Abstract:
A cross-track plunging constant velocity joint assembly includes an inner race having an outer diameter, an axial length, inner ball tracks, and a spline engageable with a first torque transfer member. An outer race has an inner diameter, an outer diameter, and outer ball tracks. The outer race is connectable to a second torque transfer member. A cage having multiple windows is disposed between the inner and outer races. A plurality of balls (N) having a ball diameter are held by the cage within the windows and engage pairs of the inner and outer ball tracks. The balls define a joint pitch circle diameter (PCD). The inner race has a plunge depth within the outer race. The ratio of 1.2≦(outer race outer diameter/outer race inner diameter)≦1.7 is satisfied.

Description:
BACKGROUND 
     Constant velocity joints connecting shafts to drive units are common components in automotive vehicles. The drive unit typically has an output shaft or an input shaft for receiving the joint. Typically, the drive unit is an axle box, transfer case, transmission, power take-off unit or other torque device, all of which are common components in automotive vehicles. Typically, one or two joints are assembled to the shaft to form a propeller or drive shaft assembly. The propeller shaft assembly may be connected, for instance, at one end to the output shaft of a transmission and, at the other end, to the input shaft of a differential. The shaft may be solid or tubular with ends adapted to attach the shaft to an inner race of the joint. An outer race of the constant velocity joint may be connected to the drive unit. The inner race of the joint is typically press fit, splined, or pinned to the shaft, making the outer race of the joint available to be bolted or press fit to a hub connector, flange or stubshaft of the particular drive unit. At the other end of the propeller shaft, a similar connection is made to a second drive unit when connecting the shaft between the two drive units. 
     Motor vehicles may use propeller or drive shafts to transfer torque via the constant velocity joint from the one input unit to an output unit, for example, from a front drive unit to a rear axle differential such as in rear wheel and all wheel drive vehicles. Propeller shafts are also used to transfer torque and rotational movement to the front axle differential in four-wheel drive vehicles. In particular, two-piece propeller shafts connected by an intermediate joint are commonly used when larger distances exist between the front drive unit and the rear axle of the vehicle. Similarly, inboard and outboard axle drives are commonly used in motor vehicles to transfer torque from a differential to the wheels. The torque transfer is achieved by using a propeller shaft assembly consisting of one or two joints assembled to an interconnecting shaft in the manner indicated above. 
     Joint types that may be used include Cardan, Hooke or Rzeppa type universal joints. Typically, Rzeppa type constant velocity joints are employed where transmission of a constant velocity rotary or homokinetic motion is desired or required. Constant velocity joints include tripod joint, double offset joint, and cross groove designs having plunging or fixed motion capabilities. The tripod type constant velocity joint uses rollers or trunnions as torque transmitting members and the other constant velocity joint types use balls as torque transmitting members. These types of joints assembled to an interconnecting shaft are applied in inboard axle and outboard axle drives for front wheel drive vehicles and on the propeller shafts found in rear wheel drive, all-wheel-drive, and four-wheel drive vehicles allowing for angular articulation or axial motion. As between the fixed and plunging types of constant velocity joints, the plunging joint typically experience more noise, vibration and harshness (“NVH”) issues due to sliding forces as well as clunking noise due to joint tolerances. 
     The torque transfer capability of a cross-track constant velocity joint is also influenced by its moment of inertia, which is primarily a function of the maximum radii of the constant velocity joint&#39;s parts, rather than their mass. Thus, it would be desirable to have an improved cross-track constant velocity joint that benefits from the torque transfer to radius relationship to reduce the mass of the assembly. Moreover, a cross-track constant velocity joint that provides a reduced package size for a particular application would also be of benefit. Also, a cross-track constant velocity joint with optimized ratios would provide additional benefits, such as weight reduction, package size control, reduced part envelope and/or part runout, improved vibration deadening, increased strength per package size, and increased torque transfer capability per unit weight. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of an automotive drive system for an exemplary four wheel drive vehicle employing an exemplary plunging cross-track constant velocity joint. 
         FIG. 2  is an exploded perspective view of the exemplary constant velocity joint. 
         FIG. 3A  illustrates an outer joint portion of the exemplary constant velocity joint. 
         FIG. 3B  is an illustration of outer race ball tracks employed with the outer race. 
         FIG. 3C  is an enlarged view of a ball employed with the exemplary constant velocity joint shown engaging an outer race of the outer joint portion of the constant velocity joint. 
         FIG. 4A  is a side cross-sectional view of a cage employed with the exemplary constant velocity joint. 
         FIG. 4B  is a front cross-sectional view of the cage. 
         FIG. 5A  is a side cross-sectional view of an inner joint portion of the exemplary constant velocity joint. 
         FIG. 5B  is a front elevational view of the inner joint portion of the exemplary constant velocity joint. 
         FIG. 5C  is an illustration of inner race ball tracks employed with the inner joint portion of the exemplary constant velocity joint. 
         FIG. 5D  is an enlarged view of the ball employed with the exemplary constant velocity joint shown engaging an inner race of the inner joint portion of the constant velocity joint. 
         FIGS. 6A and 6B  provide a table identifying various design parameters of the exemplary constant velocity joint and their corresponding ranges. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the discussion that follows and also to the drawings, illustrative approaches to the disclosed systems and methods are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the disclosed device. Further, the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
     While the device is described with respect to an exemplary cross-track constant velocity joint (CVJ) for use in a vehicle, the following apparatus is capable of being adapted for various purposes including automotive vehicles drive axles, motor systems that use a propeller shaft, or other vehicles and non-vehicle applications that require CVJ&#39;s for torque transmission. 
     An exemplary drive system  10  for a typical four-wheel drive vehicle is shown in  FIG. 1 . While a four-wheel drive system is shown and described, the concepts here presented could apply to a single drive unit system or multiple drive unit system, including rear wheel drive only vehicles, front wheel drive only vehicles, all wheel drive vehicles, and four-wheel drive vehicles. 
     The exemplary drive system  10  includes an engine  12  that is connected to a transmission  14  and a power take-off unit (PTU)  16 . A front differential  18  has a front right hand side half shaft  20  and front left hand side half shaft  22 , each of which are connected to a wheel  24  and deliver power to the wheels. Attached to the ends of the right hand side half shaft  20  and left hand side half shaft  22  are constant velocity joints  26 . A propeller shaft  28  connects the transmission  18  to a rear differential  30 . The rear differential  30  includes a rear right hand side shaft  32  and a rear left hand side shaft  34 , each of which has a wheel  24  attached to one end thereof. Constant velocity joints  26  are located on both ends of the half shafts  32 ,  34  that connect to the wheels  24  and the rear differential  30 . The propeller shaft  28  may be a two piece propeller shaft that includes several high-speed constant velocity joints  26  and a high-speed shaft support bearing  36 . The propeller shaft  28  includes first and second interconnecting shafts  38 ,  40 . The shafts  20 ,  22 ,  38 ,  40 ,  32 ,  34  may be solid or tubular with ends adapted to attach each shaft to a particular constant velocity joint  26 , as appropriate for the particular application. 
     The constant velocity joints  26  transmit power to the wheels  24  through the propeller shaft  28  even if the wheels or the propeller shaft  28  have changed angles due to steering or raising and lowering of the suspension of the vehicle. The constant velocity joints  26  may be any of a variety of joint types, including but not limited to a plunging tripod, a cross groove joint, a fixed joint, a fixed tripod joint, or a double offset joint, all of which are recognized terms for identifying different varieties of constant velocity joints  26 . The constant velocity joints  26  allow for constant velocity torque transmission within the joint at operating joint angles that are typically encountered in every day driving of automotive vehicles in both the half shafts and propeller shafts of these vehicles. Optionally, each constant velocity joint may be replaced with any other types of joint. Thus, any of the constant velocity joints identified in  FIG. 1  at  26  or  36  may include a constant velocity joint. Because the torque transfer capability of the constant velocity joint is influenced by its moment of inertia, which is a function of the maximum radii of the constant velocity joint parts, and is less effected by the mass of the constant velocity joint parts, it may be beneficial to have a cross-track constant velocity joint with optimized ratios that benefits from the torque/radius transfer relationship in order to reduce the mass of the system or to optimize its performance. 
     With reference to  FIGS. 2 and 3A  thru  3 C, an exemplary cross-track constant velocity joint  42  may include an annular outer race  44  having a generally cylindrical inner face  46  defining an inner diameter D bore , and a generally cylindrical outer face  48  defining an outer diameter D OR . Outer race  44  has a front face  50  and a rear face  52  that define an axial outer race length OR L . 
     Arranged on inner face  46  of outer race  44  are first and second outer ball tracks  54  and  56 . Each outer ball track  54  and  56  has a track depth t D  corresponding to a radial distance measured from inner face  46  to a bottom  58  and  60  of outer ball tracks  48  and  50 , respectively. Outer ball tracks  54 ,  56  have substantially the same track depth t D . Outer ball tracks  54 ,  56  extend over the entire length OR L  of outer race  44  from front face  50  to rear face  52 . 
     Outer race  44  may be secured to a drive shaft of a drive unit, for example, PTU  16 , front differential  18  and rear differential  30 , as illustrated in  FIG. 1 , or any other member capable of transmitting a torque to or from constant velocity joint  42 . Various means may be used to attach outer race  46  to the corresponding drive shaft. For example, outer race  46  may be bolted to the drive shaft using a plurality of bolts received in corresponding bolt holes  62  extending lengthwise through outer race  46  from front face  50  to rear face  52 . Other connection means may also be employed depending on the requirements of the particular application. 
     Referring to  FIGS. 2 and 5A  thru  5 D, arranged within outer race  44  is an inner race  64  having an outer face  66  and inner first and second ball tracks  68  and  70 . Outer face  66  of inner race  64  has, as seen in longitudinal section ( FIG. 5A ), a generally roof-shaped contour that is interrupted by the inner ball tracks  68 ,  70 . Outer face may also have any of a variety of other contours, including but not limited to circular, elliptical, parabolic, and linear, to name a few. The roof-shaped outer face  66  includes a generally cylindrical midsection region  72  flanked by generally conical surface portions  74  adjoining the latter tangentially. Midsection region  72  defines a maximum outer diameter D IR  of inner race  64 . Inner race  64  has a front face  76  and a rear face  78  that define an axial inner race length IR L . 
     Inner ball tracks  68  and  70  have a track depth t d  corresponding to a radial distance measured from midsection region  72  of outer face  66  of the inner race to a bottom  80 ,  82  of inner ball tracks  68  and  70 , respectively. Inner ball tracks  68 ,  70  have substantially the same track depth t D . Inner ball tracks  68 ,  70  extend over the entire length IR L  of inner race  64  from front face  76  to rear face  78 . 
     Inner race  64  may include a central orifice  86  extending lengthwise through the inner race from front face  76  to rear face  78 . An inner surface of orifice  86  includes a series of longitudinal toothing  88  defining a spline  91  having a length LS. Orifice  86  is configured for rotationally fixed insertion of a correspondingly configured drive shaft, such as a journal shaft of a drive unit or any other member capable of transmitting a torque to or constant velocity joint  42 . The contact points between the spline  91  of inner race  64  and the spline of the drive shaft received in orifice  86  define a spline pitch circle diameter PCD spline . The distance from an outer diameter of the spline to the bottom  80 ,  82  of inner ball tracks  68 ,  70  corresponds to a spline inner distance S IR . 
     Referring to  FIGS. 2  thru  5 D, multiple balls  90  having a diameter “d” are guided in pairs of ball tracks consisting in each case of one outer first ball track  54  and one inner first ball track  68 , and one outer second ball track  56  and one inner second ball track  70 . A cage  92  is arranged between the outer race  44  and the inner race  64 , and includes circumferentially distributed windows  94  in which the balls  90  are received. With particular reference to  FIGS. 4A and 4B , cage  92  includes a set of long windows  96  and short windows  98  alternately arranged over the circumference of the cage. Large windows  96  have a circumferential length Lc and receive balls  90  guided in the track pairs consisting of outer second ball tracks  56  and inner second ball tracks  70 . Small windows  98  have a circumferential length L S  and receive balls  90  guided in the track pairs consisting of outer first ball tracks  54  and inner first ball tracks  68 . Long and shorts windows  96 ,  98  each have a width W c  producing a ball window clearance  100  between a circumferential inside surface  102  of the window and an outer circumference of ball  90  received in the window. 
     Cage  92  has an inner face  104  and an outer face  106 . Inner face  104  includes, as seen in longitudinal section ( FIG. 4A ), a generally cylindrical recessed midsection region  108  flanked by generally cylindrically shaped surface portions  110  adjoining the latter tangentially. Midsection region  108  defines a maximum cage inner diameter D i  and the adjoining cylindrically shaped surface portions  110  define a minimum cage inner diameter d i . Outer face  106  of cage  92  has, as seen in longitudinal section ( FIG. 4A ), a generally peaked contour that is interrupted by the windows  94 . The outer face  106  includes a generally arcuate midsection region  112  flanked by generally conical surface portions  114  adjoining the latter tangentially. Midsection region  112  defines a maximum outer diameter Do of cage  92 . Cage  92  has a front face  116  and a rear face  118  that define an axial cage length B. 
     Cage  92  has a side cross sectional area  120 , as seen in longitudinal section ( FIG. 4A ), bounded by conical region  114  of cage outer face  106 , cylindrical region  110  of cage inner face  104 , window circumferential edge  102 , and front and rear faces  116 ,  118  of cage  92 . Cage  92  also has a center cross-sectional area  122 , as seen in circumferential section ( FIG. 4B ), bounded by midsection region  112  of cage outer face  106 , midsection region  108  of cage inner face  104 , and a peripheral end surface  124  of adjacent long and short windows  96 ,  98 . 
     Continuing to refer to  FIGS. 3A  thru  5 D, the first pairs of tracks that include outer and inner first ball tracks  54 ,  68 , and the second pairs of tracks that include outer and an inner second ball tracks  56 ,  70 , are alternately arranged over the circumference of the respective inner and outer races  64 ,  44 . Multiple webs  126  are formed between each two inner first and second ball tracks  68 ,  70  that are arranged adjacent to one another in the circumferential direction. Similarly, multiple webs  128  are formed between each two outer first and second ball tracks  54 ,  56  that arranged adjacent to one another in the circumferential direction. In each case, two first pairs of ball tracks  54 ,  68  and two balls  90  lie diametrically opposite one another with respect to a joint longitudinal mid-axis A-A. Likewise, in each case, two second pairs of ball tracks  56 ,  70  and two balls  90  lie diametrically opposite one another with respect to the joint longitudinal mid-axis A-A. With the joint aligned, such that a longitudinal mid-axis B-B of the outer race  44  is substantially aligned with a longitudinal mid-axis C-C of the inner race  64 , only the balls  90  guided in the pairs of first ball tracks  54 ,  68  transfer a torque, whereas an axial force for controlling ball cage  92  occurs at the balls  90  guided by the pairs of second ball tracks  56 ,  70 . When the joint articulates, the balls  90  guided in the pairs of second ball tracks  56 ,  70  may also transfer torque. The amount of torque transferred is a function of the articulation angle of the joint. 
     Outer first and second ball tracks  54 ,  56  have a generally elliptical shaped cross-sectional profile, as shown in  FIG. 3C . The balls  90  guided in the outer first and second ball tracks  54 ,  56  engage the tracks at two points  93 ,  95  located at a radius R COR . Center points  97  of a pair of balls  90  seated in diametrically opposite ball tracks  54 ,  56  define an outer race pitch circle diameter PCD O . Similarly inner first and second ball tracks  68 ,  70  have a generally elliptical shaped cross-sectional profile, as shown in  FIG. 5D . The balls  90  guided in the inner first and second ball tracks  68 ,  70  engage the tracks at two points  99 ,  101  located at a radius R CIR . Center points  97  of a pair of balls  90  seated in diametrically opposite ball tracks  68 ,  70  define an inner race pitch circle diameter PCD I . 
     For purposes of discussion, the constant velocity joint  42  is shown to include four axially parallel pairs of ball tracks  54 ,  68  and four joint axis-intersecting pairs of ball tracks  56 ,  70 . The pairs of ball tracks are alternately arranged over the circumference of the respective inner and outer races  64 ,  44 , and receive a total of eight balls  90 . It shall be appreciated, however, that constant velocity joint  42  may also be configured to include three or five axially parallel pairs of ball tracks  54 ,  68 , and a corresponding number of joint axis-intersecting pairs of ball tracks  56 ,  70  that alternate over the circumference of the inner and outer races and receive a total of either six or ten balls  90  depending on the number of pairs of ball tracks employed. 
     With the joint aligned, the outer first ball tracks  54  and the inner first ball tracks  68  have axially parallel center lines  130 ,  132 , respectively. The first ball tracks  54 ,  68  operate in conjunction with balls  90  to transfer torque between inner race  64  and outer race  44 , while providing little or no control of the ball cage  92 . The outer second ball tracks  56  form an outer track angle TA OR  with the joint longitudinal mid-axis A-A in a radial view, with the joint aligned. The corresponding opposite inner second ball tracks  70  have, with respect to the joint longitudinal mid-axis A-A, an equal and opposite inner track angle TA IR  in a radial view, with the joint aligned. This arrangement results in a centerline  136 ,  134  of the respective inner and outer second ball tracks  58 ,  50  intersecting one another in a radial view. The balls  90  received by each pair of inner and outer second tracks  70 ,  56  have their center points  97  located at the intersection point of the centerlines  134 ,  136  of the second pairs of ball tracks  56 ,  70 . 
     The second inner ball tracks  70  of the inner race  64  arranged at an inner track angle TA IR  relative to the joint longitudinal mid-axis A-A are all obliquely inclined co-directionally with respect to one another. Similarly, the corresponding opposite second outer ball tracks  56  of the outer race  44  are all obliquely inclined co-directionally with respect to one another. 
     The balls  90  received in the windows  94  of the ball cage  92  control the positioning of ball cage  92  within constant velocity joint  42 . The centrally symmetrical arrangement of the balls  90  received in the first ball track pair  54 ,  68 , and the balls  90  received in the second ball track pair  56 ,  70 , results in two torque-transferring balls  90  and two controlling balls  90  lying diametrically opposite one another when the joint is aligned. 
     The operating and performance characteristics of constant velocity joint  42  may be affected by a variety of parameters. Several of these parameters are listed in the tables shown in  FIGS. 6A and 6B . For example, the torque transfer capability of a cross-track constant velocity joint is a function of its mass, material properties and the maximum radii of the constant velocity joint&#39;s parts. Thus, the performance characteristics of constant velocity joint  42  may be enhanced by maximizing the torque transfer to radius relationship in order to reduce the mass of the constant velocity joint. Maximizing the performance parameters identified in  FIGS. 6A and 6B  may provide additional benefits, such as weight reduction, package size control, reduced part envelop and/or part runout, improved vibration deadening, increased strength per package size, and increased torque transfer capability per unit weight. Thirty-four parameters are identified in the tables in  FIGS. 6A and 6B . Each parameter includes an identified range that may maximize one or more of the performance characteristics of constant velocity joint  42 . 
     With regard to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, although the steps of such processes, etc. have been described as occurring according to a certain ordered sequence, such processes could be practiced with the described steps performed in an order other than the order described herein. It further should be understood that certain steps could be performed simultaneously or generally simultaneously, that other steps could be added, or that certain steps described herein could be omitted. In other words, the descriptions of processes herein are provided for the purpose of illustrating certain embodiments, and should in no way be construed so as to limit the claimed invention. 
     It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future embodiments. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims. 
     All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.