Patent Publication Number: US-2016238090-A1

Title: Wedge clutch with centrifugal retention

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a wedge clutch with centrifugal retention, in particular, a wedge clutch with a retention ring including retention features arranged to engage a wedge plate during free-wheel mode for the clutch to prevent the wedge plate from displacing radially outward and frictionally engaging an outer race for the clutch. 
     BACKGROUND 
     Known wedge clutches include inner and outer races and a wedge plates radially disposed between the inner and outer races. Typically, to initiate a locked mode, in which the inner and outer races and wedge plate are non-rotatably connected, the inner race displaces relative the wedge plate to displace the wedge plate radially outward to frictionally engage the outer race. Ideally, during free-wheel mode, when the inner and outer races are rotatable with respect to each other, the wedge plate rotates with the inner race and is free of frictional engagement with the outer race or the extent of frictional engagement between the wedge plate and outer race is insufficient to initiate the locked mode. However, with sufficiently high rotational speeds for the inner race, centrifugal force can displace the wedge plate radially outward, creating sufficient frictional force for an undesired and unplanned switch from the free-wheel mode to the locked mode. Such a switch can cause malfunction of a torque transfer device including the clutch, can damage the clutch and/or the torque transfer device, and may create a safety hazard for a vehicle using the clutch in its drive train. 
     SUMMARY 
     The present disclosure broadly comprises a wedge clutch, including: an inner race including first and second sides facing in first and second opposite axial directions, respectively and a radially outermost surface sloping radially inward from the second side to the first side; an outer race located radially outward of the inner race; a wedge plate radially disposed between the inner and outer races and including third and fourth sides facing in the first and second axial directions, respectively, a radially innermost surface sloping radially inward from the fourth side to the third side, and a first plurality of retention features; and an axially displaceable retention ring including a second plurality of retention features. In a locked mode, the inner race, the wedge plate and the outer race are non-rotatably connected. In a free-wheel mode the inner and outer races are rotatable with respect to each other and the second plurality of retention features is engaged with the first plurality of retention features to block radially outward expansion of the wedge plate. 
     The present disclosure broadly comprises a wedge clutch, including: an inner race including first and second sides facing in first and second opposite axial directions, respectively and a radially outermost surface sloping radially inward from the second side to the first side; an outer race located radially outward of the inner race; a wedge plate radially disposed between the inner and outer races and including third and fourth sides facing in the first and second axial directions, respectively, a radially innermost surface sloping radially inward from the fourth side to the third side, and a first plurality of retention features; a retention ring including a second plurality of retention features; and an actuation assembly arranged to displace the inner race in the first axial direction to implement a locked mode in which the inner race, the wedge plate and the outer race are non-rotatably connected and displace the inner race in the second axial direction to implement a free-wheel mode in which the inner and outer races are rotatable with respect to each other. In the free-wheel mode, the second plurality of retention features are engaged with the first plurality of retention features to block radially outward expansion of the wedge plate. 
     The present disclosure broadly comprises a wedge clutch, including: an inner race including first and second sides facing in first and second opposite axial directions, respectively, and a radially outermost surface sloping radially inward from the second side to the first side; an outer race located radially outward of the inner race; a wedge plate radially disposed between the inner and outer races and including third and fourth sides facing in the first and second axial directions, respectively, a radially innermost surface sloping radially inward from the fourth side to the third side, and a first plurality of retention features; a retention ring including a second plurality of retention features; a resilient element urging the inner race in the first axial direction to implement a locked mode in which the inner race, the wedge plate and the outer race are non-rotatably connected; and an electromagnet arranged to displace the inner race in the second axial direction to implement a free-wheel mode in which the inner and outer races are rotatable with respect to each other. In the free-wheel mode, the second plurality of retention features are engaged with the first plurality of retention features to block radially outward expansion of the wedge plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The nature and mode of operation of the present disclosure will now be more fully described in the following detailed description of the present disclosure taken with the accompanying figures, in which: 
         FIG. 1  is a perspective view of a cylindrical coordinate system demonstrating spatial terminology used in the present application; 
         FIG. 2  is a cross-section view of a torque transfer unit including a wedge clutch with centrifugal retention; 
         FIG. 3  is a detail of area  3 ,  4  in  FIG. 2  showing a locked mode for the wedge clutch; 
         FIG. 4  is a detail of area  3 ,  4  in  FIG. 2  showing a free-wheel mode for the wedge clutch; 
         FIG. 5  is a perspective view of the inner race shown in  FIG. 2 ; 
         FIG. 6  is a perspective view of the wedge plate shown in  FIG. 2 ; 
         FIG. 7  is a perspective view of the retention ring shown in  FIG. 2 ; 
         FIG. 8  is a perspective view of the inner race, retention ring and wedge plate shown in  FIG. 2 ; 
         FIG. 9  is a perspective view of a retention ring for a wedge clutch with centrifugal retention; 
         FIG. 10  is a perspective view of a wedge plate for a wedge clutch with centrifugal retention; and, 
         FIG. 11  is a perspective view of a retention ring for a wedge clutch with centrifugal retention. 
     
    
    
     DETAILED DESCRIPTION 
     At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the disclosure. It is to be understood that the disclosure as claimed is not limited to the disclosed aspects. 
     Furthermore, it is understood that this disclosure is not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the present disclosure. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. It should be understood that any methods, devices or materials similar or equivalent to those described herein can be used in the practice or testing of the disclosure. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this present disclosure belongs. It should be appreciated that the term “substantially” is synonymous with terms such as “nearly”, “very nearly”, “about”, “approximately”, “around”, “bordering on”, “close to”, “essentially”, “in the neighborhood of”, “in the vicinity of”, etc., and such terms may be used interchangeably as appearing in the specification and claims. It should be appreciated that the term “proximate” is synonymous with terms such as “nearby”, “close”, “adjacent”, “neighboring”, “immediate”, “adjoining”, etc., and such terms may be used interchangeably as appearing in the specification and claims. 
       FIG. 1  is a perspective view of cylindrical coordinate system  10  demonstrating spatial terminology used in the present application. The present application is at least partially described within the context of a cylindrical coordinate system. System  10  includes longitudinal axis  11 , used as the reference for the directional and spatial terms that follow. Axial direction AD is parallel to axis  11 . Radial direction RD is orthogonal to axis  11 . Circumferential direction CD is defined by an endpoint of radius R (orthogonal to axis  11 ) rotated about axis  11 . 
     To clarify the spatial terminology, objects  12 ,  13 , and  14  are used. An axial surface, such as surface  15  of object  12 , is formed by a plane co-planar with axis  11 . Axis  11  passes through planar surface  15 ; however any planar surface co-planar with axis  11  is an axial surface. A radial surface, such as surface  16  of object  13 , is formed by a plane orthogonal to axis  11  and co-planar with a radius, for example, radius  17 . Radius  17  passes through planar surface  16 ; however any planar surface co-planar with radius  17  is a radial surface. Surface  18  of object  14  forms a circumferential, or cylindrical, surface. For example, circumference  19  is passes through surface  18 . As a further example, axial movement is parallel to axis  11 , radial movement is orthogonal to axis  11 , and circumferential movement is parallel to circumference  19 . Rotational movement is with respect to axis  11 . The adverbs “axially,” “radially,” and “circumferentially” refer to orientations parallel to axis  11 , radius  17 , and circumference  19 , respectively. For example, an axially disposed surface or edge extends in direction AD, a radially disposed surface or edge extends in direction R, and a circumferentially disposed surface or edge extends in direction CD. 
       FIG. 2  is a cross-section view of torque transfer unit TTU including wedge clutch  100  with centrifugal retention. 
       FIG. 3  is a detail of area  3 ,  4  in  FIG. 2  showing a locked mode for wedge clutch  100 . 
       FIG. 4  is a detail of area  3 ,  4  in  FIG. 2  showing a free-wheel mode for wedge clutch  100 . 
       FIG. 5  is a perspective view of inner race  102  shown in  FIG. 2 . 
       FIG. 6  is a perspective view of the wedge plate shown in  FIG. 2 . The following should be viewed in light of  FIGS. 2 through 6 . Clutch  100  includes inner race  102 , outer race  104 , wedge plate  106  and retention ring  108 . Race  102  includes: sides  110  and  112  facing in opposite axial directions AD 1  and AD 2 , respectively, and, radially outermost surface  114  sloping radially inward from side  112  to  110 . Race  104  is located radially outward of inner race  102 . Wedge plate  106  is radially disposed between races  102  and  104  and includes: sides  116  and  118  facing in directions AD 1  and AD 2 , respectively; radially innermost surface  120  sloping radially inward from side  118  to side  116 ; and retention features  122 . Ring  108  is non-rotatably connected to race  102 , is axially displaceable, and includes retention features  124 . By “non-rotatably connected” elements (for example two elements), we mean that the two elements are connected so that whenever the first element rotates, the second element rotates and whenever the second element rotates, the first element rotates. Radial and/or axial movement of one or both of the two elements with respect to each other is possible, but not required, when the two elements are non-rotatably connected. 
     In a locked mode for clutch  100 , inner race  102 , wedge plate  106  and outer race  104  are non-rotatably connected. In a free-wheel mode for clutch  100 , races  102  and  104  are rotatable with respect to each other, and retention features  124  are engaged with retention features  122  to block radially outward expansion of wedge plate  106  in radial direction RD. Inner race  102  is displaceable in axial direction AD 1  to initiate the locked mode and is displaceable in axial direction AD 2  to initiate the free-wheel mode. 
     In an example embodiment, in the locked mode, at least portion  124 A of retention features are radially outward of retention features  122 . In an example embodiment, in the locked mode, retention features  124  are misaligned with wedge plate  106  so that no line L in radial direction RD, orthogonal to axis of rotation AR for wedge plate clutch  100 , passing through retention features  124 , also passes through wedge plate  106 . That is, features  124  are disengaged from features  122  and do not interfere with the displacement of wedge plate  106  in direction RD. 
       FIG. 7  is a perspective view of retention ring  108  shown in  FIG. 2 . 
       FIG. 8  is a perspective view of the inner race, retention ring and wedge plate shown in  FIG. 2 . The following should be viewed in light of  FIGS. 2 through 8 . In an example embodiment: retention features  122  include slots  126  in wedge plate  106 ; retention ring  108  includes body portion  108 A including inner circumference  128  of ring  108 ; and retention features  124  include protrusions  130  extending in axial direction AD 1  or AD 2  from body portion  108 A. In the example of  FIGS. 2 through 8 , protrusions  130  extend in direction AD 2 . Each slot  126  extends radially outward from end  132  formed by wedge plate  106 . In the free-wheel mode, protrusions  130  are in contact with ends  132 . 
     In an example embodiment, surface  114  includes segments  134 . Each segment  134  includes respective ends  136 A and  136 B and respective center portion  138  located between ends  136 A and  136 B in circumferential direction CD. Ramps  139 A and  139 B are formed between ends  136 A and portion  138  and ends  136 B and portion  138 , respectively. Ends  136 A and  136 B define circumferential extent  140  of a respective segment  134 . Each center portion  138  is at radial distance  142  from axis AR and ends  136 A and  136 B are at radial distance  144 , less than distance  142 , from axis AR. Thus, center portions  138  extends radially inward further than ends  136 A and  136 B. 
     In an example embodiment, surface  120  includes segments  146 . Each segment  146  includes respective ends  148 A and  148 B and respective center portion  150  located between ends  148 A and  148 B in circumferential direction CD. Ramps  151 A and  151 B are formed between ends  148 A and portion  150  and ends  148 B and portion  150 , respectively. Ends  148 A and  148 B define circumferential extent  152  of a respective segment  146 . Each center portion  150  is at radial distance  154  from axis AR and ends  148 A and  148 B are at radial distance  158 , greater than distance  156 , from axis AR. Thus, center portions  150  extend radially inward further than ends  148 A and  148 B. 
     In an example embodiment, portions  150  are disposed in portions  138  to maintain a circumferential alignment of wedge plate  106  with respect to inner race  102 . Thus, since ring  108  is non-rotatably connected to race  102 , wedge plate  106  remains circumferentially aligned with ring  108 , for example, maintaining circumferential alignment of retention features  122  and  124 . 
     Clutch  100  includes actuation assembly  158 . In an example embodiment, assembly  158  is located in housing  160 . Actuation assembly  158  is arranged to displace inner race  102  in directions AD 1  and AD 2 . In an example embodiment, assembly  158  includes resilient element  162  and electromagnet  164 . Element  162  is engaged with housing  160  and inner race  102  and urges inner race  102  in axial direction AD 1 . Electromagnet  164  is arranged to be energized so that electromagnet  164  displaces inner race  102  in axial direction AD 2  to initiate free-wheel mode. The electromagnet is arranged to be un-energized to enable resilient element  162  to displace inner race  102  in the axial direction AD 1  to initiate locked mode. In an example embodiment, clutch  100  includes plate  166  made of magnetic material and fixedly connected to race  102 . By “magnetic material” we mean a material that can be attracted by a magnet. Electromagnet  164  is arranged to be energized such that electromagnet  164  attracts plate  166 , displacing race  102  in direction AD 2 . Resilient element  162  can be any suitable resilient element known in the art and electromagnet  164  can be any electromagnet known in the art. Thrust bearing  167  enables relative rotation of resilient element  162  with respect to housing  160 . 
       FIG. 9  is a perspective view of a retention ring for wedge clutch  100  with centrifugal retention. 
       FIG. 10  is a perspective view of a wedge plate for wedge clutch  100  with centrifugal retention. 
       FIG. 11  is a perspective view of a retention ring for wedge clutch  100  with centrifugal retention. The following should be viewed in light of  FIGS. 2 through 11 . It should be understood that clutch  100  is not limited to the number, shape, size, or configuration of retention elements  122  and  124  shown in  FIGS. 2-8 . In an example embodiment as shown in  FIG. 9 , ring  108  includes protrusions  130  extending radially beyond outer circumferential edge  168  for the ring. The discussion for protrusions  130  in  FIGS. 2 through 8  is applicable to  FIG. 9 . In an example embodiment as shown in  FIGS. 10 and 11 , wedge plate  106  includes features  122  in the form of holes, or indentations,  170  and ring  108  includes features  124  in the form of cylindrical protrusions  130 . For the free-wheel mode, race  102  displaces in direction AD 2  to insert cylindrical protrusions  130  into holes  170  to prevent further displacement of wedge plate  106  in radially outward direction RD. For the locked mode, race  102  displaces in direction AD 1  to remove cylindrical protrusions  130  from holes  170  to enable wedge plate  106  to displace radially outward to frictionally engage race  104 . 
     The following provides further detail regarding clutch  100 . In general, wedge plate  106  is biased radially inward so that surface  114  and  120  are in contact, in particular, ramps  139 A and  139 B are in contact with ramps  151 A and  151 B, respectively. The biasing of plate  106  and the radial expansion and contraction of plate  106  described below is enabled by gap  171  and slots  126  and  173 . In the free-wheel mode, the complimentary slopes of surfaces  114  and  120  and the contact of the ramps result in outer circumferential surface  172  being radially inward of inner circumferential surface  174  by a sufficient amount to eliminate or reduce the frictional contact between surfaces  172  and  174 . As a result the lack of frictional contact between surfaces  172  and  174 , inner race  102  and wedge plate  106  are rotatable with respect to outer race  104 . 
     To switch from the free-wheel mode to the locked mode, assembly  158  displaces race  102  in direction AD 1 . The complimentary slopes of surfaces  114  and  120  result in outer circumferential surface  172  being displaced radially outward to frictionally engage inner circumferential surface  174 . As a result of the frictional contact between surfaces  172  and  174 , race  104  causes wedge plate  106  to rotate with respect to inner race  102 . Regardless of the relative rotation of races  102  and  104  with respect to each other, points  138  and  150  move toward each other. For example, for rotation of wedge plate  106  with respect to race  102  in circumferential direction CD 1 , ramps  151 A slide up ramps  139 A forcing surface  172  radially outward. For example, for rotation of wedge plate  106  with respect to race  102  in circumferential direction CD 2 , ramps  151 B slide up ramps  139 B, forcing surface  172  radially outward. Once the ramps have slid far enough, wedge plate is non-rotatably connected to races  102  and  104  by force in radial direction RD. Continued relative rotation strengthens the force, increasing torque carrying capacity of clutch  100 . 
     To switch from the locked mode to the free-wheel mode, assembly  158  displaces race  102  in direction AD 2 . The complimentary slopes of surfaces  114  and  120  and the bias of wedge plate  106  result in outer circumferential surface  172  displacing radially inward to break the frictional contact between surfaces  172  and  174  and relieve the force on wedge plate  106  in direction RD. The displacement of race  102  in direction AD 2  also engages features  122  and  124 , preventing further displacement of wedge plate  106  in direction RD. 
     In an example embodiment, surface  172  is chamfered and includes segments  172 A and  172 B. In an example embodiment, surface  174  is a groove in race  104  and includes segments  174 A and  174 B. In an example embodiment, electromagnet  164  includes chamfered surfaces  176  and plate  166  includes chamfered surfaces  178 . 
     In an example embodiment, TTU includes housing H, input shaft IS and output shaft OS. Bearings B 1  and B 2  enable rotation of housing H with respect to output shaft OS. Snap rings SR 1  and SR 2  axially fix component C 1  of shaft OS with respect to component C 2  of shaft OS. Component C 1  is non-rotatably connected to race  104  by splines  180  on race  104 . Race  102  is non-rotatably connected to shaft IS by splines  182  on race  102 , which enable axial displacement of race  102  with respect to shaft IS. 
     As noted above, during free-wheel mode for a wedge clutch, centrifugal force can cause a wedge plate for the wedge clutch to displace radially outward, causing an unplanned for switch from the free-wheel mode to the locked mode. Advantageously, wedge plate  106  and retention ring  108 , in particular, features  122  and  124  prevent the undesired radial displacement of wedge plate  106  during free wheel mode. Specifically, during free-wheel mode, feature  124  engage features  122  to block further radially outward displacement of wedge plate  106 . At the same time, features  122  and  124  enable the required radially outward expansion of wedge plate  106  to initiate the locked mode. 
     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.