Patent Publication Number: US-2020277926-A1

Title: Camshaft phaser including a heat-treated target wheel

Description:
TECHNICAL FIELD 
     The present disclosure relates to a position sensor target wheel for a camshaft phaser with a heat-treated tab to protect the tab from damage during assembly of the camshaft phaser and a camshaft phaser including the position sensor target wheel with the heat-treated tab. 
     BACKGROUND 
     A known camshaft phaser includes a target wheel engaged with a rotor of the camshaft phaser. A sensor is used to detect a rotational position of the target wheel to enable proper phasing of a camshaft connected to the rotor. During installation of the target wheel in the camshaft phaser, during installation of the camshaft phaser in an engine, and/or due to rough handling of the camshaft phaser prior to installation in the engine, tabs of the position sensor target wheel contact the rotor, and plastic deformation of the tabs can occur. The plastic deformation results in mis-alignment of the target wheel with respect to the rotor and the camshaft. The mis-alignment impairs the ability of a sensor of the engine to properly read the rotor and camshaft positions, causing errors in the timing of the camshaft. Plastic deformation of the tabs also can lead to premature failure of the target wheel. 
     SUMMARY 
     According to aspects illustrated herein, there is provided a target wheel for a camshaft phaser, including: a radially disposed wall facing in a first axial direction; a first circumferentially disposed wall connected to the radially disposed wall; a second circumferentially disposed wall connected to the radially disposed wall; and a first tab directly connected to the first circumferentially disposed wall and the second circumferentially disposed wall, extending radially outward past the first circumferentially disposed wall and the second circumferentially disposed wall, and including a heat-treated portion. 
     According to aspects illustrated herein, there is provided a camshaft phaser, including: a stator arranged to receive rotational torque and including a plurality of radially inwardly extending protrusions; a rotor including a plurality of radially outwardly extending protrusions circumferentially interleaved with the plurality of radially inwardly extending protrusions and an indentation bounded by a wall; a plurality of phaser chambers, each phaser chamber circumferentially bounded by a respective radially inwardly extending protrusion included in the plurality of radially inwardly extending protrusions and a respective radially outwardly extending protrusion included in the plurality of radially outwardly extending protrusions; a target wheel including a tab with a heat-treated portion; and a bias spring urging the target wheel in a first circumferential direction and the heat-treated portion into contact with the wall of the rotor. A sensor is arranged to detect a rotational position of the target wheel for use in rotating the rotor, with respect to the stator, to change a phase of a camshaft connected to the rotor. 
     According to aspects illustrated herein, there is provided a method of fabricating a target wheel for a camshaft phaser, including: forming the target wheel to include a radially disposed wall facing in an axial direction, a first circumferentially disposed wall connected to the radially disposed wall, a second circumferentially disposed wall connected to the radially disposed wall, and a tab arranged to engage a rotor for a camshaft phaser, directly connected to the first circumferentially disposed wall and the second circumferentially disposed wall, and extending radially outward past the first circumferentially disposed wall and the second circumferentially disposed wall; and heat-treating a portion of the tab. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments are disclosed, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, in which: 
         FIG. 1  is a front isometric view of a target wheel, for a phaser, including a heat-treated tab; 
         FIG. 2  is a back isometric view of the target wheel shown in  FIG. 1 ; 
         FIG. 3  is a detail of area  3  in  FIG. 1 ; 
         FIG. 4  is a cross-sectional view generally along line  4 - 4  in  FIG. 3 . 
         FIG. 5  is back isometric view of a camshaft phaser including the target wheel shown in  FIG. 1 ; 
         FIG. 6  is a section line generally along line  6 - 6  in  FIG. 5 ; 
         FIG. 7  is a detail of area  7  in  FIG. 6 ; and 
         FIG. 8  is a schematic block diagram including the camshaft phaser shown in  FIG. 5 . 
     
    
    
     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. 
       FIG. 1  is a front isometric view of target wheel  100  for a phaser including a heat-treated tab. 
       FIG. 2  is a back isometric view of target wheel  100  shown in  FIG. 1 . 
       FIG. 3  is a detail of area  3  in  FIG. 1 . The following should be viewed in light of  FIGS. 1 through 3 . Target wheel  100  includes: central opening  102 ; radially disposed wall  104 ; circumferentially disposed wall  106  connected to wall  104 ; circumferentially disposed wall  108  connected to wall  104 ; and tab  110 . Axis of rotation AR passes through central opening  102 . In the example of  FIG. 1 , portion  112  of tab  110  is heat-treated. Wall  104 : bounds central opening  102 ; and includes surface  114  facing in axial direction AD 1 , and surface  116  facing in axial direction AD 2 , opposite axial direction AD 1 . Radially inwardly facing surface  118  of wall  106  is at uniform distance UD from axis AR; and, radially inwardly facing surface  120  of wall  108  is at uniform distance UD from axis AR. Stated otherwise, walls  106  and  108  are in the shape of respective portions of a cylinder. 
     Tab  110  connects wall  106  and  108  and extends past wall  106  and wall  108  in radially outward direction RD 1 . In an example embodiment, tab  110  includes portion  122  of radially disposed wall  104 . Tab  110  includes: side wall  124 ; wall  126 ; outer wall  128 ; linking wall  130 ; and linking wall  132 . Side wall  124  extends radially outwardly and in circumferential direction CD 1  with respect to circumferentially disposed wall  106  and includes substantially planar surface  134 , facing radially outwardly and in direction CD 2 , opposite direction CD 1 . Wall  126  extends radially outwardly and in circumferential direction CD 2  from wall  108 . Linking wall  130  connects wall  106  and side wall  124  and includes surface  136  facing radially outwardly. Linking wall  132  connects side wall  124  and outer wall  128  and includes surface  138  facing radially outwardly. Wall  126  is connected to outer wall  128 . 
     In an example embodiment, wall  124  and surface  134  include segment  140  of heat-treated portion  112 . In an example embodiment, wall  130  and surface  134  include segment  142  of heat-treated portion  112 . In an example embodiment, wall  132  and surface  138  include segment  144  of heat-treated portion  112 . In an example embodiment (not shown), only one or two of segments  140 ,  142 , and  144  are heat-treated. In an example embodiment (not shown), areas of target wheel  100  greater than portion  112  are heat-treated as described for portion  112 . For example, a larger portion of tab  110 , all of tab  110 , all of tab  110  and a portion of target wheel  100  beyond tab  110 , or an entirety of target wheel  100  is heat-treated. 
     Tab  110  includes radially disposed surface  146  facing in direction AD 1 . Surface  146  is connected to surfaces  134 ,  136 , and  138  by edge  148 . In an example embodiment, segment  140  extends to edge  148 . In an example embodiment, segment  142  extends to edge  148 . In an example embodiment, segment  144  extends to edge  148 . 
       FIG. 4  is a cross-sectional view generally along line  4 - 4  in  FIG. 3 . The following should be viewed in light of  FIGS. 1 through 4 . Portion  112  is heat-treated using a low temperature ferritic nitrocarburizing process. Portion  112  has a surface hardness of at least 500 Knoop Hardness. Heat-treated segments  140 ,  142 , and  144  include surface layers  150 ,  152 , and  154 , respectively. In an example embodiment, layers  150 ,  152 , and  154  each have a thickness  156  greater than or equal to 0.005 millimeters and less than or equal to 0.025 millimeter. Thickness  156  is exaggerated in  FIG. 4  for purposes of illustration. 
     In an example embodiment, target wheel  100  includes tab  158 . Tab  158 : is directly connected to circumferentially disposed wall  106  and circumferentially disposed wall  108 ; extends radially outward past circumferentially disposed wall  106  and circumferentially disposed wall  108 ; and is located beyond tab  110  in axial direction AD 2 . 
     In an example embodiment, target wheel  100  includes tab  160  extending radially outwardly beyond walls  106  and  108  and connecting walls  106  and  108 . The discussion for tab  110  is applicable to tab  160 . 
       FIG. 5  is back isometric view of camshaft phaser  200  including target wheel  100  shown in  FIG. 1 . 
       FIG. 6  is a section line generally along line  6 - 6  in  FIG. 5 . Camshaft phaser  200  includes: stator  202  arranged to receive rotational torque and including radially inwardly extending protrusions  204 ; rotor  206  including radially outwardly extending protrusions  208  circumferentially interleaved with radially inwardly extending protrusions  204 ; phaser chambers  210 ; bias spring  212  connected to rotor  206 ; and target wheel  100 . Each phaser chamber  210  is circumferentially bounded by: a respective radially inwardly extending protrusion  204 ; and a respective radially outwardly extending protrusion  208 . Tab  110  and tab  158  axially bracket spring  212 , grip spring  212 , and are fixed to spring  212 . 
       FIG. 7  is a detail of area  7  in  FIG. 6 . Thickness  156  of surface layers  150 ,  152 , and  154  in  FIG. 7  is exaggerated for purposes of illustration. Rotor  206  includes indentation  214  bounded by wall  216  in directions RD 1 , CD 1 , and CD 2 . Portion  218  of wall  216  bounds indentation  214  in direction CD 2 . Tab  110  is disposed in indentation  214  and bias spring  212  urges tab  110  in direction CD 2  and into contact with portion  218  of wall  216 , resulting in contact between portion  218  and some or all of heat-treated segments  140 ,  142 , and  144 . 
       FIG. 8  is a schematic block diagram including camshaft phaser  200  shown in  FIG. 5 . As is known in the art, target wheel  100  is arranged to interface with position sensor PS to detect a rotational, or circumferential, position of target wheel  100 , and through the rotational position of target wheel  100 , respective rotational, or circumferential positions of rotor  206  and camshaft CS, non-rotatably connected to rotor  206 . For example, sensor PS sends signal S, including the rotational, or circumferential, position of target wheel  100 , to control unit CU for engine E including camshaft phaser CS. Control unit CU uses signal S and other data to control phasing of camshaft CS. 
     The following should be viewed in light of  FIGS. 1 through 8 . The following describes a method of fabricating a target wheel for a camshaft phaser. Although the method is presented as a sequence of steps for clarity, no order should be inferred from the sequence unless explicitly stated. A first step forms the target wheel to include: a first circumferentially disposed wall; a second circumferentially disposed wall; a tab arranged to engage a rotor for a camshaft phaser, directly connected to the first circumferentially disposed wall and the second circumferentially disposed wall, and extending radially outward past the first circumferentially disposed wall and the second circumferentially disposed wall. A second step heat-treats a portion of the tab, all of the tab, the tab and a portion of the target wheel beyond the tab, or all of the target wheel. 
     In an example embodiment, heat-treating the portion of the tab includes heat-treating the portion of the tab using a low temperature ferritic nitrocarburizing process. In an example embodiment, heat-treating the portion of the tab includes: heat-treating the portion of the tab to a surface hardness of at least 500 Knoop Hardness; or heat-treating a surface layer of the tab, with a thickness greater than or equal to 0.005 millimeters and less than or equal to 0.025 millimeter, to a surface hardness of at least 500 Knoop Hardness. 
     In an example embodiment: forming the target wheel to include the tab includes forming a side wall extending radially outwardly and in a first circumferential direction with respect to the first circumferentially disposed wall, forming a wall extending radially outwardly and in a second circumferential direction from the second circumferentially disposed wall, forming an outer wall connected to the wall, forming a first linking wall connecting first circumferentially disposed wall and the side wall, and forming a second linking wall connecting the side wall and the outer wall; and heating treating the portion of the tab includes heat-treating a portion of one or more of the side wall, the first linking wall, or the second linking wall. 
     During assembly of camshaft phaser  200 , spring  212  rotates target wheel  100  with respect to rotor  206  such that tab  110  contacts rotor  206 . Further, rough handling prior to installation of spring  212  can cause contact between tab  110  and rotor  206 . However, heat-treated portion  112  of tab  110 , which would typically contact rotor  206 , is strengthened due to the heat-treating process, which greatly reduces or eliminates possible damage to tab  110  and possible mis-alignment of target wheel  100  with respect to rotor  206  and camshaft CS. For example, portion  112  resists bending so that: angle  162  between walls  106  and  124  is maintained; and angle  164  between walls  124  and  128  is maintained. Thus, sensor PS properly reads the rotational positions of target wheel  100 , rotor  206 , and camshaft CS, ensuring proper phasing of camshaft CS. Heat-treating portion  112  also increases the durability and service life of target wheel  100 . Further, the increased strength of heat-treated portion  112  enables the fabrication of target wheel  100  using thinner sheet steel in a stamping process, reducing production costs as well as reducing inertia due to target wheel  100 . 
     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. 
     LIST OF REFERENCE CHARACTERS 
     AD 1  axial direction
 
AD 2  axial direction
 
AR axis of rotation
 
CD 1  circumferential direction
 
CD 2  circumferential direction
 
RD 1  radially outward direction
 
UD uniform distance
 
 100  target wheel
 
 102  central opening
 
 104  radially disposed wall
 
 106  circumferentially disposed wall
 
 108  circumferentially disposed wall
 
 110  tab
 
 112  heat-treated portion, tab
 
 114  surface, wall  104 
 
 116  surface, wall  104 
 
 118  surface, wall  106 
 
 120  surface, wall  108 
 
 122  portion, wall  104 
 
 124  side wall, tab
 
 126  wall, tab
 
 128  outer wall, tab
 
 130  linking wall, tab
 
 132  linking wall, tab
 
 134  planar surface, wall  124 
 
 136  surface, wall  130 
 
 138  surface, wall  132 
 
 140  segment, portion  112 
 
 142  segment, portion  112 
 
 144  segment, portion  112 
 
 146  surface, tab
 
 148  edge, tab
 
 150  surface layer, segment  140 
 
 152  surface layer, segment  142 
 
 154  surface layer, segment  144 
 
 156  thickness, surface layer
 
 158  tab
 
 160  tab
 
 162  angle
 
 164  angle
 
 200  camshaft phases
 
 202  stator
 
 204  protrusion, stator
 
 206  rotor
 
 208  protrusion, rotor
 
 210  phase chamber
 
 212  bias spring
 
 214  indentation, rotor
 
 216  wall, indentation
 
 218  portion, wall  216