Abstract:
The invention relates to a hydrokinetic coupling device ( 10 ) characterized by the fact that the web ( 74 ) comprises, at the inner radial end thereof, a collar ( 86 ), which axially extends toward the front between the turbine wheel ( 32 ) and the turbine hub ( 40 ) and which is rotationally joined by friction welding respectively: at the front, to the turbine wheel ( 32 ) by a first weld joint ( 88 ) provided between a front annular contact face ( 90 ) of the collar ( 86 ) and a rear welding face ( 92 ) opposite the inner radial periphery of the turbine wheel ( 32 ) and; at the rear, to the turbine hub ( 40 ) by a second rear weld joint ( 96 ) provided between a rear annular contact face ( 98 ) of the collar ( 86 ) and a front welding face ( 100 ) opposite the outer radial periphery of the turbine hub ( 40 ).

Description:
INTERNATIONAL PATENT APPLICATION NO. PCT/FR2005/050130, PUBLICATION NO. WO2005/085678 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to hydrokinetic coupling apparatus, especially for a motor vehicle. 
     2. Description of the Related Art 
     Numerous hydrokinetic coupling apparatuses are known in the current state of the art, among which are various designs of apparatus according to their applications, and in particular apparatus of the “monoface”, “biface” or again “multi-disc” types. 
     It is for example known, from the documents FR-A-2 825 770 or FR-A-2 765 938, to provide a hydrokinetic coupling apparatus of the “monoface” type, which comprises, considered axially from front to rear:
         a casing consisting of a rear shell which is adapted to be coupled in rotation to a driving shaft, an impulse wheel, and a front shell;   a turbine wheel, which is arranged for rotation with a turbine hub, which is adapted to be coupled in rotation to a driven shaft;   a lock-up clutch for coupling the driving shaft and the driven shaft together, which is operatively interposed between the turbine wheel and the rear shell and comprises a piston, which is movable axially for releasably coupling together the rear shell and the driven shaft), and which includes a damping device, the damping device comprising at least one guide ring which constitutes the input element, a damper plate constituting the output element, and circumferentially acting elastic members interposed between the input element and output element, which are coupled together in rotation but with the ability to perform predetermined circumferential displacement,   and of the type in which the turbine wheel, the turbine hub and the damper plate of the damping device are coupled in rotation by means of joints that are rigid, i.e. they have no play.       

     In general terms, the rigid rotational couplings between the turbine wheel and turbine hub or an input or output element of the damping device, which is also called the damper, can be achieved with any appropriate kind of joint, and especially by riveting, welding or meshing engagement. 
     Thus, there are generally, in particular, a first rigid joint by means of which the turbine wheel is coupled in rotation to the turbine hub, and a second rigid joint by means of which the turbine wheel is coupled in rotation to an element of the damper. 
     In the document FR-A-2 825 770, the hydrokinetic coupling apparatus of the “monoface” type includes a first coupling between the turbine wheel and the turbine hub, which is formed by riveting, and a second coupling between the turbine wheel and the damper plate which is formed by welding. 
     In a modified version in the document FR-A-2 765 938, the second coupling between the turbine hub and the damper plate of the damper is also made by riveting. 
     Hydrokinetic coupling apparatuses of the “multi-disc” type are also known, in which the coupling means between the turbine wheel, turbine hub and input element of the damping device are axial rivets, and such an arrangement is for example described in the document FR-A-2 839 128. 
     However, riveting is a method of making a joint which does not always give full satisfaction. Riveting has various disadvantages, and in particular it requires costly machining operations by way of precision drilling in each of the components to be coupled together in rotation, to form the holes for the passage of the bodies of the rivets. 
     In addition, the heads of the rivets increase the general axial size of the apparatus, and although riveting is simple to apply, it is an expensive way of fastening because of the overall time needed to carry out all the various operations. 
     The document U.S. Pat. No. 5,975,261 describes a further hydrokinetic coupling apparatus of the “multi-disc” type, in which a first rigid coupling is made by friction welding, and the second coupling is made by mating cooperation between, on the one hand, lugs which are formed in the guide ring, and secondly apertures provided in the turbine hub. 
     Rigid couplings of the meshed type also have disadvantages, in particular as regards treatments and precision machining operations in order to make the complementary male and female parts, and they are therefore expensive. In addition, a coupling of this kind is not reliable enough in respect of its liability to wear, so that undesirable noise will tend to occur. 
     That is why welding, and more particularly friction welding, is often the preferred fastening method for coupling the turbine wheel, turbine hub and damper plate, or one of the guide rings of the damper, rigidly together. 
     However, with welding it is also necessary that the weld bands be accessible, in particular in order to enable operations of control and cleaning of the weld bands to be carried out. 
     Nevertheless, in currently known apparatus designs, the turbine wheel, turbine hub and damper plate do not enable operations of these kinds to be easily performed, and therefore do not give any guarantee as to the quality and reliability of the welded joints. 
     In addition, in current motor vehicles, the space available for fitting the engine is becoming smaller and smaller, especially because of the addition of further components, so that smaller size, and consequently a high degree of axial compactness, of the apparatuses, is constantly being sought. 
     More precisely, in the case where the turbine hub is interposed axially between the turbine wheel and the damper plate of the damper, it is necessary to control the first welded joint, at the front, which couples the turbine wheel with the turbine hub in rotation, and also the second joint at the rear which couples the hub rigidly to the damper plate of the damper. 
     Now, those designs which are currently known do not enable access to be gained satisfactorily to the weld bands of the first and second joints, and particularly to the inner rear weld band of the second joint. 
     SUMMARY OF THE INVENTION 
     A main object of the invention is to provide a remedy for the disadvantages discussed above, and to provide a hydrokinetic coupling apparatus of the type defined earlier herein which will be reliable, simple and inexpensive, both in manufacture and in assembly. 
     With this is in view, the invention proposes a hydrokinetic coupling apparatus of the type defined above, characterised in that the damper plate comprises at its inner radial end a flange portion which extends axially forward between the turbine wheel and the turbine hub, and which is coupled in rotation, by friction welding, respectively:
         at the front, to the turbine wheel by means of a first welded joint formed between an annular front contact face of the flange portion and a rear weld face in facing relationship with the inner radial periphery of the turbine wheel, and   at the rear, to the turbine hub through a rear second welded joint formed between an annular rear contact face of the flange portion and a front weld face in facing relationship with the outer radial periphery of the turbine hub.       

     Thanks to the invention, reliable joints are achieved, and the controlled performance of the friction welding operations enables high precision to be obtained during assembly of the turbine wheel, damper plate and turbine hub in a unitary sub-assembly. 
     In addition, friction welding is an advantageous manufacturing method which enables high precision, with high repeatability, to be obtained in mass production. 
     Preferably, this unitary sub-assembly includes a front space which is delimited, firstly, axially at the front by the rear face of the turbine wheel and at the rear by the front face of the radial plate portion of the turbine hub, and secondly, delimited radially on the outside by inner axial face of the flange portion, in such a way as to permit access to the inner weld bands of the first welded joint and the second welded joint respectively, in particular with a view to effecting visual control and/or cleaning of the said weld bands. 
     The weld bands of the welded joints have the advantage of being easily accessible, which facilitates the operations of control and/or cleaning, and it reduces the time which has hitherto been needed to carry out these operations. 
     According to further features of the invention:
         the mean diameters of the annular contact faces, namely the front contact face and rear contact face, of the flange portion are substantially equal to each other;   the first welded joint, between the annular front transverse contact face of the flange portion and the transverse rear weld face of the turbine wheel, comprises an outer front weld band and an inner front weld band, the flange portion of the damper plate extending axially over a predetermined length such as to permit access to the outer weld band and inner weld band, respectively, of the first welded joint, in particular with a view to performing visual control and/or cleaning of the said bands;   the second welded joint, between the annular rear transverse contact face of the flange portion and the front transverse weld face of the turbine hub, comprises a rear outer weld band and a rear inner weld band;   the mean diameters of the front inner weld band and rear inner weld band of the first and second welded joints are substantially equal to each other;   the mean diameters of the front inner weld band and the rear inner weld band of the first and second welded joints are substantially equal to the internal diameter of the flange portion;   the turbine hub includes a radial plate portion, the outer radial periphery of which includes an annular boss which extends axially forwards and is substantially equal to the greatest external diameter of the radial plate portion of the turbine hub;   the mean diameter of the rear outer weld band is substantially equal to the greatest external diameter of the radial plate portion of the turbine hub;   the flange portion of the damper plate is press-formed.       

     Further features and advantages of the invention will appear on a reading of the following description, for an understanding of which reference will be made to the single drawing, which shows diagrammatically a half view in axial cross section of a hydrokinetic coupling apparatus according to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a cross sectional view of a hydrokinetic coupling apparatus according to the instant invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description, those components which are identical, similar or analogous to each other will be designated by the same reference signs. 
     In order to facilitate understanding of the description and claims, we will use, though without limitation, “front” and “rear” orientations which correspond to the left and right hand sides respectively in the drawing; and “axial—radial” and “external/outer/outside—internal/inner/inside” orientations with respect to the general axis of rotation X-X of the hydrokinetic coupling apparatus. 
     The drawing shows a hydrokinetic coupling apparatus  10  which in this case is of the “monoface” type and which comprises a torque converter  14  and a lock-up clutch  16 , which are arranged within a sealed casing  12  filled with oil. 
     The function of a hydrokinetic coupling apparatus  10  of this kind is to couple together two shafts, namely a driving shaft B and a driven shaft A respectively in the case of an application to an automatic transmission for a motor vehicle. In that case, the driving shaft B is the output shaft of the engine of the vehicle, while the driven shaft A is coupled to means for changing speed ratios. 
     The casing  12  comprises a front shell  18  and a rear shell  20 , which are preferably assembled together sealingly by welding. 
     The rear shell  20  has a transverse wall  22  which extends radially, and the outer end of which is extended in length, after a portion welded at 90□, by an axially oriented skirt portion  24  which extends forward. The free terminal edge  26  of the skirt portion is preferably so designed that it enables it to be joined by laser type welding with the free end of the rear shell  20 . 
     The transverse wall  22  of the rear shell  20  of the casing  12  includes on its rear face coupling means  28  which, in the present example, are attached by welding on the radial periphery of the wall  22 , and which comprise means defining a nut which is arranged to receive screws (not shown) for fastening the apparatus  0 . 10  to a connecting face plate member of the engine (not shown). 
     The torque converter  14  comprises an impulse wheel  30  at the front, a turbine wheel  32  at the rear, and a central reaction wheel  34 . 
     The impulse wheel  30  includes vanes  36  which are carried by the front shell  18  of the casing  12 , which is adapted to be coupled in rotation (i.e. drivingly or non-rotatably coupled) to the driving shaft B. 
     The turbine wheel  32  similarly includes vanes  38  which lie facing towards the vanes  36  of the impulse wheel  30 . 
     The turbine wheel  30  is coupled in rotation to a turbine hub  40 , which is adapted to be coupled, through driving means  42 , to the driven shaft A coaxial with the axis X-X of the apparatus  10 . 
     The rotational drive means  42  operatively interposed between the hub  40  and the driven shaft A are, in the present example, defined by mating cooperation between complementary axial grooves and splines which are formed respectively on those two components. 
     The hub  40  and shaft A each have a groove which, in the hub  40 , is towards the rear and, more precisely, in line with the drive means  42  and towards the inside, while in the shaft A it is towards the outside, and once the hub  40  and shaft A are coupled together, the respective grooves define a housing  44  in which a sealing ring  46  is mounted. 
     The driven shaft A preferably includes at its rear end a chamfer for facilitating fitting of the seal  46 . 
     The lock-up clutch  16  comprises a piston  48  which is axially movable, so as to couple the turbine wheel  32  releasably to the driven shaft A, together with a damping device, or damper,  50 . 
     The radially outer part of the turbine hub  40  includes, axially at the front, a radial plate portion  52  which extends radially outwards and which delimits, by its transverse rear abutment face  54 , an annular sliding surface  56  on which the piston  48  is mounted. 
     The piston  48 , which extends generally transversely, includes at its inner radial periphery an L-shaped portion that includes a sleeve portion  58  which extends axially forward and which cooperates sealingly with the surface  56  of the hub  40  which it surrounds. 
     More precisely, a sealing means  60 , such as a segment or sealing ring, is interposed between the inner surface of the sleeve portion  58  of the piston  48  and the surface  56 , in such a way as to provide sealing between a rear first chamber  62 , referred to as the control chamber, and a front second chamber  64  which is referred to as the turbine chamber. 
     The sealing means  60  in this example is carried by the hub  40 , though in a modified version it can be carried by the piston  48 , and it is mounted in an annular groove  66  formed in the surface  56 . 
     Preferably, the surface  56  is formed with a terminal chamfer at its rear axial end, so as to facilitate the fitting of the said sealing means  60  by insertion. 
     Because the apparatus  10  is of the “monoface” type, the lock-up clutch  16  includes an annular friction liner  68  which in this example is carried by the rear face of the outer radial periphery of the piston  48  on which the said liner  68  is, for example, attached by adhesive bonding, the liner being adapted to come into contact with a friction surface  70  which is situated in axial facing relationship with it on the front face of the transverse wall  22  of the rear shell  20  of the casing  12 . 
     Preferably, the friction liner  68  has grooves (not shown), the profile of which is variable according to the application, and which, in particular, enables cooling to be improved in the vicinity of the friction surface  70 , which works in controlled sliding movement. 
     The lock-up clutch  16  for coupling the driving shaft with the driven shaft A, which is operatively interposed between the turbine wheel  32  and the rear shell  20 , is brought into operation after the vehicle has been started and the driving shaft B and driven shaft A have been coupled together hydraulically, so as to avoid the loss of output which is in particular caused by sliding effects between the turbine wheel  32  and the impulse wheel  30 . 
     Thus, in the course of a first operating phase which is called the conversion phase, the torque from the driving shaft is transmitted to the impulse wheel  30 , which drives the turbine wheel  32  by virtue of the flow of oil between the vanes  36  and  38 . 
     During this conversion phase, the damper  50  does not play a part in the damping out of torsional vibrations or oscillations which are caused, in particular, by acyclic effects in the engine, and which are not transmitted at all, or hardly transmitted, because the transmission of the engine torque from the driving shaft to the driven shaft A is achieved solely through the kinetic energy of the oil in the torque converter  14 . 
     In the course of a second operating phase, by causing the pressure to vary on either side of the piston  48 , that is to say between the control chamber  62  and turbine chamber  64 , the piston  48  is displaced axially towards the rear in order to proceed to lock-up, also referred to as bridging, and it is reversed so as to be displaced forward subsequently so as to effect unlocking, or de-bridging. 
     Thus, when the piston  48 , moved by pressure, is displaced axially towards the rear in order to grip the friction liner  68  against the friction surface  70  of the transverse wall  22  of the casing  12 , the torque is transmitted from the wall  22  of the casing  12  to the turbine wheel  32 , across the damping device  50 , and no longer through the turbine wheel  32  and impulse wheel  30  of the torque converter  14  as it was during the conversion phase. 
     The torsion device  50  of the lock-up clutch  16  comprises, in this example, an input element which comprises a guide ring  72 , an output element which comprises a damper plate  74 , and circumferentially acting elastic members  76  which are interposed between the input element  72  and output element  74 , and which are thus coupled in rotation with each other, but with the ability to perform a predetermined angular displacement. 
     In the known way, the guide ring  72  includes, firstly, a radially inner portion  78  which extends generally transversely and which is riveted on the piston  48  so as to couple the input side of the damper  50  in rotation with the piston  48 , and secondly, a generally C-shaped radially outer portion or half-torus, with windows  82  in which the circumferentially acting elastic members  76  are received. 
     The elastic members  76  are thus in engagement, firstly on the lateral edges of the windows  82 , and secondly on a portion of the damper plate  74 . 
     For this purpose the damper plate  74  has at its outer radial periphery lugs  84  which extend axially towards the rear and against the lateral faces on which the elastic members  76  bear. 
     The turbine wheel  32 , the turbine hub  40  and, in the present case, the damper plate  74  of the damper  50  are coupled in rotation with each other by rigid joints, i.e. joints not having any play, which are made by welding, and in particular by friction welding. 
     In accordance with the invention, the damper plate  74  includes at its inner radial end a flange portion  86  which extends axially forward between the turbine wheel  32  and the turbine hub  40 , and which is coupled in rotation to each of those components respectively by friction welding. 
     More precisely, the flange portion  86  of the damper plate  74  is coupled in rotation by friction welding, respectively:
         at the front, to the turbine wheel  32  through a welded joint  88  which is made between an annular front contact face  90  of the flange portion  86  and a rear weld face  92  in facing relationship with the radial inner periphery  94  of the turbine wheel  32 , and   at the rear, to the turbine hub  40  through a second welded joint  96  which is made between an annular rear contact face  98  of the flange portion  86  and a front weld face  100 , which is in facing relationship with the outer radial periphery of the radial plate portion  52  of the turbine hub  40 .       

     The invention enables a unitary sub-assembly to be constructed, which consists of the turbine wheel  32 , the turbine hub  40 , and, in the present case, the damper plate  74  of the damper  50 , and in which the inner and outer bands, respectively, of the first welded joint and the second welded joint are easily accessible so that, in particular, it is possible to control them and/or clean them visually. 
     Preferably, the first welded joint is made in the course of a first step, and the second welded joint in the course of a second step. 
     In addition, the mean diameters of the annular contact faces of the flange portion  86 , namely the front contact face  90  and rear contact face  98 , are substantially equal to each other. 
     More precisely, the first welded joint  88  between the annular front transverse contact face  90  of the flange portion  86  and the transverse rear weld face  92  of the turbine wheel  32 , comprises a front outer weld band  102  and a front inner weld band  104 , the flange portion  86  of the damper plate  74  extending axially over a predetermined length such as to permit access to be obtained to the outer weld band  102  and inner weld band  104  respectively of the first welded joint  88 , in particular with a view to effecting visual control and/or cleaning of the said weld bands. 
     Similarly, the second welded joint  96 , between the annular rear transverse contact face  98  of the flange portion  86  and the transverse front weld face  100  of the turbine hub  40 , comprises a rear outer weld band  104  and a rear inner weld band  106 . 
     Preferably, the mean diameters of the front inner weld band  104  and rear inner weld band  108  of the first and second welded joints  88  and  96  are substantially equal to each other, so as, more particularly, to facilitate access from the rear to the outer weld band of the second joint. 
     The mean diameters of the front inner weld band  104  and rear inner weld band  108  of the first and second welded joints  88  and  96  are preferably substantially equal to the inside diameter of the flange portion  86 , so that the inner weld bands of the first and second joints are disposed substantially in the same plane as the internal face of the flange portion, and can therefore be easily controlled and/or cleaned. 
     The radial plate portion  52  of the turbine hub  40  includes at its radially outer periphery an annular boss  110  which extends axially forward and which carries the said front weld face  100  of the turbine wheel  40 . 
     The mean diameter of the rear outer weld band  106  is substantially equal to the greatest external diameter of the radial plate portion  52  of the turbine hub  40 , that is to say the outer diameter of the radial end of the radial plate portion  52  or of the boss  100 . 
     The damper plate  74  is in one piece made from metal plate or similar material, in such a way that the flange portion  86  is preferably made by press-forming. 
     The application of the present invention is of course not limited to a hydrokinetic coupling apparatus in which the lock-up clutch is of the “monoface” type. 
     Accordingly, the arrangements could be used in hydrokinetic coupling apparatuses in which the lock-up clutch is of the “bi-face” type, that is to say those in which the lock-up clutch includes, in particular, a friction disc which is arranged to be gripped axially by the piston against the transverse wall of the rear shell of the casing, to which the said piston is coupled in rotation with axial mobility, or in which the lock-up clutch is of the “multi-disc” type, also called “three-way” by comparison with the “monoface” and “bi-face” types which only have two discs. 
     For more details about the operation of these apparatuses, reference should be made for example to the following documents: FR-A-2 748 539, FR-A-2 814 790 or FR-A-2 816 019 for apparatus of the “bi-face” type, and, for apparatus of the “multi-disc” type, to the documents FR-A-2 839 128 or FR-A-2 843 433.