FR2725286A1 - Torque limiter for motor vehicle - Google Patents

Abstract

The torque limiter is attached to a flywheel (1) at the end of the driving shaft, pressing a disc (4) against the face of the flywheel to transmit torque. Annular friction linings (41) on inner and outer faces of the disc ensure strong friction coupling. A central hub (3) is attached to the edge of the disc, and is coupled in rotation to the driven shaft. The perimeter of the flywheel carries a counter-plate (5) that presses on the outer face of the disc. A spring washer (7) extending round the periphery of the plate presses the counter-plate against the friction plate. The friction surface between the flywheel and the disc is thus effectively doubled.

Description

 The present invention relates to torque limiters, in particular for a motor vehicle, of the type comprising a flywheel integral in rotation with a driving shaft, a bearing disc for fastening, on each of its faces, friction linings, a hub coupled to the disc. and integral in rotation with a driven shaft.

Such a limiter is described in the document
US-A-4,318,283.

 In it, the friction linings are intended to be clamped between two plates linked in rotation to the steering wheel, with axial mobility, by means of pins interposed between the steering wheel and a closing plate fixed to the steering wheel.

 One of the plates is adjacent to the closing plate and the other to the steering wheel while being subjected to the action of a plurality of helical springs each mounted in a housing formed in the steering wheel.

 The disc is coupled to the hub by a spline mounting.

 This axially compact solution requires housing in the steering wheel for mounting the coil springs.

 In addition it uses a large number of helical springs and pins, which requires storing these and complicates the assembly.

 In addition, this embodiment uses two plates respectively doubling the steering wheel and the closing plate so that one does not take advantage of the steering wheel and that this further increases the number of parts.

 The object of the present invention is to overcome these drawbacks in a simple and economical manner while retaining the advantage of a reduced axial size.

 According to the invention, a limiter of the above-mentioned type is characterized in that the friction linings are interposed axially between the flywheel, forming reaction plate, and a counter-plate, forming pressure plate, linked in rotation to the flywheel, with mobility axial, by means of elastic tongues fixed to said counter-plate and to a closing part integral with the steering wheel, and in that an elastic washer with axial action bears on the closing part for action on the counter-plate and tightening the friction linings between said pressure and reaction plates.

 Thanks to the invention, the closing piece, of simple shape, has a double function because, on the one hand, it serves as a support for the elastic washer with axial action interposed axially between the counter-plate and said piece of support, and, on the other hand, it allows the fixing of the elastic tabs allowing good axial mobility of the counter-plate.

 As a result, compared with the prior art, the risks of jamming of the parts of the limiter are reduced in favor of a better functioning of the latter and that the flywheel, having a simple shape, is more robust and has a increased inertia due to the absence of housings to be made in said flywheel.

 This flywheel offers a friction face to one of the friction linings just like the counter-plate, of simple shape, so that, in combination with the elastic washer with axial action, the number of parts is considerably reduced, which simplifies assembly and storage of parts.

 This is all the more so as the pins of the prior art are eliminated.

 It will be appreciated that the single elastic washer exerts a more regular load on the counter-plate so that the load from which the limiter will skate is better controlled.

 It will be appreciated that the limiter is of reduced axial size as in the prior art.

 Indeed, the closure part is of reduced thickness than the closure plate of the prior art and there is no need to provide two plates, so that, despite the presence of the elastic washer with axial action , we generally find the same axial size as in the prior art with a reduced number of parts and a thicker counter-plate therefore less subject to deformation - than one of the plates of the prior art.

The axial action elastic washer may consist of a wavy washer but, advantageously, it consists of a tapered washer in the free state, such as a Belleville washer or a diaphragm having a washer-shaped part.
Beautiful city.

 Given the characteristic curve of this type of washer, it follows, in a manner known per se, that said frustoconical washer exerts a generally constant load despite the wear of the friction linings. In addition, the axial size is reduced.

 Advantageously, the axial action elastic washer is located radially above the elastic tongues, so that the deformations of the closure part are minimized and that the torque transmitted by the torque limiter is greater.

 These elastic tabs can be of the radial type, but advantageously they are of the tangential type so that space is freed internally.

 In one embodiment, the tangential elastic tongues are mounted outside the closure part so that it is possible to form a sub-assembly of the closure part - elastic washer with axial action - pressure plate.

 Indeed, the tongues are then allowed to come into abutment against the closure piece advantageously in the vicinity of the fastenings of the tongues to the pressure plate.

 Thanks to the invention, the disc can constitute the input part of a conventional torsion damper so that it is possible to use the components of a clutch friction for the benefit of better standardization and cost reduction.

The following description illustrates the invention with reference to the accompanying drawings in which
- Figure 1 is an axial sectional view of a torque limiter according to the invention with representation of the outline of the torsion damper
- Figure 2 is a view along arrow 2 of Figure 1 with local cutaway, to show the springs and the web of the torsion damper, removal of the steering wheel and partial representation of the elastic washer with axial action
- Figure 3 is a partial sectional view along line 3-3 of Figure 4
- Figure 4 is a partial view with local cutaway according to arrow 4 in Figure 3
- Figure 5 is a partial sectional view for yet another embodiment
- Figure 6 is a view along arrow 6 in Figure 5.

 In these figures, we see at 1 a flywheel integral in rotation with a driving shaft, here the crankshaft (not visible) of an internal combustion engine of a motor vehicle. This is achieved here using screws 13 each passing through a passage 14 of the flywheel 1 for fixing the latter to the crankshaft.

The flywheel 1 belongs to a torque limiter 2 also comprising a disc 4 coupled to a hub 35
(Figure 2) rotatably attached, here by a spline mounting, a driven shaft 100 forming the input shaft of a multi-plate clutch in oil bath 101 shown schematically.

 The output shaft 102 of the clutch 101 forms the input shaft of a transmission box shown diagrammatically at 103.

 The torque limiter 2 is therefore mounted between the flywheel 1 and the transmission 103 and makes it possible, in a manner known per se, to spare the transmission 103 in the event of overtorque, the clutch 101 being adapted here to transmit a large torque.

 This limiter 2 comprises for this purpose elastic means with axial action 7 making it possible to tighten friction linings 41 mounted on the external periphery of the disc 4.

 The linings 41 brought together, here by bonding as a variant by riveting, by the disc 4 on either side thereof (on each of its faces) are associated with the flywheel 1 so that, in a manner known per se , in the event of overtorque determined by the force exerted by the elastic means 7, the linings 41 move angularly relative to the flywheel 1 to protect the transmission 103.

 In order to simplify the torque limiter 2, to reduce the manufacturing costs and to make the said limiter 2 axially compact, the invention proposes to tighten the friction linings 41 of the disc 4 between the flywheel 1, forming a reaction plate, and a counterplate 5, forming a pressure plate, linked in rotation to the flywheel 1, with axial mobility, by means of elastic tongues 9 fixed to said counter plate 5 and to a closing piece 6 integral with the flywheel 1, said elastic action means axial 7 consisting of an elastic washer 7 with axial action bearing on the closure part 6 for action on the counter-plate 5 and clamping of the friction linings 41 between said pressure 5 and reaction plates 1. Thus the linings 41 are axially interposed between the flywheel 1 and the counter plate 5 and the washer 7 between the part 6 and the counter plate 5.

 The flywheel 1 thus has a face 65 forming a friction face for the friction lining 41 concerned, while the counter-plate 5 offers a friction face 55, opposite the face 65, for the other friction lining 41 .

 The linings 41, the outer periphery of the disc 4, the backing plate 5, the washer 7 and the tongues 9 are therefore housed, in one embodiment, in a cavity delimited axially by the closure part 6 and the flywheel 1.

 This cavity is open radially inward.

 Thus in FIG. 1, the flywheel 1, for example made of cast iron like the counter-plate 5, has for this purpose, at its external periphery, an annular rim of axial orientation 11, possibly split, and the closure part 6 consists in a simple thin washer, for example made of sheet metal, fixed at its outer periphery to the flange 11. The flange 11 surrounds the linings 41, the disc 4, the backing plate 5 and the washer 7.

 Here, the closing washer 6 is fixed by a plurality of screws 63, each passing through a bore 64 of the washer 6, on the free end of the flange 11.

 Of course the flywheel 1 can be devoid of a rim 11, the closure part 6 then having the shape of a hollow plate to present an annular rim surrounding the parts 7, 5, the disc 4 and the linings 41.

 As a variant, the part 6 can be added by welding or crimping to the flange 11.

 The elastic washer 7 may consist of a corrugated elastic washer but here, in particular for reduction of the axial size, it consists of a Belleville washer bearing on its outer periphery on the closing washer 6 and on its inner periphery on the counter plate 5 radially generally in the middle of the linings 41. A good distribution of the loads is thus obtained. Of course, the Belleville washer 7 can be replaced by a diaphragm having a continuous part in the form of a Belleville washer extended by another part fragmented into radial fingers by slots. This diaphragm, like the Belleville washer 7, has a frustoconical shape in the free state. It is this washer 7 which determines the maximum torque transmitted without sliding by the limiter 2, the linings 41 being normally clamped between the plates 1, 5.

 The tongues 9, here made of metal, are located radially below the elastic washer with axial action 7.

 These tongues 9 exert a return action of the plate 5 in the direction of the part 6. Their return force is low compared to the load exerted by the washer 7 on the plate 5 with a central hole.

 They may have a radial orientation, but here they are advantageously generally of tangential orientation (FIG. 2) in particular in order to reduce the radial size towards the axis of the assembly of the plate 5 and of the washer 6.

 It will be appreciated that the rim 11 makes it possible to center, by its internal bore, the washer 7.

 In this FIG. 1, the pressure plate 5 has, at its internal periphery, a flange 8 of radial orientation and of reduced thickness to allow the housing of the rivet heads 51 between the flange 8 and the disc 4. These rivets 51, forming a fixing member, pass through the flange 8 to each allow the fixing of one or more tangential tabs 9 superimposed on the pressure plate 5. At one of their ends these tabs 9 are therefore fixed by riveting to the plate 5. At their at the other end, these tongues 9 are also fixed by rivets 61 to the closing washer 6.

 Alternatively, the fixing of the tongues 9 can be carried out using screws or bolts and the flange 8 can be divided into fixing lugs for mounting rivets 51, screws or bolts.

 It will be noted that the washer 6 has clearance openings 62 opposite the rivet passage holes 51 made in the flange 8.

Thus, the tangential tongues 9 are first fixed to the washer 6 and then, after the washer 7 has been inserted between the parts 5, 6, the tongues 9 are fixed to the flange 8. It is thus possible to create a subassembly comprising the plate 5, the tabs 9
(regularly distributed here in three sets - figure 2), and the washers 6, 7.

 Thanks to the invention, the disc 4, forming a support disc for the friction linings 41, can constitute the inlet part of a conventional torsional damper 3.

 Thus the parts of a clutch friction of a conventional clutch can be used for the benefit of better standardization and a reduction in manufacturing costs.

 In FIGS. 1 and 2, the torsion damper comprises the disc 4 fixed at its internal periphery to a guide washer 32 by means of balusters 41 also serving for the fixing of another guide washer 33.

 These washers 32, 33, metallic as the disc 4, are arranged on either side of a web 34 secured, for example by crimping, to the hub 35 fixed in rotation on the shaft 100.

 The veil 34 has windows 37 for mounting coil springs 36 with circumferential action also mounted in pairs in stampings 38 made opposite the windows 37 in the guide washers 32, 33. The balusters 41 extend radially above the veil 34.

 The springs 36 are mounted without circumferential play in the windows 37 and the stampings 38.

 Of course, the stampings 38 may consist of windows and the windows 37 may be replaced by recesses open to the outside.

 Certain springs 36 can be mounted, for delayed action, without play in the housings 38 of the washers 32, 33 and with play in the windows 37 of the web 34, all of this depends on the applications as does the number of tabs 9.

 Likewise, the web 34 can be integral in rotation with the hub 35, possibly after taking up a clearance, the web 34 and the hub 35 having, for this purpose, grooves meshing with clearance.

 Thus, in all cases, a good filtration of the vibrations in the kinematic chain going from the flywheel 1 to the transmission 103 is obtained, and in the event of overtorque the friction linings 41 slide in friction respectively in contact with the faces 65, 55 of the reaction plate 1. and pressure 5 to limit the transmitted torque.

 Of course, the present invention is not limited to the embodiment described.

 In particular, the disc 4 can be rigidly fixed to the web 34, while being rigidly coupled to the hub 35.

 The structures can be reversed, the tongues 9 then being located radially above the washer 7.

 The friction linings 41 instead of being continuous, as in FIGS. 1 and 2, can be fragmented into studs.

 Of course, instead of being made of cast iron, as in FIG. 1, the pressure plate 5 can be made of sheet metal as visible in FIGS. 3 and 4. This plate 5 then has a sinuous shape and has at its internal periphery a annular rim 50 of transverse orientation for fixing the tangential tongues 90 mounted on the external face of the rim 50 and of the closure part 6, that is to say on the faces of the rim 50 and of the part 6 turned to the opposite of reaction plate 1 and disc 4.

 These tongues 90 are fixed, as in FIGS. 1 and 2, by rivets 61 to the rim 50 and by rivets 51 to the closure part 6.

 To do this, the closing piece 6 has lugs 91 (FIG. 4) so that the tongues 90 are able to come into contact with said lugs 91 to limit the axial movement of the pressure plate 5 when the closing piece 6 does not is not mounted on reaction plate 1.

 The rim 50 is interrupted at the level of the legs 91 (FIG. 4) and the tongues 90 are allowed to abut against the legs 91 at the level of the rivets 61.

 It is thus possible to form a unitary, manipulable and captive assembly comprising the closure part 6, the elastic washer with axial action 70 consisting here of a wavy washer, the pressure plate 5 rotatably coupled to the closure part 6 by the tabs 90 allowing axial movement of the pressure plate 5.

 After fixing the assembly, there is a clearance between the tongues 90 and the legs 91.

 It will be noted in FIG. 3 that we mainly see the torsional damper 3.

 Of course (FIGS. 5 and 6) the pressure plate 5 can be made of cast iron and comprise at its internal periphery tabs 500 each passing through a notch 501 formed in the closure part for fixing tangential tongues 90 at the level of the external face of the closing part 6 as in FIGS. 3 and 4.

 These tongues are clean before fixing the closing piece 6 to abut against the closing piece in the vicinity of the fixing rivets 51 of the tongues 90 to the legs 500.

 Thus, as in FIGS. 3 and 4, it is possible to form a unitary sub-assembly.

 Of course in FIG. 1, it is possible to form such a unitary assembly using elastic clamps resting on the external face of the closing washer and on the internal face of the flange 8 facing the reaction plate 1 .

 After mounting the unitary subassembly, the clamps are manually removed.

Claims (12)

 1) Torque limiter, in particular for a motor vehicle, of the type comprising a flywheel (1) integral in rotation with a driving shaft, a disc (4) bearing, on each of its faces, friction linings (41) , a hub (35) coupled to the disc (4) and integral in rotation with a driven shaft, characterized in that the friction linings (41) are interposed axially between the flywheel (1), forming a reaction plate, and a counter plate (5), forming pressure plate, linked in rotation to the flywheel (1), with axial mobility, by means of elastic tongues (9) fixed to said counter plate (5) and to a closure part ( 6) integral with the steering wheel (1) and in that an elastic washer with axial action (7) is supported on the closure part (6) for action on the counter-plate (5) and tightening of the friction linings between said pressure (5) and reaction (1) plates.  2) Limiter according to claim 1, characterized in that the axial action elastic washer (7) has a frustoconical shape in the free state.  3) Limiter according to claim 2, characterized in that said elastic washer (7) consists of a Belleville washer.  4) Limiter according to any one of claims 1 to 3, characterized in that the elastic washer with axial action (7) is located radially above the elastic tongues (9).  5) Limiter according to claim 4, characterized in that the elastic washer with axial action (7) consists of a tapered washer in the free state bearing on its outer periphery on the closure part (6) and its internal periphery on the counter plate (5).  6) Limiter according to any one of claims 1 to 5, characterized in that the elastic tongues (9) are generally of tangential orientation.  7) Limiter according to any one of claims 1 to 6, characterized in that the counterplate (5) has at its internal periphery a collar (8), optionally fractionated, generally of radial orientation and of reduced thickness for fixing the elastic tabs (9).  8) Limiter according to claim 7, characterized in that the elastic tongues (9) are fixed by riveting to the closure part (6) and in that said closure part (6) has clearance openings (62) in look of rivet holes  (51) made in the collar (8).  9) Limiter according to any one of claims 1 to 5, characterized in that the counterplate (5) has a sinuous shape and has at its internal periphery a fixing flange (50) for fixing the elastic tongues (90) of tangential orientation also fixed on the external face of the closure part (6) turned away from the flywheel (1).  10) Limiter according to any one of claims 1 to 5, characterized in that the pressure plate (5) has at its internal periphery legs  (500) passing through openings (501) made in the closing part (6) for fixing tangential tabs on the external face of the closing part (6) facing away from the flywheel (1).  11) Limiter according to any one of claims 1 to 10, characterized in that the closing part (6) consists of a simple washer fixed at its external periphery on an annular rim (11) of axial orientation, possibly split, presented by the steering wheel at its outer periphery.  12) Torque limiter according to any one of claims 1 to 11, characterized in that the disc (4) forms the input element of a torsion damper comprising two guide washers (32,33) arranged axially on either side of a web (34) integral in rotation, possibly after taking up a clearance, of the hub (35), springs (36) being interposed between the web (34) and the guide washers ( 32.33).