Abstract:
A planetary gearset is provided in a transmission for a vehicle. The planetary gearset includes a carrier that rotates about the axis. Tone wheels can be used as part of a speed-sensing mechanism in which the tone wheel includes surface features on an outside surface, and a speed sensor senses the surface features as they rotate about the axis and past the speed sensor. The tone wheel is connected to the carrier via a press-fit or interference-fit. To do so, the tone wheel includes legs or flanges that extend inward from an inner surface of the tone wheel. The legs or flanges flex as the tone wheel is pressed onto the carrier. The legs or flanges securely attach the tone wheel to the carrier.

Description:
TECHNICAL FIELD 
     This disclosure generally relates to a tone wheel configured to interact with a speed sensor. More particularly, the tone wheel is for a planetary gearset and is configured to attach via an interference fit with a gear of the planetary gearset. 
     BACKGROUND 
     Modern vehicles include a plethora of electronic sensors that provide information to one or more controllers. One such sensor is a rotational speed sensor that detects the speed of a rotating component. A tone wheel can either be formed integrally with the rotating component or attached to it. The tone wheel includes slots, grooves, or other surface features. As the rotating component rotates, the surface features of the tone wheel also rotate and an electrical pulse is generated each time a surface feature rotates past the sensor. 
     Transmissions in vehicles have many rotating parts, and a speed of the rotating parts is helpful in many different control settings. One example of a mechanism in a transmission with rotating parts is a planetary gearset. Planetary gearsets include a sun gear, planet gears, a planet carrier, and a ring rear. Any one of these gears can be configured to rotate about the central axis. The detected rotating speed of one of these gears can typically make the rotational speeds of the other gears known through the given gear ratio of the planetary gear set. For example, a tone wheel may be provided about and secured to the carrier to make the speed of the carrier known; hence, the speed of the sun and planet gears also known. 
     SUMMARY 
     In one embodiment, a transmission includes a planetary gearset having a carrier. An annular-shaped tone wheel is connected to the carrier, and has an inner-diameter surface and an outer-diameter surface. The tone wheel further includes a pair of legs extending inward from the inner-diameter surface. An interference fit is provided between the legs and the carrier. 
     In another embodiment, a tone wheel for a transmission of a vehicle is provided. The tone wheel has a body having a convex outer surface, a concave inner surface, and a plurality of flanges. The outer surface has a plurality of surface features arranged annularly thereon about a central axis. The flanges extend inward from the inner surface toward the central axis. Each flange has a mating surface for contacting a carrier. The mating surface is axially offset from the inner surface of the body. 
     In yet another embodiment, a method of assembling a planetary gearset is provided. The method includes connecting a plurality of planet gears to a carrier, wherein the carrier has a plurality of surfaces each located between adjacent planet gears. The method also includes press-fitting a pair of legs of a tone wheel onto each surface to secure the tone wheel to the carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of a planetary gearset with an attached tone wheel; 
         FIG. 2  is a front view of the tone wheel of  FIG. 1  in isolation; 
         FIG. 3  is a perspective view of the tone wheel of  FIG. 2 ; 
         FIG. 4  is a perspective view of a portion of the planetary gearset, illustrating the interference fit between the tone wheel and a carrier of the planetary gearset; and 
         FIG. 5  is a perspective view of the planetary gearset and attached tone wheel, along with an accommodating sensor. 
     
    
    
     DETAILED DESCRIPTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     Referring to  1 - 4 , a planetary gear set  10  for a transmission of a vehicle is illustrated. The planetary gearset  10  includes a sun gear (not shown) that shares a central axis with that of the gearset  10 . Radially outward from the sun gear are three planet gears  14 . The planet gears  14  include meshing teeth  16  that correspond to teeth on the sun gear. As the sun gear rotates, each of the planet gears  14  rotates about its own respective axis. 
     A carrier  18  is driveably connected to each of the planet gears  14 . The carrier  18  can transfer rotational movement to and from the planet gears  14  such that the planet gears  14  can rotate in unison about the sun gear. As the carrier  18  rotates about the central axis, the planet gears  14  rotate about the central axis and their own individual axis as well. 
     A tone wheel is illustrated generally at  20 , and shown in isolation in  FIGS. 2 and 3 . The tone wheel  20  couples to the planet carrier  18  to rotate with the carrier with the same rotational speed. Functioning as part of a rotational speed sensor, rotation of the tone wheel  20  is sensed to determine the rotational speed of the carrier  18  and thus the rotational speed of other components within the planetary gearset through known mathematical gear relationships. 
     The tone wheel  20  is generally round in shape and therefore includes a general diameter. The tone wheel  20  includes an outer-diameter surface  22 . A continuous series of grooves, holes, undulations, or other such surface features  24  are stamped, formed, or otherwise provided on the outer-diameter surface. As will be described below with reference to  FIG. 5 , a pulse is created by a sensor when these surface features pass by the sensor. The speed or frequency of the pulse corresponds to the rotational speed of the tone wheel  20 . 
     Utilizing a tone wheel  20  enables a vehicle controller to determine the rotational speed of the carrier and other portions of the planetary gearset  10 . Accurate determination of the rotational speed of these components is useful for knowing the speeds going into and out of the planetary gear set. 
     During assembly of the planetary gearset  10 , the tone wheel  20  must be installed onto the carrier  18  after the planet gears  14  and the carrier  18  are assembled together. Welding the tone wheel  20  to the carrier  18  can increase the risk of contamination getting into the planet gears and bearings of the planetary gearset  10 . And, typical press-fit applications deform surfaces of the pressed part to assure a tight fit. Precise location and clearance between the tone wheel  20  and the associated sensor is imperative for accurate speed readings. 
     According to the present disclosure, the tone wheel  20  of the planetary gearset  10  is provided with structure that enables it to be press-fit onto the carrier  18 . This eliminates the need for the time, expense, and potential contaminants that come naturally with welding. 
     To accomplish the press-fit, the tone wheel  20  includes an inner-diameter surface  30  with a plurality of legs  32  extending therefrom. The legs  32  are relatively flexible in that they can flex relative to the inner- and outer-diameter surfaces  22 ,  30  of the tone wheel  20 . This allows the legs  32  to be pressed onto the carrier  18  and deform to assure a secure press-fit without deforming the outer-diameter surface  22  on which the surface features  24  are provided. In other words, the legs  32  provide a surface to be press-fit onto an associated surface of the carrier  18  while maintaining the shape of the outer-diameter surface  22 . 
     The legs  32  can come in pairs. As shown in  FIG. 1 , for example, the tone wheel  20  includes three pairs of legs  32 , with each pair contacting one corresponding contact region  34  of the carrier  18 . This embodiment is beneficial for a three-planet-gear gearset in which the carrier includes three regions that extend over and between two of the planet gears  14 . As illustrated in  FIG. 1 , the contact regions  34  can be flanges that extend from an area axially-outward of the planets  14  toward and in-between the planets  14 . The legs  32  can contact opposing sides of this contact region  34  of the carrier  18 . Between two of the pairs of legs  32  are concave regions  36  of the inner-diameter surface  30 . This provides clearance for the individual planet gears  14  to rotate. 
     The tone wheel  20  shown in the figures is but one embodiment in which the tone wheel  20  has three sets or pairs of legs  32  for each of three contact regions  34  of the carrier. This corresponds to the planetary gearset having three planet gears  14 . However, it should be understood that more or less than three planet gears  14  can be provided, and as such, the carrier  18  can be designed to have more or less than three contact regions  34  that extend between a respective pair of planet gears  14 . This can lead to a design of the tone wheel  20  having more or less than three pairs of legs  32 . For example, the planetary gearset  10  may have five planet gears, and the tone wheel  20  can include five pairs of legs  32 , with each pair of legs  32  contacting one respective contact region of the carrier. 
     To make an interference-fit or press-fit secure between the tone wheel  20  and the carrier  18 , a mechanical press (not shown) may be utilized. The press can be hydraulically equipped or otherwise capable of providing a large press force to the tone wheel  20 . The mechanical press can be operated to press the tone wheel  20  along the carrier  18  in the direction of the central axis of the planetary gearset  10 . As the tone wheel  20  is pushed along the carrier, the legs  32  are the first and only part of the tone wheel  20  to contact the carrier  18 . The legs  32  deform slightly outward from the central axis and provide resistance against the contact regions  34  of the carrier  18 . When the press is finished pressing the tone wheel  20  onto the carrier  18 , a secure interference fit is provided between the legs  32  and the contact region  34 . 
     As the legs  32  come in pairs, each pair of legs  32  provide an interference fit with the carrier  18  at two separate locations. Each pair of legs provides two loading points per contact region  34  of the carrier  18 . If three pairs of legs  32  are provided, as illustrated in the figures, then six different loading points are provided. With six different loading points, the mechanics of the deflection of forces with the interference fit is generally hexagonal in shape. If, in contrast, the tone wheel were to have single weld spots or the like to secure the tone wheel to the carrier, only three loading points would be provided and therefore the mechanics of deflection would be triangular in shape. Utilizing pairs of legs  32  to have additional loading points reduces the magnitude of deflection forces at each loading point by spreading the load to additional load points. 
     To further assist with a secure press-fit, the legs  32  are axially offset from the main portion of the tone wheel  20 . In particular, the tone wheel  20  includes an interior body portion  40  that extends from the inner-diameter surface  30 . This interior body portion  40  may extend about the entire inner-diameter surface  30 , and also includes other regions such as the concave regions  36 . The legs  32  extend from the interior body portion  40  and away from the inner-diameter surface and toward the central axis of the tone wheel  20 . The legs  32  also extend in a direction along the central axis from the interior body portion  40  such that the legs  32  are axially offset from the main body portion  40 . This provides the legs  32  with a contact surface  42  that is axially offset from the main body portion  40  for engaging with the contact region  34 . Thus, the point of engagement between the carrier  18  and the tone wheel  20  can be axially offset from the interior body portion  40  and inner-diameter surface  30  of the tone wheel  20 . Having an axially-offset location of contact allows the tone wheel to bend and yield during fitting in a non-functioning area. 
     As explained above, the legs  32  provide a mechanism to allow an interference fit between the carrier  18  and the tone wheel  20  with minimal or no distortion of the outer-diameter surface  22  of the tone wheel itself during assembly. This enables the tone wheel  20  to maintain a critically-accurate and relatively small clearance between the tone wheel  20  and an accommodating speed sensor  50  at all locations along the outer-diameter surface  22 . This is shown in  FIG. 5 . When the tone wheel  20  spins with rotation of the carrier  18 , a pulse is generated by the sensor  50  when the surface features  24  pass by the sensor  50 . The speed or frequency of the pulse corresponds to the rotational speed of the tone wheel  20 . A gap or clearance  52  between the sensor  50  and these surface features  24  can be about 1 mm, and between 0.5 and 1.5 mm in preferred embodiments. Maintaining the size and consistency of this gap  52  as the tone wheel  20  spins is important for accuracy of speed readings. The legs  32  assure the outer-diameter surface  22  is not distorted during the process of fitting the tone wheel  20  to the carrier  18 . This maintains the gap  52  at a preferable size. 
     To further a secure fit between the tone wheel  20  and the carrier  18 , nubs  54  may extend away from each leg  32 . The nubs can be arranged such that when the tone wheel  20  is fitted onto the carrier  18 , each contact region  34  can be held within a pair of the nubs  54  on either end of the contact region. The nubs can also be used as locating features to quickly align the tone wheel  20  to the carrier prior to press-fitting. 
     While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.