Abstract:
A rotor assembly with a cylindrical body having a radial disc that is perpendicularly aligned with a hub of a vehicle and an exciter ring through which a sensor detects rotation of the radial disc. The exciter ring is concentrically installed within the cylindrical body to define a gap between a flange thereon and the radial disc. Reluctance sections on the flange are axially aligned with the sensor to generate a signal indicative of rotation. Friction members engage the radial disc and generate thermal energy that is conducted a mounting flange. Thermal energy level may cause the rotor assembly to expand and change the alignment of the radial disc from perpendicular and non-perpendicular with respect to the hub. The gap allows the radial disc and exciter ring to independently move such that the reluctance sections remain axially aligned with the sensor and sensed information is an accurate indication of rotation.

Description:
BACKGROUND OF INVENTION 
   This invention relates to a rotor that is mounted on a hub that is retained on an axle with an exciter ring attached to the rotor wherein the exciter ring remains substantially concentric to the axle whenever the rotor experiences thermal expansive changes resulting from a brake application such that information detected by a sensor regarding the rotative movement of the rotor is not effected by changes in a perpendicular relationship between the rotor and the hub. 
   It is common to provide a vehicle with an electronic control that includes means to detect rotation of the wheels. Information relating to the rotation of the wheels is most often used to effect a brake application of a wheel when information is sensed that may adversely effect the safety or operation of a vehicle. Some of the information is often obtained from an electronic device that detects movement of a rotor by sensing reluctance changes in an exciter ring attached to a hub, as illustrated in U.S. Pat. No. 3,793,545. A wheel for the vehicle is attached to the hub that is retained on an axle of the vehicle. This type structure functions in a satisfactory manner for most applications but in some vehicles the space for locating an exciter ring in the hub is limited and it was suggested the exciter ring could be relocated as an integral part of the rotor to detect rotative movement thereof as disclosed in U.S. Pat. Nos. 5,067,597 and 5,332,065. An integral exciter ring functions in an adequate manner under most operational conditions however under an extreme brake duty cycle during which friction members sequentially engage the rotor for a long period of time without a sufficient time to allow the rotor to cool between periods of engagement, the rotor will experience thermally expansion. This thermal expansion may cause a rotor to be skewed from a perpendicular to a non perpendicular alignment with the hub and effect the validity of some sensed information relating to the rotation of the rotor. 
   SUMMARY OF INVENTION 
   An advantage of the present invention resides in structure that allows for independent thermal expansion of the rotor and an exciter ring and as a result information obtained with respect to rotation of the rotor is not effected by the generation of thermal energy between the rotor and friction members. 
   According to this invention, a rotor assembly for a vehicle is mounted on a hub that is retained on an axle of a vehicle. The rotor assembly is distinguished by a radial disc that is offset from a mounting flange that is fixed to the hub by a cylindrical body and an exciter ring through which a sensor detects rotation of the radial disc with respect to the axle. The radial disc has a first surface that functions as a first friction face and a second surface that functions as a second friction face for first and second friction members. The first and second friction members respectively engage the first and second surfaces to attenuate the rotation of the radial disc during a brake application. The first and second friction members on engagement with the first and second friction faces generate thermal energy that is carried from the radial disc toward the mounting flange by way of the cylindrical body of the rotor. The radial disc reacts to a predetermined thermal energy level by being distorted from perpendicular alignment to non-perpendicular alignment with respect to the hub. The exciter ring is characterized by a cylindrical member having a first end that is concentrically located within the cylindrical body of the rotor to define a gap between a face on an outwardly extending flange on a second end thereof and the radial disc. The outwardly extending flange has a plurality of reluctance sections located thereon that are aligned with the sensor. The sensor reacts to movement of the reluctance sections to provide an electronic control unit with information relating to the rotation of the radial disc, The gap allows the radial disc to move independently with respect to the outwardly extending flange such that the plurality of reluctance sections remain aligned with the sensor whenever the radial disc changes from perpendicular to non-perpendicular alignment with respect to the hub. 
   An advantage of this invention resides in structure that allows a rotor disc to independently move in response to thermal expansive changes while an exciter ring remains in a desired alignment with respect to a sensor that provides an electronic control unit with information relating to the rotation of the rotor. 
   A further advantage of this invention resides in an attachment of a rotor with a hub whereby the retention of an exciter ring with respect to a rotor is not skewed by deflection of the rotor resulting from thermal expansion. 
   A still further advantage of this invention resides in an attachment arrangement for an exciter ring to a rotor whereby the exciter ring is retained during a thermal expansion event of the rotor and not pushed toward a sensor. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
       FIG. 1  is a sectional view of a rotor and exciter ring of the prior art for use in a brake system; 
       FIG. 2  is a sectional view of the rotor and exciter ring of  FIG. 1  with an enlarged view illustrating a relationship that may occur between the rotor and a sensor when thermal energy generated during a brake application causes deflection of the rotor; 
       FIG. 3  is a sectional view of a rotor with an exciter ring made according to the present invention for use in a brake system; 
       FIG. 4  is a sectional view showing a relationship between the exciter ring of  FIG. 3  and the rotor when high thermal energy generated during a brake application causes the rotor to move from a perpendicular to a non-perpendicular alignment with respect to a hub; 
       FIG. 5  is a perspective view of the rotor ring of  FIG. 3 ; 
       FIG. 6  is a sectional view taken along lines  6 — 6  of  FIG. 5 ; 
       FIG. 7  is a sectional view of a rotor and a first exciter ring that are attached to a hub of a vehicle through a fastener system; 
       FIG. 8  is a perspective view of the exciter ring of  FIG. 7 ; 
       FIG. 9  is a sectional view of a rotor and second exciter ring for that are attached to a hub of a vehicle through the fastener system of  FIG. 7 ; and 
       FIG. 10  is a perspective view of the exciter ring of  FIG. 9 . 
   

   DETAILED DESCRIPTION 
   In the description that follows, components of the disc brake in the various embodiments that are identical may be identified by a same number or the same number plus whenever necessary to better describe a functional relationship with another component. 
   The present invention is designed to be incorporated in a corner assembly  10  and may be of a type such as disclosed in U.S. Pat. No. 5,984,422 or 6,718,634, wherein a hub  14  and bearing  16  are retained in a knuckle  12  as illustrated in  FIG. 1 . The bearing  16  includes an inner race  22  with a flange  20  that has a plurality of openings  18  (only one is shown) for receiving a corresponding plurality of studs  19  through which a rotor  42  and ultimately a rim of a wheel are attached to an axle of the vehicle. The inner race  22  of bearing  16  is located on a mounting surface  24  of the hub  14  and separated from an outer race  26  by a plurality of rollers  32 , 34  (only two are shown) that are located between the inner race  22  and outer race  26  in a radial arc around the axial of the hub  14 . The outer race  26  has a plurality of ears  28 , only one of which is shown, with an openings therein through which bolts  30  fix the outer race  26  to the knuckle  12 . A first portion  22   a  of the inner race  22  of bearing  34  is initially positioned on mounting surface  24  on hub  14  and a second portion  22   b  of bearing  32  is later positioned on the mounting surface  24 . The second portion  22   b  has splines  25  thereon that are mated with corresponding splines on the hub  14  such that the second portion  22   b  and hub  14  function as a unit. A nut  13  is attached to the end  14   a  of the hub  14  to engage the second portion  22   b  of the inner race  22  and move the second portion  22   b  toward the first portion  22   a  to align the bearings  32 , 34  between the inner  22  and outer race  26  and affix the hub  14  to the knuckle  12 . When the hub  14  is attached to the knuckle  12 , the flange  20  on the inner race  22  is located in a plane that is perpendicular to the axis of hub  14  such that an annular surface  36  is concentric to the axis of the hub  14  on the inner race  22  and provides a guide for receiving a mounting flange  40  of a rotor  42 . 
   The rotor  42  that includes a radial disc  44  that is offset from the mounting flange  40  by a cylindrical body  46 . The radial disc  44  has a first surface  48  that functions as a first friction face and a second surface  50  that function as a second friction face. The radial disc  44  has a plurality of passages  45  (only one is shown) therein that provide a flow path for the circulation of air to cool the radial disc  44 . The mounting flange  40  includes a corresponding plurality of openings  52  that are matched with the openings  18  in flange  20 . For some vehicles, bolts or studs  19  extend for the mounting of the rim of a wheel of the corner assembly  10  while in larger applications for trucks separate bolts or studs (not shown) are used to attach a rim to the flange  20 . The mounting flange  40  engages flange  20  such that the radial disc  44  is aligned in a perpendicular relationship with the hub  14  and the first  48  and second  50  radial surfaces are positioned in a caliper  53  with first  54  and second  56  friction members being respectively located adjacent first  48  and second  50  surfaces. Once bearing  16  is secured to the hub, the radial disc  44  is maintained in the same perpendicular radial alignment with respect to the hub  14  such that surfaces  48  and  50  are located in parallel planes with respect to the caliper. 
   An exciter ring  60  of a type disclosed in U.S. Pat. No. 5,332,065 is integrally molded into the cylindrical body  46  and located on face  43 . The exciter ring  60  is defined by a plurality of teeth  74 , only one is shown, that are located in axial alignment with a sensor  80  retained on knuckle  80 . The teeth  74  are of a different material than the cylindrical body  46  and as a result produce a different reluctance signal when sensed by sensor  80  that is retained on knuckle  12 . The signal as measured or detected by sensor  80  may be either a magnetic signal or an optical signal as the sensor  80  detects changes in the reluctance between a solid section and an open section or between different materials on surface  43  to create a signal that provides information that is supplied to an electronic control unit (ECU)(not shown) from which information is derived relating to the rotation of the rotor  42 . 
   When an operator desires to effect a brake application, the first and second friction member are brought into corresponding engagement with surfaces  48  and  50  to attenuate the rotation of the radial disc  44 . The signal received from sensor  80  provides the ECU with information relating to a change in rotation of the radial disc  44  and coordinates the braking in accordance with the braking desires of the operator and safe operation of the vehicle. During a brake application, on engagement of the first and second friction members with surfaces  48  and  50 , thermal energy is created that may effect the effectiveness of the friction members. The passages  45  provide a flow path for air to cool the radial disc  44  but under certain conditions such as a rapid sequential engagement of the friction members with surfaces  48  and  50  the generated thermal energy is such that the volume of air flowing through passages  45  is not sufficient to cool the rotor and as a result the rotor  42  may expand both axially and radially and as result the radial disc  44  may change from a perpendicular, illustrated in  FIG. 1 , to a non-perpendicular alignment, illustrated in  FIG. 2 . It has been determined that a transfer of heat generated during such a brake event occurs in a direction from the radial disc  44  toward the mounting flange  40  with expansion changes following in a correspond manner from the radial disc  44  toward the mounting flange  40  with expansive changes being essentially negligible in the flange  40  but significant thermal expansion may occur in the radial disc  44  and in particular at end  70  of cylindrical body  46  and along face  43 . Unfortunately a reluctance signal detected by sensor  80  from movement of openings  74  or the sequential different materials or surface configuration on face  43  may be effected by such thermal expansion and as a result the information developed by the ECU relating to the rotation of rotor  42  may correspondingly be skewed from what actually is occurring at any particular interval of time. It has been suggested that deflection in the radial disc  44  could be reduced with an increase in the thickness of the cylindrical body  46  but such an increase would also result in an increase in the weight of the rotor and most vehicle manufacturers would regard this as a unacceptable solution correct a functional change in the manner information is obtained relating to the operation of the vehicle. 
   The present invention as illustrated by the various embodiments in  FIGS. 3–10  was developed for use in a corner assembly  110  to obtain information relating to the operation of a vehicle and provide an assurance that the information obtained by sensor  80  is not affected by changes in a perpendicular alignment of the radial disc  44  of a rotor  42  caused by thermal expansion of the rotor  42  resulting from the development of thermal energy during braking of a vehicle. 
   In more particular detail, the relationship between the radial disc  44  and in particular the cylindrical body  46  and an exciter ring  160  for the corner assembly  110  is such that the rotor  42  may independently more from a perpendicular to a non-perpendicular alignment with respect to hub  14  while the exciter ring  160  remains in axial alignment with sensor  80 . 
   The exciter ring  160  is defined by a cylindrical member  162  having a first end  164  and a second end  166 . The second end  166  has an outwardly extending radial flange  168  with an axial lip  170  thereon, see  FIGS. 5 and 6 . The flange  168  has a plurality of radial slots  172 , 172 ″ . . .  172   n , that extend from an inner peripheral surface  174  on the cylindrical member  162  toward the axial lip  170 . The first end  164  of the exciter ring  160  is pushed into peripheral surface  62  on cylindrical body  46  of rotor  42  until either end  164  engages a shoulder  63  or lip  170  engages shoulder  65  on face  43  to define a gap  175  between face  177  on flange  168  and shoulder  65 . The cylindrical member  162  may be resiliently retained in peripheral surface  62  but is desirable to retain the cylindrical member  162  to cylindrical body  46  by a fastener defined by a screw or pin  178  that is inserted through the cylindrical member  162  into the cylindrical body  46  to assist in locating the exciter ring  160  on the cylindrical body  46 . Flange  168  has a plurality of radial slots  172 , 172 ″ . . .  172   n  that extending from the inner peripheral surface  174  of the cylindrical member  162  toward the lip  170  such that gap  175  is opened to the environment and as a result moisture that could contribute to the development of oxidation of the rotor  42  is not retained by the exciter ring  160  or debris (friction dust) developed during braking is not retained in a manner that would accumulate in a slot and effect the reluctance signal sensed by sensor  80 . 
   A corner assembly  110  that includes an exciter ring  160  functions in a same manner as the prior art during normal braking activities but now when a predetermined thermal energy level occurs during a braking sequence and the radial disc  44  of rotor  42  is drawn from a perpendicular to a non-perpendicular alignment, as illustrated in  FIG. 4 , due to the coefficient of expansions of the rotor  42  as the thermal energy is conducted from the radial disc  44  toward the mounting flange  40  by way of the cylindrical body  46 , the exciter ring  160  remains in axial alignment with sensor  80 . The gap  175  allows corner  65   a  on face  43  of the radial disc  44  to pivot about the mounting flange  40  without engaging radial flange  168 . Thus, information obtained by sensor  80  and provided to an ECU would not be effected by changes in the radial alignment of the radial disc  44 . 
   For some applications it may be desirable to directly attach an exciter ring to the flange  20  of hub  14  in a corner assembly  210 . Exciter ring  260  illustrates such a modification of the invention that may be achieved by combining several arcuate segments  262  illustrated in  FIG. 8  to define a ring. The arcuate segments  262  are attached to the flange  20  of the hub  14  by studs  19  as illustrated in  FIG. 7 . Each segment of the arcuate segments  262  is defined by a cylindrical member  263  with a first end  264  having an inwardly extending flange  265  and a second end  266  having an outwardly extending flange  268 . The width of the cylindrical member  263  is selected to be greater than the width of the offset of the cylindrical body  46  such that when flange  265  abuts mounting flange  40  of rotor  42  and is located between flange  20  on hub  14  a gap  275  is created between the outwardly extending flange  268  and corner  65   a  on face  43  of radial disc  44  for rotor  42 . This exciter ring  260  functions in a same manner as exciter ring  160  such that when the radial disc  44  deviates from a perpendicular alignment with hub  14 , the exciter ring  260  remains in axial alignment with sensor  80  and the reluctance information gained from the movement of the radial slots  272 , 272 ″ . . .  272   n  with respect to the sensor  80  and provided to the ECU is not skewed in a manner to effect a brake application. 
   In order to reduce the weight of an exciter ring it was decided that an exciter ring may not need to be attached to the flange  20  of hub  14  by each stud and as a result an exciter ring  360  was developed for a corner assembly  310  as illustrated in  FIG. 10 . The exciter ring  360  is defined by a plurality of segments  362  each of which is defined by a cylindrical member  363  with a first end  364  having an inwardly extending flange  365  and a second end  366  having an outwardly extending flange  368 . The inwardly extending flange  365  has a plurality of ears  372 , 372 ′ to define a slot  370  between the mounting holes  376 , 376 ′ though which the mounting studs  19  extend while the width of the cylindrical member  363  is selected to be greater than the width of the offset of the cylindrical body  46  such that when flange  365  abuts mounting flange  40  of rotor  42  and is located between flange  20  on hub  14  a gap  375  is created between the outwardly extending flange  368  and corner  65   a  on face  43  of radial disc  44  for rotor  42 , see  FIG. 9 . In addition, the cylindrical member  363  includes an offset  358  such that the gap  375  extends a distance along the peripheral surface  62  of cylindrical body  46  such that thermal energy is not conducted into the exciter ring  360  in a manner that would effect a change in the axial alignment with sensor  80 . This exciter ring  360  functions in a same manner as exciter ring  260  such that when the radial disc  44  deviates from a perpendicular alignment with hub  14 , the exciter ring  360  remains in axial alignment with sensor  80  and the reluctance information gained from the movement of the radial slots  372 , 372 ″ . . .  372   n  with respect to the sensor  80  and provided to the ECU is not skewed in a manner to effect a brake application.