc of circle centered on the axis of rotation. These chutes 32 are continuous over the entire length of the springs and are housed with the springs in an annular cavity of the primary flywheel 2 which is closed by an annular cover 34 made of sheet metal fixed on the primary flywheel 1 on the side of the secondary flywheel.

  Axial bosses 36, 38 are formed facing each other in the sheet 12 of the primary flywheel and in the cover 34 to serve as lateral supports at the ends of the springs, which can also be applied diametrically on radial tabs 40 an annular web 42 fixed to the secondary flywheel 4 by rivets 44. The tabs 40 extend radially between the bosses 36, 38.

  The springs 30 have an initial rectilinear shape and are not pre-bent before assembly. During the assembly of the damper, a load is exerted on their ends to bend and return into the annular chamber where they come to bear on the chutes 32. When the damper comprises two springs 30 which each extend about 180 as shown in Figure 1, each spring 30 is bent about a semicircle and its median portion is supported on the chute 32 while its end portions remain almost straight and leave a radial clearance 50 between them and the chute 32.

  The ends of each spring 30 are made by simply cutting the wire without additional grinding operation, the last turn of the spring is not tightened and the entire spring has a constant pitch. The end turns engage in notches 52 in an arc of the radial edges of the tabs 40 of the web 42, so that each tab 40 bears on the last turn of a spring at two diametrically opposite points, radially inside. and outside respectively. The last turn is thus held radially against the centrifugal force by the corresponding inner notch 52, a reduced radial clearance possibly being left between the latter turn and the chute 32.

  The end 54 of the spring wire is not wound and extends substantially rectilinear and tangential to the periphery of the spring. It exceeds the outside diameter of the spring to come along a side face of the annular chamber, on the plate 12 at one end of the spring and on the lid 34 at the other end of the spring to prevent rotation of the spring around its axis. Small bosses 56 and 58 are formed on the plate 12 and on the cover 34 just before the end of the wire, and serve as abutment and friction surfaces to separate this end from the side face of the annular chamber or cover to prevent scratching or removal of material that would be caused by the sharp edge formed by the cut of this end.

  With this arrangement, the orientation of the ends of the springs is maintained permanently and in particular when the springs alternately pass the supports of a steering wheel to those of the other steering wheel. Each spring is always supported in the same way on the bosses 36, 38 or tabs 40, this support respecting the inclination of the last turn and not providing additional constraints.

  At rest, as seen in Figure 1, each spring end portion spaced radially from the chute 32 has 8 to 12 turns approximately.

  The radial clearance 50 between each end portion of a spring 30 and the chute 32 improves the filtering of vibrations by the double damping flywheel. If the spring were bent permanently before assembly, the centrifugal force in operation would press the spring 30 on the chute 32 with a significant pressure over its entire length, which would generate friction opposing the sliding of all the turns of the spring and degrade its operation. This friction can even completely block the spring, the damper then transmitting all the vibrations.

  The end parts of the springs according to the invention tending to remain straight and spaced from the trough 32, the game 50 present at rest is preserved in part at least during the rotation of the steering wheels thanks to the fact that the last turns are maintained radially by the tabs 40 of the web, so that these end portions of the spring remain more free to compress normally. In practice, the deflection angle corresponding to the compression of a few turns at the end of the spring may be sufficient to improve the vibration damping.

  FIG. 3 represents a variant of the invention according to which the ends 54 of the springs comprise a first straight part 60 substantially tangent to the spring then a second part 62 curved towards the inside of the annular chamber. This arrangement allows the straight portion 60 to bear against a side face of the annular chamber (on the plate 12 or the cover 34) to prevent the rotation of the end of the spring and the curved end portion 62 bent towards the inside separates the end of the wire from the wall of the annular chamber, thus avoiding a risk of wear and tear of material by the sharp edge of the cut end of the wire.

  An alternative embodiment of the spring support means on the tabs 40 of the annular web 42 is shown in FIGS. 4, 5 and 6.

  In this variant, the radial edges of the lugs 40 each comprise two indentations 52 in an arc of a circle whose radius corresponds to that of the wire of the spring 30, as in the previous embodiment, and a nose 66 projecting between the two notches 52 to form a centering means of the last turn of the corresponding spring 30, the nose 66 being substantially U-shaped or trapezoidal and narrowing in the opposite direction to the tab 40. The nose 66 and the notch radially inner 52 form a radial positioning and retaining means of the radially inner portion of the last turn of the spring 30.

  As can be seen in FIGS. 5 and 6, which are sectional views of the bottoms of notches 52 receiving the last turn of spring 30, the bottoms of these notches form bearing faces 68 and 70, respectively, which are not exactly perpendicular to a circumferential direction, that is to say to the axis 72 of the spring 30, but which are inclined obliquely on one side and the other respectively of this axis to follow exactly the winding angle helical spring wire 30.

  In this example, the bearing face 68 of the radially outer notch 52 of the tab 40 makes an angle α with the axis 72 of the spring 30 (on one side of the annular web 42), this angle a being slightly smaller at 90, while the bearing face 70 of the radially inner notch 52 makes with this axis 72 and the same side of the annular web 42 an angle b which is slightly greater than 90, so that each bearing face 68 , 70 applies flat on the corresponding turn portion of the spring 30. Thus, the resultant bearing force of the radial lug 40 on the end of the spring 30 is well directed in the axis of this spring.

  In the variant embodiment of the invention shown in FIGS. 7 to 11, the springs 30 are applied to the bosses 36, 38 of the annular plate 12 and the annular cover 34 as well as to the radial lugs 40 of the annular veil 42. , not directly but through cups shown more visibly in Figures 9, 10 and 11.

  These cups 76 are of generally cylindrical annular shape and comprise at one end a peripheral annular flange 78 extending radially outwards while their other end comprises a peripheral annular flange 80 extending radially inwards and delimiting a central orifice 82.

  The peripheral annular flange 78 of the first end of the cup 76 is not perpendicular to the axis 84 of the cup but is wound helically about this axis 360, the helix angle being equal to that of the corresponding spring 30, and the two circumferential ends of this annular flange 78 being connected to each other by an axial flange 86 intended to form a bearing abutment of the cut end 54 of the spring 30.

  The cylindrical wall 88 of each cup 76 further comprises an annular rib or boss 90 projecting outwardly as shown in FIG. 7, or tabs 92 projecting outwards, formed by punctures of the cylindrical wall 88 (FIG. FIGS. 9 to 11), which serve to maintain axially on the cup 76 of the last turn of the spring 30.

  On assembly, the outer annular rim 78 outside the cup 76 is applied to the above-mentioned bosses 36 and 38 of the annular plate 72 of the primary flywheel 4 and the annular cover 34 (the bosses 36, 38 being slightly offset with respect to the other circumferentially to follow the winding angle of the last coil of the spring 30 as shown in Figure 7), the last coil of the spring 30 is applied to the peripheral annular flange 78 of the cup 76 and is retained in the axis of the spring by the boss or the annular rib 90 or by the aforementioned tabs 92 of the cylindrical wall 88 of the cup and the cut end 54 of the spring wire is in the immediate vicinity of the end axial face 86 of the annular rim 78 of the cup, which prevents the spring 30 from rotating about its axis in a clockwise direction in FIG. 8.

  The other end of this spring 30 is mounted on an identical cup 76 whose peripheral annular flange 78 also has an axial face 86 which forms a stop of the other cut end 54 of the spring and prevents it from rotating about its axis. in the opposite direction.

  Thus, each spring 30 is held in rotation about its axis at its ends and holds the cups 76 axially.

  The radial tabs 40 of the annular web 42 secured to the second wheel 4 are shaped to engage the cups 76 and abut on the end flanges 78 of these cups. The central orifices 82 of the ends of the cups allow a circulation of the lubricating agent which in general partially fills the annular chamber in which the springs 30 are located.

  In addition, as seen in FIG. 7, the end flanges 80 of the cups 76 form bearing faces for ground ends 94 of coil springs 96 which extend inside the springs 30, on the the whole length of these or only part of that length.

  As the ground ends 94 of the internal springs 96 form a flat face perpendicular to the axis of the springs, the problem of maintaining in rotation these internal springs 96 does not arise.

  Alternatively, it can be provided on the cups 76 means for axial retention and rotation retention of the ends of the inner springs 96, which then avoids the grinding operation of the ends of these springs and significantly reduces their cost.

Claims (7)

  A dual damping flywheel for an internal combustion engine, comprising a primary flywheel (2), a secondary flywheel (4) centered on the primary flywheel, a damping device mounted between the two flywheels and connecting them in rotation, comprising springs ( 30) circumferentially mounted in an annular chamber of one of the flywheels and applied at their ends to bearing means of both flywheels, characterized in that the springs (30) being springs helicoidal not pre-bent before mounting in the annular chamber and unmolded ends, the support means of the ends of the springs cooperate with these ends of the springs to prevent rotation of the springs about their axis.   2- Double damping flywheel according to claim 1, characterized in that at least one end of each spring (54) extends beyond the outer diameter of the spring (30) and cooperates by abutment with a flywheel to prevent rotation the end of the spring around its axis.   3 - Double damping flywheel according to claim 2, characterized in that the end of the spring which extends beyond the outer diameter of the spring (30) is supported on a side face of the annular chamber.   4 - Double damping flywheel according to claim 2 or 3, characterized in that said end of the spring (30) is supported on a boss (56, 58) of a side face of the annular chamber.   - Double damping flywheel according to claim 2 or 3, characterized in that said end of the spring (30) comprises a straight portion (60) substantially tangential to the periphery of the spring and ends with a reentrant curved portion (62).   Double damping flywheel according to one of the preceding claims, characterized in that the support means of the ends of the springs (30) on the other of the flywheels comprise radial tabs (40) which extend substantially diametrically with respect to the springs (30) and whose edges bearing on the ends of the springs (30) each comprise two notches (52) in an arc of a circle receiving two diametrically opposite parts of the end turn of the spring (30) and forming means radial retention of this end turn.   7. Double damping flywheel according to claim 6, characterized in that the faces (68, 70) of the notches (52) resting on the turn of the spring (30) are obliquely oriented on one side and the other respectively. relative to the axis (72) of the spring (30), to follow the helical winding of the wire of this spring.   Double damping flywheel according to one of claims 1 to 5, characterized in that cups (76) interposed between the ends of the springs and the support means on the flywheels (2, 4) comprise a peripheral annular portion (78). ) extending helically around a central axis (84) and for receiving an end turn of the spring (30), said peripheral annular portion (78) having an axial end flange (86) forming a stop for the end (54) of the spring (30) and preventing the rotation of the spring about its axis in the direction applying its end (54) on the aforementioned radial face (86) of the cup.   Double damping flywheel according to Claim 8, characterized in that the other end (54) of the spring (30) bears against another cup (76) of the same type as the aforementioned cup and having a peripheral annular portion (78). ) end axial flange (86) cooperating with said other end (54) of the spring to prevent its rotation about its axis in the opposite direction to the aforementioned direction.   Double damping flywheel according to claim 8 or 9, characterized in that each cup (76) comprises a cylindrical wall (88) for centering the end of the spring (30), this cylindrical part comprising a boss or an annular rib ( 90) or projecting lugs (92) formed for example by punctured, for the axial retention of the cup (76).   11 - Dual damping flywheel according to one of the preceding claims, characterized in that each spring (30) extends at rest on about a half circle.   Double damping flywheel according to one of the preceding claims, characterized in that the end portions of each spring (30) are at rest spaced radially inwardly from a peripheral guide surface (32) formed by or attached to on the bottom of the annular chamber in which the springs are mounted.