Patent Document

CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a Continuation of U.S. patent application Ser. No. 11/258,563 entitled “Rigid Joint Sealing System” filed on Oct. 25, 2005. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention relates generally to motor vehicle shaft joints, and more particularly concerns a joint system for rigid sealing.  
       BACKGROUND OF THE INVENTION  
       [0003]     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, transfer case, transmission, power take-off unit or other torque device, all of which are common components in automotive vehicles. Typically, one or more joints are assembled to the shaft to form a propeller or drive shaft assembly. It is the propeller shaft assembly which is 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 is solid or tubular with ends adapted to attach the shaft to an inner race of the joint thereby allowing an outer race connection to a 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, the same typical connection is made to a second drive unit when connecting the shaft between the two drive units. Optionally, the joint may be coupled to a shaft for torque transfer utilizing a direct torque flow connection. Regardless of the connection type, constant velocity joints require, for improved joint life, a sealed environment.  
         [0004]     Elastomer boots of the flexible or soft type improve the life of a constant velocity joint by sealing out contaminates and retaining joint lubrication. Elastomer boots are primarily used for sealing two parts that can be articulated relative to one another and which, more particularly, rotate at the same time. These parts constitute a joint. A typical application refers to sealing joints of the constant velocity and universal types. For this purpose, a boot with a cylindrical portion, typically having a smaller diameter is slipped on to a shaft connected to a first joint component, and an annular portion with a greater diameter is connected either directly or via an intermediate element to a second joint component. Between the cylindrical portion mentioned first and the annular portion with the greater diameter, there extends a wall. The wall has the shape of half a torus for a roll boot and has a bellows shape for a convoluted boot. When the two joint components articulate relative to one another, the radius of curvature of the wall decreases on the inside of the angle and increases on the outside of the angle. When the joint rotates in the articulated condition, the change in curvature in the roll boot wall moves across the circumference, so that during a complete  360  degree rotation, each point of the boot wall passes through a curvature maximum and a curvature minimum causing flexing of the boot wall. Flexing also occurs for each rotation of the boot due to gravitational and centripetal forces. However, the soft boot may be subject to material decay caused by mechanical, chemical and thermal attack caused by the environment in which it is used.  
         [0005]     Moreover, a soft boot may be prone to puncture or tearing. Additionally, the soft boot may blow out or rupture when subjected to increase pressure, has shorter boot life when used in high-speed high angle joint seal applications, and typically requires multiple crimped connections to seal the soft boot to the joint parts.  
         [0006]     It would be advantageous to have a boot and sealing system that overcomes some of the attributes indicated above.  
       SUMMARY OF THE INVENTION  
       [0007]     Accordingly, the present invention provides a rigid joint sealing system. The rigid joint sealing system provides the benefit of having a hard boot for sealing a constant velocity joint (CVJ) that is less prone to puncture or tearing. The inventive rigid joint sealing system may be used with CVJ assemblies having shaft to drive torque transfer utilizing direct torque flow connectors or traditional shaft connectors. Additional benefits with the rigid joint sealing system may include improved boot blow out protection, higher allowable internal joint pressure, improved environmental resistance, use in high speed high angle joint seal applications, improved seal life due to internal sealing structure and may eliminate crimped connections.  
         [0008]     In one embodiment, the rigid joint sealing system includes an inner joint part, a hard boot, an outer joint part and a seal. The hard boot includes an internal surface and is axially secured to the inner joint part. The outer joint part includes an external surface and is rotationally secured to the inner joint part. Wherein the seal is connected to one of the surfaces while having sealing engagement with the other surface.  
         [0009]     In another embodiment of the present invention, a hard boot for use with a rigid joint sealing system is provided. The hard boot includes a first end adapted for axial retention on an inner joint part, where the inner joint part is rotationally coupled to an outer joint part. The hard boot also includes a boot housing extending from the first end having an inner semi-spherical surface, the boot housing being adapted for partially surrounding the outer joint part while engaging a membrane seal there between.  
         [0010]     A further embodiment of the present invention provides a rigid joint sealing system having a hard boot optimisation ratio. In particular, the hard boot optimisation ratio is adapted to one of the embodiments of the inventive rigid joint sealing system. The rigid joint sealing system includes: an inner joint part comprising inner ball tracks; a hard boot axially secured to the inner joint part, and comprising an inner surface defining an internal radius (R 1 ); an outer joint part comprising outer ball tracks and an outer surface defining an external radius (R 2 ); a membrane seal having a designed compression thickness (CT) coupled to one of the surfaces having sealing engagement with the other of said surfaces; a cage between the inner joint part and the outer joint part; and a plurality of balls held by the cage and engaging pairs of the inner and outer ball tracks, wherein the hard boot optimisation ratio (HB) is satisfied such that: 
 
0.7 ≦HB≦ 1.3 
 
 wherein, 
 
 HB =(( R 2 +CT )/ R 1). 
 
         [0011]     The present invention has advantages by providing a rigid joint sealing system. The present invention itself, together with further intended advantages, will be best understood by reference to the following detailed description and taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0013]      FIG. 1  shows a plan view of an exemplary drive system for a typical 4-wheel drive automobile wherein the present invention may be used to advantage.  
         [0014]      FIG. 2  shows a first embodiment of an inventive rigid joint sealing system of a constant velocity universal joint.  
         [0015]      FIG. 3  shows a second embodiment of an inventive rigid joint sealing system of a constant velocity universal joint.  
         [0016]      FIG. 4  shows a partial cross sectional view of the embodiment shown in  FIG. 2 .  
         [0017]      FIG. 5  shows a partial cross sectional view of the embodiment shown in  FIG. 3 .  
         [0018]      FIG. 6  shows a partial cross sectional view of a third embodiment of an inventive rigid joint sealing system.  
         [0019]      FIG. 7  shows a partial cross sectional view of a fourth embodiment of an inventive rigid joint sealing system.  
         [0020]      FIG. 8  shows a partial cross sectional view of a fifth embodiment of an inventive rigid joint sealing system.  
         [0021]      FIG. 9  shows a partial cross sectional view of a sixth embodiment of an inventive rigid joint sealing system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     In the following description, various operating parameters and components are described for one or more constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.  
         [0023]     While the invention is described with respect to a rigid joint sealing system of a constant velocity universal joint 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 which require propeller shaft assemblies for torque transmission.  
         [0024]     An exemplary drive system  12  for a typical 4-wheel drive automobile is shown in  FIG. 1 . While a 4-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. In this example, the drive system  12  includes an engine  14  that is connected to a transmission  16  and a power take-off unit  18 . A front differential  20  has a right hand side half shaft  22  and left hand side half shaft  24  each of which are connected to a wheel and deliver power to the wheels. On both ends of the right hand side half shaft  22  and left hand side half shaft  24  are constant velocity joints  10 . A propeller shaft  26  connects the front differential  20  to a rear differential  28  wherein the rear differential  28  includes a rear right hand side shaft  30  and a rear left hand side shaft  32 , each of which ends with a wheel on one end thereof. Constant velocity joints  10  are located on both ends of the half shafts  30 ,  32  that connect to the wheels and the rear differential  28 . The propeller shaft  26 , shown in  FIG. 1 , is a three-piece propeller shaft that includes a plurality of cardan joints  34  and one high-speed constant velocity joint  10 . The propeller shaft  26  includes interconnecting shafts  23 ,  25 ,  27 . The constant velocity joints  10  transmit power to the wheels through the propeller shaft  26  even if the wheels or the propeller shaft  26  have changed angles due to steering, raising or lowering of the suspension of the vehicle. The constant velocity joints  10  may be any of the standards types known, such as a plunging tripod, a cross groove joint, a fixed ball joint, a fixed tripod joint, or a double offset joint, all of which are commonly known terms in the art for different varieties of constant velocity joints  10 . The constant velocity joints  10  allow for transmission of constant velocities at angles typically encountered in every day driving of automotive vehicles in both the half shafts, interconnecting shafts and propeller shafts of these vehicles. Optionally, each cardan joint  34  may be replaced with any other suitable type of joint, including constant velocity joint types. The inventive rigid joint sealing system may be utilized to advantage for any of the above mentioned joint locations not requiring a plunging type of joint.  
         [0025]     The shafts  22 ,  23 ,  24 ,  25 ,  27 ,  30 ,  32  may be solid or tubular with ends adapted to attach each shaft to an inner race or an outer race of a joint in accordance with a traditional connection, thereby allowing the outer race or inner race to be connected to a hub connector  36 , a flange  38  or stubshaft  40  of each drive unit, as appropriate, for the particular application. Thus, any of the traditional connections identified in  FIG. 1  at  10  or  34  may be direct torque flow connections in accordance with a first embodiment ( FIG. 2 ) of the present invention or may be a typical joint connection in accordance with a second embodiment ( FIG. 3 ) of the present invention.  
         [0026]     For completeness of the description of the first embodiment of the present invention as given in  FIG. 2 , the term direct torque flow (DTF) connection refers to a direct connection from the inner race of a CV joint to the shaft of a differential, transmission or transfer case, generally supplied by the customer. The direct connection typically is in the form of a spline because of its robust design features as understood by one skilled in the art. However, it is anticipated that other forms of direct connection are appropriate including fixed and releasable connections between the inner race and shaft. A mating key connection is just one example, without limitation, of a releasable connector between the inner race and the shaft. A welded connection would be a fixed direct connection example. Thus, a DTF connection refers to the inner race coupling to the shaft of a drive unit, such as a differential, transmission or transfer case without limitation, as opposed to the traditional connection mentioned above.  
         [0027]     Also, as used herein, a DTF connector refers to a joint coupled to a shaft which forms a DTF propshaft assembly. Only together with the shaft of a differential, for example, does a DTF connector combine to make a DTF connection. It is recognized that the shaft of the drive unit may include the shaft of any input or output drive unit and is not necessarily limited to a shaft of a differential, transmission or transfer case.  
         [0028]     Although the present invention as described in the first embodiment illustrated in  FIG. 2  utilizes a DTF clip CVJ connector type, it is intended that the inventive rigid joint sealing system may be applied equally to constant velocity joints having other connection types.  
         [0029]      FIG. 2  shows a first embodiment of an inventive rigid joint sealing system  102  of a constant velocity universal joint  54 . The constant velocity universal joint in this embodiment is a DTF clip CVJ having a DTF connection assembly arranged between a shaft journal  111  and a DTF connector constant velocity universal joint  112 . The shaft journal  111  is supported by a bearing  113  in a housing  114 , which, in this case, is illustrated in the form of a housing in the driveline drive unit of a motor vehicle. The bearing  113  is axially tensioned by a tensioning nut  118  which has been threaded on to a threaded portion  115  of the shaft journal  111 . A shaft seal  120  seals the tensioning nut  118  relative to the axle housing  114 . By way of a cover  121  secured to the tensioning nut  118 , the shaft seal is protected against damage.  
         [0030]     The DTF connector constant velocity universal joint  112  of the rigid joint sealing system  102  is connected to a propeller shaft  117  of the motor vehicle driveline. The DTF connector constant velocity universal joint  112  comprises an outer joint part  122  welded to the propeller shaft  117  by a collar  123 , an inner joint part  124 , torque transmitting balls  126  as well as a ball cage  125 . The inner joint part  124  having an internal spline  148  is axially secured on a toothed shaft portion  116  of the shaft journal  111  in a rotationally fast way. Between the collar  123  and the outer joint part  122  there is inserted a cover  131 , which seals the joint towards the propeller shaft  117  and, more particularly, contains lubricants within the joint. Furthermore, a membrane seal  150  circumferentially connected to an outer circumference  152  of the outer joint part  122  is in sealing relationship with the inner circumference  154  of a hard boot  133  and which, in a way to be further described, seals the DTF connector constant velocity universal joint relative to the shaft journal  111 . While the membrane seal  150  may be selectively positioned on the outer circumference of the outer joint part  122  in order to seal against the hard boot  133 , the membrane seal may optionally be selectively connected to the inner circumference of the hard boot in sealing relationship with the outer circumference of the outer joint part. The seal, whether connected to the outer joint part or to the hard boot, provides an effective barrier during joint motion over the applicable semispherical sealing surface. Moreover, optionally, a wiper  132  encloses the outer end of the hard boot  133  and which environmentally seals the DTF connector constant velocity universal joint relative to the membrane seal  150 . The wiper  132  is sealingly positioned on the outer joint part  122 . The wiper  132  may be made from any pliable material and may be welded, glue, rolled and/or affixed in any other applicable way known to one of skill in the art onto the outer surface of the outer joint part  122 . The DTF connector constant velocity universal joint  112  includes pairs of ball tracks  127 ,  128 ,  129 ,  130 . The orientation of each ball track set is dependent upon the type of universal joint selected, which is well understood to a person having skill in the art. However, the ball tracks of the present invention are of the non-plunging type for CVJ applications requiring angular offset between the shafts that connect via the joint.  
         [0031]     The inner joint part  124  further includes a front face  144 , a back face  146 , a clamping groove  156 , a neck  158  and insertion grooves  172 . The insertion grooves  172  are for receiving a clip  170  for axially securing the inner joint part  124  to the shaft journal  111  by way of a shaft reception groove (not shown). The hard boot  133  is axially form-fitting and positively secured to the neck  158  of the inner joint part  124  by way of a clamping strip  142  secured into the clamping groove  156  and further sandwiched between the clip  170  to prevent axial motion. A backup seal  160  between the inner joint part  124  and the hard boot  133  may optionally be provided.  
         [0032]      FIG. 3  shows a second embodiment of an inventive rigid joint sealing system  202  of a constant velocity universal joint  212 . The constant velocity universal joint in this embodiment is a fixed ball CVJ used to advantage in a typical shaft connection assembly. The constant velocity universal joint  212  comprises an outer joint part  222 , a collar  223 , an inner joint part  224 , torque transmitting balls  226  as well as a ball cage  225 . The inner joint part  224  includes a connection, such as an internal spline (not shown), for axially securing to a shaft journal, shaft, or stub flange for torque transmission in an rotationally fast way. The inner joint part may be coupled as is known by a person having skill in the art. Between the collar  223  and the outer joint part  222  there is inserted a vent cover  231  which may seal the joint when coupled to a propeller shaft or other connection and, more particularly, contains lubrication within the joint. Furthermore, a membrane seal  250  circumferentially connected to an outer circumference  252  of the outer joint part  222  is in sealing relationship with the inner circumference  254  of a hard boot  233  and which, in a way to be further described, seals the constant velocity universal joint relative to the inner joint part. While the membrane seal  250  may be selectively positioned on the outer circumference of the outer joint part  222  in order to seal against the hard boot  233 , the membrane seal  250  may optionally be selectively connected to the inner circumference  254  of the hard boot  233  in sealing relationship with the outer circumference  252  of the outer joint part  222 . The seal  250 , whether connected to the outer joint part  222  or to the hard boot  233 , provides an effective barrier during joint motion over the applicable semi-spherical sealing surface. Moreover, optionally, a wiper  232  encloses the outer end of the hard boot  233  and which environmentally seals the constant velocity universal joint relative to the membrane seal  250 . The wiper  232  is positioned on the outer joint part  222  and functions as a backup barrier for sealing the joint. The wiper  232  may be made from any pliable material and may be welded, glue, rolled and/or affixed in any other applicable way know to one of skill in the art onto the outer surface of the outer joint part  222 . The constant velocity universal joint  212  also includes pairs of ball tracks  227 ,  228 ,  229 ,  230 .  
         [0033]     The inner joint part  224  of the second embodiment includes an inner race part  243  connected to an extension part  245 . The inner race part  243  includes a front face  244 , and a circlip groove  256  for retentively engaging a connection shaft. The extension part includes a flange  255  coupled to the front face of the inner race part by bolts  257 , a neck  258 , a step  259  and retention bolts  272 ,  273 . The hard boot  233  is axially form-fitting and positively secured to the neck  258  of the extension part  245  of the inner joint part  224  by way of retention bolts  272 ,  273  secured into the extension part  245  and further sandwiched between the step  259  to prevent axial motion between the parts.  
         [0034]     Optionally, the inner race part  243  or the extension part  245  of the inner joint part  224  may be solid. Accordingly, a person of skill in the art would recognized the alternate connection types required in order to utilize a CVJ having a solid inner joint part  224 .  
         [0035]     The hard boot may be made from any material consistent with the intent and scope of the present invention. Specifically, the inventive rigid seal system provides a boot and a seal combination that enables the seal to have angular motion with respect to the outer joint part or the hard boot in such a way that the seal integrity and structural integrity is maintained between selected moving parts. In the present embodiment, the material of the hard boot is selected to have a substantially small amount of deflection or distortion during angular gyrations of the joint parts. Suitable materials would include wood, metal, or hard plastic, without limitation. The hard boot of the present embodiment is made from carbon steel. However, it is recognized that soft plastic, i.e., materials used for the traditional neoprene boots, may not have the requisite rigidity to properly maintain the sealing requirements as described herein. The word “hard” as used with the hard boot of the present invention is not meant to be limiting, but is provided to distinguish the boot of the present invention requiring only one fixed attachment from the prior art boots requiring at least two fixed attachment points in order to effectuate a sealed system.  
         [0036]     While the material, coupling and treatment of the various other DTF parts have not been discussed; appropriate selection would be well understood by a person of skill in the art.  
         [0037]     An additional aspect of the present invention, the Applicant has discovered certain relationship between the outer joint part and the hard boot that enable a robust rigid joint sealing system. The relationship is explained in detail below with reference to the first and second exemplary embodiments.  
         [0038]     In order to obtain additional advantages, the outer joint part and the hard boot have a hard boot optimisation ratio (HB). The optimisation ratio represents one metric for providing geometric tolerance for further improvement to the rigid joint sealing system of the present invention. The parameters used to determine the hard boot optimisation ratio are: 1) an internal radius R 1  defined by the axis origin of the inner joint part to the inner circumference of the hard boot; 2) an external radius R 2  defined by the axis origin of the outer joint part to the outer circumference of the outer joint part; and 3) a membrane seal designed compression thickness CT. The seal designed compression thickness is a constant.  
         [0039]     The hard boot optimisation ratio helps to minimize distortion of the inner circumference of the hard boot and or the outer circumference of the outer joint part. Furthermore, the hard boot optimisation ratio helps to maintain proper compression upon the membrane seal for proper sealing capability. The hard boot optimisation ratio is equal to the external radius plus the membrane seal designed compression thickness all divided by the internal radius. The hard boot optimisation ratio is calculated for optimised minimum distortion of the inner circumference of the hard boot and or the outer circumference of the outer joint part and is controlled substantially in the range defined by: 
 
0.7&lt;(( R 2 +CT )/ R 1)&lt;1.3. 
 
         [0040]     The hard boot optimisation ratio has improved range at approximately 0.9≦HB≦1.1, with even better range at approximately 0.98≦HB≦1.02.  
         [0041]     Generally,  FIGS. 4 through 9  illustrate partial cross sectional views of the first through sixth embodiments of the inventive rigid joint sealing systems  102 ,  202 ,  302 ,  402 ,  502 ,  602 , respectively. Generally, Each of the rigid joint sealing systems  102 ,  202 ,  302 ,  402 ,  502 ,  602  include a membrane seal  150 ,  250 ,  350 ,  450 ,  550 ,  650  circumferentially connected to the outer circumference  152 ,  252 ,  352 ,  452 ,  552 ,  652  of the outer joint parts  122 ,  222 ,  322 ,  422 ,  522 ,  622 , in sealing relationship with the inner circumference  154 ,  254 ,  354 ,  454 ,  554 ,  654  of the hard boot  133 ,  233 ,  333 ,  433 ,  533 ,  633 , respectively. The membrane seals or seals in general are utilized to separate one environment from another environment. These environments may include the separation of gases, liquids, solids, heat regimes and pressure regimes, without limitation, in order to maintain the desired environmental relationship, such as retention of lubrication within the joint of the present invention. Seals, including material selection and design factors, used to accomplish environmental control are understood by persons of skill in the art and may be utilized to advantage in the various embodiment of the inventive rigid joint sealing system. Accordingly, any suitable material may be utilized to advantage, such as rubber, without limitation, for the seal. Moreover, composite seal designs may also be used to advantage. The membrane seals for the first through sixth embodiments will now discussed.  
         [0042]      FIG. 4  shows the membrane seal  150  having a single blade  151 . In an optimal setting, the seal  150  may be compressed having focused sealing pressure or compression at the blade  151  and the hard boot  133  interface.  FIG. 5  shows the membrane seal  250  having two single blades  251 ,  253  thereby providing better assurance of seal contact during angular motion of the CVJ.  
         [0043]      FIG. 6  shows the membrane seal  350  having two wiper blades  351 ,  353 . The two wiper blades  351 ,  353  may interface with the hard boot  333  by resilient loading of the material, compressive loading between the parts or by environmental pressure loaded in both seal directions. An advantage of the two wiper blade design, is that during angular joint motion, with or without an environmental pressure differential, one wiper blade is likely to maintain sealing contact with the hard boot.  FIG. 7  shows the membrane seal  450  having two double wiper blades  451 ,  453 .  
         [0044]      FIG. 8  shows the membrane seal  550  having a blades  551  and retention spring  581 . The retention spring  581  securely fastens the seal to the outer joint part  522  thereby allowing the seal to have higher compressive loading between the seal and the wiping or sealing surface of the hard boot.  FIG. 9  shows the membrane seal  650  having two blades  651 ,  653  and two retention springs  681 ,  682  being used to advantage.  
         [0045]     While the above embodiments of the membrane seals are provided as examples, it is recognized that various other types of membrane seal configurations may also be used with the inventive rigid joint sealing system.  
         [0046]     From the foregoing, it can be seen that there has been brought to the art a new and improved rigid joint sealing system. While the invention has been described in connection with one or more embodiments, it should be understood that the invention is not limited to those embodiments. On the contrary, the invention covers all alternatives, modifications, and equivalents as may be included within the spirit and scope of the appended claims.

Technology Category: 4