FR2757590A1 - Hydraulic clutch control receiver, especially for motor vehicle - Google Patents

Abstract

A hydraulic receiver consists of a fixed section formed from an inner metal guide tube (5) and an outer concentric housing (4) which form a blind annular cavity (7) designed to be fed with fluid and containing an axially moving piston (6) with a pressure element (9) designed to act on the clutch release mechanism. The base of the cavity (7) is formed by the inner rim (15) of the outer housing (4), facing towards the axis of symmetry of the guide tube. The inner rim is thicker than the wall of the guide tube and has a groove in it for a static seal (17). The outer housing (4) can be made e.g. from a moulded synthetic material, e.g. a plastics reinforced by fibres, and the piston can also be of a synthetic material.

Description

 The present invention relates to hydraulic receivers, for clutch control, in particular for a motor vehicle, comprising a fixed part comprising an internal guide tube and a concentric external body defining a blind annular cavity suitable for being supplied with fluid and inside. which is axially movable mounted a piston carrying a clean element to act on the declutching device of a clutch.

 Such a receiver, also called a receiving hydraulic cylinder, is described in document EP-B-O 168 932.

 In it, the inner guide tube is metallic and protrudes axially relative to the outer body. This tube has at its rear end a transverse flange trapped, in use, between two opposite surfaces formed respectively on the outer body and on a fixed structure on which the outer body is fixed.

 In addition, it is planned to fix the flange to the body by crimping as visible in Figure 1 of this document. A static seal is interposed between the flange and the dorsal face of the outer body. In use the pressure varies in the cavity defining with the piston a variable volume control chamber.

 In some cases it may be desirable not to pinch the flange between the fixed structure and the external body as this requires providing a specific surface on the fixed structure.

 In this case one can consider using only a fixing by crimping the flange on the metal outer body of moldable material, for example based on aluminum.

 A problem of resistance of the fixing arises under the effect of pressure variations occurring, in use, in the cavity knowing that the flange of the tubeguide forms the bottom of this cavity.

 To do this, one can consider stiffening the internal periphery of the flange, for example, using a bead projecting axially relative to the external periphery of the flange. This increases the cost of the guide tube.

 The object of the present invention is to overcome these drawbacks in a simple and economical manner.

 It is therefore an object of the invention to make the attachment of the tubeguide to the external body more robust. It is another object of the invention to reduce the cost of the guide tube.

 According to the invention a receiver of the above-mentioned type, in which assembly means intervene between the external body and the guide tube to fix the guide tube on the external body, is characterized in that, the bottom of the blind cavity is formed by an inner rim of the outer body directed radially towards the axis of axial symmetry of the guide tube. Thanks to the invention, it is not a radial flange of the guide tube, but an internal rim of the external body which is subject in use to variations in pressure during disengagement and engagement operations of the clutch.

 This internal rim is more robust so that the assembly means are provided. The attachment of the guide tube to the outer body is more robust, more reliable and more durable.

 In addition, the guide tube is arranged because it is the external body which undergoes the pressure variations. The guide tube is less stressed so that the piston slides and therefore moves more precisely and more faithfully.

 In one embodiment, the assembly means intervene between the internal rim and the guide tube.

 The guide tube being fixed on the internal rim therefore calls for less consumption of material since its fixing to the external body is made closer to the axis of axial symmetry of the guide tube. The static seal intervening between the external body and the guide tube is also provided since it is the internal rim and therefore the solid external body which undergoes the pressure variations. This seal is also more economical because it is smaller than that of the prior art.

 In one embodiment, the sealing and the fixing of the guide tube are carried out between the internal periphery of the internal rim and the external periphery of the tube guide.

 Thanks to these characteristics, the guide tube can be devoid of a transverse flange and thus be of purely tubular shape. This reduces costs, as well as the material consumed and the manufacturing operations. The guide tube is easier to store and handle. The static seal is as small as possible and can be axially oblong for better sealing.

 In one embodiment, the seal is mounted in a sealing groove which has the internal rim at its internal periphery. Of course, the structures can be reversed, the groove being formed by stamping in the metal tube.

 The assembly means may consist of a local discharge or creep of material from the guide tube into an assembly groove of the inner rim. The assembly groove can be produced at the internal periphery, of axial orientation, of the internal rim or in the transverse face, turned away from the cavity, of the internal rim. Thus the attachment is robust and reliable, the internal flange being thicker than the guide tube.

 The assembly groove can be merged with the sealing groove, the seal being interposed between the bottom of the groove, preferably of flared shape towards the guide tube, and the local discharge of material from the guide tube. This reduces the number of machining of the external body.

 Alternatively, the assembly groove is separate from the sealing groove and has a radially oblong shape for receiving an open ring and of radially wavy shape. The ring is retractable and radially deformable.

 The guide tube has a groove facing the assembly groove for partial reception of the corrugated ring. The assembly of the guide tube with the external body is done by snap-fastening. Thanks to this arrangement, the guide tube can be symmetrical in shape and comprise, at its other end, an identical groove for receiving a circlip or rod limiting the axial movement of the piston relative to the guide tube.

 The two grooves are produced by the discharge of material radially in the direction of the axis of axial symmetry of the guide tube. When the assembly is carried out at the transverse face of the internal rim, the guide tube can be immobilized axially using a circlip, a nut.

 In the above, the material of the external body does not undergo a crimping operation. This body is therefore formed and can thus be made of moldable plastic. Alternatively, the rim of moldable plastic can be reinforced by an insert, for example metallic.

 It will be appreciated that the fixed structure does not need to be machined to provide a bearing surface for the guide tube.

 The outer body may have at the rear of the internal rim a housing for a rotating joint intervening between the outer body and a rotating shaft, such as the input shaft of the gearbox passing through the guide tube, which can surround the rotating joint.

 It will be noted that the internal rim is easily obtained by molding.

 Because the guide tube is arranged, the piston can slide directly on the guide tube, and carry at its front end a metal load-bearing part obtained by stamping.

 The piston can be made of synthetic material such as moldable plastic reinforced with fibers. Preferably, this material has good sliding qualities.

 The bearing part, in one embodiment, serves as a support for an elastic washer with axial action, called a self-centering washer, pressing an internal radial rim of one of the ball bearing rings in contact with a support section of the load-bearing part. The bearing part also carries the end of a sealing bellows and a preload spring surrounded by the bellows.

 The ball bearing is intended to cooperate with the declutching device and is advantageously sealed.

The declutching device may consist of fingers of a diaphragm forming clutch engagement means or of clutch levers separate from the clutch means then consisting of coil springs or of a washer.
Belleville acting between the cover and the clutch pressure plate. This clutch can be provided with a wear take-up device compensating at least the wear of the friction linings of the clutch friction that the clutch comprises.

 As a variant, the external body may consist of a large closing plate attached to the casing of a transmission box to close the opening of said box through which an input shaft passes.

 The closure plate has an internally hollow protuberance belonging to the fixed part of the concentric receiver of the hydraulic clutch control.

 The protuberance is advantageously in one piece with the plate and internally has the internal rim according to the invention.

 In one embodiment, the assembly means are then offset axially and radially relative to the static seal.

 In another embodiment, the guide tube has a transverse flange directed radially outward and crimped in contact with the rear face of the transverse rim.

Other advantages will appear in the light of the description which follows, with reference to the appended drawings in which:
- Figure 1 is a front view of a closure plate carrying an internal radial rim according to the invention;
- Figure 2 is a sectional view along line AA of Figure 1;
- Figure 3 is a partial sectional view on a large scale showing the coupling of the non-rotating ring of the clutch release bearing to the piston of the receiver;
- Figure 4 is a partial view on a large scale of the crimping of the tubeguide;
- Figure 5 is a perspective view of a receiver for a second embodiment
- Figure 6 is an axial sectional view of the receiver of Figure 5;
- Figure 7 is a partial view of Figure 6 showing the assembly groove;
- Figure 8 is a partial view in axial section of the receiver showing the rear thereof and another means of assembling the guide tube to the outer body of the concentric receiver;
- Figure 9 is a view similar to Figure 8 for another embodiment
- Figure 10 is a sectional view along line 10 of Figure 9;
- Figures 11 to 13 are views similar to Figure 8 for other embodiments.

 In the figures, all the elements common to the various embodiments will be given the same references.

 In the figures is shown the concentric receiver 1 of a hydraulic clutch control comprising, in a known manner, a transmitter, the output of which is connected via a pipe 2 to a supply input 3 of the receiver 1 provided with a chamber variable volume.

 The transmitter is activated in different ways and comprises a piston 6 movable inside a fixed body 4, 5.

 As this is an application for a motor vehicle, the transmitter can be activated by the driver via the clutch pedal.

 As a variant, the transmitter can be activated in an assisted manner, for example using an electric motor, one of the supply terminals of which is connected to a computer controlling the starting of the motor according to determined programs. output shaft of said motor forming the input element of a mechanical transmission with elastic assistance means, said transmission comprising an output element for example in the form of a pusher acting on the piston of the transmitter. In all cases, the piston defines with the fixed body of the transmitter a variable volume chamber. When the transmitter is activated its piston is moved axially so that the variable volume chamber is pressurized, as well as the variable volume chamber of the receiver 1, which increases in volume while that of the transmitter decreases in volume.

 When the transmitter is deactivated, the chambers of the transmitter and the receiver are depressurized, the chamber of the receiver decreasing in volume while that of the transmitter increasing in volume. There is therefore during these operations transfer of control fluid from one room to another. Note that the diaphragm, which conventionally includes a friction clutch, exerts a piston return action when the clutch is re-engaged; the receiver chamber resuming its initial volume.

 The control fluid can be gaseous in nature. It may for example be compressed air. Here the control fluid is hydraulic in nature and consists of oil.

 For simplicity, the control will be called hydraulic control, whatever the nature of the fluid.

 As is known, the receiver chamber 1 is delimited by a fixed part 4 and 5 and by a mobile part 6 in relation to cylinder-piston.

 The fixed part 4.5 delimits a cavity 7 of annular shape into which the supply inlet 3 opens.

 The movable part is a piston 6 of annular shape movable axially inside the cavity 7 to define therewith the aforementioned variable volume chamber.

 The cavity 7, as well as the said chamber, is therefore allowed to be pressurized and depressurized from the inlet 3 via the pipe 2.

 Here the fixed part 4,5 and the movable part 6 - the piston 6 - are coaxial being arranged concentrically. Receiver 1 is therefore of the concentric type; the cavity 7 being blind, of axial and annular orientation.

 More precisely, the fixed part 4.5 is here in two concentric parts 4.5.

 One of the parts, namely the external part 4, generally of annular shape and referred to hereinafter as the external body, centrally comprises a generally tubular end portion before the end 8 surrounding the other part 5 in the form of a tubeguide 5 and belonging to a protrusion 20, generally of tubular shape. This tube 5 is metallic. It is thin to reduce the radial size and to an axis of axial symmetry XX ′.

 The thickness of the tube 5 is less than the thickness of the tubular portion 8, of axial length less than that of the tube 5.

 The tube 5, here metallic, projects axially with respect to the tubular portion 8 and serves as a guide for the piston 6, which thus surrounds the main part of the tube 5, being surrounded by the tubular portion 8.

 The piston 6 carries at its rear end a dynamic lip seal 80.

This seal penetrates inside the cavity 7 and makes it waterproof. The front end of the piston 6 acts on a clutch release bearing 9, which here consists of a ball bearing comprising a rotating ring, forming an attack element, capable of acting on the diaphragm of the clutch and a non-rotating ring in relationship with piston 6.

This piston 6 acts by its front end on the non-rotating ring, separated from the rotating ring by balls.

 Here the rings of the bearing 9 are concentric and coaxial. This thrust bearing is carried by the piston 6 sliding axially along the metal tube 5.

 The bearing 9 can be fixed radially, for example by being force-fitted by its non-rotating ring on the piston 6.

 Here the bearing can move radially relative to the piston 6 and to the diaphragm of the clutch to reduce wear, knowing that the axis of axial symmetry, of the diaphragm, is not confused with that of the receiver 1.

 The centering of the bearing 9 relative to the diaphragm may not be maintained. For example, an element made of elastic material, such as elastomer, can be interposed radially between the piston 6 and the non-rotating ring of the bearing.

This element also couples the piston bearing.

 Here a radial clearance exists between the front end of the piston 6 and the bearing 9 and an elastic washer with axial action 10 couples the bearing to the piston 6. The bearing 9 can travel radially relative to the piston until it finds its centering position relative to the diaphragm. This centering is subsequently maintained by the elastic washer 10. The clutch release bearing 9 is thus self-centering maintained.

 The rotating ring, here the outer ring, is profiled for local contact with the diaphragm, more precisely for local contact with the inner end of the fingers thereof.

 Thus, when the internal end of the fingers of the diaphragm, which is centrally open, is of convex shape, the front face of the rotating ring, intended to cooperate with said end, is of generally planar shape.

 When the internal finger end of the diaphragm is flat, the external face of the rotating ring is then curved.

 Here the stop 9 is suitable for acting on the internal end, shown at 102 in FIG. 6, of the diaphragm fingers, the peripheral part of which, in the form of a Belleville washer, acts on the clutch pressure plate to normally bias said plate towards the vehicle engine flywheel, forming reaction plate, in order to tighten the friction linings of the clutch friction between said reaction and pressure plates integral in rotation with the crankshaft of the vehicle engine.

 This friction, also called friction disc, centrally comprises a hub rigidly or resiliently coupled to a disc carrying the friction linings. The hub is internally grooved for its rotational connection to a shaft driven here the input shaft 100 of the gearbox. This shaft 100 crosses the tubeguide 5 while being surrounded by it. The clutch is therefore normally engaged, the volume of the variable chamber of the receiver 1 then being minimum. A return spring 11 is interposed axially between the portion 8 and the ball bearing in order to maintain, in known manner, the rotating ring of the bearing 9 in permanent contact with the diaphragm to reduce wear. The torque from the motor shaft is therefore transmitted to the input shaft of the gearbox.

 To disengage the clutch, the cavity 7 of the receiver is pressurized in the aforementioned manner, which causes the chamber of the latter to increase in volume and the piston 6 and the stop 9 to move to the left in FIG. 2.

 The diaphragm, pivotally mounted on a cover secured to the flywheel, tilts until its action on the pressure plate is canceled.

The clutch is then disengaged because the friction linings of the clutch friction are then released.

 The engine torque is then no longer transmitted to the input shaft of the gearbox having a casing 12. Of course, the clutch can be equipped with a device for taking up wear on the friction linings.

 When the cavity 7 is depressurized, the diaphragm moves the clutch release bearing and the piston to the right of FIG. 2. The volume of the chamber of the receiver 1 is then minimal and the piston 6 returns to its initial position. In this position, a residual pressure exists in the cavity 7.

 The fixed part 4.5 is intended to be fixed here on the front wall 12 of the fixed casing of the gearbox. The wall 12 is crossed by the input shaft 100 of the gearbox with the intervention of a seal 101, called a rotating joint (better visible in FIG. 6) between the wall 12 and the input shaft so described below. This wall 12 is therefore provided with an opening for crossing the input shaft. This opening is important here and is closed in FIGS. 1 to 4 by a ribbed plate 4 provided with numerous holes 13 for fixing the plate 4 to the wall 12 using screws whose threaded barrel passes through the holes 13 to come in engagement with the internal threads of the wall 12.

 The heads of the screws bear on the front face of the plate 7, here generally of ovoid shape. This plate 4 serves as a closure plate for opening the above-mentioned wall 12.

 According to one characteristic, use is made of this plate 4 to integrate this plate into the hydraulic receiver 1 and form the above-mentioned external body 4 surrounding the guide tube 5.

 Thus the protuberance 20 with its tubular portion 8, of axial orientation, is integral with the plate. This protuberance 20 can be added by welding to the perforated plate 4 for passage of the input shaft of the gearbox. Here the protrusion 20 is of annular shape and is in one piece with the plate 4 of moldable material. This plate 4 is here based on aluminum. We take advantage of this, taking into account the robustness of the plate 4, to extend the latter, behind the wall 8, by a transverse rim 15 directed radially inwards constituting the bottom of the blind cavity 7. This rim 15 will be called internal rim and is thicker than the guide tube 5. It is directed radially towards the axis XX ′.

 This arrangement makes it possible to limit the deformation of the cavity 7 under the effect of the pressure variations of which it is the subject during clutch disengagement and re-engagement operations. The displacement of the piston 6 is thus more precise and more faithful.

 In addition, the guide tube 5 and more precisely the means 16 for assembling it to the closing plate 4, as well as the static seal 17 of the cavity 7 are housed. The seal 17 is of O-shape. .

 Here the assembly means 16 consist of an attachment by crimping a flange 51, of transverse orientation, directed radially outward, which has the guide tube 5 at its rear end.

 These crimping means 16 are offset axially and radially with respect to the seal 17 acting between the internal periphery of the internal rim 15, directed radially inwards, and the external periphery of the guide tube 5. Here the seal 17 is carried by the internal rim 15 while being mounted in an unreferenced sealing groove which the latter has at its internal periphery. This rim 15 is of low height and belongs to the aforementioned protuberance 20, here in one piece with the plate 4. The crimping means 16 are offset rearward relative to the seal.

 The tubular portion 8 constitutes the front part of this protuberance 20, comprising at its external periphery two projections 18, 19 directed generally radially outwards.

 The protrusions 18, 19 are provided with holes, as visible in FIG. 2, extended in the mass of the protuberance to open into the bottom of the blind control cavity 7. The holes therefore open out at the level of the front face of the rim 15, knowing that the projections 18, 19 belong respectively to the supply inlet 3 and to the purge circuit. The return spring 11 surrounds the tubular portion 8 while being centered by the latter. A shoulder is formed at the junction of the tubular portion 8 with the main part of the protuberance 20 suitable for being crossed here by the input shaft 100 of the gearbox.

 This shoulder serves as a support for an end bead that has a protective bellows 21 surrounding the spring 11, in the form of a coil spring. The spring 11 is supported at one of its ends on said bead. The other end of the bellows 21 is hung on a transverse web 22 which has the piston 6 at its front end. The web 22 is directed radially outwards and serves here by its front face to the non-rotating ring of the clutch release bearing 9 and by its rear face to the other end of the spring 11.

 As mentioned above, a radial clearance exists between the piston 6 and this non-rotating ring, here the internal ring. The self-centering spring 10 consists (FIG. 3) of a Belleville washer resting on the front edge of the non-rotating ring and on a sheet metal assembly part 23 fitted on the internal periphery of a recess (not referenced) that presents the piston 6 at its front end. This recess serves as a housing for a scraper seal 150 surrounded by the part 23 and resting on a radial rim directed inwards, which the said part 23 has at its rear end. At its front end, the part 23 has a radial rim directed outwards to support the washer 10.

 The protuberance 20, internally hollow, therefore internally has a front portion, partially defining the cavity 7 open axially towards the front, and a stepped rear portion separated from one another by the internal rim 15. This rear portion is stepped and is internally delimited by a first cylindrical portion of axial orientation 24 and a second cylindrical portion of axial orientation 25 of larger diameter.

 The portion 24 is delimited axially at the front by the flange 15 and at the rear by a flange 26 (FIG. 4) of transverse orientation directed radially outwards. The rim 26, called the outer rim, serves as a support for the rear flange 51 of the guide tube 5. The rim 26 therefore serves as an abutment shoulder for the flange 51. The tubeguide 5 conforms externally to the shape of the first portion 24 and from the rear face of the rim 15 while being in intimate contact therewith.

 The diameter of the main part of the tube 5 is therefore less than that of its rear cylindrical portion 52. The portion 24 therefore forms a bearing surface for the rear portion 52 of the tube 5.

 From the rear end of the plate 4, the material from the second portion 25 of the protuberance 20 is pushed axially in known manner using a crimping tool, to form crimping sectors 16, with axial immobilization of the collar 51 between the shoulder 26 of the protuberance 20 and the crimping sectors 16, in the form of annular sectors, knowing that during this operation the material flows radially inwards. The flange 51 is also locked in rotation under the effect of the clamping force caused by the crimping. Of course as a variant, the crimping sectors 16 can form a continuous ring.

 It will be noted that the diameter of the first portion 24, forming a bearing surface, is generally equal to the external diameter of the tubular portion 8, here being slightly greater than the latter.

 A much more robust crimping is thus obtained than that described in document EP-A-0 168 932 because the hydraulic pressure for supplying the annular cavity 7 is exerted on the flange 15 so that the flange 51 is formed.

 This makes the assembly of the guide tube 5 more reliable and more robust. The life of this receiver is therefore increased, in a simple and economical manner, the metal guide tube 5 being easily obtained by repelling material, while the plate 4 of moldable material is easily obtained by molding. The seal 17 is also provided because the crimping is not carried out at this level unlike the arrangement described in document EP-A-0 168 932. The seal 17 is not axially crushed.

 The tightness of the receiver 1 is therefore improved by being more reliable. In addition, the rear portion 52 of the tube 5 can serve as a centering surface for the seal shown diagrammatically at 101, in contact with the input shaft of the gearbox.

The internal staging of the rear portion of the tube 5 and of the plate 4 promotes this.

 It will be appreciated that the ribbed plate 4 is robust and that the incipient fractures are greatly reduced compared to a solution in which the receiver is fixed by ears to the casing of the gearbox.

 This is due to the large number of fixing holes 13. Of course a seal (not visible) is interposed between the casing 12 and the plate 4, knowing that the plate 4 is fixed at the edge of the opening of the casing 12 of the gearbox to close said opening.

 Of course, as a variant, the gearbox can be replaced by another gearbox, for example with variable pulleys.

 As a variant, the assembly means 16 may consist of a fixing by means of screws of the flange 51 on the abutment shoulder 26.

 Any other means of assembly is possible.

 As will be understood, the external rim 26 delimits at the front the second cylindrical portion 25 serving as a centering surface for the collar 51 while being in intimate contact with the external periphery of the collar 51.

 In FIG. 2, therefore, the traces of the material repulsion leading to widening the second portion 25 can be seen.

 It will be noted that the plate 4 is provided with ribs (FIG. 1) connecting its protuberance to zones provided with fixing holes 13.

 This alternative attachment can be achieved by riveting or using bolts.

 Of course, the presence of a large closure plate is not compulsory. The plate 4 can be replaced by a smaller external body and the crimping can be carried out in the vicinity of the flange 15.

 Thus, in FIG. 5, it is the external part 4 of the fixed part 4.5 which is fixed to the casing of the gearbox, at the aforementioned opening of the casing.

 More precisely, this part 4 forms an overall body of generally annular shape e

 According to one characteristic, we take advantage of this, taking into account the robustness of the body 4, to extend the latter, behind the wall 8 and the plate 120, by a transverse flange 15, directed radially inwards, constituting the bottom of the blind cavity 7. This rim 15, called the internal rim, belongs to a rear tubular section 121 extending at the rear of the plate 120. The rim 15, directed radially towards the axis XX ′, is thicker than tube 5.

 The flange 15 makes it possible to limit the deformation of the cavity 7 under the effect of the pressure variations of which it is the subject during clutch disengagement and re-engagement operations. The displacement of the piston 6 is thus more precise and more faithful.

 In addition, the tube 5 and more precisely the means 16 for assembling it to the body 4, as well as the static seal 17 of the cavity 7 are housed. This seal 17 is here toroidally shaped, being axially oblong shape for good contact with the tube 5 and good sealing.

 Here the assembly means 16 consist of a fixing by crimping.

 More precisely, the rear section 121 is notched, as in FIG. 2, for housing the seal 101 and delimiting the flange 15. An assembly groove 32 is produced at the rear of the flange 15 and the metal of the tube 5 inside the groove 32, here of semi-circular section favorable for good fixing. The thickness of the tube 5 makes this possible. It will be noted that the seal 101 rests here, unlike FIG. 2, directly on the face of the rim 15 facing away from the cavity 7. Thanks to this method of assembly, in combination with the rim 15, the tube is simple in shape and does not have a transverse flange at the rear for fixing it by crimping to the body 4. Material is saved. The tube 5 being of purely tubular form.

The tube 5 undergoes very small deformations under the effect of pressure variations in the cavity 7. The piston 6 moves under good conditions
These crimping means 16 are offset axially towards the rear with respect to the seal 17 acting between the internal periphery of the flange 15, directed radially inwards, and the external periphery of the guide tube 5. Here, the seal 17 is carried by the internal rim 15, while being mounted in a flared sealing groove, not referenced, which the latter has at its internal periphery. The sealing groove is flared radially inwards in the direction of the axis XX ′ and axially is wider than the assembly groove 32. This flange 15 is of low height and belongs to the rear part of the body 4, whose plate 120 is pierced to form the supply inlet 3 opening into the bottom of the cavity 7. The pipe 2 is attached by screwing its base on the upper edge of the plate 120, in the extension of the inlet 3. The crimping means 16 - local creep of the tube 5 in the groove 32 - are located axially between the seals 17 and 101. Note that the solution is simpler than that of Figures 1 and 2 because the channel 3 is made in the thickness of the plate 120.

 The preload spring 1 1 surrounds the tubular portion 8 while being centered by the latter. A shoulder 105 is formed at the junction of the tubular portion 8 with the plate 120 suitable for being crossed by the shaft 100.

 It will be noted that the body 4 does not have a purge channel, this being carried out at the external periphery of the pipe 2 at 119.

 More precisely, the pipe 2 extends outside the casing of the gearbox and crosses said casing. This pipe has outside of said casing a tubular protuberance 119 used to perform the purge. This protuberance is normally covered by a protective cap 118. The pipe has an external end 117 shaped as a plug-in female connector with a pin 116 engaged in slots at the end 117 to receive the male connector of a pipe coming from the transmitter.

 The pipe 2 has a square shape with a vertical part attaching to the plate 120 and a generally horizontal part extending outside the gearbox casing and carrying the drain 119 and the end fitting. Here, the pipe 2 has a base with two laterally holes for screw passage for fixing the base on the outer edge of the plate 120 (Figure 5). Of course, the pipe 2 can be attached by pinning or screwing onto the body 4.

The shoulder 105 serves to support an end bead which, as in FIG. 2, has a protective bellows 21 surrounding the spring 11, in the form of a coil spring. The spring 11 is supported at one of its ends on said bead by means of a metal support piece 123 interposed between the spring and the bead. The part 123 has two transverse parts connected to each other by a generally horizontal part. One of the transverse parts is in contact with the end bead radially above the other transverse part in contact with the spring 11 centered by an extra thickness, which has the rear end of the front tubular portion 8.

 The other end of the bellows 21 is hooked on a metallic support and support piece 122, called carrier piece 122, of annular shape.

 The support piece 122 is here made of sheet metal and carries the elastic washer 10, usually called self-centering washer, the bearing 9 and the front end bead of the bellows 21.

 The part 122 is partially embedded (anchored) in the piston 6 made of synthetic material, here made of plastic reinforced with fibers. The piston 6 may for example be based on Delrin or may be in any other material having good sliding qualities. At the front of the piston 6, there is provided the scraper seal 150, in order, in a known manner, to avoid polluting the friction linings of the friction disc.

 The part 122 has, to be made, holes for its firm anchoring in the piston 6 by the overmolding technique. The piece 122 is therefore fixed by overmolding to the piston 6 made of synthetic material. The part 122 carries the washer 10, the seal 150, the ball bearing 9, the outer ring of which cooperates with the end 102 of the diaphragm fingers, the end of the bellows 21 and of the preload spring 11. The part serves as support at the inner edge of the bearing 9 in the form of a flag and waterproof. In Figure 6, we see at 80 the dynamic seal. Of course, the piece 122 can be attached by snap-fastening on the piston 6. It will be appreciated that the bearing 9 extends mainly above the piece 122 while being directed axially towards the plate 120 to reduce the axial bulk.

 As a variant, the means of assembly 16 of the tube 5 to the body 4 may have another shape. Thus in FIG. 8, the seal 17 is mounted in the bottom of an assembly and sealing groove section 132 of trapezoidal shape. The local material discharge 116 from the tube 5 is carried out directly in this groove 132.

 The seal 17 is compressed between the discharge 116, directed opposite the axis XX 'and the bottom of the groove 132. In this case, the machining of the flange 15 is reduced.

 Alternatively, Figures 9 and 10, the seal 17 is like Figure 6 placed in a particular assembly groove 332 narrower axially than the sealing groove. The assembly is carried out using a radially open corrugated ring 226 mounted in a radial groove 332 of oblong-shaped assembly formed in the flange 15 and in a groove 333 formed in correspondence in the rear end of the tube 5. This groove 333 leads to locally repress the tube 5 inwards in a similar manner to form the groove 153. Thus the assembly of the tube 5 with the body 5 is done by snap-fastening, the circlips being placed in advance in the groove 332 This circlip 226 is elastically deformable radially inwardly to close, then relax and fall into the groove 333 during assembly of the tube 5 with the body 4.

 The inner tube 5 therefore has a symmetrical shape, this tube having at a front end a groove (not referenced in Figure 6) for mounting a circlip.

This groove has the same shape as the groove 333. Of course, the seal 80 comprises an external lip, for contact with the internal periphery of the portion 8 of the body 4, and an internal lip for contact with the external periphery of the tube 5.

 Of course, the outer body can be mounted indirectly on the fixed structure, via the gearbox casing, via an adaptation sole as described, for example, in the document FR-A- 2,745,616.

 In this case, the external body is standard and it is the sole which carries the fixing ears of the assembly means of the bayonet type, acting between the sole and the external body. The clutch release bearing can have, by reversing the structures, a rotating inner ring and a non-rotating outer ring, provided with an internal rim, intended to bear, under the action of the self-centering elastic washer, against the transverse section. support presented by the supporting part 122.

 As is evident from the description of the drawings, the internal rim 15, advantageously obtained by molding, is thicker than the guide tube 5.

The assembly means 16 can be crimping or snap-fastening means and make it possible to fix the guide tube 5 to the internal rim 15. The assembly grooves 32, 132, 332, of the internal rim, open at the internal periphery edge 15.

 The outer body 4 can be made of moldable synthetic material, such as plastic reinforced with fibers.

 The circlip of FIG. 6 forms a stop for the piston 6. This stop can have another shape.

 It will be noted that the entry of the control fluid, here oil, into the cavity 7 takes place under very good conditions. Indeed, in all the figures, the entry 3, in the form of a channel, opens at the upper part of the front face of the internal rim 15. This upper part forms a recess (a notch) of rounded shape extended by a inclined face.

 The internal bore of the portion 8 is also notched at its rear part at the level of the inlet 3. This makes it possible to run in and prevents the upper lip of the seal 80 from coming into contact with the flange 15. The clearance of the front face of the rim 15, delimiting the cavity 7, therefore also affects the rear end of the internal periphery of the front portion 8.

 Of course, the tube 5 can have, as in FIGS. 1 to 4, an end flange 215, directed radially in the opposite direction of the axis XX 'and crimped at 216 in contact with the rear transverse face 115 of the flange 15 turned to the opposite of the cavity 7. The tube does not have an end flange.

 The crimping 216 is here of the axial type, the material of the rear section 121 being crushed axially for preferably the formation of crimping sectors as in the embodiment of FIGS. 1 to 4. It is not the material of the tube which flows and material is saved compared to the embodiments of FIG. 2.

 Of course, in FIG. 12, the static seal 117 can be installed in a groove (not referenced) made in the transverse face 115, a radial clearance exists between the tube 5, the flange 215 of which is crimped as in FIG. 11, and the internal periphery of the rim 15.

 As a variant, (FIG. 13) the flange 15 has at its internal periphery a flange 315 extending its face 115.

 The tube 5 has a thickness reduction at its end adjacent to the collar 315 for the formation of a shoulder formed thanks to the reduction in thickness and cooperating with the front face of the collar 315 facing the cavity 7. After , the material of the free end of the guide tube 5 is folded down in contact with the rear face of the collar 315 for fixing by crimping the tube 5 on the collar 315, the seal 17 being mounted in a sealing groove as in Figures 1 and 16.

 Of course, the various embodiments can be combined with one another, the rotary joint not necessarily being carried by the external body.

 Thus, the assembly modes in FIGS. 6 to 10 can be produced in the rear face 115 of the internal rim 15.

 This face can therefore include an assembly groove which may or may not be separate from a sealing groove, the material of the flange 215 being forced back inside the assembly groove, preferably flared in the opposite direction from the cavity 7.

 This gives good locking in rotation of the tube 5 thanks to the flaring of the assembly groove possibly also forming a sealing groove.

 To prevent the flange 215 from escaping axially in the direction opposite to the cavity, the flange 215 is axially blocked using, for example, a circlip engaged in a groove in the body to pinch the flange 215 between the face 115 and the circlip. Advantageously, the assembly groove is located radially above the sealing groove. As a variant, the body 4 is internally threaded at the rear for mounting an externally threaded washer. This washer forms a nut to pinch the flange between the face 115 and said nut.

 Alternatively, one can use an intermediate piece crimped as a decree in document FR - 96 11888, filed on 30/11/1996, to perform the axial setting.

 Of course, the flange 215 can be bonded to the face 115 when in particular the body 4 is made of plastic.

 2 - Receiver according to claim 1, characterized in that the internal flange (15) is thicker than the guide tube (5).

 3 - Receiver according to claim 1 or 2, characterized in that a static seal occurs between the internal flange (15) and the guide tube (5) while being mounted in a sealing groove formed in the flange internal (15).

 4 - Receiver according to any one of claims 1 to 3, characterized in that the assembly means (16, 116) intervene between the internal flange (15) and the guide tube (5) to fix the guide tube on the outer body (4).

 5 - Receiver according to claim 4, characterized in that the assembly means (16) comprise an assembly groove (32, 132, 332) formed in the internal flange (15).

 6 - Receiver according to claim 5, characterized in that the sealing groove (132) is merged with an assembly groove (132).

 7 - Receiver according to claim 5, characterized in that the sealing groove is separate from the assembly groove (32, 332).

 8 - Receiver according to claims 7 or 8, characterized in that the assembly means (16) consist of crimping means and in that the material of the guide tube (5) is discharged locally into the assembly groove (32, 132).

 9 - Receiver according to claim 8, characterized in that the seal (17) is interposed between the bottom of the assembly groove and the local discharge of material from the guide tube (5).

 10 - Receiver according to any one of claims 5 to 9, characterized in that the assembly means (16) intervene between the external periphery of the guide tube (5) and the internal periphery of the internal flange (15).

Claims (3)

it - Receiver according to claim 10, characterized in that a static seal (17) intervenes between the internal periphery of the internal rim (15) and the external periphery of the guide tube (5).  12 - Receiver according to claim 10, characterized in that the assembly means are latching means.  13 - Receiver according to claim 5, characterized in that the assembly means comprise an open ring and of wavy shape (270) radially engaged in an oblong assembly groove (332) formed in the internal rim and in a groove in vis-à-vis the guide tube (5) at one of its axial ends.  14 - Receiver according to any one of claims 1 to 13, characterized in that the piston is made of synthetic material and slides directly on the guide tube (5).