Patent Publication Number: US-9850995-B2

Title: Hydrokinetic torque coupling device for a motor vehicle

Description:
FIELD OF THE INVENTION 
     The present invention relates to a hydrokinetic torque coupling device for a motor vehicle, such as a torque converter, for instance. 
     BACKGROUND OF THE INVENTION 
     A known hydrodynamic torque converter is schematically and partially illustrated in  FIG. 1  and makes it possible to transmit a torque from the output shaft of an internal combustion engine in a motor vehicle, such as for instance a crankshaft  1 , to a transmission input shaft  2 . 
     The torque converter conventionally comprises an impeller wheel  3 , able to hydrokinetically drive a turbine wheel  4  through a reactor  5 . 
     The impeller wheel  3  is coupled to the crankshaft  1  and the turbine wheel  4  is coupled to guiding washers  6 . 
     A first group of elastic members  7   a ,  7   b  of the compression spring type is mounted between the guiding washers  6  and a central hub  8  coupled to the transmission input shaft  2 . The elastic members  7   a ,  7   b  of the first group are arranged in series through a phasing member  9 , so that said elastic members  7   a ,  7   b  are deformed in phase with each other, with said phasing member  9  being movable relative to the guiding washers  6  and relative to the hub  8 . 
     A second group of elastic members  7   c  is mounted with some clearance between the guiding washers  6  and the central hub  8  in parallel with the first group of elastic members  7   a ,  7   b , with said elastic members  7   c  being adapted to be active on a limited angular range, more particularly at the end of the angular travel of the guiding washers  6  relative to the central hub  8 . The angular travel, or an angular shift α, of the guiding washers  6  relative to the hub  8 , is defined relative to a rest position (α=0) wherein no torque is transmitted through damping means formed by the above-mentioned elastic members  7   a ,  7   b.    
     The torque converter further comprises clutch means  10  adapted to transmit a torque from the crankshaft  1  to the guiding washers  6  in a determined operation phase, without any action from the impeller wheel  3  and the turbine wheel  4 . 
     The second group of elastic members  7   c  makes it possible to increase the stiffness of the damping means at the end of the angular travel, i.e. for a significant a angular offset of the guiding washers  6  relative to the hub  8  (or vice versa). 
     It can be seen that the representation of function M=f(α) which defines the M torque transmitted through the device according to the α angular shift, comprises a first linear portion of slope Ka (for the low values of the α angular shift) and a second, more important, linear portion of slope Kb (for the high value of the α angular shift). Ka and Kb are the angular stiffness of the device, at the beginning and at the end of the angular travel respectively. If K 1  defines the cumulated stiffness of the first springs of each pair of the first group, and K 2  defines the cumulated stiffness of the second springs of each pair of the first group, and K 3  defines the cumulated stiffness of the springs of the second group, then Ka=(K 1 ·K 2 )/(K 1 +K 2 ) and Kb=Ka+K 3 . 
     The break of slope between the first and second portions of the curve may generate vibrations and a significant hysteresis upon operation of the torque converter which might affect the quality of filtration obtained using the damping means. 
     SUMMARY OF THE INVENTION 
     The invention more particularly aims at providing a simple, efficient and cost-effective solution to this problem. 
     For this purpose, it provides a hydrokinetic torque coupling device for a motor vehicle comprising a torque input element intended to be coupled to a crankshaft, a turbine wheel, an impeller wheel rotationally coupled to the torque input element and able to hydrokinetically drive the turbine wheel, a torque output element intended to be coupled to a transmission input shaft, damping means, clutch means adapted to rotationally couple the torque input element and the torque output element in an engaged position, through the damping means, and able to rotationally uncouple the torque input element and the torque output element in a disengaged position, with the damping means being adapted to act against the rotation of the torque input element relative to the torque output element, in the engaged position of the clutch means, with the damping means comprising at least one elastic blade which rotates together with the torque output element or the clutch means respectively, and a supporting member carried by the clutch means or the torque output element respectively, with the blade being elastically maintained supported by said supporting member, with said elastic blade being adapted to bend upon rotation of the torque input element relative to the torque output element, in an engaged position, with the supporting means or the elastic blade respectively being mounted on at least one supporting flange being so mounted as to pivot on the torque output element through a rolling bearing such as a ball bearing, for instance. 
     Such damping means give a characteristic gradual curve, without any break of slope. The invention thus makes it possible to reduce the vibrations generated in operation and provides a high quality of filtration. 
     Besides, such a hydrokinetic torque coupling device is easy to mount and rather inexpensive. 
     It should be noted that the words “radial” and “axial” are defined with respect to the hydrokinetic torque coupling device, which is the axis of rotation of the impeller wheel or of the turbine wheel. 
     It should be noted that a hydrokinetic torque coupling device may be a torque converter when the hydrokinetic torque coupling means comprise an impeller wheel, a turbine wheel and a reactor, or may be a hydrokinetic coupling device when the hydrokinetic torque coupling means have no reactor. 
     Mounting the supporting flange on the central hub through a bearing provides a frictionless guiding which ensures a frictionless relative rotation while enabling the stresses to be taken over. 
     The supporting flange may comprise a radially internal part mounted about the torque output element through the bearing, and a radially external part whereon the supporting member is mounted, with the radially internal and external parts being fastened together, by rivets, for instance. 
     According to one embodiment, the radially internal part of the supporting flange may comprise a cylindrical rim surrounding the bearing. 
     In another embodiment, the radially internal part of the supporting flange may comprise a shoulder delimiting a cylindrical surface extending at one end into a radial surface, with the bearing being accommodated in said shoulder and adapted to rest on the radial surface of said shoulder. 
     The hydrokinetic torque coupling device may comprise at least one internal flange which rotates together with the torque output element and at least one radially external flange positioned radially at least partially outside the internal flange, and pivoting relative to the internal flange, with the elastic blade rotating together with the internal flange, respectively the external flange, with the supporting member being connected to the external flange, respectively the internal flange. 
     Besides, the hydrokinetic torque coupling device may comprise two radially internal flanges rotating together with the torque output element and two radially external flanges so mounted as to pivot about said internal flanges, with the elastic blade being mounted in a space axially arranged between the internal flanges and/or between the external flanges, with the supporting member being mounted in a space axially arranged between the external flanges, respectively the internal flanges, with one of the external flanges being formed by the supporting flange. 
     The turbine wheel may be rotationally coupled to the torque output element and to the internal flange. 
     The clutch means may comprise at least one piston rotationally coupled to the supporting flange, with the piston being able to move between an engaged position wherein it is rotationally coupled to the torque input element and a disengaged position wherein it is rotationally uncoupled from the torque input element. 
     The torque output element then comprises a radial surface, with the motion of the piston in the engaged position being limited by the piston resting on said radial surface of the torque output element. 
     Besides, the torque output element may comprise a central hub. 
     The bearing may be a rolling bearing or a ring, for instance a guiding ring made of plastic or bronze, or more generally a ring having a low coefficient of friction comprising a non-stick coating. Such a ring may be mounted, through a friction-type connection, on the supporting flange or on the torque output element. 
     Besides, the hydrokinetic torque coupling device may comprise a reactor, with the impeller wheel being adapted to hydrokinetically drive the turbine wheel through the reactor. The hydrokinetic torque coupling device thus forms a hydrodynamic torque converter. 
     The hydrokinetic torque coupling device may also comprise one or more of the following characteristics:
         the supporting member comprises at least one rolling body, such as a roller so mounted as to pivot about a shaft, for instance through a rolling bearing, such as a needle bearing, for instance.   the supporting member is mounted on the radially external periphery of the supporting flange,   the impeller wheel is rotationally coupled to a cover wherein the impeller wheel, the turbine wheel, the reactor and/or the damping means are at least partially accommodated.   the torque input element comprises said cover,   the elastic blade is so designed that, in the engaged position, in a relative angular position between the torque input element and the torque output element different from a rest position, the supporting member exerts a bending stress on the elastic blade causing a cross reaction force of the elastic blade on the supporting member, with such reaction force having a circumferential component which tends to move back the torque input element and the torque output element toward said relative rest position.   the elastic blade is so designed that, in the engaged position, in a relative angular position between the torque input element and the torque output element different from a rest position, the supporting member exerts a bending stress on the elastic blade causing a cross reaction force of the elastic blade on the supporting member, with such reaction force having a circumferential component which tends to move back the torque input element and the torque output element toward said relative rest position.   in the engaged position, the angular displacement of the torque input element relative to the torque output element is greater than 20° and preferably greater than 40°.   the elastic blade comprises a fastening portion and an elastic portion comprising a radially internal strand, a radially external strand and a bowed or bent portion connecting the internal  31   a  and the external strand.   the damping means comprise at least two elastic leaves, with each elastic blade rotating together with the torque output element, or the torque input element in engaged position respectively, with each blade being associated with a supporting element rotationally linked with the torque input element in engaged position, or the torque output element respectively, with each blade being elastically maintained supported by said matching supporting element, with each elastic blade being adapted to bend upon rotation of the torque input element relative to the torque output element in engaged position.   the impeller wheel is rotationally coupled to the torque input element and is adapted to hydrokinetically drive the turbine wheel, through a reactor.   the turbine wheel and the flange are rotationally connected to the central hub by a common fastening means or are each rotationally connected to the central hub by a different fastening means.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood, and other details, characteristics and advantages of the invention will appear upon reading the following description given by way of a non restrictive example while referring to the appended drawings wherein: 
         FIG. 1  is a schematic representation of a torque converter of the prior art, 
         FIG. 2  is a sectional view along an axial plane, of a torque converter according to a first embodiment of the invention, 
         FIG. 3  is a sectional front view illustrating a supporting member and an elastic blade of a torque converter according to the invention, 
         FIG. 4  is a view corresponding to  FIG. 2 , illustrating a torque converter according to a second embodiment of the invention, 
         FIG. 5  is a view corresponding to  FIG. 2 , illustrating a torque converter according to a third embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     A hydrokinetic torque coupling device according to a first embodiment of the invention is shown in  FIGS. 2 and 3 . The hydrokinetic torque coupling device is more particularly a hydrodynamic torque converter. Such device makes it possible to transmit a torque from the output shaft of an internal combustion engine in a motor vehicle, such as for instance a crankshaft  1 , to a transmission input shaft  2 . The axis of the torque converter bears reference X. 
     In the following, the words “axial” and “radial” are defined relative to the X axis. 
     The torque converter conventionally comprises an impeller wheel  3 , able to hydrokinetically drive a turbine bladed wheel  4  through a reactor  5 . 
     The impeller wheel  3  is fastened to a cover consisting of two bell-shaped parts  11   a ,  11   b  assembled together by welding and defining an internal volume  12  accommodating the impeller wheel  3 , the turbine wheel  4  and the reactor  5 . Said cover  11   a ,  11 B, also more generally referred to as cover  11 , comprises fastening means  13  making it possible to rotationally couple said cover  11  with the crankshaft  1 . 
     The torque converter further comprises a central hub  8 , the radially internal periphery of which is ribbed, with an X axis and accommodated in the internal volume  12  of the cover  11 . The central hub  8  comprises an annular rim  14  which radially extends outwards and a front end, facing the turbine wheel, which forms a radial surface  15 . 
     The turbine wheel  4  is fastened to the first annular rim  14  of the central hub  8 , for instance by rivets  16  or by welding. 
     Two radially internal annular flanges  17  are mounted in said internal volume  12 , with the two flanges  17  being fastened by their radially internal periphery to the rim  14  of the hub  8  by rivets  16 , as mentioned above, or by welding, for instance. 
     The flanges  17  radially extend and comprise each a radially internal portion  17   a  and a radially external portion  17   b . The radially internal portions  17   a  of both flanges  17  are axially closer to each other than the radially external portions  17   b  of both flanges. 
     Two radially external annular flanges  19 ,  20  are further mounted in the internal volume  12  of the cover  11  around the internal flanges  17 . The external flanges  19 ,  20  are fastened together as will be described in greater details hereunder, 
     The external flange  19  positioned behind or in the vicinity of the turbine wheel  4  is totally positioned radially outside the internal flanges  17 . The external flange  20  positioned on the front, partially extends radially beyond the internal flanges  17  and partially extends radially opposite said internal flanges  17 . The external flange  20  more specifically comprises a first radially internal part  20   a , and a second radially external part  20   b  fastened together by rivets, for instance. The second part  20   b  of the flange  20  comprises a radial zone  20   c  fixed to the first part  20   a  and a cylindrical rim  20   d  mounted about a cylindrical part  8   a  of the central hub  8  through a rolling bearing  18 , such as a ball bearing, for instance. The cylindrical rim  20   d  for example surrounds the external ring of the rolling bearing  18 . 
     Two supporting members or rolling bodies  21  shaped as rollers or cylindrical rollers, are fixed on the radially external periphery of the external flanges  19 ,  20 . The rolling bodies  21  are positioned so as to be diametrically opposed. The rolling bodies  21  are more specifically mounted about shafts  22  which axially extend between the two external flanges, with said shafts being mounted on the external flanges  19 ,  20  using bolts  23  or rivets, for instance. The rolling bodies  21  are mounted on the shafts  22  through rolling bearings  24 , such as needle bearings, for instance. 
     The shafts  22  form spacers which make it possible to preserve the spacing between the external flanges  19 ,  20  with the latter being fastened together at least by bolts  23  or matching rivets. 
     Two elastic leaves  25  are mounted between the internal and the external flanges. As can be best seen in  FIG. 3 , each elastic blade  25  more specifically comprises a fastening portion  25   a  mounted between the radially external parts  17   b  of both internal flanges  17  and fastened to the latter by rivets  26 , here three in number for each blade  25 , and an elastic portion comprising a radially internal strand  25   b , a radially external strand  25   c , and a bowed or bent portion  25   d  connecting the internal strand  25   b  and the external strand  25   c . The bowed or bent portion  25   d  has an angle of approximately 180°. In other words, the elastically deformable portion of the elastic blade  25  comprises two regions radially shifted relative to each other and separated by a radial space. 
     The external strand  25   c  develops on the circumference with an angle ranging from 120° to 180°. The radially external strand  25   c  comprises a radially external surface  25   e  which forms a raceway supported by the corresponding rolling body  21 , with said rolling body  21  being positioned radially outside the external strand  25   c  of the elastic blade  25 . The raceway  25   e  has a globally convex shape. The raceway  25   e  may directly consist of a zone of the external strand  25   c  or of a part which is added onto said external strand  25   c.    
     Each external strand  25   c  is adapted to axially rest on opposite radial surfaces  31  of the external flanges  19 ,  20 . 
     Between each elastic blade  25  and the matching rolling body  21 , the transmitted torque is broken down into radial stresses and peripheral stresses. Radial stresses make it possible for the matching blade  25  to bend and peripheral stresses make it possible for the matching rolling body  21  to move on the raceway  25   e  of the blade  25  and to transmit the torque. 
     The torque converter further comprises clutch means  10  adapted to rotationally couple the cover  11  and the external flanges  19 ,  20  in the engaged position, and adapted to release the cover  11  of the external flanges  19 ,  20  in a disengaged position. 
     The clutch means  10  comprise an annular piston  27  which extends radially and is accommodated in the inner space  12  of the cover  11 , the radially external periphery of which comprises a resting area equipped with clutch lining  28  and adapted to rest on the part  11   b  of the cover  11  in an engaged position, so as to provide a rotational coupling of the cover  11  and the piston  27 . 
     A linking member  29  is fastened to the piston, for instance by rivets, in a zone positioned radially inside the clutch lining  28 . The linking member  29  and the cover  11  may of course consist of one single part, without the operation of the torque converter being affected. 
     The linking member  29  comprises at least protruding zones  32  engaged in recessed zones  33  of the flange  20 . More particularly, the protruding parts are lugs  32  formed by cutting and folding the linking member for instance. 
     The piston  27  is thus rotationally coupled to the external flanges  19 ,  20  while enabling the axial motion of the piston  27  relative to the flange  20  between the engaged and disengaged positions thereof. The motion of the piston  27  is controlled by pressure chambers positioned on either side of the piston  27 . Besides, the motion of the piston  27  in the disengaged position may be limited by the radially internal periphery of the piston  27  resting on the radial surface  15  of the central hub  8 . 
     It should be noted that, in this embodiment, the piston  27  can be so mounted as to pivot directly about the transmission input shaft  2 . 
     Such clutch means  10  make it possible to transmit a torque from the crankshaft  1  to the transmission input shaft  2 , in a determined operation phase, without any action by the hydrokinetic coupling means consisting of the impeller wheel  3 , the turbine wheel  4  and the reactor  5 . 
     In operation, the torque from the crankshaft  1  is transmitted to the cover  11  through the fastening means  13 . In the disengaged position of the piston  27 , the torque goes through the hydrokinetic coupling means, i.e. the impeller wheel  3  and then the turbine wheel  4  fixed to the flange  8 . The torque is then transmitted to the transmission input shaft  2  coupled to the hub through the internal ribs of the hub  8 . 
     In the engaged position of the piston  27 , the torque from the cover  11  is transmitted to the external flanges  19 ,  20 , then to the internal flanges  17  through the damping means formed by the elastic leaves  25  and by the supporting members  21 . The torque is then transmitted to the internal hub  8  whereon the internal flanges  17  are fastened, then to the transmission input shaft  2  coupled to the hub  8  through the internal ribs of said hub  8 . 
     In the engaged position of the piston  27 , when the torque transmitted between the cover  11  and the hub  8  varies, the radial stresses exerted between each elastic blade  25  and the matching rolling body  21  vary and the bending of the elastic blade  25  is modified. The modification in the bending of the blade  25  comes with a motion of the rolling body  21  along the matching raceway  25   e  due to peripheral stresses. 
     The raceways  25   e  have profiles so arranged that, when the transmitted torque increases, the rolling bodies  21  each exert a bending stress on the matching elastic blade  25  which causes the free distal end of the elastic blade  25  to move towards the X axis and a relative rotation between the cover  11  and the hub  8  such that the later move away from their relative rest position. Rest position means the relative position of the flange  11  relative to the hub  8 , wherein no torque is transmitted between the latter. 
     The profiles of the raceways  25   e  are thus such that the rolling bodies  21  exert bending stresses having radial components and circumferential components onto the elastic leaves  25 . 
     The elastic leaves  25  exert, onto the rolling bodies  21 , a backmoving force having a circumferential component which tends to rotate the rolling bodies  21  in a reverse direction of rotation and thus to move back the turbine wheel  4  and the hub  8  towards their relative rest position, and a radial component directed outwards which tends to maintain the raceway  25   e  supported by the matching rolling body  21 . 
     When the flange  11  and the hub  8  are in their rest position, the elastic leaves  25  are preferably radially pre-stressed toward the X axis so as to exert a reaction force directed radially outwards, so as to maintain the leaves  25  supported by the rolling bodies  21 . 
     The profiles of the raceways  25   e  may equally be so arranged that the characteristic transmission curve of the torque according to the angular displacement is symmetrical or not relative to the rest position. According to an advantageous embodiment, the angular displacement may be more important in a so-called direct direction of rotation than in an opposite, so-called reverse direction of rotation. 
     The angular displacement of the cover  11  relative to the hub  8  may be greater than 20°, preferably greater than 40°. 
     The elastic leaves  25  are regularly distributed around the X axis and are symmetrical relative to the X axis so as to ensure the balance of the torque converter. 
     The torque converter may also comprise friction means so arranged as to exert a resisting torque between the flange  11  and the hub  8  during the relative displacement thereof so as to dissipate the energy stored in the elastic leaves  25 . 
       FIG. 4  shows a second embodiment of the invention, which is different from the one shown in  FIGS. 2 and 3  in that the second part  20   b  of the flange  20  comprises a shoulder delimiting a cylindrical surface  34  extending at its front end in a radial surface  35 , with the rolling bearing  18  being accommodated in said shoulder and adapted to rest on the radial surface  35  of said shoulder. 
     The central hub  8  further comprises a shoulder delimiting a cylindrical surface  36  extending at its rear end in a radial surface  37 , with the rolling bearing  18  being accommodated in the shoulder of the central hub  8  and being adapted to rest on the matching radial surface  37 . 
     In this embodiment too, the piston  27  can be mounted around a cylindrical part  38  of the central hub  8  formed at the front end of said hub  8  for instance. The radial surface  15  supporting the piston  27  in the disengaged position is formed behind the above-mentioned cylindrical part. 
       FIG. 5  shows a third embodiment of the invention which is different from the one shown in  FIGS. 2 and 3  in that the flange  20  is formed in one single part, the radially internal periphery of which comprises a rim  39  surrounding the rolling bearing  18 . Besides, in this embodiment, the piston  27  can be mounted around a cylindrical part  38  of the central hub  8  formed at the front end of said hub  8  for instance. The radial surface  15  supporting the piston  27  in the disengaged position is formed behind the above-mentioned cylindrical part  38 .