Abstract:
The over-running bi-directional clutch is used to synchronize gears in a transmission to allow for locking and unlocking the gears in an efficient manner.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention concerns an over-running bi-directional clutch (ORBDC) used as a gear synchronizer, or coupler or any applications between a relatively moveable internal shaft, or the like, and an external shaft, gear, or other couplable element that is external to the ORBDC. 
         [0002]    Applicant proposes use of the ORBDC hereof during a power shift in transmissions of the automated manual type or in active or passive transfers in four wheel drive or all wheel drive vehicle applications. 
         [0003]    ORBDCs in general and the ORBDC hereof in particular are distinguishable from traditional manual transmissions and transfer case systems which utilize synchronizer components (forks, rings, cones, dog teeth, etc.) to match gear input/output speeds during gear selection and shifting, and to lock the selected gear for power transfer. These components are expensive, heavy, and large. Therefore traditional systems are relatively more expensive, more massive, and require larger packaging volume than the proposed solution ORBDC of the present invention. The invention therefore reduces system package size and mass as compared with traditional synchronizer component systems. 
         [0004]    ORBDC is a known construction and examples of it appear U.S. Pat. Nos. 6,409,001; 6,997,296; and 6,974,400. It provides two operational modes in its position in a typical application, e.g., inside a speed gear and fixed to a power transmission shaft: 1) as an over-running plain bearing for gear rotation when the clutch is unblocked, and 2) as a rigid coupling for transfer of torque from the gear to the shaft, or vice versa, when the clutch is blocked. Both functions are effective bi-directional, i.e. performed during either clockwise or counterclockwise rotation. 
       BACKGROUND OF ORBDC AND ITS USE 
       [0005]    Referring to  FIG. 1 , the ORBDC is basically comprised of three component sets. There is a drawn outer shell  1  of bearing quality steel, which is split to allow expansion of the outer diameter of the shell and the ORBDC. Ramped surfaces are formed on the inner diameter or surface of the outer shell. 
         [0006]    There is a drawn inner shell  2  of bearing quality steel with a solid inner diameter for being press-fit onto a shaft. The inner shell has ramped surfaces on the outer diameter or surface thereof. The ramps on the outer shell as well on the inner shell are produced by forming axial direction depressions or grooves in one or both of the shell surfaces in which the below described needles or rollers sit and the inclined walls of those depressions or grooves define the ramps on which the needles or rollers move during operation described below. 
         [0007]    A plurality of needles or bearing rollers  3  are disposed between the inner and outer shells and are received in the axial direction grooves or recesses formed by the ramped surfaces of each shell. The diameter of the needles or rollers allows them to move into the grooves or recesses. The recesses or grooves in the ramped surfaces of the inner and outer shells are shaped and disposed so that in a neutral position, the inner and outer shell depressions or grooves may be radially aligned. 
         [0008]    When the ORBDC is in its “neutral” position, that is, no tangential rotational loads are applied to the outer shell, the ramps in the outer and inner shell align, forming grooves or pockets which loosely contain the needles or rollers. The outer shell in this position is in its unstressed, un-deformed state, which is at its smallest outer diameter. Thus the ORBDC functions as an over-running plain bearing and its state is unblocked. 
         [0009]    When a relative tangential load is applied to the outer shell, it forces the outer shell to shift rotationally relative to the inner shell, thus misaligning the grooves in each shell. This motion causes the needles  3  to shift in their grooves or pockets into an interference condition with the shells. As the load builds, the needles are forced against the ramped surfaces and begin to “ride the ramps” toward the outer diameter of the assembly. This transfer of load from tangential to radial, and the split in the outer shell, allows the outer shell&#39;s effective diameter to increase. As the diameter increases, the clearance between the ORBDC and the speed gear around it is reduced until the gap between them is eliminated. The gear is then locked to the clutch via friction. If the ORBDC is properly designed, the friction force is sufficient to lock the gear, even as torque increases because the higher torque is reflected as a higher tangential load, thus producing a higher radial load, and finally producing a higher frictional load. 
         [0010]    The relative tangential load may be applied to the outer shell via an active force, such as a drag band, or a passive force, such as drag from oil shear of the speed gear. 
         [0011]    Design of the ORBDC is key to the present invention. Previously known configurations of the ORBDC either utilize no inner shell (by forming ramps directly on the inner shaft) or utilize an inner shell with no hole for an actuation pin to pass through. In one embodiment hereof, the outer shell is instead prevented from moving in relation to the inner shell by a key member which is rotationally fixed to the shaft and thus to the inner shell. This key member is slid into engagement with a notch in the outer shell via movement along the shaft axis, very much like traditional synchronization components are used to lock gears in manual transmissions. U.S. Pat. No. 6,409,001 details such an arrangement. 
       SUMMARY OF THE INVENTION 
       [0012]    The invention concerns controlling the application of the relative tangential load. Control of the load application is accomplished via a movable actuation member positioned integral with the inner and outer shells. When the actuation member is in a position to lock both the inner and outer shells in a selected relative angular position, the ORBDC is in neutral and cannot block relative rotation. When the actuation member is actuated to allow relative rotational motion of the outer shell with respect to the inner shell, the clutch will block and the gear will be locked to the shaft by the clutch. 
         [0013]    As an example, when the invention is applied to a dual-clutch powershift transmission, the desired odd or even gear would be blocked via actuation of the appropriate ORBDC. All other corresponding gears (odd or even) would be locked in their neutral position. The opposite gear set (odd or even) would be pre-selected to the appropriate gear and its ORBDC would also be blocked awaiting application of the corresponding main clutch. The remaining gears in this set too would be locked in neutral. Engine power would be transferred through the first selected gear via the first main clutch until the need to shift. At that time, the first and second main clutches would respectively release and clamp, thus transferring power to the second selected gear, which is already pre-selected and locked. At this time, the first gear set would pre-select another gear, and so on. 
         [0014]    The movable actuation member used to lock and unlock the inner and outer shells in relative angular position can be designed in many configurations. In its simplest form, it is a pin which extends through the ORBDC radially from the inner shell outward through the outer shell. The pin could fit into a matching hole in both inner and outer shells. When the pin is in place, the shells are locked. When the pin is removed from at least one shell, the shells can rotate relative to each other, and the ORBDC will block. As is obvious, depending on the actuation member design, the inner and outer shell design will also need to be adjusted to accommodate. 
         [0015]    The invention is designed to be used with an actuation member which is positioned within the inner power transmission shaft, as opposed to a member that slides along the axis of the shaft. For this reason, the ORBDC in one embodiment hereof includes a hole that passes through both the inner and outer shells. The actuation member hereof passes through this hole and either prevents or allows the outer shell to rotate relative to the inner shell. Given that a gear will ride on the outer diameter of the outer shell, the actuation member cannot protrude above this outer diameter. For this reason, the outer shell has a recessed step to bring it in closer proximity to the inner shell. This reduces the length of the pin, which protects the pin from interference with the gear and also lowers the forces on the pin. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0016]      FIG. 1  illustrates a power transmission system in which the present invention is embodied; 
           [0017]      FIG. 2  is a detail of one ORBDC from  FIG. 1 ; 
           [0018]      FIG. 3  is a perspective view of an ORBDC; 
           [0019]      FIG. 4  is a cross-section through the ORBDC of  FIG. 3 ; 
           [0020]      FIG. 5  is a cross-section through one embodiment of the ORBDC; 
           [0021]      FIG. 6  is a cross-section through a second embodiment of an ORBDC; 
           [0022]      FIG. 7  is a perspective view of the ORBDC in  FIG. 6 ; 
           [0023]      FIG. 8  is a cross-section along the axis showing a third embodiment of the invention; 
           [0024]      FIG. 9  is a cross-section of the third embodiment across the axis; 
           [0025]      FIG. 10  is an illustrative perspective view of a fourth embodiment of an ORBDC; 
           [0026]      FIG. 11  is an enlarged cross-sectional view showing the ORBDC of  FIG. 10  in the free and locked states; 
           [0027]      FIG. 12  is a perspective view showing a fifth embodiment of an ORBDC; and 
           [0028]      FIG. 13  shows their ORBDC of  FIG. 12  in free and locked states. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    Several preferred designs for the actuation member are shown herein: 
         [0030]      FIGS. 3 and 4  show basic elements of an ORBDC in which the invention may be embodied. It includes an outer shell  1 , inner shell  2  and needle rollers  3  between the shells. The outer shell is split at  4 . There may be a notch at the split as described with reference to the embodiment of  FIG. 12 . 
         [0031]    Referring to the embodiment of  FIG. 5 , the actuation member is a radially movable pin  11  which is integrated in the inner power transmission shaft  12 . An actuation tube  13  internal to the power shaft has a grooved or cammed surface  16  to actuate the pin  11  to either protrude through both of the inner  14  and outer  15  shells as shown by pin  18 , or to retract as shown by pin  19  and thus free the outer shell to rotate and block the ORBDC. While an inner shell on a shaft is shown, the surface with ramps which cooperates with the needles may be formed in the shaft itself. Also, the grooves or depressions or ramps may be formed in only one of the shells. 
         [0032]    The needles or rollers in all embodiments have a diameter so that they can enter a groove or depression and avoid riding a ramp. 
         [0033]    Referring to the embodiment of  FIGS. 6 and 7 , the actuation member is a rotating pin  21  which is integrated in the inner power transmission shaft  22 . The pin  21  can be actuated, that is, rotated, by various arrangements. The preferred design is a rotating drum  23  with cam lugs  24  thereon that contact the bottom  25  of the pin and rotate the pin. When the pin  21  is in the neutral position shown by pin  26 , the ORBDC  27  will be locked from rotation and thus the gear  28  will free spin on the outer shell, and no torque will be transmitted. When the illustrated pin  29  is rotated to the locked position, due to contact between lugs  24  and the respective pin  25 , the outer shell of the ORBDC will be free to shift and thus ride the ramps, expand the outer shell, and lock the gear in rotation to the inner power shaft. 
         [0034]    Referring to the embodiment of  FIGS. 8 and 9 , the actuation member is a rocker pin  31  which is installed into the ORBDC at a circumferential location of and in place of one of the needle rollers  32 . The rocker pin  31  has a pivot center  33 , a lock tab  34 , an interlock tab  35 , and an engagement tab  36 . A selection drum  37  is rotated to transfer between the ORBDC being in its neutral or locking conditions. When the inner selection drum  37  is rotated so that the respective interlock cam  38  on the drum contacts the interlock tab  35 , the pin  31  pivots so that the lock tab  34  protrudes through the outer shell  39  of the ORBDC, thus allowing the gear to spin freely over the outer shell. When the selection drum  37  is rotated so that the respective engagement cam  40  on the drum contacts the engagement tab  36 , the pin  31  pivots such that the lock tab  34  retracts out of engagement with the outer shell, thus allowing the shell to rotate relatively and lock the gear  41  to the shaft  42 . 
         [0035]    In the embodiment of  FIGS. 10 and 11  hereof, the outer shell is instead prevented from moving in relation to the inner shell by a key member (not shown) which is rotationally fixed to the shaft and thus to the inner shell. This key member is slid into engagement with a notch  52  in the outer shell via movement along the shaft axis, very much like traditional synchronization components are used to lock gears in manual transmissions. 
         [0036]    Referring to  FIGS. 12 and 13 , the actuation member is positioned within the inner power transmission shaft (not shown) and is not a member that slides along the axis of the shaft. For this reason, the ORBDC in this embodiment hereof includes a hole  61  that passes through both the inner and outer shells. The actuation member hereof (not shown, but from one of the Figures above) passes through the hole  61  and either prevents or allows the outer shell to rotate relative to the inner shell. Because a gear (not shown) will ride on the outer diameter of the outer shell, the actuation member cannot protrude above the outer diameter of the outer shell. For this reason, the outer shell has a recessed step  62  to bring it in closer proximity to the inner shell. This reduces the length of the pin, which protects the pin from interference with the gear and also lowers the forces on the pin. Further, this permits operation of the actuation member within the width of the ORBDC, rather than requiring adding an actuator axially outboard of the outer shell, which would widen ORBDC and possibly the entire system including it. 
         [0037]    It is not required that the ORBDC have both an inner and outer shell to make use of the recessed step outer shell in  FIG. 10 . This can also be used if the inner shell is eliminated via directly forming ramps as described above on the inner shaft. In such a case, the step would come in close proximity with the shaft and still allow actuation from within the shaft without interfering with the gear. 
         [0038]    Although the present invention has been described in relation to particular embodiments thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.