Abstract:
The present invention provides clutch systems for the control of the transmission of torque to the front (or rear) wheels of a vehicle (e.g., an ATV), thus being operable to change the vehicle from a two-wheel, rear-drive (or front-drive) vehicle to a four wheel drive vehicle by engaging the clutch systems thereof. The clutch system is contained within an extended portion of a housing that also contains a differential system, thus eliminating the need for fastening a separate clutch system housing to the differential housing. The clutch system is actuated by energizing a coil which in turn causes tab members of an actuation disk to disengage from notches formed on an inner race, allowing the actuation of a roller clutch system. When the coil is de-energized, the actuation disk engages the inner race and prevents inadvertent or undesired actuation of the clutch system.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to clutches, and more particularly, to clutch systems useful in conjunction with four wheel drive control systems for all-terrain vehicles (ATV&#39;s), although the present invention can also be practiced with automotive drivelines. More specifically, the present invention provides clutch systems for the control of the transmission of torque to the front (or rear) wheels, thus being operable to change the vehicle from a two-wheel, rear-drive (or front-drive) vehicle to a four wheel drive vehicle by engaging the clutch systems thereof.  
       BACKGROUND OF THE INVENTION  
       [0002]     Currently, a variety of different clutch systems are used for various vehicles, such as ATV&#39;s, including roller clutch systems. Many of these clutch systems employ a dog clutch or splined collar arrangement that can be engaged by pulling a lever. Additionally, there are some electronically-actuated clutch systems that have been recently developed, as well.  
         [0003]     These roller clutch systems are typically packaged in their own housings and bolted to the front transmission output flanges. The inner race is typically splined to the male output shaft from the transmission, whereas the clutch outer race has a female spline that is adapted to the front drive shaft. For example, certain roller clutch systems employ a roller clutch in a separate housing bolted to the front differential housing. In most of these systems, the input comes from the front driveshaft, and is connected to the roller clutch outer race. The clutch inner race is splined onto the front differential&#39;s pinion shaft.  
         [0004]     One disadvantage with conventional roller clutch systems is that the dog clutch can be damaged during engagement while the vehicle is moving, as well as being complex and expensive to design and manufacture. Additionally, because separate housings are employed for the differential and clutch units, separate seals are needed on the input and output portions, and the clutch unit is required to be pre-greased before final assembly. Furthermore, ball bearings and a needle roller bearing are generally required to position the parts relative to each other and within the clutch housing. Also, the coil wire must be fed through the outer wall at the back end of the clutch housing during installation of the coil, a process that is quite time-consuming and difficult.  
         [0005]     Therefore, there exists a need for new and improved clutch systems, especially those operable to provide control of the transmission of torque to the front (or rear) wheels, thus being operable to change the vehicle from a two-wheel, rear-drive (or front-drive) vehicle to a four wheel drive vehicle by engaging the clutch systems thereof.  
       SUMMARY OF THE INVENTION  
       [0006]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.  
         [0007]     In accordance with a first embodiment of the present invention, a selectively operable clutch system for a vehicle is provided, comprising: (1) an inner race member; (2) an outer race member, a portion of which is disposed about a portion of the inner race member; (3) an actuation member operably associated with the inner race member; and (4) an actuation system operably associated with the actuation member, wherein the actuation system is operable to cause the actuation member to either engage or disengage the inner race member, wherein when the actuation member is engaged with the inner race member, the clutch system is not operable to apply a torque force to a drivable member, wherein when the actuation member is disengaged from the inner race member, the clutch system is operable to apply a torque force to a drivable member.  
         [0008]     In accordance with a second embodiment of the present invention, a selectively operable clutch system for a vehicle is provided, comprising: (1) an inner race member; (2) an outer race member, a portion of which is disposed about a portion of the inner race member; (3) a roller clutch system operably associated with the inner and outer race members; (4) an actuation member operably associated with the inner race member; and (5) an actuation system operably associated with the actuation member, wherein the actuation system is operable to cause the actuation member to either engage or disengage the inner race member, wherein when the actuation member disengages from the inner race member, the roller clutch system is operable to cause the inner and outer race members to rotate together in the same direction, wherein when the actuation member is engaged with the inner race member, the roller clutch system is not operable to apply a torque force to a drivable member, wherein when the actuation member is disengaged from the inner race member, the roller clutch system is operable to apply a torque force to a drivable member.  
         [0009]     In accordance with a third embodiment of the present invention, a selectively operable torque transmission system for a vehicle is provided, comprising: (1) a differential system disposed within a housing; and (2) a clutch system, wherein the housing includes an extended portion operable to receive at least a portion of the clutch system, wherein the clutch system is operably associated with the differential system, wherein the clutch system comprises: (a) an inner race member; (b) an outer race member, a portion of which is disposed about a portion of the inner race member; (c) a roller clutch system operably associated with the inner and outer race members; (d) an actuation member operably associated with the inner race member; and (e) an actuation system operably associated with the actuation member, wherein the actuation system is operable to cause the actuation member to either engage or disengage the inner race member, wherein when the actuation member disengages from the inner race member, the roller clutch system is operable to cause the inner and outer race members to rotate together in the same direction, wherein when the actuation member is engaged with the inner race member, the roller clutch system is not operable to apply a torque force to a drivable member, wherein when the actuation member is disengaged from the inner race member, the roller clutch system is operable to apply a torque force to a drivable member.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]      FIG. 1  illustrates a broken-away view of a differential system incorporating a clutch system, in accordance with the general teachings of the present invention;  
         [0012]      FIG. 2  illustrates a sectional view of a clutch system, in accordance with a first embodiment of the present invention;  
         [0013]      FIG. 3A  illustrates a front exploded view of a clutch system, in accordance with a second embodiment of the present invention;  
         [0014]      FIG. 3B  illustrates a rear exploded view of a clutch system, in accordance with a third embodiment of the present invention;  
         [0015]      FIG. 4A  illustrates a top perspective view of a clutch system, in accordance with a fourth embodiment of the present invention;  
         [0016]      FIG. 4B  illustrates a rear perspective view of a clutch system, in accordance with a fifth embodiment of the present invention;  
         [0017]      FIG. 5  illustrates a seal member/endplate-coil assembly of a clutch system, in accordance with a sixth embodiment of the present invention  
         [0018]      FIG. 6  illustrates a plan view of an actuation disk, in accordance with a seventh embodiment of the present invention;  
         [0019]      FIG. 7  illustrates a sectional view taken along line  7 - 7  of  FIG. 6 , in accordance with an eighth embodiment of the present invention;  
         [0020]      FIG. 8  illustrates a sectional view of an inner race lock out notches, in accordance with a ninth embodiment of the present invention; and  
         [0021]      FIG. 9  illustrates a partial sectional view of detail area  9  of  FIG. 8 , in accordance with a tenth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0023]     Referring to the Figures generally, and specifically to  FIG. 1 , there is shown a torque transmission system  10 , wherein system  10  includes a differential system  12  and a clutch system  14  in operable association therewith. By way of a non-limiting example, differential system  12  can be either the front and/or rear differential systems of a vehicle, such as but not limited to those vehicles that employ front wheel drive, rear wheel drive, four-wheel drive, and/or all-wheel drive systems. Additionally, system  10  and system  14  can be used in conjunction with any driving member/driven member system.  
         [0024]     Referring to  FIGS. 1-4B , the primary components of clutch system  14  can include, without limitation, an actuation disk  16 , a bearing  18 , an inner race bushing  20 , a centering spring  22 , a coil rotor  24 , an inner race  26 , an outer race  28 , a plurality of rollers  30 , a retainer or roller cage  32 , a wave spring  34 , a coil member  35 , an endplate member  36 , and a seal member  37  (e.g., lip seal, can seal, O-ring, and/or the like). A wire member or harness  38  can be provided and is operable to be in communication with coil member  35 , e.g., through an aperture  39  formed in endplate member  36 . A coil housing  40  is also provided to house the coil member  35 . It should be appreciated that other components, such as fastening members (e.g. screws, bolts, and/or the like), bearings, bushings, seals, gaskets, springs, and/or the like can also be employed, as is known in the art.  
         [0025]     Clutch system  14  has the outer race  28  splined through female spline portion  28   a  to the pinion shaft  100  of the front differential  102 , while the inner race  26  has a splined extension  104  to connect to the front driveshaft (not shown). The inner race  26  envelopes the hub section  106  of the outer race  28 , providing additional support and structural stability. More importantly, the entire clutch system  14  is operable to easily slide into an extended portion  108  of the differential pinion housing  110  and is sealed in place by endplate member  36 .  
         [0026]     Clutch system  14  is compact, simple, and has a relatively small number of components. An important feature of the present invention is that clutch system  14  does not require its own separate housing, i.e., clutch system  14  is installed into and surrounded by extended portion  108  of the existing differential pinion housing  110 , and so requires only minor modifications to existing casting molds.  
         [0027]     Furthermore, the present invention does not require internal seals, so clutch system  14  can simultaneously use the differential lubricant, thus obviating the need for two different lubrications systems. The seal member  37  is fitted into endplate member  36 , thus allowing clutch system  14  to be less complex and costly to manufacture.  
         [0028]     Referring to  FIGS. 1-4B  and  6 - 7 , actuation disk  16  is intended to function as the trigger mechanism to force engagement of the roller clutch system  200 . Actuation disk  16 , which can be comprised of a simple stamped disk with short axial, bent tabs  202 , is part of the electromagnetic trigger clutch, clamping axially onto coil rotor  24  when coil member  35  is energized. Slots  204  in actuation disk  16  engage axial tabs  206  on retainer  32 , allowing actuation disk  16  to move axially relative to retainer  32 , but preventing relative rotation of these two parts. When coil member  35  is energized, the magnetic flux in coil rotor  24  attracts actuation disk  16  (e.g., overcoming the axial force of wave spring  34 ) until actuation disk  16  clamps onto coil rotor  24 . The frictional force generated between coil rotor  24  and actuation disk  16  forces retainer  32  to rotate with coil rotor  24  (and thus outer race  28 ), overcomes the force of centering spring  22 , and forces rollers  30  to move along the flat, cammed surfaces  26   a  of inner race  26  until rollers  30  wedge into engagement between the flat cammed surfaces and the inner diameter of outer race  28 . Coil rotor  24  is preferably pressed into an inner diameter surface of outer race  28 . The inner diameter of actuation disk  16  also provides radial support for retainer  32  and maintains close relative positioning of retainer  32  with respect to inner race  26 .  
         [0029]     Referring to  FIGS. 1-4B  and  6 - 9 , wave spring  34  and bent axial tabs  202  of actuation disk  16  engage notches  206  on inner race  26  to lock actuation disk  16  in the disengaged position unless magnetic flux (e.g., from coil rotor  24 ) brings actuation disk  16  axially out of this locked out position. This feature allows for the prevention of inadvertent actuation which could damage clutch system  14 . This feature is especially important during cold weather conditions and high speed over-running conditions, e.g., when there is a large speed difference between the inner and outer races  26 ,  28 , respectively. Under these conditions, it is possible that the viscous shear of the lubricant between coil rotor  24  and actuation disk  16  can overcome the centering spring  22  force, causing retainer  32  to rotate relative to inner race  26 , causing the roller clutch system  200  to engage, even though the electromagnetic coil rotor  24  was not energized. With these axial tabs  202  engaged into their receptor areas (e.g., notches  206 ) of inner race  26 , clutch system  14  cannot be engaged under any such conditions.  
         [0030]     Actuation disk  16  should be made of a suitable magnetic material such as but not limited to SAE  1008  or SAE  1012  steel. By way of a non-limiting example, a somewhat tight tolerance is specified on the inner diameter thereof to hold close positioning of retainer  32  relative to inner race  26 .  
         [0031]     Bearing  18  is disposed between the coil member  35  and endplate member  36  and the shaft portion  300  of inner race  26 . Bearing  18  is intended to be used to locate the coil member  35  relative to the rest of the electromagnetic trigger clutch components, providing closer tolerance and better positioning than conventional journal bushings. Bearing  18  can be pressed onto shaft  300  of inner race  26  with the coil member  35  and endplate member  36 , keeping the whole clutch system  14  together during shipping and installation. Bearing  18  in the coil member  35  and endplate member  36  combination also positions the whole clutch system  14  within housing  110  (specifically extended portion  108 ), so the need for any outer bushings and/or rotor bushings can be eliminated. By eliminating the outer bushing, the relative speed difference between the rotating clutch assembly and the stationary housing is handled much better and frictional heating is reduced. The diameter of shaft  300  of inner race  26  onto which bearing  18  can be pressed is the same one that the seal lips ride upon. The close tolerances and smooth finish required for bearing  18  press are also used for the seal lips, which also require a smooth finish.  
         [0032]     Inner race bushing  20  is intended to function as a journal bushing between inner race  26  and hub section  106  of outer race  28 . The material can be bearing bronze or any other suitable bearing-type material such as but not limited to TORLON or NYLON66. Somewhat tight tolerances are required to maintain close positioning of outer race  28  relative to inner race  26  to provide good actuation of the roller clutch system  200  and prevent inadvertent actuation.  
         [0033]     Centering spring  22  is intended to hold retainer  32  in position relative to inner race  26 . More specifically, this spring  22  is inserted into a groove or recess in inner race  26  and has radial tabs  400  which extend outwardly, engaging retainer  32  to urge retainer  32  into a position in which rollers  30  are held in the middle of the flat sections  26   a  of inner race  26 , on which position clutch system  14  is effectively disengaged. When this biasing force of centering spring  22  is overcome, radial tabs  400  of centering spring  22  deflect and retainer  32  can rotate relative to inner race  26 , allowing rollers  30  to move along the flat sections  26   a  of inner race  26  until they engage outer race  28 , engaging the roller clutch system  200 .  
         [0034]     Centering spring  22  can be comprised of any suitable spring steel. Although the current design of centering spring  22  is an “omega” shape, other shapes are possible, as long as retainer  32  can be held in position relative to inner race  26 , but overcome when the “trigger” clutch system engages.  
         [0035]     Coil rotor  24  is intended to be pressed into the open end of outer race  28  and serves to focus the magnetic flux from the stationary coil member  35  upon actuation disk  16  to “trigger” the actuation of the roller clutch system  200 . Axial slots  500  of approximately 60-70 degrees are cut or otherwise formed in the circumferential direction in the face of coil rotor  24 , forcing magnetic flux to “jump” across the smaller air gap to actuation disk  16 , drawing actuation disk  16  axially until it clamps onto this axial face of coil rotor  24 .  
         [0036]     Relatively tight tolerances are required on the coil rotor  24  outer diameter and inner diameter of the outer race  28  to press coil rotor  24  into outer race  28 . The coil rotor  24  can be comprised of any suitable magnetic material, such as but not limited to SAE  1008  or SAE  1012  steel.  
         [0037]     The press-in feature of coil rotor  24  is intended to keep all the components into one assembly, making the unit easier to ship. Coil rotor  24  is the last part of the assembly that gets installed and is pressed into the open end of outer race  28 . Coil rotor  24 , once assembled to clutch system  14 , holds all the components into the envelope described by outer race  28 , wherein only the input shaft section  300  of inner race  26  protrudes. The press fit is sufficient to keep all the parts together, even if the assembly is picked up by the input shaft, dropped, shaken, or pulled upon manually. This feature allows for clutch system  14  to be shipped, handled, and installed intact, with no chance of the assembly coming apart inadvertently. From a manufacturer&#39;s standpoint (and that of prospective customers), this is a great advantage because clutch system  14  can be shipped complete, ready to install, with no additional hardware installation.  
         [0038]     Inner race  26  includes a series of flat cammed surfaces  26   a  that are intended to function as the inner part of the roller clutch system  200 , engaging rollers  30  and wedging them against the inner diameter of outer race  28 , locking up clutch system  14 . As previously noted, inner race  26  also has shaft  300  that extends axially out of the assembly to engage the input driveshaft (not shown), preferably with a splined connection  104 . Shaft  300  also has a smooth surface to allow the outboard seal  37  (installed in the endplate member  36 ) to ride smoothly to prevent leakage of differential lubricant and keep out dust, dirt, debris and water.  
         [0039]     With inner race  26  surrounding hub section  106  of outer race  28 , this relationship can be maintained more easily. Side loading caused by the sharp torque spikes encountered during acceleration is carried by inner race  26 /input shaft through inner race bushing  20  into this hub section  106 . Any movement of the inner race  26  caused by this moment loading will act upon the outer race  28 , minimizing relative movement between these two components. The hub section  106  of the outer race  28  also serves as the output, connecting to the pinion shaft, usually by a spline. Moving this splined section inside the envelope of the inner race  26  reduces overall axial length of the assembly, allowing a shorter front driveshaft, providing more efficient transmission of torque and better NVH (i.e., noise, vibration, harshness) characteristics.  
         [0040]     Referring to  FIGS. 6-9 , recessed notches  206  are included in the outer section of inner race  26  to mate with male axial tabs  202  on actuation disk  16  to serve as a lock-out mechanism and prevent inadvertent actuation. A recessed diameter is provided on the end opposite shaft  300  to fit over inner race bushing  20  to provide close relative positioning of inner race  26  relative to outer race  28 . On the same side of inner race  26  as this recessed section is a semi-circular extension into which centering spring  22  is installed. A radial gap in this extension allows the radial tabs  400  of centering spring  22  to extend outwards to engage retainer  32 . Tight tolerances are required on the diameters that run against inner race bushing  20 . In addition, tight tolerances are called out for the flat sections so that close control is possible of the positions of rollers  30  during actuation to equalize the forces at each roller, ensure coincidental engagement of all of rollers, and prevent inadvertent actuation.  
         [0041]     Outer race  28  includes a hub section  106  with a female spline for connection to the differential pinion gear shaft. The outer surface of this hub section  106  fits into inner race bushing  20  which then fits into inner race  26 , providing critical, close relative positioning of these two raceways. The outer section of outer race  28  has three different inner diameters,  28   b ,  28   c , and  28   d , respectively. The smallest diameter,  28   b , with the thickest wall section constitutes the outer diameter of the clutch section, providing the contact surface for rollers  30  and the thickness to withstand the considerable hoop stresses generated when clutch system  14  engages. The diameter  28   d  closest to the “open” end of outer race  28  is the contact surface into which coil rotor  24  is pressed as the last part of assembly of roller clutch system  200 . The intermediate diameter  28   c  provides a small air gap between coil rotor  24  and outer race  28  to prevent short-circuiting of the magnetic flux, improving performance of the electromagnetic trigger clutch.  
         [0042]     Outer race  28  is typically made of hardened, bearing quality steel to resist brinnelling and deformation due to the high Hertzian contact stresses generated by the engagement of the roller clutch. However, non-bearing grade materials could also be used if the stresses were kept low enough. Outer race  28  is connected to the pinion shaft (output) and inner race  26  is connected to the input shaft (driveshaft). This is generally the reverse of conventional clutch systems where the inner race is splined onto the pinion shaft and the outer race has a female spline connection for mating to the front driveshaft. In contrast, the present invention has the “open” end of the assembly facing outwards, allowing the coil member  35  to be on the outside with the inherent advantages of installation (e.g., coil insertion and wiring connections) and reduction in the number of components.  
         [0043]     Like outer race  28 , inner race  26  would preferably be made of hardened, bearing quality steel to provide good wear characteristics and suitable resistance to the high Hertzian contact forces generated when the clutch is engaged under high torque conditions.  
         [0044]     Rollers  30  can be standard needle rollers to allow the lowest possible cost. Preferably, rollers  30  will have no crowning, allowing equal distribution of the contact forces across rollers  30  and serve to prevent skewing during engagement. Rollers  30  will have typical tight tolerances and would be made of suitable hardened steel.  
         [0045]     Roller cage or retainer  32  is intended to function to position rollers  30  relative to inner race  26 . Preferably, rollers  30  are maintained in identical positions relative to the flat cammed surfaces  26   a  of inner race  26 . On this same end is a diameter which runs against a mating diameter of inner race  26  to keep close positioning of these two parts. Retainer  32  has a radial notch in one end to mate with the radial tabs  400  of centering spring  22 , maintaining the relative positions of inner race  26  and retainer  32 . Axial tabs  206  are provided at one end of retainer  32  to fit into slots  204  in actuation disk  16 . These slots  204  are closely toleranced to allow axial movement of actuation disk  16  relative to retainer  32 , but prevent relative rotation of the two parts. With these features, actuation disk  16  can move axially to engage coil rotor  24  when the electromagnetic clutch is energized, and actuation disk  16  will force retainer  32  to rotate with it in either direction, engaging roller clutch system  200 .  
         [0046]     Wave spring  34  is intended to function to urge actuation disk  16  away from coil rotor  24  to facilitate disengagement when coil member  35  is de-energized. The axial force of this wave spring  34  must be balanced against the force generated by the electromagnetic clutch. If wave spring force is too high, then actuation disk  16  cannot move axially when coil member  35  is energized, preventing engagement of the roller clutch system  200 . Conversely, if the axial force of wave spring  34  is too small, then disengagement could be slowed or inhibited altogether, particularly during extremely cold weather conditions when the lubricant gets very viscous. When installed, wave spring  34  is held in a groove on the axial face of coil rotor  24 . This part is relatively simple and inexpensive, and other types of springs or similar mechanisms could be used to urge actuation disk  16  away from coil rotor  24 .  
         [0047]     Endplate member  36  is intended to enclose and seal the open end of clutch system  14  and is in proximity to coil rotor  24  and actuation disk  16 . The coil wires  38  (not shown) exit from the back of the coil housing directly through the endplate member  36 . Therefore, they don&#39;t have to be snaked through a small hole  39  at the bottom of a long cylindrical hole in the clutch housing, like conventional clutch systems. Therefore, the endplate member  36  and coil member  35  can be shipped as a single unit from the coil manufacturer with the connector in place, rather than attaching it after the wires have been routed through the housing. This allows much quicker and easier installation, with the wires being simply snap-connected to the vehicle&#39;s wiring harness (not shown). By way of a non-limiting example, coil member  35 /endplate member  36  combination is the last part installed, serving as the external seal and allowing easier routing of the coil wires  38 . The seal member  37  is then fitted over the combination of the endplate member  36  and coil member  35 , which is shown in  FIG. 5 . The coil housing  40  is spot welded to the endplate member  36  with features to provide an interface with a standard lip seal on the inner diameter thereof. The outer diameter of the endplate member  36  seals against an O-ring (not shown) fitted into the inner diameter of the outer housing. This sealing coil member  35 /coil housing  40 /endplate member  36  combination is held in place with a snap ring (not shown) and/or the like.  
         [0048]     The present invention provides several advantages over conventional clutch systems, such as: (1) the new design fits into an extension of the existing differential housing, reducing cost and complexity; (2) there are no internal seals, so the assembly uses the differential lubricant; (3) the coil member/endplate member combination is the last part installed, serving as the external seal and allowing easier routing of the coil rotor wires; (4) the inner race fits over a hub section of the outer race, providing additional structural stability and stiffness; (5) axial tabs stamped into the actuation disk fit into notches on the outer section of the inner race, providing a low cost method of preventing inadvertent actuation; (6) the press-in coil rotor acts to keep all the components into one assembly, making the unit easier to ship (an alternative design for this rotor includes a snap-fit to the outer race, also keeping the assembly together while also reducing cost and weight, isolating the magnetic flux paths for better performance and also serving as the outer journal bushing to reduce friction against the outer housing); and (7) the outer race is connected to the pinion shaft (output) and the inner race is connected to the input shaft (driveshaft).  
         [0049]     While the present invention is primarily intended for use in conjunction with ATV&#39;s, it could also be practiced with many other automotive applications including any number of different types of multi-wheel vehicles. And while the present invention is primarily intended for mounting on the front differential of a rear-wheel drive four wheeled vehicle, it could also be used on the rear differential of a front-drive vehicle, for example.  
         [0050]     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.